HAP44 Advanced Manual 10-08-08

HAP V 4.4 Advanced Training Seminar Copyright Carrier Corp. © 2008

Hourly Analysis Program

Version 4.4

Advanced Training Seminar

HAP V 4.4 Advanced Training Seminar Copyright Carrier Corp. © 2008 2

Carrier Corporation

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Table of Contents EARNING CEU CREDITS FOR SUCCESSFUL COMPLETION OF THIS TRAINING ...........................................4 COURSE LEANING OUTCOMES .................................................................................................................4 WELCOME TO HAP 4.4 ............................................................................................................................5 WORKBOOK ORGANIZATION ...................................................................................................................5 PROJECT DATA MANAGEMENT................................................................................................................5 PROJECT DEFINITION AND OUTLINE ........................................................................................................9 WORKSHOP # 1 - PROJECT CREATION AND WEATHER DATA .................................................................16 WORKSHOP # 2 – EDITING SCHEDULES..................................................................................................24 WORKSHOP # 3 – WING D AIR SYSTEM INPUT 4PFCU..........................................................................32 WORKSHOP # 4 – WING D AIR SYSTEM INPUT–PACKAGED ROOFTOP UNIT ..........................................47 WORKSHOP # 5 – MODELING CHILLERS, BOILERS, & TOWERS..............................................................68 WORKSHOP # 6 – FINALIZING CHILLER AND BOILER PLANTS................................................................94 WORKSHOP # 7 – DEFINING AND SIMULATING BUILDINGS .................................................................119 WINDOWS SOFTWARE BASICS .............................................................................................................164 USING HAP 4.4 FOR SYSTEM DESIGN LOADS......................................................................................169 APPENDIX “C” .....................................................................................................................................176 THE SIZING DILEMMA..........................................................................................................................176 WHICH SIZING METHOD TO USE? .......................................................................................................177 PUTTING LOAD CALCULATION METHODS IN PERSPECTIVE..................................................................179 THE BENEFITS OF THE TRANSFER FUNCTION / HEAT EXTRACTION LOAD CALCULATION

METHOD ..........................................................................................................................................182 DIAGNOSING THE “THERMOS BOTTLE EFFECT”...................................................................................183 USING OUTDOOR VENTILATION CONTROL OPTIONS ...........................................................................188 DEMAND CONTROLLED VENTILATION CONTROL ................................................................................189 UNDERSTANDING ZONE LOADS AND ZONE CONDITIONING .................................................................192 PITFALLS OF ECONOMIZER OPERATION ...............................................................................................195 DIFFERENCES BETWEEN PEAK COIL LOAD CFM, MAX BLOCK CFM, SUM OF PEAK ZONE CFM.......198 SELECTING EQUIPMENT WHEN COIL CFM (L/S) DIFFER.....................................................................201 HOW VENTILATION LOADS ARE CALCULATED IN HAP .......................................................................202 SYSTEM BASED DESIGN LOAD CALCULATIONS...................................................................................204 APPENDIX “D”.....................................................................................................................................212 NOTES..................................................................................................................................................224

For Technical Support Please contact Software Systems Network at 1.800.253.1794 or e-mail: [email protected]

For additional information and Program Downloads visit us at: www.commercial.carrier.com


Earning CEU Credits for Successful Completion of this Training E20 software training as part of Carrier’s Technical Training Center has been reviewed and approved as an Authorized Provider by the International Association for Continuing Education and Training (IACET). IACET's mission is to promote and enhance quality in continuing education and training through research, education, and standard setting. IACET Authorized Providers undergo a strict evaluation of their educational processes according to the IACET Criteria and Guidelines, including two reviews by IACET's Commission and a site visit by an IACET Commissioner. Members of the organization are the educational professionals that strive to provide the highest quality in continuing education and training. Continuing Education Units (CEUs) One (1) IACET CEU is equal to ten (10) contact hours of participation in an organized continuing education experience under responsible sponsorship, capable direction, and qualified instruction. After successfully completing this training, the student will receive an appropriate number of CEU’s based on the classroom contact time. In addition, the student should feel very comfortable using the E20 software to enhance their HVAC related job responsibilities. Course Leaning Outcomes As part of this software training, each student will learn how to use the Hourly Analysis Program (Energy Simulation) by completing a series of hands-on project exercises. These exercises are intended to confirm the student’s ability to understand the course learning outcomes. These are:

• Define and input the following o Energy simulation weather data, internal load schedules including profiles

used for energy analysis, unitary packaged equipment power requirements, water chillers, boilers, cooling towers, hydronic distribution systems, electric and fuel rate structures, miscellaneous building energy use

• Generate and interpret simulation reports for air systems and plants • Generate and interpret diagnostic reports for air systems and plants • Trouble shoot air systems and plants • Generate and interpret annual cost reports for a base and alternate design case • Determine best practices from energy simulation reports

This Symbol is used throughout this manual and represents required learning outcomes. Each student is expected to comprehend the subject content and successfully demonstrate competency in these areas.


Welcome to HAP 4.4 his manual was created for the engineers and designers using the Carrier Hourly Analysis Program v4.4 for calculating commercial building cooling and heating loads and energy simulation. This manual is a companion to the hands-on training for the Hourly Analysis Program Basic Training course facilitated by Carrier Software

Systems Network. This manual includes all class exercises and workflow tips. The goal of this manual is to make each student comfortable and familiar with the input routines and the calculated results of the HAP design loads and energy simulation.

Workbook Organization The intent of the sections in this manual is to follow the logical process of the hands-on workshops and workflow. We cover the common process and special features of the Carrier HAP program. We arranged the topics of discussion in the same order as our hands-on training classes. The first two sections address the program installation, basic system requirements and general housekeeping. We also highlight and discuss the program interface and functionality. The remaining sections follow the logical path of the program’s modules including detailed discussions and examples of the workflow process used to create a complete HAP data set. This includes detailed discussions of the input forms, editing, document outputs and more. This manual also includes three appendixes. Appendix A consists of detailed schematics of all air system types in the HAP program. Appendix B, includes a discussion on basic HAP and Windows program functions Appendix C includes detailed discussions of common questions about the HAP program. Appendix D includes several white papers discussing the advantages of the HAP program.

Project Data Management This topic discusses projects and the management of project data. What is a Project? All the data you enter and calculate in HAP is stored together within a "project.” A Project is simply a container for your data. However, a project can hold data for other programs as well as HAP. For example, if you create a project for a building design job, it might contain load estimating and system design data from HAP, air handler selection data from the Carrier AHU Builder program, and air terminal selection data from the Carrier Air Terminal Selection program. Keeping this data together in a single container is often more efficient than keeping the data in several separate locations. Using Projects. HAP provides a variety of features for performing common tasks with projects. You can:

• Create a new project by using the New option on the Project Menu. • Edit data in an existing project by using the Open option on the Project Menu • Save changes in a project by using the Save option on the Project Menu • Save changes to a new project using the Save As option on the Project Menu • Delete an existing project using the Delete option on the Project Menu

T


• Edit descriptive data for the project, such as the project name, using the Properties option on the Project Menu

• Archive project data for safe keeping using the Archive option on the Project Menu

• Retrieve data that you earlier archived using the Retrieve option on the Project Menu

• Convert data from a previous version of HAP using one of the Convert HAP Data options on the Project Menu

• Import data from another project into the current project using the Import Data option on the Project Menu

How Project Data is Stored. When a new project is saved for the first time, you designate the folder that will hold the project files (either by accepting the default folder \E20-II\Projects\ProjectName or by specifying a folder yourself). This folder is the permanent storage location of project data. When you open the project to work with its data, temporary copies of the project’s data files are made. As you enter data, make changes and perform calculations, all this data is stored in the temporary copy of the data files. Only when you use the Save option on the Project Menu, are the changes you have made copied to permanent storage. Therefore, if you ever need to undo changes you have made to a project, simply re-open the project without saving the changes you have made. When you re-open the project, the changes stored in the temporary copy of the data files are discarded, and data from your last project/save is restored. Recommended Project Management Practices. Project data represents an important investment of your time and effort. And, as the saying goes, ‘time is money’. Therefore, it is important to safeguard your investment in project data. We recommend adopting the following practices when working with projects:

• Create a separate project for each job you work on. It is usually more efficient to keep data for separate jobs in separate projects. It is also safer to store data in smaller, focused units. If you keep data for all jobs in a single project, and this project becomes damaged, your data loss will be greater than if you keep data for separate jobs in separate projects.

• Use a descriptive name for the project so you can quickly recognize what it contains,

both now and when you need to refer to the project in the future. Because the selection list for projects is arranged alphabetically, it is useful to use a consistent naming convention. Many firms begin the project name with their internal project number followed by descriptive text (e.g., P2002-47 Lincoln School).

• Save early and often. While entering data, changing data and generating reports,

save the project periodically. This practice is useful in the event that you make a mistake and need to undo changes. If the last time you saved the project was 15 minutes ago, undoing your mistake will only cause you to lose 15 minutes of work. On the other hand, if the last time you saved the data was 4 hours ago, undoing a mistake may cause you to lose 4 hours worth of work.

• Archive your data periodically for safekeeping. These days, data on hard disks is

relatively safe. However, it is still possible for hard disk drives to become damaged, or for files on the hard disk to be damaged or erased. Therefore, it is a good practice to periodically archive your project data. Data can be archived to a separate location on


your hard disk, to a different hard disk drive or to removable media such as a compact disk, zip drive or floppy disks. For example, if you archive data for a large project at the end of each day and your hard disk drive fails, at most you will have lost one day’s worth of work. On the other hand, if data for the same large project was never archived and your hard disk drive fails, all the project data would be lost.

What is New in HAP 4.4? This topic describes enhancements in HAP v4.40. It is intended for readers who have upgraded from HAP v4.34 to v4.40. Most of the enhancements made in v4.40 relate to two major themes:

1. Theme 1 – Using HAP for LEED Energy and Atmosphere Credit 1 Analysis.

HAP was modified to streamline steps in performing a LEED EA Credit 1 analysis making it faster and easier to perform. Specific modifications include:

• LEED NC 2.2 EA Credit 1 Summary Report. This new report provides data found in sections 1.1, 1.3, 1.5, 1.8.1, 1.8.1b, 1.8.2 and 1.8.2b of the LEED NC 2.2 EA Credit 1 on-line submittal template and imitates the format of the submittal template. This report eliminates the tedious work of assembling submittal template report data from multiple HAP reports.

• Duplicate Building with Spaces and HVAC Eqpt option. This new option automatically duplicates a HAP building and all the systems, plants, spaces, chillers, cooling towers and boilers it contains in one-step. This option is useful when starting definition of the Baseline building based on a duplicate of data for the Proposed Building. More importantly, it facilitates placing Proposed and Baseline buildings in a single project so the Credit 1 Summary Report can be generated.

• Perform LEED (90.1 PRM) Rotations option. This new option automatically makes three copies of the "Baseline 0 Degree" building and all of its systems, plants, spaces, chillers, cooling towers and boilers. In the three copies, spaces are rotated 90 deg, 180 deg and 270 deg respectively. This provides a rapid way to generate the three rotations of the Baseline building. It also makes it efficient to place all Proposed and Baseline buildings in a single project so the Credit 1 Summary Report can be generated.

• Autosizing for DX and Plant Equipment. This feature allows you to specify that equipment gross capacity be automatically determined as peak load plus a specified percent oversizing factor. For example, peak cooling load + 15%.

• Input DX Equipment Performance as EER or COP. This feature allows you to specify DX equipment as EER for cooling or COP for heating. The software then automatically decompiles the EER or COP to determine compressor kW for use in the simulation.

• All Terminal Units Use Same Settings. When defining equipment performance for DX fan coils, WSHP, GWSHP or GSHP equipment, this new option allows you to specify one set of EER or COP performance values to apply to all zone terminal units in a system. This saves you from having to define compressor kW for each zone fan coil or heat pump separately.

• Baseline Fan kW Calculated per ASHRAE 90.1 Appendix G section G3.1.2.9. When defining air systems for a Baseline building, you have the option of defining supply fan performance be automatically calculated per the equation in section G3.1.2.9. This equation sets the total fan kW for the system.

• Fan Performance Defined as W/CFM. When specifying fan performance for fan powered mixing box terminals, performance can be input as W/CFM (W/L/s). The program will then automatically derive the fan watts from the design CFM for the box.


• ASHRAE 90.1 Appendix G VAV Fan Part-Load Curve. VAV fan part-load performance can be modeled using the VAV fan curve found in Appendix G Table G3.1.3.15.

• Water Flow Rate Inputs as gpm/Ton or Delta-T. New options allow water flow rates to be defined in terms of gpm/Ton (L/s/kW) or delta-T in addition to gpm.

• Water Pump Performance as W/gpm or kW. New options allow water pump performance to be defined in terms of W/gpm (W/L/s) or kW in addition to the existing specification of pump head.

2. Theme 2 - Adding Features for Preliminary or Schematic Design. Throughout its history, HAP has focused on system design and energy analysis tasks typically occurring in the detailed design phase of a project. These tasks involve detailed definition of the building envelope, layout and HVAC equipment, and require time-consuming data entry to create a suitably detailed building model. When performing energy analysis in the preliminary or schematic design phase of a project, the objective is to quickly and roughly compare a large set of design alternatives to identify the most promising designs. This work typically does not require as detailed a definition of the building and its HVAC equipment. To make HAP more efficient for performing these types of analyses, new Wizard features have been added to allow users to rapidly generate input data for an analysis. This work builds on the Building Wizard feature offered in HAP v4.3. Specific enhancements include:

• New Wizards Menu. Provides options for running Building Wizard or Equipment Wizard alone, and for running an integrated session linking Building and Equipment Wizards together.

• Building Wizard Option. The Building Wizard option on the Wizards Menu can be used to rapidly generate space data for a building. The Building Wizard has been revised and upgraded for HAP v4.4.

• Equipment Wizard Option. The Equipment Wizard option on the Wizards Menu can be used to rapidly generate HVAC equipment for a building - specifically all of the air systems, plants, chillers, cooling towers and boilers, as applicable.

• Full Wizard Session Option. The "Full Wizard Session" option on the Wizards Menu allows you to run the Building Wizard and Equipment Wizard in tandem. In as single Wizard session you can generate space data and data for multiple equipment designs. This essentially creates 95% of the input data for an energy cost study in minutes rather than hours or days. Only weather and utility rate data must be added before running calculations.


Project Definition and Outline Our project for this hands-on training is a small private school building constructed in St. Louis, MO. There are eight separate workshops with numerous work sessions in each of the workshops requiring use and understanding of all modules in the HAP program. The first uses includes updating the weather data by adding the simulation weather data set to the project folder. This step also includes defining annual holidays. The second workshop requires updating of the fractional schedules and their assignments. In the third workshop, we define a new air system type for Classroom wing “D,” calculate the design and energy simulation and; discuss the results. Workshop # 4 is an alternate air system for the Classroom Wing “D” that utilizes Packaged Rooftop Units with different capacity controls for each workshop. In workshop # 5, we retrieve a second archive that brings in all air systems required for the different case studies. Additionally, we will add chillers, towers and boilers to our project library. Workshop # 6 links our chillers, towers and boilers to the building’s plant type. We then simulate the different plant case studies and compare operating characteristics. In workshop # 7, we will add the utility rates to the project library. This workshop looks at simple and complex rate structures for electric and natural gas. We also look at the Utility Rate Time of Day schedule. We then defining the different building case studies, perform the energy simulation and compare the results; thus enabling us to offer the best solution to the building owner and decision makers.







Workshop # 1 Inputs


This Page is Intentionally Left Blank


Workshop # 1 – Create New Project and Enter Weather Data

Our first workshop focuses on expanding an existing design load analysis to include a complete energy simulation. We will retrieve an archived system design load project developed in the HAP Basic Training Seminar. The retrieval of this project includes all spaces, air systems and library items so we can focus on the additional input requirements for completing an energy analysis. Take the following steps to get started in this workshop.

PROJECT DATA Launch HAP on your training laptop. On the project menu bar, select “Project/Retrieve.” The program will look in the default location for the archive file. Retrieve the archive “HAP 44 ADVANCED ARCHIVE 1 UNSOLVED.E3A.” After successfully retrieving the project, click on “Project, “Save as” to create a project folder. Use the default data path for the location of the project folder, and name the project. Next, left click on “View/Preferences,” then in the “General” tab check the option “Enable Energy Analysis Features.”

WEATHER DATA Review the already configured design weather data to insure that you are using default ASHRAE design weather data for St. Louis, MO. In the simulation input form under the simulation tab, configure energy simulation data for the same city. Select simulation weather by left clicking on the “Change City” button and navigating to the USA_MISSOURI_ST. LOUIS.TMY2.HW1 file. This action will link the TMY-2 simulation weather data to the project. The first day of the year selection, (use the default day Wednesday) determines where the weekends occur. The next step is to add the following dates to the Holidays List by double left clicking the date on the calendar:

January 1 April 18

May 26 July 4 September 1 November 27, 28 December 25, 26,29,30,31


Note: Please remember to “save early and save often” Design and simulation weather reports are displayed on the following pages. Weather reports are available by highlighting “weather” in the left tree then left clicking on “Reports” and choosing “Print/View Input Data” or right click on < Weather Properties> and choose “Print/View Input Data”. Select the weather reports shown below. “Design” weather data is used for peak heating and cooling load calculations and equipment sizing purposes. HAP uses 8760 hourly “Simulation” weather data to simulate building energy consumption and calculate an annual operating cost.


Weather Reports Design Parameters: City Name ................................................................................................. St. Louis IAP Location ........................................................................................................... Missouri Latitude .................................................................................................................... 38.8 Deg. Longitude ................................................................................................................. 90.4 Deg. Elevation ................................................................................................................ 564.0 ft Summer Design Dry-Bulb ........................................................................................ 95.0 °F Summer Coincident Wet-Bulb .................................................................................. 76.0 °F Summer Daily Range ............................................................................................... 18.3 °F Winter Design Dry-Bulb .............................................................................................. 2.0 °F Winter Design Wet-Bulb ............................................................................................. 0.3 °F Atmospheric Clearness Number .............................................................................. 0.95 Average Ground Reflectance ................................................................................... 0.20 Soil Conductivity ..................................................................................................... 0.800 BTU/(hr-ft-°F) Local Time Zone (GMT +/- N hours) .......................................................................... 6.0 hours Consider Daylight Savings Time ............................................................................... Yes Daylight Savings Begins ................................................................................... April, 11 Daylight Savings Ends ................................................................................ October, 24 Simulation Weather Data ............................................................... St. Louis IAP (TM2) Current Data is ..................................................................... 2001 ASHRAE Handbook Design Cooling Months ............................................................... January to December Design Day Maximum Solar Heat Gains (The MSHG values are expressed in BTU/(hr-ft²) ) Month N NNE NE ENE E ESE SE SSE SJanuary 19.1 19.1 19.1 82.2 145.6 201.6 228.2 239.2 240.5February 23.3 23.3 43.6 125.8 183.5 221.7 236.9 232.1 226.0March 27.7 27.7 98.7 156.5 208.2 227.8 223.6 203.9 191.0April 32.1 66.8 134.7 186.0 208.8 213.1 188.5 157.7 139.2May 35.3 99.1 154.7 196.5 208.9 195.5 161.6 120.2 99.7June 43.8 109.2 162.0 198.1 204.6 186.9 148.2 104.6 83.9July 36.2 95.9 154.8 193.0 202.2 192.1 157.1 117.6 97.2August 33.8 63.1 131.9 178.7 201.8 205.8 182.9 152.7 134.9September 28.8 28.8 92.1 151.1 195.0 218.3 213.5 196.6 185.1October 24.0 24.0 51.6 112.9 177.1 214.5 229.0 224.8 219.2November 19.4 19.4 19.4 79.7 145.9 194.6 227.1 237.3 236.6December 17.2 17.2 17.2 65.2 127.9 188.2 219.6 237.4 238.9Month SSW SW WSW W WNW NW NNW HOR MultJanuary 241.1 231.3 197.5 149.1 80.5 19.1 19.1 132.0 1.00February 231.7 236.6 223.7 183.6 120.5 53.3 23.3 176.0 1.00March 202.8 221.2 229.0 203.3 162.6 97.2 27.7 215.0 1.00April 157.6 188.4 213.1 209.1 186.0 134.5 67.1 240.1 1.00May 120.6 161.0 196.0 208.2 196.6 155.6 98.4 252.3 1.00June 103.9 149.0 186.0 205.4 197.6 160.5 110.1 254.3 1.00July 116.1 158.1 190.4 205.1 192.6 151.6 99.2 249.8 1.00August 152.0 181.6 205.4 201.8 179.7 130.6 66.6 236.3 1.00September 197.2 214.7 216.8 197.4 147.9 92.1 28.8 207.5 1.00October 224.8 228.4 213.6 175.5 120.6 42.7 24.0 172.8 1.00November 235.4 224.2 197.9 142.8 80.8 19.4 19.4 131.3 1.00December 237.6 219.2 188.2 127.4 65.3 17.2 17.2 111.8 1.00 Mult. = User-defined solar multiplier factor.


Table 1. Descriptive Parameters: City ............................................................................................................................... St. Louis IAP Location .............................................................................................................................. Missouri Type of Data ............................................................................................................................. (TM2) Latitude ....................................................................................................................................... 38.8 Deg. Longitude .................................................................................................................................... 90.4 Deg. Elevation ................................................................................................................................... 564.3 ft Local Time Zone (GMT +/- N hours) ............................................................................................. 6.0 hours Daylight Savings Begins ...................................................................................................... April, 11 Daylight Savings Ends ................................................................................................... October, 24 Average Ground Reflectance ...................................................................................................... 0.20 Table 2. Dry-Bulb Temperature Statistics ( °F ):

Month Absolute Average Average Average Absolute Maximum Maximum Minimum Minimum January 64.0 37.2 27.2 19.1 3.0 February 64.9 42.9 32.7 23.2 1.9 March 80.1 53.9 44.9 36.3 15.1 April 91.9 68.5 57.6 48.0 30.0 May 90.0 77.4 67.2 56.9 41.0 June 93.9 84.1 75.0 65.8 50.0 July 100.0 87.5 78.2 69.3 55.0 August 100.9 85.5 77.6 69.8 57.0 September 91.0 79.5 69.1 60.0 46.0 October 81.0 65.9 55.0 45.6 34.0 November 75.9 53.3 44.7 36.4 19.9 December 57.9 38.8 30.4 22.6 0.0

Table 3. Daily Solar Radiation Statistics:

Daily Total Solar on Horizontal ( BTU/ft² ) Daily Clearness Number (dimensionless) Month Maximum Average Minimum Maximum Average Minimum January 1051.6 687.6 358.9 0.697 0.483 0.277 February 1489.0 942.6 469.3 0.695 0.499 0.270 March 1950.1 1308.9 505.3 0.722 0.522 0.195 April 2201.3 1613.6 881.3 0.744 0.520 0.310 May 2555.8 1890.7 830.7 0.743 0.538 0.236 June 2684.7 2049.8 1106.1 0.727 0.557 0.302 July 2525.1 2024.7 1163.9 0.692 0.564 0.326 August 2362.8 1716.8 714.9 0.704 0.528 0.219 September 2072.7 1433.8 764.6 0.733 0.528 0.282 October 1691.7 1090.9 370.2 0.717 0.522 0.192 November 1159.8 724.4 350.5 0.668 0.469 0.249 December 945.2 576.0 313.4 0.700 0.449 0.235


Table 4. Time of Occurrence for Maximums and Minimums:

Month Highest Dry-Bulb Lowest Dry-Bulb Maximum Total Minimum Total Temperature Temperature Solar Solar January Jan 29, 1500 Jan 6, 0600 Jan 24 Jan 3 February Feb 18, 1200 Feb 3, 0300 Feb 27 Feb 7 March Mar 17, 1500 Mar 7, 0600 Mar 25 Mar 20 April Apr 28, 1600 Apr 5, 0600 Apr 7 Apr 1 May May 28, 1600 May 9, 0500 May 8 May 16 June Jun 28, 1400 Jun 3, 0500 Jun 24 Jun 5 July Jul 31, 1600 Jul 21, 0400 Jul 8 Jul 20 August Aug 28, 1500 Aug 7, 0600 Aug 9 Aug 16 September Sep 5, 1600 Sep 25, 0700 Sep 10 Sep 16 October Oct 27, 1500 Oct 13, 0700 Oct 3 Oct 24 November Nov 19, 1400 Nov 30, 0700 Nov 3 Nov 25 December Dec 15, 1400 Dec 10, 0500 Dec 1 Dec 3

Table 5. Calendar Data: Day of Week for January 1st .......................................................................................... Wednesday Holidays:

Jan 1

Apr 18

May 26

Jul 4

Sep 1

Nov 27 28

Dec 25 26 27 28 29 30 31


Friday, August 1 Hour Dry-Bulb Wet-Bulb Beam Solar Total Solar

( °F ) ( °F ) on Horiz. on Horiz. ( BTU/(hr-ft²) ) ( BTU/(hr-ft²) )

0000 76.3 66.4 0.0 0.0 0100 75.0 65.6 0.0 0.0 0200 72.9 64.4 0.0 0.0 0300 72.0 63.8 0.0 0.0 0400 70.2 62.6 0.0 0.0 0500 68.7 61.7 0.0 0.0 0600 66.0 60.4 0.5 11.0 0700 65.5 60.4 23.9 52.7 0800 66.9 60.5 83.7 120.2 0900 70.0 61.6 111.6 169.9 1000 73.0 63.2 166.2 217.2 1100 75.9 63.1 207.4 261.6 1200 77.0 62.4 189.7 260.7 1300 80.1 64.5 195.1 274.3 1400 80.1 63.5 153.4 221.6 1500 81.0 63.8 161.0 227.6 1600 82.0 63.8 126.3 186.8 1700 82.0 64.7 102.2 139.3 1800 81.0 64.8 44.0 71.9 1900 80.1 64.1 5.6 18.6 2000 78.1 63.4 0.0 0.6 2100 75.9 62.7 0.0 0.0 2200 73.9 62.0 0.0 0.0 2300 72.0 61.3 0.0 0.0

Saturday, August 2 Hour Dry-Bulb Wet-Bulb Beam Solar Total Solar

( °F ) ( °F ) on Horiz. on Horiz. ( BTU/(hr-ft²) ) ( BTU/(hr-ft²) )

0000 71.1 61.0 0.0 0.0 0100 70.0 61.1 0.0 0.0 0200 70.0 60.0 0.0 0.0 0300 68.0 61.0 0.0 0.0 0400 68.0 59.9 0.0 0.0 0500 66.9 60.0 0.0 0.0 0600 66.9 60.6 1.0 9.6 0700 68.0 61.0 25.2 50.2 0800 70.0 61.6 28.8 84.0 0900 72.0 64.1 33.6 114.4 1000 78.1 65.5 19.9 97.2 1100 79.0 64.1 203.7 268.0 1200 82.0 66.1 257.3 282.3 1300 84.0 67.4 175.6 253.3 1400 86.0 69.0 127.7 234.2 1500 87.1 70.0 136.7 212.1 1600 87.1 70.0 134.9 180.2 1700 86.0 69.7 74.1 121.0 1800 87.1 70.0 52.8 74.7 1900 84.9 69.8 13.3 22.5 2000 82.9 69.3 0.0 1.0 2100 81.0 69.3 0.0 0.0 2200 80.1 69.0 0.0 0.0 2300 78.1 69.0 0.0 0.0


Workshop # 2 Inputs




Workshop # 2 – Editing Schedules SCHEDULES

This workshop focuses on editing the schedules created for our system design load. The following three schedules were created during the design load phase of the project and retrieved in the archive. Please add the following additional profiles to each schedule as noted: LIGHTS – CLASSROOMS Profile #3 – Energy Weekday

00-06: 10% 07: 50% 08-11:100% 12: 00% 13-15: 100% 16: 50% 17: 20% 18-23: 10%

Profile #4 – Energy Weekend Hours 00-23: 10%

On the assignments tab, assign Profile #3 to day types Monday Thru Friday in all months except July. Assign existing Profile #2 from the design load phase to day types Monday thru Friday in the month of July only.

Assign Profile #4 to day types Saturday, Sunday, and Holiday for all twelve (12) months.

PEOPLE - CLASSROOMS Profile #3 – Energy Weekday Hours 00-07: 00% Hours 08-11: 100% Hour 12: 0% Hours 13-15: 100% Hour 16: 40% Hour 17: 10% Hours 18-23: 00% Profile #4 – Energy Weekend Hours 00-23: 00%

On the assignments tab, assign Profile #3 to day types Monday Thru Friday in all months except July. Assign Profile #2 to day types Monday through Friday for July only.

Assign Profile #4 to day types Saturday, Sunday, and Holiday for all twelve (12) months.


PEOPLE – CORRIDORS Profile #3 – Energy Weekday

Hours 00-06: 00% Hours 07-16: 50% Hours 17-23: 00%

Profile #4 – Energy Weekend Hours 00-23: 00% On the assignments tab, assign Profile #3 to day types Monday Thru Friday in all moths except July. Assign existing Profile #2 to day types Monday thru Friday for the month of July only. Assign Profile #4 to day types Saturday, Sunday, and Holiday for all twelve (12) months. OCCUPIED (FAN/THERMOSTAT) SCHEDULE – CLASSROOM Profile #3 – Energy Weekday

Hours 00-05: Unoccupied Hours 06-17: Occupied Hours 18-23: Unoccupied

Profile #4 – Energy Weekends = Unoccupied 00-23 Apply Profile #2 to the month of July only Copies of workshop # 3 schedule input forms are displayed below.


Lights – Classroom, Schedule Input Data Lights - Classrooms (Fractional) Hourly Profiles: 1:Design Day

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 10 10 10 10 10 10 10 10 100 100 100 100 100 100 100 100 30 10 10 10 10 10 10 10

2:Summer Shutdown De

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 0 0 0 0 0 0 0 0 60 60 60 60 60 60 60 60 60 0 0 0 0 0 0 0

3:Energy Weekday

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 10 10 10 10 10 10 10 50 100 100 100 100 0 100 100 100 50 20 10 10 10 10 10 10

4:Energy Weekend

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

Assignments:

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Design 1 1 1 1 1 1 2 1 1 1 1 1

Monday 3 3 3 3 3 3 2 3 3 3 3 3 Tuesday 3 3 3 3 3 3 2 3 3 3 3 3

Wednesday 3 3 3 3 3 3 2 3 3 3 3 3 Thursday 3 3 3 3 3 3 2 3 3 3 3 3

Friday 3 3 3 3 3 3 2 3 3 3 3 3 Saturday 4 4 4 4 4 4 4 4 4 4 4 4

Sunday 4 4 4 4 4 4 4 4 4 4 4 4 Holiday 4 4 4 4 4 4 4 4 4 4 4 4


People – Classroom, Schedule Input Data People - Classrooms (Fractional) Hourly Profiles: 1:Design Day

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 0 0 0 0 0 0 0 5 100 100 100 100 100 100 100 100 40 10 0 0 0 0 0 0


Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 0 0 0 0 0 0 0 0 40 40 40 40 40 40 40 40 40 0 0 0 0 0 0 0

3:Energy Weekday

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 0 0 0 0 0 0 0 0 100 100 100 100 0 100 100 100 40 10 0 0 0 0 0 0

4:Energy Weekend

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Assignments:


Monday 3 3 3 3 3 3 2 3 3 3 3 3 Tuesday 3 3 3 3 3 3 2 3 3 3 3 3


Friday 3 3 3 3 3 3 2 3 3 3 3 3 Saturday 4 4 4 4 4 4 4 4 4 4 4 4

Sunday 4 4 4 4 4 4 4 4 4 4 4 4 Holiday 4 4 4 4 4 4 4 4 4 4 4 4


Occupied Schedule – Classroom (Fan/Thermostat) Input Data Occupied Schedule - Classroom (Fan / Thermostat) Hourly Profiles: 1:Design Day

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value U U U U U U O O O O O O O O O O O O U U U U U U


Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value U U U U U U O O O O O O O O O O O U U U U U U U

3:Energy Weekday

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value U U U U U U O O O O O O O O O O O O U U U U U U

4:Energy Weekends

Hour 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Value U U U U U U U U U U U U U U U U U U U U U U U U

O = Occupied; U = Unoccupied Assignments:


Monday 3 3 3 3 3 3 2 3 3 3 3 3 Tuesday 3 3 3 3 3 3 2 3 3 3 3 3


Friday 3 3 3 3 3 3 2 3 3 3 3 3 Saturday 4 4 4 4 4 4 4 4 4 4 4 4

Sunday 4 4 4 4 4 4 4 4 4 4 4 4 Holiday 4 4 4 4 4 4 4 4 4 4 4 4




Workshop # 3 Inputs




Workshop # 3 – Wing D Air System Input 4PFCU AIR SYSTEM

For our next workshop we will enter a four pipe fan coil air system for Wing D. This new system will be added to the existing air systems already contained in archive #1. Refer to the following pages for required input details. Upon completion data input, please perform the energy simulation for the air system. We will discuss the results in the seminar. Right click on “Systems” in the left tree and ask for “new” or double click on “<new default system>” and enter the following in the Air System Properties: C8 – 4PFCU D1 Wing D Air System Inputs 1. General Details: Air System Name .............................................. C8 - 4PFCU D1 - Wing D (all) Equipment Type ........................................................................ Terminal Units Air System Type ....................................................................... 4-Pipe Fan Coil Number of zones ............................................................................................ 15 Ventilation ......................................................... Common Ventilation System 2. Ventilation System Components: Ventilation Air Data: Airflow Control ................................................... Constant Ventilation Airflow Ventilation Sizing Method ............................................. ASHRAE Std 62-2001 Unocc. Damper Position ........................................................................ Closed Damper Leak Rate ........................................................................................... 5 % Outdoor Air CO2 Level ................................................................................. 400 ppm Cooling Coil Data: Setpoint ....................................................................................................... 72.0 °F Coil Bypass Factor .................................................................................... 0.100 Cooling Source ........................................................................... Chilled Water Schedule .............................................................................. JFMAMJJASOND Heating Coil Data: Setpoint ....................................................................................................... 70.0 °F Heating Source ................................................................................. Hot Water Schedule .............................................................................. JFMAMJJASOND Ventilation Fan Data: Fan Type ................................................................................ Forward Curved Configuration ..................................................................................... Draw-thru Fan Performance ........................................................................................ 2.00 in wg Overall Efficiency ........................................................................................... 54 %

% Airflow 100 90 80 70 60 50

% kW 100 91 81 72 61 54

% Airflow 40 30 20 10 0

% kW 46 40 33 27 21 Duct System Data: Return Duct or Plenum Data: Return Air Via ............................................................................ Ducted Return 3. Zone Components: Space Assignments:

Zone 1: Zone 1 D100-Computer Closet x1 Zone 2: Zone 2 D101-Classroom x1 Zone 3: Zone 3


D102-Classroom x1 Zone 4: Zone 4 D103-Classroom x1 Zone 5: Zone 5 D104-Classroom x1 Zone 6: Zone 6 D105-South Vestibule x1 Zone 7: Zone 7 D106-Classroom x1 Zone 8: Zone 8 D107-Classroom x1 Zone 9: Zone 9 D108-Music Auditorium x1 Zone 10: Zone 10 D109-Music Practice x1 Zone 11: Zone 11 D110-Music Files x1 Zone 12: Zone 12 D111-Music Office x1 Zone 13: Zone 13 D112-West Vestibule x1 Zone 14: Zone 14 D113-Corridor x1 Zone 15: Zone 15 D114-Corridor x1

Thermostats and Zone Data: Zone .............................................................................................................. All Cooling T-stat: Occ. .................................................................................... 72.0 °F Cooling T-stat: Unocc. ................................................................................ 85.0 °F Heating T-stat: Occ. .................................................................................... 70.0 °F Heating T-stat: Unocc. ................................................................................ 60.0 °F T-stat Throttling Range ............................................................................... 3.00 °F Thermostat Schedule ................................ Occupied Schedule - Classroom Unoccupied Cooling is ....................................................................... Available Common Terminal Unit Data: Cooling Coil: Design Supply Temperature ....................................................................... 58.0 °F Coil Bypass Factor .................................................................................... 0.100 Cooling Source ........................................................................... Chilled Water Schedule .............................................................................. JFMAMJJASOND Heating Coil: Design Supply Temperature ..................................................................... 110.0 °F Heating Source ................................................................................. Hot Water Schedule .............................................................................. JFMAMJJASOND Fan Control ........................................................................................... Fan On Terminal Units Data: Zone .............................................................................................................. All Terminal Type ..................................................................................... Fan Coil Minimum Airflow ........................................................................................ 15.00 CFM/person Fan Performance ........................................................................................ 0.75 in wg Fan Overall Efficiency .................................................................................... 50 % 4. Sizing Data (Computer-Generated): System Sizing Data: Hydronic Sizing Specifications: Chilled Water Delta-T .................................................................................. 10.0 °F Hot Water Delta-T ....................................................................................... 20.0 °F Safety Factors:


Cooling Sensible .............................................................................................. 0 % Cooling Latent .................................................................................................. 0 % Heating ............................................................................................................. 0 % Zone Sizing Data: Zone Airflow Sizing Method ................................. Sum of space airflow rates Space Airflow Sizing Method ............................. Individual peak space loads 5. Equipment Data No Equipment Data required for this system.

After completing the inputs above, right click on C8-4PFCU D1- Wing D air system and “Print/View Simulation Data”

Shown below is the simulation report viewer prior to running a simulation. Notice the graph option is turned off and the category list in the bottom window is blank. Graphical reports are available however, after an initial simulation is run. For our C8-4PFCU D1- Wing D air system, preview these simulation tabular reports:


Air System Simulation Reports Viewer

Air System Simulation Results (Table 1) :

Month

Precool Coil Load

(kBTU)

Preheat Coil Load

(kBTU)

Terminal Cooling Coil

Load(kBTU)

Terminal Heating Coil

Load(kBTU)

Ventilation Fan (kWh)

Terminal Fan(kWh)

Lighting(kWh)

January 0 36889 17258 11764 384 916 10270

February 0 28705 20330 6400 349 823 9316

March 458 18429 31617 1703 367 852 9953

April 1738 9312 45223 102 367 851 9845

May 2574 4218 56228 0 367 865 9954

June 8324 1183 77538 0 367 893 9843

July 11223 364 60683 0 352 846 6248

August 9897 296 79687 0 367 888 9950

September 3058 2417 60507 0 367 867 9846

October 441 11035 42480 117 402 930 10585

November 126 15378 24526 3991 314 738 8898

December 0 25207 15917 14965 314 769 9005

Total 37839 153434 531994 39042 4317 10237 113713

Graphs Not Available Yet


Air System Simulation Results (Table 2) :

Month

Electric Equipment

(kWh) January 1535

February 1396

March 1466

April 1466

May 1466

June 1466

July 737

August 1466

September 1466

October 1605

November 1256

December 1256

Total 16579


Daily Air System Simulation Results for August (Table 1) :

Day

Precool Coil Load

(kBTU)

Preheat Coil Load

(kBTU)


Load(kBTU)


Load(kBTU)

Ventilation Fan (kWh)

Terminal Fan(kWh)

Lighting(kWh)

1 235 26 2823 0 17 40 423

2 0 0 569 0 0 3 107

3 0 0 942 0 0 4 107

4 508 0 3810 0 17 41 423

5 237 0 2964 0 17 40 423

6 95 68 2689 0 17 40 423

7 96 105 2571 0 17 40 423

8 166 52 2628 0 17 40 423

9 0 0 447 0 0 3 107

10 0 0 641 0 0 3 107

11 368 2 3369 0 17 41 423

12 276 0 3479 0 17 40 423

13 174 6 2713 0 17 40 423

14 261 35 2804 0 17 40 423

15 122 0 3077 0 17 40 423

16 0 0 12 0 0 0 107

17 0 0 1051 0 0 5 107

18 848 0 4462 0 17 42 423

19 826 0 4136 0 17 41 423

20 744 0 4016 0 17 41 423

21 268 0 3615 0 17 40 423

22 117 0 2951 0 17 40 423

23 0 0 198 0 0 1 107

24 0 0 1053 0 0 5 107

25 594 0 4156 0 17 41 423

26 905 0 4085 0 17 41 423

27 1333 0 4249 0 17 41 423

28 1232 0 4311 0 17 41 423

29 491 0 3933 0 17 41 423

30 0 0 783 0 0 4 107

31 0 0 1147 0 0 6 107

Total 9897 296 79687 0 367 888 9950


Daily Air System Simulation Results for August (Table 2) :

Day

Electric Equipment

(kWh) 1 70

2 0

3 0

4 70

5 70

6 70

7 70

8 70

9 0

10 0

11 70

12 70

13 70

14 70

15 70

16 0

17 0

18 70

19 70

20 70

21 70

22 70

23 0

24 0

25 70

26 70

27 70

28 70

29 70

30 0

31 0

Total 1466


Table 1.1 Hourly Air System Simulation Results for Friday, August 1

Hour

Precool Coil Load

(MBH)

Preheat Coil Load

(MBH)


Load(MBH)


Load(MBH)

Ventilation Fan (kW)

Terminal Fan(kW)

Lighting(kW)

0000 0.0 0.0 1.3 0.0 0.0 0.0 4.5

0100 0.0 0.0 0.8 0.0 0.0 0.0 4.5

0200 0.0 0.0 0.6 0.0 0.0 0.0 4.5

0300 0.0 0.0 0.0 0.0 0.0 0.0 4.5

0400 0.0 0.0 0.0 0.0 0.0 0.0 4.5

0500 0.0 0.0 0.0 0.0 0.0 0.0 4.5

0600 0.0 9.2 163.5 0.0 1.5 3.4 4.5

0700 0.0 11.0 180.3 0.0 1.5 3.4 22.3

0800 0.0 6.0 261.1 0.0 1.5 3.4 44.5

0900 0.0 0.0 265.2 0.0 1.5 3.4 44.5

1000 8.5 0.0 277.8 0.0 1.5 3.4 44.5

1100 18.8 0.0 276.4 0.0 1.5 3.4 44.5

1200 22.7 0.0 159.5 0.0 1.5 3.4 0.1

1300 33.7 0.0 278.2 0.0 1.5 3.4 44.5

1400 33.7 0.0 280.3 0.0 1.5 3.4 44.5

1500 36.9 0.0 282.3 0.0 1.5 3.4 44.5

1600 40.4 0.0 213.1 0.0 1.5 3.4 22.3

1700 40.4 0.0 176.8 0.0 1.5 3.4 8.9

1800 0.0 0.0 1.4 0.0 0.0 0.0 4.5

1900 0.0 0.0 1.7 0.0 0.0 0.0 4.5

2000 0.0 0.0 1.1 0.0 0.0 0.0 4.5

2100 0.0 0.0 0.9 0.0 0.0 0.0 4.5

2200 0.0 0.0 0.5 0.0 0.0 0.0 4.5

2300 0.0 0.0 0.3 0.0 0.0 0.0 4.5

Total 235.1 26.2 2823.1 0.0 17.5 40.4 422.9


Table 1.2 Hourly Air System Simulation Results for Friday, August 1

Hour

Electric Equipment

(kW) 0000 0.0

0100 0.0

0200 0.0

0300 0.0

0400 0.0

0500 0.0

0600 0.0

0700 0.0

0800 9.3

0900 9.3

1000 9.3

1100 9.3

1200 0.0

1300 9.3

1400 9.3

1500 9.3

1600 3.7

1700 0.9

1800 0.0

1900 0.0

2000 0.0

2100 0.0

2200 0.0

2300 0.0

Total 69.8


1. Zone Temperature Statistics


Now that we have run a simulation, graphics options are automatically turned on, and the graph category list will become visible. To demonstrate graphs for our workshop example, Print/View Simulation Data once again. Re-run Simulation Reports

Air System Simulation Reports Viewer With Graph Options Ask for graphs for the fan coil (terminal) cooling and heating coil loads shown above.


Monthly Simulation Results For Fan Coils In Wing D

0

10000

20000

30000

40000

50000

60000

70000

80000

kBTU

MonthJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Precool Coil Load (kBTU) Terminal Cooling Coil Load (kBTU)

Daily Simulation Results For Fan Coils In Wing D (August)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Daily Simulation Results for August

kBTU

Day of Month2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Precool Coil Load (kBTU) Terminal Cooling Coil Load (kBTU)


Hourly Simulation Results For Fan Coils In Wing D (August 1)




Workshop # 4 Inputs




Workshop # 4 – Wing D Air System Input–Packaged Rooftop Unit AIR SYSTEM

Another air system for Wing D could be multiple package rooftop units. These will be modeled as multiple single zone constant air volume air systems with built-in gas heat and DX cooling, one per zone. Due to the time constraints of this seminar, we will model only one packaged rooftop unit on a single zone, classroom D 101. Create a new air system called “D28 – RTU D2 – Classroom D 101” Please complete the inputs for the Rooftop system for classroom D101. The following pages include copies of the required inputs to use.


Air System properties For D28 RTU D2 For Classroom D 101 1. General Details: Air System Name ....................................... D 28 - RTU D2 - Classroom D101 Equipment Type ....................................................... Packaged Rooftop Units Air System Type .................................................................... Single Zone CAV Number of zones .............................................................................................. 1 2. System Components: Ventilation Air Data: Airflow Control ................................................... Constant Ventilation Airflow Ventilation Sizing Method ............................................. ASHRAE Std 62-2001 Unocc. Damper Position ........................................................................ Closed Damper Leak Rate ........................................................................................... 5 % Outdoor Air CO2 Level ................................................................................. 400 ppm Economizer Data: Control ................................................................ Integrated enthalpy control Upper Cutoff ................................................................................................ 72.0 °F Lower Cutoff .............................................................................................. -60.0 °F Central Cooling Data: Supply Air Temperature .............................................................................. 58.0 °F Coil Bypass Factor .................................................................................... 0.094 Cooling Source ......................................................................... Air-Cooled DX Schedule .............................................................................. JFMAMJJASOND Capacity Control ............................ Cycled or Staged Compressor - Fan On Central Heating Data: Supply Temperature ................................................................................. 110.0 °F Heating Source ..................................................... Combustion - Natural Gas Schedule .............................................................................. JFMAMJJASOND Capacity Control ............................ Cycled or Staged Compressor - Fan On Supply Fan Data: Fan Type ................................................................................ Forward Curved Configuration ..................................................................................... Draw-thru Fan Performance ........................................................................................ 1.00 in wg Overall Efficiency ........................................................................................... 54 % Duct System Data: Supply Duct Data: Duct Heat Gain ................................................................................................ 0 % Duct Leakage ................................................................................................... 0 % Return Duct or Plenum Data: Return Air Via ............................................................................ Ducted Return 3. Zone Components: Space Assignments:

Zone 1: Zone 1 D101-Classroom x1

Thermostats and Zone Data: Zone .............................................................................................................. All Cooling T-stat: Occ. .................................................................................... 72.0 °F Cooling T-stat: Unocc. ................................................................................ 85.0 °F Heating T-stat: Occ. .................................................................................... 70.0 °F Heating T-stat: Unocc. ................................................................................ 60.0 °F T-stat Throttling Range ............................................................................... 3.00 °F Diversity Factor ............................................................................................ 100 % Direct Exhaust Airflow ............................................................................... 400.0 CFM Direct Exhaust Fan kW ................................................................................. 0.0 kW Thermostat Schedule ................................ Occupied Schedule - Classroom Unoccupied Cooling is ....................................................................... Available Supply Terminals Data: Zone .............................................................................................................. All Terminal Type ...................................................................................... Diffuser Minimum Airflow .......................................................................................... 0.00 CFM/person


Zone Heating Units: Zone .............................................................................................................. All Zone Heating Unit Type ............................................................................ None Zone Unit Heat Source ..................................................... Electric Resistance Zone Heating Unit Schedule ................................................ JFMAMJJASOND 4. Sizing Data (Computer-Generated): System Sizing Data: Hydronic Sizing Specifications: Chilled Water Delta-T .................................................................................. 10.0 °F Hot Water Delta-T ....................................................................................... 20.0 °F Safety Factors: Cooling Sensible .............................................................................................. 0 % Cooling Latent .................................................................................................. 0 % Heating ............................................................................................................. 0 % Zone Sizing Data: Zone Airflow Sizing Method ................................. Sum of space airflow rates Space Airflow Sizing Method ............................. Individual peak space loads 5. Equipment Data Central Cooling Unit - Air-Cooled DX Design OAT ................................................................................................ 94.5 °F Equipment Sizing ............................................................................ Auto-Sized Capacity Oversizing Factor ........................................................................... 0.0 % ARI Performance Rating ........................................................................... 10.30 EER Conventional Cutoff OAT ............................................................................ 55.0 °F Low Temperature Operation ..................................................................... Used Low Temperature Cutoff OAT ....................................................................... 0.0 °F Central Heating Unit - Combustion Equipment Sizing ............................................................................ Auto-Sized Capacity Oversizing Factor ........................................................................... 0.0 % Average Efficiency ...................................................................................... 82.0 % Misc. Electric 0.200 kW

These are program defaults and are not applicable to this air system type. No data entry is required in these fields


Air System Properties- Equipment Tab The 5th tab in Air System Properties (shown below) is the Equipment tab. Because this workshop uses a packaged “self-contained” air system with DX cooling and built–in combustion heating, it does not utilize separate “plants” to produce hot and cold air. The heating and cooling plants are integral to the air system. For simulation calculations, equipment data is entered in the air system properties form under the “equipment” tab. In the Equipment tab click the “Edit Equipment Data” button for “Central Cooling Unit”.

1. Notice the Estimated Maximum Load is not yet displayed as shown here. 2.Select Auto-Sized Equipment Capacity and set over-sizing factor to 0%. 3. Select ARI Performance Rating from dropdown. 4. Select Low Temp Operation and set OAT cutoff to 0.0ºF.

Edit Equipment Data


Design Load Not Run

Run the Design Load for “D28 – RTU D2 – Classroom D 101”and then re-check the equipment tab under Air System Properties. It will now display the Estimated Maximum Load for cooling and heating as shown below. Now we can input actual equipment data for energy simulation. The rooftop unit equipment data used for simulations should reflect a gross cooling capacity of 51.0 MBH and a gross heating capacity of 36.2 MBH. Now we will show how to obtain actual rooftop unit data from Carrier in a direct transfer mode. E-Mail Project Archive To Your Carrier Representative At this point, the project can be archived and e-mailed to your Carrier representative in order to obtain actual equipment selection data. After a selection is made, the data can be returned to you to complete the HAP Equipment tab inputs for modeling energy simulations. We will demonstrate this in workshop # 4. Manufacturer’s product literature can also be used to obtain the equipment data required for HAP simulations. The Email address of your Carrier Sales Engineer can be entered under ‘View” and “Preferences”. This new HAP feature is done once and will apply to all subsequent projects. To obtain specific project data, the Design Engineer highlights “Send Email to Sales Engineer” under the “Project” pull down.

Load Values Appear After Design Load Is Calculated

Enter Email Address of Your Carrier Representative.

Actual Values Should Be Entered In Place Of Default Values Of 1.0


Send Email To Sales Engineer HAP will automatically archive the entire project in the user’s E20-II/archive folder and attach the Project.E3A file to an e-mail message. HAP Automatically Stores Project Archive In E20-II/archive Folder


HAP Automatically Attaches The Project Archive And Generates An Email At this point, the design Engineer sends the Email to the Carrier representative who performs an electronic selection based on the HAP requirements in the archive. For workshop # 4, the D28 -RTU D2 - Classroom 101 rooftop unit has been selected from this Carrier software.


RTU Builder Populated With HAP Data

RTU Selected For Job Requirements

For this example workshop, we will choose nominal 5-ton unit (006 size). This unit gives us a high efficiency and delivers a close sensible capacity to our HAP requirements. This unit is also equipped with a belt drive evaporator fan and enthalpy economizer.

Capacity Requirements and Coil Conditions Are Used Based On The HAP Design Load Calculation


Final Equipment Performance Summary For D28 RTU D2 For Classroom D 101

Notice the actual bypass factor is greater (.163) than (.094) used in our initial load calculation.


We can now extract the required data from this equipment selection to enter into the HAP equipment data tab, if desired: Gross Cooling Capacity = 60.79 MBH Gross Heating Capacity = 60.8 MBH Compressor Power Input = 3.99 kW OD Fan kW = (volts) (FLA) (1.73)/1000 = 230 x 1.5 x 1.73/1000 = 0.6 kW Enter Final Equipment Data In Equipment Tab Double click on the Air System Properties for the D28 – RTU D2 – Classroom D101 and go to the Equipment Tab. Enter the data calculated under “Edit Equipment Data” for the Central Cooling Unit and Central Heating Unit. Preview the following Design Load Reports.


Workshop # 4 Solutions


Air System Information Air System Name .. D 28 - RTU D2 - Classroom D101 Equipment Class ....................................... PKG ROOF Air System Type ............................................... SZCAV

Number of zones ............................................................ 1 Floor Area ............................................................... 840.0 ft² Location .................................... St. Louis IAP, Missouri

Sizing Calculation Information Zone and Space Sizing Method:

Zone CFM ....................... Sum of space airflow rates Space CFM ................... Individual peak space loads

Calculation Months ........................................ Jan to Dec Sizing Data ..................................................... Calculated

Central Cooling Coil Sizing Data

Total coil load .......................................................... 4.2 Tons Total coil load ........................................................ 51.0 MBH Sensible coil load .................................................. 38.7 MBH Coil CFM at Aug 1500 .......................................... 1770 CFM Max block CFM .................................................... 1770 CFM Sum of peak zone CFM ....................................... 1770 CFM Sensible heat ratio .............................................. 0.759 ft²/Ton .................................................................. 197.8 BTU/(hr-ft²) ............................................................ 60.7 Water flow @ 10.0 °F rise ...................................... N/A

Load occurs at ................................................. Aug 1500 OA DB / WB .................................................... 94.5 / 75.9 °F Entering DB / WB ............................................ 79.1 / 66.8 °F Leaving DB / WB ............................................. 58.5 / 57.4 °F Coil ADP ................................................................... 56.3 °F Bypass Factor ......................................................... 0.094 Resulting RH ................................................................ 56 % Design supply temp. ................................................. 58.0 °F Zone T-stat Check .................................................. 1 of 1 OK Max zone temperature deviation ................................. 0.0 °F

Central Heating Coil Sizing Data

Max coil load ......................................................... 36.2 MBH Coil CFM at Des Htg ............................................ 1770 CFM Max coil CFM ....................................................... 1770 CFM Water flow @ 20.0 °F drop ..................................... N/A

Load occurs at .................................................... Des Htg BTU/(hr-ft²) ................................................................ 43.0 Ent. DB / Lvg DB ............................................. 54.3 / 73.6 °F

Supply Fan Sizing Data

Actual max CFM .................................................. 1770 CFM Standard CFM ...................................................... 1734 CFM Actual max CFM/ft² ............................................... 2.11............................................................................... CFM/ft²

Fan motor BHP ......................................................... 0.52 BHP Fan motor kW ........................................................... 0.38 kW Fan static .................................................................. 1.00 in wg

Outdoor Ventilation Air Data Design airflow CFM ……………………………………400 CFM CFM/ft² …………………………………………………0.48 CFM/ft² CFM/person …………………………………………. 16.00 CFM/person


DESIGN COOLING DESIGN HEATING COOLING DATA AT Aug 1500 HEATING DATA AT DES HTG COOLING OA DB / WB 94.5 °F / 75.9 °F HEATING OA DB / WB 2.0 °F / 0.3 °F Sensible Latent Sensible LatentZONE LOADS Details (BTU/hr) (BTU/hr) Details (BTU/hr) (BTU/hr)Window & Skylight Solar Loads 96 ft² 3903 - 96 ft² - -Wall Transmission 184 ft² 323 - 184 ft² 568 -Roof Transmission 840 ft² 3381 - 840 ft² 3184 -Window Transmission 96 ft² 1190 - 96 ft² 4229 -Skylight Transmission 0 ft² 0 - 0 ft² 0 -Door Loads 0 ft² 0 - 0 ft² 0 -Floor Transmission 840 ft² 0 - 840 ft² 1101 -Partitions 0 ft² 0 - 0 ft² 0 -Ceiling 0 ft² 0 - 0 ft² 0 -Overhead Lighting 2898 W 7853 - 0 0 -Task Lighting 840 W 2538 - 0 0 -Electric Equipment 840 W 2578 - 0 0 -People 25 4133 3000 0 0 0Infiltration - 0 0 - 0 0Miscellaneous - 0 0 - 0 0Safety Factor 0% / 0% 0 0 0% 0 0>> Total Zone Loads - 25899 3000 - 9081 0Zone Conditioning - 29015 3000 - 8886 0Plenum Wall Load 0% 0 - 0 0 -Plenum Roof Load 0% 0 - 0 0 -Plenum Lighting Load 0% 0 - 0 0 -Return Fan Load 1370 CFM 0 - 1370 CFM 0 -Ventilation Load 400 CFM 8382 9261 400 CFM 28576 0Supply Fan Load 1770 CFM 1312 - 1770 CFM -1312 -Space Fan Coil Fans - 0 - - 0 -Duct Heat Gain / Loss 0% 0 - 0% 0 ->> Total System Loads - 38709 12261 - 36150 0Central Cooling Coil - 38709 12261 - 0 0Central Heating Coil - 0 - - 36150 ->> Total Conditioning - 38709 12261 - 36150 0Key: Positive values are clg loads Positive values are htg loads Negative values are htg loads Negative values are clg loads


August DESIGN COOLING DAY, 1500 TABLE 1: SYSTEM DATA Dry-Bulb Specific Sensible Latent Temp Humidity Airflow CO2 Level Heat HeatComponent Location (°F) (lb/lb) (CFM) (ppm) (BTU/hr) (BTU/hr)Ventilation Air Inlet 94.5 0.01534 400 400 8382 9261Vent - Return Mixing Outlet 79.1 0.01149 1770 821 - -Central Cooling Coil Outlet 58.5 0.01000 1770 821 38709 12261Central Heating Coil Outlet 58.5 0.01000 1770 821 0 -Supply Fan Outlet 59.2 0.01000 1770 821 1312 -Cold Supply Duct Outlet 59.2 0.01000 1770 821 - -Zone Air - 74.6 0.01036 1770 943 29015 3000Zone Direct Exhaust Outlet 74.6 0.01036 400 943 - -Return Plenum Outlet 74.6 0.01036 1370 943 0 - Air Density x Heat Capacity x Conversion Factor: At sea level = 1.080; At site altitude = 1.058 BTU/(hr-CFM-F) Air Density x Heat of Vaporization x Conversion Factor: At sea level = 4746.6; At site altitude = 4650.7 BTU/(hr-CFM) Site Altitude = 564.0 ft TABLE 2: ZONE DATA Zone Terminal Zone Sensible Zone Zone Zone CO2 Heating Heating Load T-stat Cond Temp Airflow Level Coil UnitZone Name (BTU/hr) Mode (BTU/hr) (°F) (CFM) (ppm) (BTU/hr) (BTU/hr)Zone 1 25899 Cooling 29015 74.6 1770 943 0 0

WINTER DESIGN HEATING TABLE 1: SYSTEM DATA Dry-Bulb Specific Sensible Latent Temp Humidity Airflow CO2 Level Heat HeatComponent Location (°F) (lb/lb) (CFM) (ppm) (BTU/hr) (BTU/hr)Ventilation Air Inlet 2.0 0.00044 400 400 -28576 0Vent - Return Mixing Outlet 54.3 0.00044 1770 431 - -Central Cooling Coil Outlet 54.3 0.00044 1770 431 0 0Central Heating Coil Outlet 73.6 0.00044 1770 431 36150 -Supply Fan Outlet 74.3 0.00044 1770 431 1312 -Cold Supply Duct Outlet 74.3 0.00044 1770 431 - -Zone Air - 69.5 0.00044 1770 440 -8886 0Zone Direct Exhaust Outlet 69.5 0.00044 400 440 - -Return Plenum Outlet 69.5 0.00044 1370 440 0 - Air Density x Heat Capacity x Conversion Factor: At sea level = 1.080; At site altitude = 1.058 BTU/(hr-CFM-F) Air Density x Heat of Vaporization x Conversion Factor: At sea level = 4746.6; At site altitude = 4650.7 BTU/(hr-CFM) Site Altitude = 564.0 ft TABLE 2: ZONE DATA Zone Terminal Zone Sensible Zone Zone Zone CO2 Heating Heating Load T-stat Cond Temp Airflow Level Coil UnitZone Name (BTU/hr) Mode (BTU/hr) (°F) (CFM) (ppm) (BTU/hr) (BTU/hr)Zone 1 -9081 Heating -8886 69.5 1770 440 0 0


Now ask for these simulation reports for D28 –RTU D2 – Classroom 101


Air System Simulation Reports For D28 - RTU D2 - Classroom D101 Monthly Simulation Results Air System Simulation Results (Table 1) :

Month

Central Cooling Coil

Load (kBTU)

Central Cooling Eqpt

Load(kBTU)

Central Unit Clg Input

(kWh)

Central Heating Coil Load

(kBTU)

Central Heating Eqpt Load

(kBTU)

Central Heating Coil Input

(kBTU)

Central Heating Misc. Electric

(kWh)January 0 0 0 4123 4085 4982 23

February 0 0 0 2354 2337 2850 13

March 751 751 55 860 860 1048 5

April 2123 2123 159 139 139 169 1

May 3401 3401 257 4 4 5 0

June 7887 7876 604 0 0 0 0

July 7284 7284 592 0 0 0 0

August 8724 8654 675 0 0 0 0

September 4624 4624 342 2 2 2 0

October 734 734 53 179 179 219 1

November 266 266 19 989 989 1206 5

December 0 0 0 3298 3271 3989 18

Total 35793 35714 2755 11946 11865 14470 66 Air System Simulation Results (Table 2) :

Month Supply Fan

(kWh) Lighting

(kWh)

Electric Equipment

(kWh)January 105 862 139

February 94 782 126

March 97 835 132

April 97 826 132

May 99 835 132

June 103 826 132

July 97 525 67

August 102 835 132

September 99 826 132

October 106 889 145

November 84 747 113

December 88 756 113

Total 1171 9546 1497


Unmet Load Report

1. Unmet Load Statistics - Central Cooling Unit - Air-Cooled DX

Month

Equipment Capacity is

Sufficient (hrs)

CapacityInsufficient

by 0%-5%(hrs)

CapacityInsufficientby 5%-10%

(hrs)


by >10%(hrs)

Total Hours with Unmet

Loads

Total Hourswith

EquipmentLoads

January 0 0 0 0 0 0

February 0 0 0 0 0 0

March 60 0 0 0 0 60

April 120 0 0 0 0 120

May 229 0 0 0 0 229

June 389 4 2 0 6 395

July 369 0 0 0 0 369

August 405 3 3 7 13 418

September 285 0 0 0 0 285

October 61 0 0 0 0 61

November 32 0 0 0 0 32

December 0 0 0 0 0 0

Total 1950 7 5 7 19 1969 2. Unmet Load Statistics - Central Heating Unit - Combustion

Month

Equipment Capacity is

Sufficient (hrs)


by 0%-5%(hrs)

CapacityInsufficientby 5%-10%

(hrs)


by >10%(hrs)

Total Hours with Unmet

Loads

Total Hourswith

EquipmentLoads

January 327 2 1 4 7 334

February 209 0 0 2 2 211

March 88 0 0 0 0 88

April 19 0 0 0 0 19

May 2 0 0 0 0 2

June 0 0 0 0 0 0

July 0 0 0 0 0 0

August 0 0 0 0 0 0

September 1 0 0 0 0 1

October 23 0 0 0 0 23

November 122 0 0 0 0 122

December 383 2 1 4 7 390

Total 1174 4 2 10 16 1190


Zone Temperature Report


Workshop # 5 Inputs




Workshop # 5 – Modeling Chillers, Boilers, & Towers

Next, we retrieve archive #2 into our existing project. This archive contains all air system models for the three design alternatives. These alternatives are used in the remaining workshops. Please retrieve the archive as outlined below to begin workshop #5. RETREIVAL of Archive #2

1. While in the existing project, go to the menu bar; select “Project \ Retrieve HAP v 4.4 Data.”

2. Navigate to D:\E20-II\Archives 3. From the Archives Folder - retrieve the

archive “HAP 4.4 ADVANCED ARCHIVE 2 UNSOLVED.E3A.” Allow this retrieved archive to “overwrite” the data you have created thus far in our workshops. After retrieval be sure to click “Project, Save” to update your project files. Upon completion of the retrieval process, all air systems for the remaining workshops are available.

CHILLER LIBRARY In Workshop # 5 two chiller types will be added to the Chiller Library. These chillers will then be used to create two chilled water plants. The first chiller type will be an air-cooled packaged screw chiller. The second chiller type will be a water-cooled variable speed screw chiller. The first design case for workshop # 5 uses the air-cooled packaged chiller and supplies chilled water to air systems A01- A10 (omitting A08 served by a packaged RTU)

Chiller Library And Chilled Water Plants

The chiller library is used to create a chilled water plant. The plant is used for energy simulations. The plant capacity may be handled by one chiller, but more often is divided between two or more chillers. Therefore, the plant capacity must be determined first before determining individual chiller sizes. This same concept applies to hot water and steam plants and their boilers, Plants features including piping and controls will be the focus of workshop #6. To Place Chillers In The Library, We Need To Know Their Size First. HAP will consider all the air systems assigned to the plant to determine the peak coincident or "block" load. HAP takes into account diversity on several levels. Diversity is defined as the block load divided by the sum of the individual peak loads.


HAP considers diversity between the zones within an air system and also between systems when a plant serves multiple air systems (such as in workshop # 5). The plant design load calculation looks at the total plant load (sum of air system loads) for each hour and finds the largest load. Zone and system diversity is thus built in. Any multipliers assigned to identical systems served by the plant are used to determine the number of times coil loads for an air system are added to the plant profile. HAP will find the total building, project, or campus block load taking diversity into account for sizing central cooling and heating equipment such as chillers and boilers. Size Air-Cooled Chillers For Workshop # 5 By Running The Plant Load To perform load calculations for a chilled, hot water, or steam plant, double click on <new default plant> and pull down the “generic” model from the “plant type” pull down. For the first chilled water design case in workshop # 5. label the plant “A- Base – 2 A/C Plant”. Under Plant Type, choose generic chilled water plant. “Generic” Chilled Water Plant For Performing Design Load Calculations


Assign Air Systems To The Plant Next, in the “Systems” tab, add the A01- A10 air systems (omit A08). Say “OK” and right click on the plant to run the load. Ask for the Cooling Plant Sizing Summary. Plant Design Reports


Cooling Plant Sizing Summary The peak plant load using air-cooled chillers is 307.1 tons. This reflects diversity as discussed above. For this first design case will use two (2) air-cooled chillers equally sized even though a single air-cooled chiller is available in a capacity large enough to handle the total load.

With the capacity requirements determined, the specific chillers can be selected for use in the final air-cooled chiller plant. This selection will be provided for use by the class in workshop # 5.

AIR-COOLED CHILLER SELECTION REQUIREMENTS FOR WORKSHOP # 5

Qty: 2

Capacity: 153.5 tons each @ 95F ambient EWT: 44 F

LWT: 54 F For this workshop, we will not run Carrier’s Chiller builder equipment selection software. However, the results of the selection are displayed on the following pages.


Carrier Chiller Builder Calculation Results

30 XA 160 Chiller Selected

30 XA 160 size will be selected


30 XA 160 Chiller Output From Packaged Chiller Program For workshop # 5 we will first add the air-cooled chillers to the library via IMPORT There are 3 methods of entering chiller data into HAP. 1. Import, 2. Template and 3. Chiller Type. We will use the first 2 methods in this workshop and discuss method 3. The Import Chiller button is used to import Carrier chiller data from an external (.CD2 or .CD4) file created by the Carrier Chiller Builder (selection) program. The Import function can be used if you want to model a specific Carrier chiller like the 30 XA 160 selected above. The chiller import file


(called an archive) can be obtained by running the Carrier selection program yourself or from your Carrier representative. It has a .CD2 or a .CD4 file extension. HAP users may have HAP installed on the C or D drive of their computers. Chiller import files from the Carrier selection program should be placed in the \E20-II\Temp folder on the same drive on which HAP is installed. The 30 XA import file for workshop # 5 is in C:\E20-II\Temp folder or the desktop of the class computers Double click on <New default Chiller> to bring up the chiller properties screen, then hit the Import Chiller button. Navigate to C:\E20-II\Temp and open the file “30 XA 160 A-C Chillers.cd4.” This imports the chiller into HAP.


Import The 30 XA 160 Chiller Archive Into Hap

Chiller Properties: General Tab The General tab on the Chiller form contains inputs which describe the general nature of the chiller being defined. In the General tab name the chiller “30XA 160 A - C Screw”. Notice the chiller type has been identified by the archive as “A/C Packaged Screw”

“Open” imports the archive into HAP

Imported archive shows A/C packaged screw


Tab 2: Design Inputs The Design Inputs tab on the Chiller form contains items which describe the full load performance of the chiller. The content of this tab varies depending on the type of chiller being defined. The layout of the tab shown above is for an air-cooled screw chiller. Different sets of inputs are required for other types of chillers. For workshop # 5, define the minimum load as 15%. HAP will calculate a representative value for the chiller anyway. Notice all other inputs have been automatically completed by the import data contained in the archive.

Tab 3: Performance Map The Performance Map tab on the Chiller form defines the off-design and part-load performance of the chiller. Performance Map tab data is not displayed when using a chiller import in HAP. The map data exists in the Carrier Electronic catalog program. At this point we have completed the library entry for a packaged air-cooled screw using a Carrier electronic catalog program import file. The library chiller can now be used to create a chiller plant. We will discuss chiller plants in detail in Workshop # 6.

Design Inputs completed by archive

Performance Map not displayed when chiller data provided by import


The next step for workshop # 5 will be to add a variable speed, water-cooled screw chiller to the library. As with the air-cooled design case, we will determine the plant load first, then select the chiller. This design case serves air systems C1-C8 (omit C7). These air systems comprise a mix of constant volume chilled and hot water rooftop units and 4-pipe fan coils. Double click on <new default plant> and pull down the “generic” chilled water plant” model from the “Plant Type” pull down. Label the plant “C - Alt 2 - 23 XRV WC Rotary Screw”. In the Systems tab, add the C1-C8 Air systems (omit C7) as shown below. Say “OK”, right click on the plant to run the load. .

Assign air systems C1-C8


Ask for the Cooling Plant Sizing Summary in the Plant Design Reports screen. Plant Design Reports

Cooling Plant Sizing Summary Cooling Plant Sizing Summary Comparison Class Discussion

C Alt- 2 23 XRV W/C Rotary Screw plant size


The maximum plant load for the water-cooled design case using air systems C1-C8 is 264.7 tons. Note some of these air systems are 4 pipe fan coil units. For the air-cooled design case using air systems A01-A10, the plant load was 307.1 tons. Some of these air systems are VAV. Both plants serve identical 59,553 square ft. areas. What contributes to the load difference between the plants? The answer can be found by comparing the Air System Design Load Summaries for the two plant types. (Not done as part of this workshop).The air-cooled chiller plant requires more ventilation air than the water-cooled chiller plant. That is the primary reason for the tonnage increase. Sum of ventilation air amounts for A01-A10 = 37,198 cfm or .62 cfm/sq ft Sum of ventilation air amounts for C1-C8 = 27,762 cfm or .47 cfm/sq ft The ventilation sizing method selected was ASHRAE 62-2001 for all air systems in both plants. However, each VAV air system serves multiple zones so the ASHRAE 62-2001 multiple space equation is applied to the VAV systems. In order to satisfy the critical zones requirements and comply with ASHRAE 62-2001, the VAV air systems fan must over-ventilate the other zones. The result is more total ventilation and a greater total load.

Add a Chiller To The Library Via TEMPLATE The second method of adding a chiller to the library is the Chiller Template. Template can be used for both Carrier and non-Carrier chillers. This method uses full load and IPLV or NPLV data. With this data, the Chiller Template button is used to auto-generate a complete part-load performance map for a chiller. To use the Template feature, enter a name for the chiller and then press the Chiller Template button. The template function is currently offered for modeling these chillers: W/C Centrifugal W/C Rotary Screw W/C Packaged Screw W/C Packaged Reciprocating Enter a single 265 ton water-cooled rotary screw for workshop # 5.

The chiller we will use is a new technology variable speed screw which falls under the “rotary screw” category. “Rotary screw refers to a “built to order” type chiller versus “packaged screw” which tends to be “off-the-shelf “. Double click on < New default Chiller> to bring up the Chiller Properties input screen.


Chiller Properties Select the Chiller Template button. Then, select W/C Rotary Screw from the drop down, and enter the following full load data which came from an actual selection from our Carrier engineering representative. Some of this data will be entered in Chiller Design Inputs Chiller Name Variable Speed Screw Full Load LCHWT ................................ 44.0 °F Full Load ECWT .................................. 85.0 °F Full Load Capacity ................................265 Tons Full Load Power ……………………….0.599 kW/Ton Minimum ECWT ................................. 60.0 °F Minimum Load ..................................... 15.0 % Cooler Flow Rate .............................. 635.0 gpm Cooler Pressure Drop ......................... 19.2 ft wg Condenser Flow Rate ....................... 795.0 gpm Condenser Pressure Drop ...................16.0 ft wg 75%..................................................... .452 kW/ton 50%...................................................... .346 kW/ton 25%....................................................... .451 kW/ton


Tab1: General (Chiller Template) Check to see that all inputs from the General tab were transferred into Design Inputs. Enter the cooler and condenser pressure drops as shown below. These pressure drops apply to the chiller cooler and condenser vessels, not the entire water circuit resistance.

Tab 2: Design Inputs

Enter the data from above into the chiller template form.

Enter the vessel pressure drops.


Tab 3: Performance Map

The Performance Map tab shows points filled in by HAP for the 265-ton variable speed screw chiller. The chiller Performance contains chiller input power data for off-design and part-load conditions. In this table, each row contains performance data for a different entering condenser water temperature. Each column contains part load data at specific points. Together the rows and columns in this table define a "map" of performance data across the range of expected condenser water temperatures and part-load conditions. During energy simulations, HAP will use this data to perform 2-way interpolations to determine chiller input power at specific combinations of condenser temperature and part-load ratio. .

Existing Library Chillers For Workshop #5

At this point we have added two chillers in the library. The first, a Carrier air-cooled packaged screw, was IMPORTED with an archive from the Carrier Chiller Builder selection program. The second, a water-cooled variable speed screw, was added via the TEMPLATE method.

Adding a Chiller to the Library via CHILLER TYPE Dropdown (not required for Workshop # 5).

The Chiller Type dropdown permits chiller modeling when an archive is not available to import or when the full load and part load points required for the Template method are not known. The Chiller Type dropdown contains built-in chiller data for numerous chiller types as shown below. New choices are available not offered with Import or Template method such as absorption chillers and engine driven chillers.

This method can also be used if the user knows the full load kW/ton along with all the part load points (more than just the PLV points required by Template method). In this case, sufficient part load points must be known to define the chiller performance map.


Chiller Type Dropdown Choices Following is an example of how to model a 265 ton air-cooled screw chiller knowing only the full load kW/ton. No IPLV or NPLV values or any other part load points are known.

Method 3, Chiller Type Dropdown


Tab 1: General (not required for workshop # 5)

Tab 2: Design Inputs (not required for workshop # 5) For this example we have input these full load conditions. Note the full load power of 1.2 kW/ton.

Tab 3: Performance Map (not required for workshop # 5) The resulting HAP generated full and part load performance map is shown here. This map was generated based on the 95F ambient and full capacity 1.2 kW/ton value input on the previous tab.


COOLING TOWER LIBRARY The next step in creating our chilled water plant is to add a cooling tower for the water-cooled screw chiller. The cooling tower flow must match the condenser water flow of the connected chiller(s) exactly. Double click on <New default Cooling Tower> and enter the following data into the Cooling

Cooling Tower Properties There are several important terms related to cooling towers that we should understand.

1. Entering Wet Bulb temperature is an important parameter in tower selection. For most areas in North America, an entering wet bulb temperature of 78° F is common.

2. Approach is the difference between the water leaving the tower and the entering wet bulb temperature of the air. A 7°F approach is common in HVAC systems with a 78° F entering wet bulb and 85° F water leaving the tower. (85° F - 78° F = 7° F)

3. Range is the difference in temperature of water entering the tower and water leaving the tower. An approximate 10° F range is most common in HVAC applications and reflects approximately 3 gpm/ton on the condenser loop.

Check with your local cooling tower representative to confirm the design entering wet bulb and approach values for your area. The tower range must match the chiller condenser delta T.


BOILER LIBRARY Similar to a chiller plant, the boiler plant may be comprised of one or more boilers from the library. The boiler(s) are placed in a plant which is linked to the air systems requiring the hot water, just as the chilled water plant was linked to air systems requiring chilled water. The boiler plant size reflects the largest peak heating load of all air systems connected to it. For workshop # 5, to create a library boiler, we must first size the boiler using a generic hot water plant like we did for the chiller plants. Double click on < New default Plant> and label our first boiler plant “A Base Boiler Plant AC Chillers”

Plant Properties “Generic Hot Water Plant” For Sizing Now assign the “A” air systems to the boiler plant as shown below:

Air System Assignments To Boiler Plant


Run the “A Base” Boiler plant load:

Print/View Design Data For Generic Hot water Boiler Plant Check the Heating Plant Sizing Summary: Plant Design Reports For Boiler Plant Sizing


Notice the A Base boiler plant has a required capacity of 3,223.6 MBH.

Heating Plant Sizing Summary For “A Base” Boiler Plant Now that we have run the load, we can add boilers to the library to meet the capacity requirements. The plant load was 3,223.6 MBH so we choose to use boilers of 3600 MBH output which provides some extra capacity. We will use an overall plant efficiency of 82% at all load points. Whether the plant is comprised of a single boiler or multiple boilers, the “overall” efficiency value entered in HAP should reflect the entire plant at each load point.


Double click on <New default Boiler> and enter these values:

Boiler Properties For “A Base 3600 MBH Boiler” At this point we have sized the hot water plant and created the library boiler for the “A Base” air- cooled chiller design case. Next, we will size the plant and create a library boiler for the “C Alt-2 23 XRV Rotary Screw Chiller design case. Use air systems C1-C8 (omit C7) size the hot water plant and create the library boiler. Answers are shown on the next page.


C Alt 2 Plant Properties

Heating Plant Sizing Summary For “C Alt - 2” Boiler Plant


The plant load was 2584.7 MBH so we choose to use boilers of 2800 MBH output which provides a little extra capacity. We will use an overall plant efficiency of 82% at all load points.

Boiler Properties For “C Alt - 2 2800 MBH Boiler” Chillers Boilers Tower Library Chillers, Boilers And Tower Created In Workshop # 5


Workshop # 6 Inputs


Workshop # 6 – Finalizing Chiller and Boiler Plants

Plants Created For Plant Load Sizing In Workshop # 5 A Plant is the equipment and controls used to provide cooling or heating to coils in one or more air systems. Examples include chiller plants, hot water boiler plants and steam boiler plants. This workshop consists of finalizing the two chiller plants and two boiler plants that were used in workshop # 5. The base design case chiller plant consists of two Carrier 30 XA A/C (air-cooled) packaged screw chillers. The air systems served by this plant include all “A” designated air systems. The configuration of the chiller plant is two chillers sequenced. The pumping and piping distribution system will be a Primary/Secondary, variable speed secondary system with a 12° T and 2% piping heat gain factor. The “Alternate” chiller plant serves the “C” designated 4PFCU air systems. This plant consists of one 265 ton Carrier 23XRV water-cooled, variable speed rotary screw chiller and a cooling tower. The pumping and piping distribution system will be a primary only variable speed system with a 12° T and 2% piping heat gain factor. For heating plants, the base case and alternate cases consist of a 3600 MBH and a 2800 MBH natural gas boiler respectively. All appropriate air systems are assigned to the plants. The distribution system is defined as, primary only constant speed pumping 40° T and 2% piping heat loss factor. The inputs for four (4) plants are on the following pages. There are two additional plants configured in the next archive we will retrieve into our project and no additional input is required on these imported plants. They will be used in the final workshop for energy comparisons. For workshop # 6, first step is to modify the generic plants from workshop # 5 by changing from “Generic” to Chiller or Hot Water Plant in the pull down. Then complete workshop # 6 inputs for the (4) plants on the following pages.

Plant Properties Tabs

Change Plant Type from Generic Plants




Chiller Plant Inputs – A Base 30 XA Air-Cooled Chiller Plant With A01-A10 Air Systems


Chiller Plant Inputs – 23XRV WC Rotary Screw with 4PFCU Air Systems



Boiler Plant Inputs, A Base Case 3600 MBH Boiler Input Data With A01-A10 Air Systems


Boiler Plant Inputs, C Alt- 2 2800 MBH Boiler Input Data With 4PFCU Air Systems


This Page Intentionally Left Blank


Workshop # 6 Solutions


Run all four Plant Simulation reports for the two chiller plants. For the two boiler plants omit the Daily and Hourly Simulation results.

Plant Simulation Reports On the pages that follow we will show the Plant Simulation Reports For the chiller plants first, followed by the boiler plants.


Monthly Simulation Results For A - Base Air-Cooled Chiller Plant


Daily Simulation Results For A - Base Air-Cooled Chiller Plant (Month Of August)



Hourly Simulation Results For A - Base Air-Cooled Chiller Plant (August 1st)



Unmet Load Report for A Base Case 30XA Air Cooled Chiller Plant

Monthly Simulation Results for A Base Case Hot Water Boiler


Monthly Simulation Results for A Base Case Hot Water Boiler




Workshop # 7 Inputs

Workshop # 7 – Utility Rate Modeling


The final Library items to define are the electric and fuel rate structures, required for simulating the building energy. This workshop consists of modeling one electric rate, one fuel rate and adding a time-of-day utility rate schedule. Electric Rates Highlight Electric Rates in the Library and Double click on <New default Electric Rate> then enter the following (reference input screens on following pages)

Demand Units: KW

Fixed customer charge: $ 50.00 Minimum Charge: $ 0.00

Tax rate: 7% Seasonal Schedule: Summer – May through September Winter – October through April

Time of day schedule: Create a new schedule – Utility time of day; refer to details on next page.

Demand Clause: Ratchet clause, 80% multiplier Peak Months: May to September

Applies: October to April




Define the energy charges based on the step type, season, period, block size, block units and $/unit

Check the box to expand the number of rows

Check box to include demand charges details


Highlight Fuel Rates in the Library and Double click on <New default Fuel Rate> and enter the following:

Define any additional demand clauses for the complex rate structure

Select “Simple” rate type radio button for natural gas utility


Workshop # 7 – Defining and Simulating Buildings

Defining “Buildings” In HAP For workshop # 8, we will compare the annual operating costs of four design scenarios, three of which were created in previous workshops. Each design scenario will be modeled as a separate “building”. A yearly operating cost will be calculated for each building scenario The first step in this workshop is to retrieve HAP 43 Advanced Archive 3 into the project. However, before actually working with this archive, we will discuss how HAP uses the term “building”. A building in HAP is the “container” holding all the HVAC and non-HVAC systems for one design scenario. When performing energy analysis, annual energy costs are computed for the building’s energy consuming systems. During system design load analysis in HAP, elements, spaces, zones, air systems, and plants are created like in the previous workshops. A "building" however, is only created when performing annual energy analysis. Taken literally, a building represents one individual structure, however, in HAP, the definition of a building is flexible. It can also represent a group of structures. For example, a "building" could represent a campus in which all the structures are served by central steam and chilled water plant equipment. Keep in mind, a design case can contain part of an actual building, a complete building, or many buildings. Here are the four design scenarios that will comprise the four buildings for workshop# 8. I. Building Name: A-Base PFPMXB-Complex Rate Cooling Plant: (2) 30 XA 165 Air- Cooled Chillers Heating Plant: 3600 MBH Capacity Gas Boiler(s) Air Systems: A01-A10 Air System Types: VAV PFPMXB , SZCV Ventilation Control: Constant Ventilation Sizing: ASHRAE 62-2001 II. Building Name: B Alt-1 PFPMXB- Complex Rate Cooling Plant: (2) 30 XA 165 Air- Cooled Chillers Heating Plant: 3600 MBH Capacity Gas Boiler(s) Air Systems: B01-B10 Air System Types: VAV PFPMXB , SZCV Ventilation Control: Demand Controlled Ventilation Ventilation Sizing: ASHRAE 62-2001 III. Building Name: C Alt-2 4PFCU/VSS - Complex Rate Cooling Plant: (1) 23 XR variable Speed Screw Water-Cooled Chiller Heating Plant: 2800 MBH Capacity Gas Boiler(s) Air Systems: C1-C8 Air System Types: 4- Pipe Fan Coil Units, SZCV Ventilation Control: Constant (dedicated ventilation for 4PFCU) Ventilation Sizing: ASHRAE 62-2001


IV. Building Name: D Alt-3 SZCV/RTU- Complex Rate Cooling Plant: None (Integral to RTU- Air Cooled DX) Heating Plant: None (Integral to RTU -Gas Combustion) Air Systems: D01-D36 Air System Types: SZCV RTU Ventilation Control: Constant Ventilation Sizing: ASHRAE 62-2001 Notice the “B Alt-1” scenario utilizes demand controlled ventilation. Otherwise it is identical to the “A-Base” scenario. However, the use of DCV should result in overall energy savings due to the reduction in ventilation air at partial people occupancy. The “C Alt-2” scenario uses a high efficiency screw chiller to supply chilled water to 4-pipe fan coil units and single zone air handlers. The fan coil systems utilize a common (dedicated) ventilation air system which results in a reduction in peak total ventilation airflow versus the A and B scenarios. The “D-Alt 3” scenario utilizes multiple packaged single zone constant volume RTU units. The rooftop units use self-contained DX cooling with gas heating so are not connected to a chilled water or hot water plant. Double click on <New default Building> and select these plants for the first building. Call it “A Base PFPMXB- Complex Rate”

Building Properties

Check the box for the plants to include in this base case design scenario


Building Properties- Systems Tab Miscellaneous Energy Tab

In order to save time, the schedules and profiles applicable to the miscellaneous energy items have been completed as part of the archive # 3. In the Miscellaneous Energy tab, enter the following data. Name Energy Type Peak Use Schedule

Parking Lot Lights Electric 5.0Kw Parking Lot Lights Domestic Water Heating Natural Gas 400MBH Domestic Hot Water Aerobic Pool Heater Natural Gas 600MBH Aerobic Pool Heater

Add air system A08 – RTU C5 – Mech/Storage to the building design scenario. This is a packaged unitary rooftop unit not assigned to a plant.


Misc Energy Tab

In each row for the check box enter the information for the additional building energy users not defined in the space input forms. Examples include: Domestic water heating, outdoor security lighting etc. Select the energy type, define the peak energy usage and then define a schedule.

Left click on the “Edit” button to assign a fractional schedule for each misc. energy item.

The following pages include screen captures of the schedules, profiles and assignments for the Misc.Energy items. DO NOT re-input this data, it already exist in the archive.






(end of archived data for Misc Energy tab.)


Meter Tab: For workshop # 7, link the “A Base” building to an electric and a gas meter.

Building Properties Meter Tab At this point, the first of four buildings is completed. It is necessary to perform the same steps outlined above for each of the remaining building design alternatives. Building Properties Plants Tab

Check the B- Alt – 1 plants.


.

Add system B08-RTU C5 to the building design.

Next, check the C Alt –2 plants.

Complete the Misc. Energy and Meters tabs before going on to the “C Alt -2 ” design case.


Alternate “D-Alt 3” consists of SZCV/RTU – Complex Rate and is the final building design case

Add air system C7-RTU C5 to the design scenario

Note: There are no plants to link to the D Alt-3 design scenario.


Remember to complete all four tabs for all four building scenarios. Buildings Created In Workshop # 7 At this point we have created 4 buildings, each one a different design scenario. We will now run the building simulations and preview the results.

Highlight and ADD all “D” designated RTU Packaged Rooftop air systems


Highlight all four buildings and run simulation reports. Check the two comparative reports and preview the results.

Building Simulation Reports


Workshop #7 Solutions


Annual Cost Summary Table 1,2

C-Alternate 2 – 4PFCU/VSS is the lowest Annual Operating Cost scenario.


Annual Cost Summary Table 3

Annual Energy and Emissions Summary Table 1


Annual Energy and Emissions Summary Table 2, 3


Annual Energy and Emissions Summary Table 4,5

Run the following simulation reports on the C-Alt 2 4PFCU/VSS Building. This scenario had the lowest annual operating cost.


Building Simulation Reports














Air System

s Sch

ematics

Appendix “A”













APPENDIX BHAP/Windows Software

Basics


Windows Software Basics This topic provides a brief introduction explaining how to use Windows programs. This introduction is intended for readers who are new to Windows software. Understanding the principles discussed below will make it much easier to learn and use HAP. Please note that this introduction is by no means a comprehensive guide. Readers who feel more information is needed are encouraged to consult one of the many Windows training guides, which are available in bookstores. Learn Once; Use Anywhere. One of the basic principles involved with Windows software is that all software programs should use common elements with standard operating rules. Therefore, if you learn how to operate one Windows program, you will know the basic techniques of using any Windows program. The successful application of this principle relies on using standard interface elements, which operate according to standard rules. It also relies on users of the software recognizing visual cues, which indicate which kind of interface element is being used, which in turn implies the operating rules. Mouse Input. Your mouse can be used to navigate, choose options, select items and press buttons in a Windows program. A mouse has two or three buttons designated button #1, button #2 and button #3. Mouse button #1 is typically the left-hand button and button #2 is the right-hand button. In all subsequent discussions, and throughout the HAP help system, we will use the following common notation when referring to use of the mouse:

• Click means to press the left-hand mouse button once. We assume left-hand button = button #1.

• Double-Click means to press the left-hand mouse button twice in quick succession. Again,

we assume left-hand button = button #1.

• Right-Click means to press the right-hand mouse button once. We assume right-hand button = button #2.

• Common tasks you can perform with your mouse are as follows:

• To choose a menu option or an item on a list, click on the option or item.

• To display a pop-up menu, right-click on an item.

• To press a button (such as an OK button), click on the button.

Keyboard Input. Keys on your keyboard can also be used to navigate, choose options, select items, input data and press buttons in a Windows program:

• To move the cursor from one item to the next, press the [Tab] key. To move the cursor from one item to the previous item, press [Shift] and [Tab] together.

• To choose a menu option, first press [Alt] and the access key for the menu. For example,

if the letter "P" in the name of the Project menu is underlined, "P" is the access key for this menu. Press [ALT][P] to display the Project menu’s options. To choose an option on a menu, press the access key for the desired item.

• To select an item on a list, use the up and down arrow keys to move the cursor through

the list. When the desired item is highlighted, press the [ENTER] key.


• To enter data, simply type the numeric or text information using the keyboard. When

finished, DO NOT press [ENTER]. Instead use the TAB key or the mouse to move to another input item. [ENTER] very often will execute the default command button, which may cause you to exit to a different part of the program.

• To press a button (such as an OK button), use the [Tab] keys to navigate to the button

and then press the [ENTER] key.

• Using Forms and Controls. In Windows programs, information is presented on one or more "forms.” In HAP, the main program window is an example of one kind of form, which is used to perform basic tasks. HAP input forms are another example of a kind of form which is used to enter information. Individual items that appear on a form, or entire regions of a form are referred to as "controls.” For example, on the HAP main program window, the left-hand panel in the center part of the window is a "tree view" control, which is used to switch between different categories of HAP data. A particular type of control always operates according to one consistent set of rules. Efficient use of Windows programs relies on quickly recognizing different kinds of controls and understanding how each kind of control is used. This sub-section summarizes the controls most frequently used in HAP.

• Pull-Down Menus. Pull-down menus typically appear toward the top of a form in the

"menu-bar.” To display the menu’s options, click on the menu name, or use press [ALT] and the menu’s access key. To select a menu option, click on the option name or use the arrow keys to move the highlight bar to the desired item and then press [ENTER]. An example showing HAP’s Project menu appears below.

• Toolbar Buttons. Toolbar buttons typically appear toward the top of a form and are used to perform common program operating tasks. Each toolbar button contains a picture that indicates its function. If you are uncertain of a button’s function, position the mouse cursor over the button. A "tool tip" - a short description of the button’s function - will appear. To press the button, use the mouse to click on the button. An example showing HAP’s toolbar appears below.

• Tree View. A tree view displays the relationships between data items in the form of a tree. For example, in Windows Explorer, the folder structure of your hard disk is shown in a tree view control. Branches of the tree represent folders on your hard drive and sub-folders beneath each of these folders. A tree view control is often accompanied by a list view control. In Windows Explorer, you use the tree view to locate a specific folder, and the accompanying list view displays the files in that folder.


• In the HAP main program window, a tree view is used simply to show the categories of

program data. You can perform the following tasks with this HAP tree view:

• Click on the category name to display its data in the list view. For example, clicking on the Space category name displays a list of spaces in your project in the list view.

• Right-click on the category name to display the pop-up menu for the category. Options on

this menu perform work on all data in a specific category. For example, if you choose the Print Input Data option on the Space category pop-up menu, data for all spaces in your project will be printed.

• List View. As its name implies, a list view contains a list of items that can be selected and

used for various tasks. The list view can be displayed in four different formats: list, details, large icons and small icons. These formats show the contents of the list as line items or icons arranged in column or row format. The example below shows a list view from HAP containing spaces. This example uses the details format.

Standard procedures are used to select items in a list view:

• To select a single item, click on the item. It will be highlighted to indicate it is selected.

• To select multiple, consecutive items, click on the first item in the series. Hold the [Shift] key down and click on the last item in the series. All the items in the series you selected will be highlighted.

• To select multiple, non-consecutive items, hold the [Ctrl] key down and click on each item

you wish to select. Each selected item will be highlighted.

• Other tasks that can be performed with list view items are:

In some programs double-clicking on an item in the list view performs a special function. In HAP, double clicking on an item allows you to edit its data.

In addition, right clicking on an item often displays its pop-up menu. In HAP, this feature is offered for all categories of program data.


• Text Boxes. A text box is used to enter numeric or text data. Its appearance is shown below. When you move to the text box by clicking on it or using the [Tab] key, the existing value in the text box will be highlighted indicating you are in replace mode. If you begin typing, the existing value will be replaced with the new information you enter. To modify individual characters or numerals in the text box, click on the text box a second time or press the right or left arrow key. A blinking cursor will appear. In edit mode, you can move the cursor to a desired position in the box and insert or delete individual characters or numerals. When finished entering data, DO NOT press the [ENTER] key. In Windows software the [ENTER] key has no effect on a text box. Instead, it will often execute the default command button. Rather than [ENTER] moving you to the next input item, it will send you elsewhere in the program. Instead, use your mouse or the [Tab] key to move to the next input item.

• Spin Buttons. As shown below, spin buttons sometimes accompanies text boxes. Spin buttons provide an alternate way to change data in a text box. If you click on the up button, the value in the text box will increase by a predetermined amount. If you click on the down button, the value will decrease. In the example below, the spin one uses buttons to increment or decrement the window quantity each time a spin button is pressed.

• Drop-Down Lists. Drop-down lists are used to choose from a list of items. The example shown below is a drop-down list used to choose the overhead lighting fixture type in HAP. To display the list, click on the down arrow at the right-hand end of the control. Once the list appears, click on the desired item or use the arrow keys to move the highlight bar to the desired item and then press [ENTER].

• Combo Boxes. A combo box is a modified version of a drop-down list. In addition to choosing from a list of items, a combo box allows you to enter your own item. The example shown below is a combo box for the city name from the Weather form in HAP. With this combo box, you can select from a list of pre-defined cities, or you can type in a city name of your own.

• List Boxes. A list box contains a list of items from which you can select one or more items. Standard procedures are used to select items (see List View below). Sometimes you must scroll the list to see all of its items. The example below shows a list box used to select spaces included in a zone in HAP.


• Check Boxes. A check box is typically used to indicate on/off or yes/no selections. In the example below, the box will be checked if you want the program to model glass as shaded all day, and will be unchecked if the glass is to be modeled as un-shaded. Clicking on the box changes a check box.

• Radio Buttons. Radio buttons are used for selecting one item from a group of mutually exclusive choices. In the example below, only one of the four floor types can be selected at one time. To select an item using radio buttons, click on the button opposite the desired name or on the name itself. A black dot will be placed next to the item you choose, and the dot for the prior selection will be removed automatically.

• Command Buttons. Command buttons are used to perform various tasks in a

Windows programs. The example below shows the three command buttons that appear on all HAP input forms. Pressing the OK button, for example, saves the current data and returns to the HAP main program window. To press a command button, use your mouse to click the button, or use the [Tab] key to navigate to the button and then press [ENTER]. In some situations, a command button is highlighted in some manner to show it is the default for a form. In the example below, the OK button has a darkened outline indicating it is the default. Pressing [ENTER] from anywhere on the form has the same effect as pressing the default button.


Using HAP 4.4 for System Design Loads This is a quick tutorial on using HAP to estimate heating and cooling loads and design systems and plants. It is designed for readers who want a quick description of how to use the program and are already familiar with the design load process, HAP terminology and the basic principles of operating Windows programs. When you start HAP, the main program window appears. At this point, the design process involves the following five steps to design systems and two additional steps to design plants: 1. Create a New Project

• Choose New on the Project menu. This creates a new project. A project is the container which holds your data

• Choose Save on the Project menu. You will be asked to name the project. From here on, save the project periodically.

2. Enter Weather Data· • Click on the "Weather" item in the tree view in the main program window. A "Weather

Properties" item appears in the list view • Double click on the "Weather Properties" item in the list view. The Weather input form will

appear. • Enter weather data. • Press the OK button on the Weather input form to save the data and return to the main

program window. 3. Enter Space Data

• Click on the "Space" item in the tree view in the main program window. Space information will appear in the list view.

• Double-click on the "<new default space>" item in the list view. The Space input form will appear.

• Enter data for your first space. While entering spaces, you may need to create schedules, walls, roofs, windows, doors or external shades. You can do this by choosing the "create new …" item in drop-down selection lists. For example, when entering overhead lighting data, you must choose a schedule. In the schedule drop-down list, choose the "create new schedule" item to create a schedule and automatically assign it to overhead lighting. Similar procedures are used for walls, roofs, windows, doors and external shades. An alternate approach is to create schedules, walls, roofs, windows, doors and external shading before entering space data.

• Press the OK button on the Space input form to save your data and return to the main program window.

• To enter another space, in the list view right-click on the name of the space you just created. The space pop-up menu appears.

• Choose the Duplicate option on the pop-up menu. A copy of the original space will be created and its input form will appear. This is a quick way of generating new spaces based on defaults from the previous space.

• Enter data for this new space. • Press the OK button on the Space input form to save your data and return to the

main program window. · Repeat the previous four steps to enter data for as many spaces as you need.

4. Enter Air System Data


• Click on the "System" item in the tree view in the main program window. System information will appear in the list view.

• Double-click on the "<new default system>" item in the list view. The System input form will appear.

• Enter data for your first system. While entering the system, you will need to create a fan/thermostat schedule. You can do this by choosing the "create new schedule" item in the fan/thermostat schedule drop-down list. This will create a schedule and automatically assign it to your system. An alternate approach is to create this schedule before entering air system data.

• Press the OK button on the System input form to save your data and return to the main program window.

• To enter another system, in the list view right-click on the name of the system you just created. The system pop-up menu appears.

• Choose the Duplicate option on the pop-up menu. A copy of the original system will be created and its input form will appear. This is a quick way of generating new systems based on defaults from the previous system, if successive systems are similar. If they are not, use the "new default system" option to create each new system. · Enter data for this new system.

• Press the OK button on the System input form to save your data and return to the main program window.

• Repeat the previous four steps to enter data for as many systems as you need. 5. Generate System Design Reports

• Click on the "System" item in the tree view in the main program window. System information will appear in the list view.

• Select the systems for which you want reports. • Choose the "Print/View Design Data" option on the Reports menu. • On the System Design Reports form, choose the desired reports. • To view the reports before printing, press the Preview button. • To print the reports directly, press the Print button. • Before generating reports, HAP will check to see if system design calculations

have been performed. If not, HAP automatically runs these calculations before generating the reports.

6. Enter Plant Data (if necessary) • Click on the "Plant" item in the tree view in the main program window. Plant information

will appear in the list view. • Double-click on the "<new default plant>" item in the list view. The Plant input form will

appear. • Enter data for your first plant. For plant design load purposes users will only need to select

from the first three plant types (Generic Chilled Water, Generic Hot Water, Generic Steam). HAP users have additional options for specific types of chilled water, hot water and steam plants, but these require extra data not relevant to the design load calculation. Therefore, it is best to use the Generic plant types for design loads. Later Generic plants can be converted into specific plant types without loss of data.

• Press the OK button on the Plant input form to save your data and return to the main program window.

• To enter another plant, in the list view right-click on the name of the plant you just created. The plant pop-up menu appears.

• Choose the Duplicate option on the pop-up menu. A copy of the original plant will be created and its input form will appear. This is a quick way of generating new plants based on defaults from the previous plant, if successive plants are similar. If they are not similar, use the "new default plant" option to create each new plant.

• Enter data for this new plant.


• Press the OK button on the Plant input form to save your data and return to the main program window.

• Repeat the previous four steps to enter data for as many plants as you need. 7. Generate Plant Design Reports (if necessary)

• Click on the "Plant" item in the tree view in the main program window. Plant information will appear in the list view.

• Select the plants for which you want reports. • Choose the "Print/View Design Data" option on the Reports menu in the menu bar. • On the Plant Design Reports form, choose the desired reports. • To view the reports before printing, press the Preview button. • To print the reports directly, press the Print button. • Before generating reports, HAP will check to see if plant design calculations have been

performed. If not, HAP automatically runs these calculations before generating the reports.


Using HAP to Perform Building Simulations This is a quick tutorial on using HAP for estimating annual building energy use. This tutorial is for readers wanting a quick refresher on how to use HAP for building simulation and the proper procedure for entering data. The reader should already be familiar with the design process, HAP terminology and the basic principles of operating Windows programs.

Certain steps in the building simulation process are similar to that of system design (loads) process. Building energy analysis uses data entered for system design loads.

All analysis work performed in HAP requires following the same general five-step procedure:

1. Define the Problem. First, define the scope and objectives of the Building Analysis. For example, what type of building is involved? What type of systems and equipment are required? Which alternate designs or energy conservation measures to compare in the analysis?

2. Gather Data. Gather information about the building including its environment, HVAC and non-HVAC equipment and cost for energy before simulating the building. This step involves extracting data from building plans, evaluating building usage, studying HVAC system needs and acquiring utility rate schedules. Specific types of information needed include:

• Building site climatic data • Building construction material data: • Walls and Roofs • Windows, Doors and Exterior shading devices • Floors Interior partitions • Building size and layout data including wall, roof, window, door and floor areas, exposure

orientations and external shading features


• Internal load characteristics determined by levels and schedules for occupancy, lighting systems, office equipment, appliances and machinery within the building.

• Data for HVAC equipment, controls and components • Data for chilled water, hot water and/or steam plants as applicable • Data for non-HVAC energy-consuming equipment • Utility rate information for electric service, and fuel sources

3. Enter Data Into HAP. Next, enter data into HAP for the analysis. When using HAP, your base of operation is the main program window. From the main program window, first create a new project or open an existing project. Then define the following types of data needed for the building analysis:

Enter Weather Data. Weather data defines the temperature, humidity and solar radiation conditions the building encounters during the course of a year.

These conditions influence loads and system operation throughout the year. • Select Design Weather • Select Simulation Weather • Define Holiday calendar. Enter Space Data. Describe all elements affecting heat flow in space. Space information is stored in the project database and linked to zones in an air system.

Enter Air System Data. An Air System is the equipment, controls used to provide cooling, and heating to a region of a building.

Enter Plant Data. A Plant is the equipment and controls used to provide cooling via chilled water or heating via hot water or steam to coils in one or more air systems.

Enter Utility Rate Data. Utility rate data defines the pricing rules for electrical energy use and fuel use.

Enter Building Data. A Building is simply the container for all energy-consuming equipment included in a single energy analysis case. Create one Building for each design alternative in the study.

4. Use HAP to Generate Simulation Reports. Using the Reports Menu, select and generate simulation reports.

5. Evaluate Results. Finally, use data from the simulation reports you generated to draw conclusions about the most favorable design alternates. Copies of the typical HAP Simulation Reports are included on the Hand-out CD.




APPENDIX “C”HAP Application Topics


Appendix “C” The Sizing Dilemma In HAP, users are asked to choose among four different methods of sizing zone and space airflow rates. This discussion explains why different sizing methods are used and summarizes the four methods offered in the programs.

The Sizing Dilemma. The key issue is that there is not a single “correct” way to size space airflow rates. In fact, no sizing method can guarantee comfort in all spaces at all times when a zone contains multiple spaces. The reason for this is that each zone has a single thermostat to control the comfort conditions in all the spaces in that zone. The space that contains the thermostat will maintain comfort conditions, but the other spaces in the zone will receive conditioning based on the load in the space containing the thermostat. Because of this imperfect situation, designers’ use different approaches to size space airflow rates in order to minimize conditioning problems in the spaces that do not contain the thermostat. Which approach is best varies by application. Ultimately, the choice of a sizing method depends on the designer’s judgment and experience.

Sizing Method #1:

• Zone airflow computed using peak zone load. • Space airflow computed using zone CFM/sq.ft. or L/s/sqm.

With this method, the zone airflow is computed using the maximum zone sensible cooling load. The zone airflow is divided among spaces in the zone on the basis of zone CFM/sq.ft (L/s/sqm). Therefore, space airflow is not related to space loads unless all spaces in the zone have a consistent load density in BTU/hr/sq.ft (W/sqm).

Sizing Method #2:

• Zone airflow computed using peak zone load. • Space airflow computed using coincident space loads.

With this method the zone airflow is calculated from the maximum zone sensible cooling load. The zone airflow is divided among spaces in the zone on the basis of the ratio of coincident space sensible cooling loads to peak zone sensible load. By “coincident,” we mean the space load computed for the month and hour when the zone sensible load peaks.

Sizing Method #3:

• Zone airflow computed using peak zone load. • Space airflow computed using peak space load.

With this method, the zone airflow is computed using the maximum zone sensible load. Required space airflow rates are computed using the maximum sensible load for each individual space. Note that if spaces experience peak loads at the same time the zone peak occurs, the sum of space airflow rates will equal the zone airflow rate. Otherwise, the sum of space airflows will exceed the zone airflow rate.

Sizing Method #4:

• Zone airflow computed using sum of space airflows. • Space airflow computed using peak space load.

With this method, required space airflow rates are computed using the maximum sensible load for each individual space. The zone airflow rate is calculated as the sum of space airflows for all spaces in the zone.♦


Which Sizing Method To Use? By John Deal, Regional Sales Manager, Carrier Software Systems.

The previous article titled The Sizing Dilemma discusses in detail the four sizing methods in HAP. The problem confronting the designer is that one of the four methods must be chosen and some thought is required to determine which method to use. The purpose of this article is to share some ideas to assist your decision on which sizing method to use.

The four methods summarized in the previous article (The Sizing Dilemma) are those requested by our HAP customers. If someone has another sizing method, we certainly would like to hear about it! I think we can safely say that every designer uses one of these methods almost exclusively and probably was not aware of the three alternatives until forced by an impudent software program to make a choice. The method one uses is probably from a habit formed when a load estimating methodology and calculations were first learned or passed on from a teacher, a mentor or a boss.

Methods 1 and 2 give results similar to those of “hand” calculation methodology expectations. Simplifying assumptions were made because of the amount of time it took to perform the number crunching. One could not afford the time necessary to calculate loads over a number of hours or to break up the building into numerous design zones and spaces. So, results were obtained in a simplified fashion that could be easily applied throughout the design such as CFM/sq.ft (L/s-sm), heat loss of BTU/hr/linear ft (W/m) of exposure and so forth.

Methods 3 and 4 give results expected of a methodology that can only be done on a computer. Calculating 12 months 24 hours a day to find peak loads for fans, coils, zones and spaces is a reasonable expectation. Crunching the numbers on hundreds of spaces collected into a hundred or more zones in a dozen air systems is a reasonable expectation.

I am going to make a provocative statement to start your thought process on which methods to use. If you are doing detailed final design calculations, methods 3 and 4 are the ones to use and the type of system under design will dictate which one. Variable air volume (VAV) systems use method 3. Constant volume systems use method 4.

The key function that these two methods share is that the space peak sensible load is found and reported. This gives the designer the information about the peak design parameters for every space defined. With this information, the designer can get a better handle on the magnitude of the compromises that must be made with the control zone layouts, duct design and terminal equipment sizing.

Using method 3 for a VAV terminal zone sizes the “box” for a VAV diversified CFM. The spaces in the zone are sized for their peak so no matter which space the thermostat is placed in that space can be controlled. If future reworking of zones is done, the space duct and terminal sizing is still valid. The key to good zoning practice is to have spaces with similar thermal load profiles on the same thermostat. With this method the time and month that each space peaks is reported. This helps in the decision whether the spaces have similar thermal load profiles. If all the spaces in the zone peak in the same month around the same time of day, this indicates a good probability of similar thermal load profiles for the spaces. If one or more spaces peak at different times of the year than the other spaces this indicates dissimilar load profiles and some thought should be given to “re-zoning."


Using method 4 for constant volume systems is good practice since these types of systems normally should not be sized with diversified or block load air quantities. Let us discuss one of the most common systems, the packaged rooftop unit. In HAP language, this is a single zone constant air volume system. If the designer takes the time to describe the various areas served as spaces, some valuable information can be gained. An example is the amount of air needed in different places so diffusers and the duct system can be designed with some knowledge of the actual requirements. Again, if some of the spaces were peaking at different times of the year than others this would indicate the need for better zoning (another unit if you can afford it). At least you will know that the job probably will not work very well at this stage. This method also sizes the rooftop unit CFM (L/s) undiversified. This is good since it seems you need to get all the air you can on these types of jobs.

We hope that this article has helped you think about the choices of space descriptions, zoning and sizing methods you must make. Make your choices with a purpose in mind. I am sure many of you may have differing thoughts and we would like to hear them. Even with faster computers and more complex software, system design still has a lot of art and designer experience involved. Remember this old saying: If a job is to work correctly, it must be designed right one time. The problem is when! ♦


Putting Load Calculation Methods in Perspective By Rudy Romijn, Regional Sales Manger, Carrier Software Systems

Over the years, our industry has used many methods for performing cooling load calculations. Comparing these methods provides a useful perspective on the benefits of the methods currently employed by engineers, and ultimately helps in understanding output data provided by engineering software like HAP.

Those of us who started in this business before the age of computers can appreciate Figure 1 shown below. It illustrates the relationship between complexity and accuracy that many of us have had to grapple with for five of the principal load methods that have been used over the years

Load Estimating Methods

ACCURACY

INCREASING COMPLEXITY

Instantaneous Q=U A TD

Carrier E20 Method

ASHRAE CLTD/CLF

ASHRAE Heat Balance Method

ASHRAE Transfer Functions

ASHRAE RTS

Figure 1. Load Estimating Methodologies Long ago loads were calculated by hand using the “instantaneous method” which assumed heat gains were instantly converted to cooling loads. This method was simple and fast, but was unreliable because it ignored processes such as heat storage and radiation transfer, which affect the rate at which heat gains become cooling loads.

In 1960, Carrier published its System Design Manual, which included tables of Equivalent Temperature Differences (ETD) and Storage Load Factors (SLF). These factors were used to predict cooling loads, which incorporated the effects of heat storage by building materials, and the effects of building orientation and occupancy cycle. Later, in the 1970s ASHRAE published its CLTD/CLF method, which incorporated the same kind of considerations. As hand calculation procedures, both methods did a good job of balancing complexity (and therefore effort) with accuracy. However, both methods lacked flexibility. Building loads are affected by a wide variety of factors involving design, construction, environment and building use. Table-based hand calculation methods typically dealt with a fixed set of basic conditions (such as envelope loads for July 40 degrees north latitude) and then attempted to handle other conditions via correction factors. Ultimately, this approach introduced error and reduced accuracy when compared with methods that are more complex. Some way of calculating loads specific to each design application was needed.


The Heat Balance Method, the most rigorous method of calculating building loads, provides one solution to this problem. Heat balance is actually the foundation of all the other methods of calculating building loads. The heat balance method evaluates each conductive, convective, radiative and heat storage process that occurs in the building using the fundamental laws of heat transfer and thermodynamics. Using the heat balance method to determine building heat transfer requires an equation written for each surface and mass element considering each process involved. By solving all heat balances equations simultaneously, the total rate of heat transferred to room air can be determined and the dynamic ebb and flow of heat in the room can be successfully evaluated. The Heat Balance method can be highly accurate but it is also complex and requires powerful computer hardware, detailed inputs and long calculation time.

An alternate solution is the Transfer Function Method which is endorsed by ASHRAE as the preferred method of calculating loads, and which is used in the HAP, System Design Load, Block Load and Block Load Lite programs produced by Carrier. The Transfer Function Method uses some mathematical “tricks” to simplify the heat balance solution process, thereby yielding calculation times that are faster than those of the Heat Balance Method without sacrificing too much of its accuracy. The Transfer Function procedure calculates how heat gains from sources such as warm ambient air, solar radiation, lights, people, etc. are converted to cooling loads via conduction, convection, radiation and heat storage processes. The procedures therefore account for the dynamic heat transfer found in a “real world” building. Further, calculations account for specific design, construction, environmental and building usage conditions and are therefore customized to each building application. Thus, for the current state of technology of computerized engineering tools, Transfer Functions provide a good compromise between complexity and accuracy.

Figure 2. Lighting Heat Gains and Loads


When using programs that employ the Transfer Function Method, remember that nearly all loads involve dynamic heat flow. Heat gain received from a source such as lighting is not immediately converted to a cooling load. Rather, the portion of the heat gain that is thermal radiation is transferred to massive building elements such as floors and walls, and may be stored for a period of time before being released to air in the building. Once heat is transferred to the air, it is a load that must be removed by the air conditioning apparatus. Figure 2 shows a sample relationship between lighting heat gain and load. When the lights are first turned on, a significant portion of the lighting heat gain is absorbed and held by the building mass. Over time, this stored heat is discharged to air in the building, but additional radiant heat is received. When the lights are turned off, the stored heat continues to be discharged. Thus, loads continue even after the heat gains cease. All heat sources that involve a radiant component exhibit similar behavior. These include loads for walls, roofs, windows, partitions, people, lights and electrical equipment. Transfer Function calculations account for these dynamic processes. Remembering this is often very helpful when analyzing load calculation outputs.

The Radiant Time Series method was introduced in ASHRAE 2001 Handbook of Fundamentals. It is a dynamic way of calculating loads, but is not as complex to calculate and is easier to understand than the TFM. It is a good method to obtain sizing data for a typical building. However, it is not a good method to simulate system operation. ♦


The Benefits of the Transfer Function / Heat Extraction Load Calculation Method The previous article (Putting Load Calculation Methods in Perspective) describes the transfer function and heat extraction procedures used to calculate loads in HAP. While the benefits of this calculation method for energy analysis are evident, customers often question whether such advanced calculation methods are worth using for system design applications, or whether simpler methods would be sufficient. Carrier feels that advanced methods such as transfer functions/heat extraction should be used because the method provides several important benefits to users. These include:

1. Accuracy. Advanced methods such as Transfer Functions account for the dynamic heat flow processes which occur in buildings and which significantly influence design loads and system behavior. Simpler methods either ignore these dynamics, or analyze them in much less detail than Transfer Functions. Advanced methods therefore can provide results that are more accurate.

2. Pull down Loads. One of the most important aspects of dynamic heat flow is the pull down load. Pulls down loads have a significant influence on system sizing results and therefore need to be considered. Advanced methods such as Transfer Functions/Heat Extraction are the only way to adequately account for pull down loads. Simpler methods can only make gross estimates of the effect of pull down loads.

3. Flexibility. Advanced methods such as Transfer Functions/Heat Extraction customize calculations to the application. Since loads are dynamic, loads in one hour are influenced by conditions in both the current hour and previous hours. The nature of 24-hour profiles of solar radiation, ambient temperature and internal heat gain need to be considered to accurately predict loads in any one hour. Transfer functions use the solar, temperature and internal gain profiles defined by the user for each specific application. Therefore, loads are customized to each application. Simpler table-based methods make assumptions, such as a standard operating profile or the use of July 40 deg N latitude for solar radiation. In some cases, correction factors are used to try to adjust for actual conditions. These adjustments are often not adequate and produce less accurate results than methods that customize calculations to each application. ♦


Diagnosing the “Thermos Bottle Effect” Q. I’m using HAP to analyze the benefits of various energy conservation measures for a commercial building. One measure being considered is the addition of insulation to the roof. I expected energy consumption for cooling and heating to be reduced. While my heating energy was substantially reduced, my cooling energy increased. How can this be?

A. What you are seeing is a phenomenon that has been dubbed the “thermos bottle effect.” Adding insulation to a roof reduces heat flow through the roof assembly and serves to reduce cooling coil loads during summer months. However, the added insulation can also prevent internally generated heat from escaping from the building in the spring, fall and winter months, and this can increase cooling coil loads during off-peak months. The following example demonstrates how this can happen.

Example. For this example, a 14,000-sqft (1,300-sqm.) single-story retail store was evaluated. The building is located in Chicago and therefore experiences hot summers and cold winters. Large internal heat gains are present due to lighting, occupants and electrical equipment. The original construction uses a roof assembly with a U-value of 0.104 BTU/hr/sq.ft/F (0.18 W/sqm-K). Space conditioning is provided by a constant volume packaged rooftop unit, which includes electric heat without an economizer cycle.

As an energy conservation measure, insulation was added to the roof to improve its U-value to 0.042 BTU/hr/sq.ft/F (0.073 W/sqm-K). When HAP simulations for the U= 0.104 (0.18 W/sqm-K) and U= 0.042 cases were run, the following results were obtained:

Case Cooling kWh Heating kWh Total kWhU=.104 71,571 9,260 365,633U=.042 75,720 693 361,214

While the heating energy use has been reduced substantially (93%), the cooling cost has increased by 6%. Investigation of energy consumption results for the building, plant and air system showed the root of the problem lay in the air system. Air system simulation results show that the annual heating coil load dropped from 62,972 (66,439 MJ) to 12,172 kBTU/yr (12842 MJ), but the annual cooling coil load increased from 776,844 (819,614 MJ) to 809,200 kBTU/yr (853,751 MJ). An examination of how cooling coil loads are distributed during the year begins to provide clues to why this happens.


Figure 1 is a plot of monthly total cooling coil loads for the original U= 0.104 and renovated U= 0.042 scenarios. This figure shows that the renovated case has lower cooling coil loads in the summer months, but higher cooling coil loads in the spring, fall and winter months. Increases in cooling loads during these off-peak seasons are larger than reductions in cooling loads during the summer months, so the annual effect is a net increase in cooling coil load.


Examination of hourly system performance provides further clues to what is happening. Figure 2 shows hourly cooling coil load profiles for July 19, a moderately sunny summer day in which the ambient temperature ranges between 69 F (20.5 C) and 82 F (27.8 C.) Cooling loads for this day are uniformly higher for the U=0.104 case than for the U=0.042 case.


Finally, Figure 3 shows hourly system performance for March 19, a moderately sunny day with ambient temperatures ranging between 35 F (1.7 C) and 50 F (10 C.) On this day the relationship between cooling coil loads is reversed. Coil loads for the original U= 0.104 case are uniformly less than those for the renovated U= 0.042 case.


With this system performance data as evidence, we can begin to deduce what causes the overall cooling cost to increase:

• Because this is a single story building with a large roof area, the roof is a dominant pathway for envelope heat flow. Adding insulation to the roof serves to reduce heat flow through the roof.

• When the direction of heat flow is from outside to inside, such as on a warm, sunny summer day, the added insulation reduces the heat flow and therefore reduces the cooling coil load, as shown in Figures 1 and 2.

• When the direction of heat flow is from inside to outside, such as on a cold winter day, the added insulation reduces heat loss. Normally we only think of this in terms of reducing system heating coil loads, which it does. However, in a building with large internal heat gains, envelope heat loss allows internal heat to escape from the building. Added insulation prevents the escape of this internal heat. Therefore, heat that would normally have escaped naturally from the building must be removed by mechanical cooling. Evidence of this is shown in Figures 1 and 3.

Increasing envelope insulation has this effect in many types of buildings. But generally, the summer cooling savings far outweighs increases in off-peak cooling loads due to their small size and infrequent occurrence. It is in buildings with large internal heat gains and frequent cooling loads in off-peak months that this “thermos bottle effect becomes prominent and cause an overall increase in cooling cost. ♦


Using Outdoor Ventilation Control Options When defining air-handling systems in HAP, users can choose among four different options for controlling outdoor ventilation air:

• Constant Airflow • Proportional to Supply Air • Scheduled • CO2 Sensor

This article briefly describes these options and their intended applications. Each control option will be discussed separately below.

Constant Airflow Control maintains outdoor ventilation at the design airflow rate for all occupied period hours and for unoccupied period hours when the ventilation dampers are open. For constant volume systems, constant ventilation airflow can be maintained without special controls and is the most common control option used for CAV systems. For VAV systems, it is assumed special damper controls or booster fans are used to maintain a constant ventilation rate as the supply fan airflow varies.

Note that this control also allows the user to specify whether ventilation dampers are open or closed during unoccupied periods. Thus, this control provides simple scheduling capabilities for eliminating ventilation airflow for unoccupied times.

“Proportional to Supply Air” Control represents the use of uncontrolled or partially controlled ventilation airflow for VAV systems. With this option, ventilation airflow varies naturally as the supply airflow changes. Uncontrolled outdoor airflow tends to vary as a constant percentage of supply air. Thus, if the supply fan has throttled to 60% of its design value, ventilation air is 60% of its design value also. As with Constant Airflow control, the user has the opportunity to schedule the ventilation dampers open or closed during unoccupied period hours as necessary.

CO2 Sensor Control provides a simple model for outdoor ventilation air control based on a CO2 sensor. Actual controls vary ventilation air to maintain indoor air quality based on measured C02 levels in the building. To model this control on a simple basis, the program assumes CO2 levels are directly related to the number of occupants in a zone. The program therefore varies ventilation airflow using a constant CFM/person value and the number of occupants in the building for the current hour.

Scheduled Control is used when special controls are used to vary the outdoor ventilation airflow according to a predetermined time-clock schedule. For example, based on the time clock schedule, ventilation dampers might modulate to provide 1000 CFM (472 L/s) of ventilation air from 6am to 9am, 1500 CFM (708 L/s) from 9am to 12 noon, and 1250 CFM (590 L/s) from 12 noon to 5pm. When this control option is used, the user specifies how ventilation air varies by choosing one of the schedules stored in the program schedule database. This schedule selection is made on the same input screen where you choose the method of ventilation control in HAP 4.0 for Windows.

It is important to note that the “Scheduled Control” option should not be used simply as a means of eliminating ventilation air during unoccupied times. This can be done much more easily using the “Constant Airflow” and “Proportional To Supply Air” control options. Many users often overlook this and mistakenly use the “Scheduled Control” option when “Constant Airflow” or “Proportional to Supply Air” would be a more appropriate selection. ♦


Demand Controlled Ventilation Control Introduction. Demand Controlled Ventilation (DCV) control uses zone CO2 sensors to control ventilation air. This help topic explains how HAP simulates DCV control.

HAP performs an iterative calculation to determine the steady state CO2 levels for each hour of operation simulated and the resulting control of outdoor airflow rates. This involves estimating the CO2 level in each zone. The zone CO2 levels determine how the outdoor ventilation damper is positioned. Outdoor ventilation airflow in turn influences CO2 levels in the system. Thus, elements of the analysis are interrelated and an iterative solution is needed to consider all feedback issues in the system. The following sections discuss each element in this calculation.

A. CO2 Generation by Space Occupants.

Occupants are the primary source of CO2 generation in occupied spaces. Further, occupants produce a predictable amount of CO2 based on activity level. The total CO2 generated by occupants of a zone is calculated as the sum of CO2 generated by occupants in all spaces in the zone:

Vzone = S (Vspace)(Mspace), all spaces

The CO2 generated in each space is calculated as the number of occupants present times the CO2 generated per person:

Vspace = Nocc Vocc

Where:

Vzone = Total volume of CO2 produced by occupants in a zone, CFM or L/s.

Vspace = Total volume of CO2 produced by occupants in a single instance of a space, CFM or L/s

Mspace = Space multiplier. The number of spaces of this type in the zone.

Nocc = Number of occupants in the space for the current hour. This is the product of the maximum occupants times the hourly schedule factor for the current hour.

Vocc = Total volume of CO2 produced by one occupant in the space, CFM or L/s. This value depends on the occupant activity level as described in the following paragraphs.

The calculation of CO2 generation for a single occupant is based on the fact that human activity is related to respiration. That is, the higher the level of activity or exertion, the higher the level of respiration. During respiration, the occupant exhales air that contains CO2 generated in the lungs. In HAP the relationship between occupant activity and CO2 generation is calculated as follows:

Vocc = Qtot (K) / [M At]

English Units: Vocc = Qtot (0.00002667) CFM

SI Metric Units = Qtot (0.0278) L/s

Where:

Vocc = Total volume of CO2 produced by one occupant in the space, CFM or L/s.

Qtot = Total heat gain per occupant, BTU/hr/person or W/person. This is the sum of sensible and latent heat gains defined by the occupant activity level, or directly specified by the user.

K = Curve fit coefficient. 0.00883 CFM/Met in English or 0.25 L/s/Met in Metric. Figure C-2 "Metabolic Data" from ANSI/ASHRAE Standard 62-2001, Ventilation for Acceptable Indoor Air


Quality, plots the relationship between metabolic level and CO2 generation. The relationship can be represented as the following equations: CO2 generation in CFM = 0.00883 x MetsCO2 generation in L/s = 0.25 x Mets

M = Heat flux for one metabolic unit or "Met", 18.4 BTU/hr/sqft or 5.39 W/sqm, where the sqft or sqm area refers to body surface area At.

At = Body surface area for one "typical" occupant, sqft or sqm. For this analysis, HAP assumes the average adult male has a body surface area of 19.4 sqft (1.8 sqm) and the average adult female has a body surface area approximately 85% of that for the male (16.5 sqft or 1.53 sqm). HAP considers the typical space occupant to be an average of male and female body areas: 18.0 sqft or 1.67 sqm.

The equations above are the combination of two separate equations. Stating the equations separately helps to understand the formulation better. First, the heat flux per person in Mets is calculated as:

M = (Qtot BTU/hr/person) [1 Met / (18.4 BTU/hr-sqft)] [1 / (At sqft)]

Example: One occupant with activity level of "office work" has a sensible heat gain of 245 BTU/hr/person and a latent heat gain of 205 BTU/hr/person. Therefore, the total heat gain is 450 BTU/hr/person and the metabolic rate per person is:

M = (450 BTU/hr/person) (1/18.4 BTU/hr/person) (1/18.0 sqft) = 1.36 Met/person

Second, the correlation between metabolic rate and CO2 generation, obtained via a curve fit of ASHRAE Standard 62 data is:

CO2 generation in CFM = 0.0088 x M

CO2 generation in L/s = 0.25 x M

B. CO2 Mass Balance for Zones

Once the CO2 generation rate for zone occupants is known, a CO2 mass balance can be performed for each zone in the system to estimate the CO2 level measured by a CO2 sensor in the zone. This mass balance assumes a steady state level of CO2 will be reached each hour. The mass balance is as follows:

0 = CO2 in supply air entering zone

- CO2 in direct exhaust air leaving zone.

- CO2 in return air leaving zone via the return plenum or return duct.

+ CO2 in infiltration air entering the zone.

- CO2 in exfiltration air leaving the zone.

+ CO2 generated by occupants in the zone.

To solve this equation for the zone CO2 level, the CO2 level in supply air is assumed. Later this assumption will be checked and if necessary, the calculation will be repeated with an adjusted assumption. Knowing the supply CO2 level, all the airflows and the CO2 generation by occupants, the equation can be solved for the zone CO2 level.

C. Determining Outdoor Damper Position and Outdoor Airflow

To determine outdoor damper position the DCV controller will first scan CO2 measurements by all zone CO2 sensors and identify the highest CO2 level. It then uses this CO2 reading to determine the indoor-outdoor CO2 differential:

CO2 Differential = (Highest Zone CO2 Level) – (Outdoor Air CO2 Level)


This CO2 differential is used with the DCV control profile to determine the required outdoor ventilation airflow.

The figure below shows a sample control profile. In this example the outdoor CO2 level is 400 ppm. The minimum CO2 differential is 100 ppm, which equates to a CO2 level of 500 ppm and corresponds to a base ventilation rate of 810 CFM. The maximum CO2 differential is 700 ppm, which equates to a CO2 level of 1100 ppm and corresponds to a design ventilation rate of 2700 CFM. The DCV controller sets the outdoor damper position as follows:

• If the CO2 differential determined by the DCV controller is less than the minimum setting of 100 ppm (which equals a CO2 level of 500 ppm), the outdoor dampers will be set to provide the base ventilation rate of 810 CFM.

• If the CO2 differential is greater than the maximum setting of 700 ppm (which equals a CO2 level of 1100 ppm), the outdoor dampers will be set to provide the design ventilation airflow of 2700 CFM.

• If the CO2 differential is between the minimum and maximum settings, then the outdoor dampers will be set to provide the airflow corresponding to the control profile. Thus, outdoor airflow is a linear function of CO2 differential in this range and ranges between the minimum (810 CFM) and maximum (2700 CFM) values.

D. Calculation of System CO2 Levels

Next, the program uses the zone CO2 data from part C and the outdoor ventilation airflow data from part D to calculate CO2 levels in the remainder of the system. This requires starting at the return grilles of all zones and working along the airflow path to determine CO2 levels at all state points in the return portion of the system, and then into the supply portion of the system.

For example, return air from the zones mixes in the return plenum or duct to yield a mixed CO2 concentration in return air. Return air mixes with outdoor air, to provide a mixed CO2 concentration in supply air, which is delivered to the zones.

E. Evaluation of Results and Iteration

Finally, the supply air CO2 level produced by part D is compared with the initial assumption for supply air CO2 level that was made at the start of the CO2 balance calculation in part B. If the two values differ by more than 10 ppm, the calculation in parts B, C and D is repeated using the new supply air CO2 value. In this way the program iterates to converge on a solution in which the outdoor air flow, system CO2 levels and zone CO2 levels are all balanced and consistent for the hour.


Understanding Zone Loads and Zone Conditioning Have you ever examined a HAP Air System Design Load Summary output and wondered ‘what is zone conditioning and why is it different from the total zone load?’ Judging from questions our support staff receives, many people have wondered the same thing. The answer to this question requires an explanation of the ASHRAE Transfer Function and Heat Extraction methods.

Understanding the calculation methods used by computerized engineering tools is vital to the successful use of these tools. As these tools use increasingly complex analytical methods, the methods become more difficult to grasp. This article attempts to aid understanding of the load calculation method used in Carrier’s Hourly Analysis Program (HAP) by explaining the transfer function and heat extraction methods in plain language and without the use of mathematical equations. If at the end of this discussion you understand what “zone conditioning” and “zone load” refer to and why they are different, the article will have been successful.

Objectives. First, we need to clarify our objectives for a load calculation tool. As HVAC system designers, we want:

• A calculation tool which will account for all of the processes involved with building heat flow, • A tool that is fast, • A tool that is easy to use, and • A tool that provides accurate, reliable results.

Understanding the Processes at Work. Providing accurate, reliable results requires accounting for all of the complicated heat flow processes occurring in the building. For the explanations of the Transfer Function and Heat Extraction Method later in this article to make sense, we first need to provide a quick refresher on the heat flow processes that occur in a building.

First of all, our ultimate interest is in cooling or heating loads. A “load” is the rate of heat transfer to or from the air in the building. Heat transferred to air in a room changes the room air temperature. These changes are sensed by a thermostat, which sends a signal to the HVAC equipment to provide cooling or heating.

Secondly, we are all familiar with the different sources of heat gain or loss, which influence cooling or heating demands in the building. These include solar radiation, temperature gradients across walls, heat gain from lighting, people, etc.

Therefore, we know where the heat originates (the sources) and we know where it ultimately ends up (in the air in the building). The challenging part of this engineering problem is analyzing how heat travels from its source to its destination.

As an example, let us consider the wall component of a cooling load. First, the outside surface of the wall is warmed by solar radiation and ambient air. This initiates heat flow across successive layers in the wall assembly. Heat does not flow instantaneously from outside to inside surfaces of the wall. Instead, it takes time. In addition, the amount of time depends on the intensity of heat flow at the outer surface plus the thickness, density, specific heat and thermal conductivity properties of material layers in the wall assembly.

Ultimately, heat reaches the inside surface of the wall where it raises the wall surface temperature. At this point two things happen. First, a portion of the heat is convected to air in the room, raising the air temperature. Thus, this heat has become a cooling load. Second, a substantial portion of the heat at the wall surface is transferred as thermal radiation to other wall, ceiling and floor surfaces in the room. This raises the temperature of the other surfaces and triggers convection to room air, heat storage within the material and further radiative exchanges within the room. Eventually most or all of the original heat flow becomes a cooling load, but the complete conversion of the heat to cooling load takes time.

The same sort of thermal processes occur for heat flow through roofs, windows, doors and partitions. Heat from other sources such as solar, lighting, electrical equipment and occupants is introduced directly into the room, and once in the room it undergoes the same sort of room heat


transfer processes described for walls. This is because all these heat gains are comprised of separate convective and radiative components. The convective components immediately become cooling loads. The radiative components are transferred directly to surfaces in the room and then undergo further radiant, convective and heat storage processes.

In addition, an important factor governing heat flow to the air in the room is the temperature of the room air. The temperature difference between wall, ceiling and floor surfaces and the room air govern convection. Thus, for a cooling scenario, convective heat flow from warm room surfaces decreases as the room air temperature rises. As room air temperature falls, convective heat flow from warm room surfaces increases. Recognizing this is important for two reasons. First, all thermostats have a certain operating range within which they attempt to maintain room air temperature. Thus, room air temperature varies within this operating range and this influences convective heat flow. More importantly, nighttime setup control or equipment shutdown can cause room temperature to vary by 10 F (-12.2 C) or more during a 24-hour operating cycle. A large increase in room temperature greatly reduces convective heat flow. Heat is essentially “trapped” in the massive elements in the room, and the surface temperatures of these elements rise. In the morning when cooling equipment is turned on and room air temperatures are quickly reduced, there is a “rush” of convective heat flow due to the large temperature difference between room air and the surfaces in the room. This is what is known as a pull down load.

Therefore, in summary:

• There are many factors involved in building heat flow. • This heat flow occurs over time rather than instantaneously. • Room air temperature governs heat flow from surfaces in the room to the air in the room. • The nature of the thermostat control in a room influences the rooms cooling loads by affecting

convective heat flow.

Calculating Building Heat Flow. Now, in order to calculate realistic, accurate building loads, we need to account for all of the complicated processes we have just discussed. This is quite a challenge. One way to do this is with the “Heat Balance Method” which is essentially the “mother of all load calculation methods.” With this method, each of the heat flow processes is represented by a mathematical equation drawn from the laws of conduction, convection and radiation and from the first law of thermodynamics. The result is a large number of equations, and an equally large number of unknown quantities. Typically, no one equation can be solved directly. Instead, the whole set of equations must be solved simultaneously or by iteration. The results of this calculation are the temperatures and heat flows at each surface in the room, and ultimately the temperature and heat flow to room air, which tells us the cooling load. Currently, we cannot satisfy our original objectives of “fast” and “easy” with the Heat Balance Method because computer software using this method requires too much calculation time and too much input data. However, the day is fast approaching when this method will become feasible for everyday use on desktop computers.

Until then, we need an alternate solution to our engineering challenge. That solution is the Transfer Function Method, first developed by researchers in the late 1960s. The Transfer Function Method uses several mathematical “tricks” to make solving heat balance equations much faster. While this method is faster, it continues to account for the complex processes involved in building heat flow and thus provides realistic, accurate results.

Here is how it works. Within the method, there are three kinds of transfer function equations used to analyze different aspects of the building heat flow problem:

• Conduction Transfer Function Equations are used to analyze the conductive heat flow through walls and roofs.

• Room Transfer Function Equations are used to analyze the radiative, convective and heat storage processes for all load components once heat reaches the interior of the room.

• Space Temperature Transfer Function Equations (aka Heat Extraction Equations) are used to analyze the effect of changing room temperatures on convective heat flow from


surfaces in the room to the room air. Included in this calculation is the behavior of the room thermostat in controlling room temperature levels and communicating demands to the cooling or heating apparatus.

These three kinds of transfer function equations are used in sequence to determine how heat from various heat sources is converted into cooling loads in the building.

However, there is one complicating factor that is crucial to this whole discussion. It has been said that there is “no such thing as a free lunch,” and that is certainly true in this case. As we noted earlier, the Transfer Function Method uses mathematical tricks to simplify and speed up the calculation process. The cost of increased speed is that the calculation has to be performed in two distinct stages. There are simply too many factors involved to be able to solve the entire problem in one pass when using the transfer function tricks.

In the first stage of this calculation process, we use the Conduction and Room Transfer Function Equations to calculate room loads as if the room is held at precisely one temperature 24 hours a day. For a design cooling calculation, the cooling thermostat set point is used as the fixed room temperature for this calculation. Once room loads based on this simplifying assumption have been determined, the second calculation stage “corrects” these loads to account for the true behavior of the building (rising and falling room temperatures) using the Space Air Transfer Function Equations.

In HAP, results of these two calculation stages appear throughout the system design reports. On the Air System Design Load Summary, all the results in the top portion of the report down to and including the “Total Zone Load” are from the first stage of the calculation, which assumed constant room temperature. The terms “zone load” and “space load” are used throughout the reports to refer to results from this first stage of calculations. The term “Zone Conditioning” is used to refer to the results of the second stage of calculations. The “Total Zone Loads” are corrected to produce “Zone Conditioning” by accounting for room temperature and thermostat effects. As such, Zone Conditioning represents the true amount of cooling or heating a room needs and is the basis for simulating operation of system components such as coils and fans. Results from the system simulation appear in the lower part of the Air System Design Load Summary. Differences between “Zone Loads” and “Zone Conditioning” are therefore due to the room temperature effects on heat transfer such as pull down loads and temperature variations within the thermostat throttling range.

Conclusion. The Transfer Function Method allows us to consider as many of the complex aspects of building heat flow as possible to provide accurate results, and at the same time provide a calculation tool that is fast and easy to use.

The price for these benefits is that the calculation must be performed in two distinct stages. The first stage yields what HAP calls “zone loads” and “space loads” which are calculated assuming a constant room temperature. The second stage yields what HAP calls “zone conditioning” which is derived by correcting the original zone loads to account for room air temperature effects. Zone conditioning represents the true demand for cooling or heating in a zone. Understanding this two-stage process and the results it yields is important for successfully applying program results.♦


Pitfalls of Economizer Operation Q. I am designing a single zone CAV air handling system that includes an integrated dry-bulb economizer. When I run design calculations with HAP I find that the peak cooling coil load listed on the Air System Sizing Summary is 23.2 Tons. Further, it occurs at the peculiar time of July 0900. I also notice that an unusually large portion of this coil load is latent cooling. If I run the design calculations for the same system without an outdoor air economizer, the peak load is 17.0 Tons, it occurs at July 1500 and it has a more reasonable sensible heat ratio. This indicates that an economizer increases rather than decreases the load, which is illogical. What is happening here?

A. This case illustrates one of the pitfalls of outdoor air economizer operation. While economizer controls can provide significant energy and cost savings, they can also cause problems under certain conditions, increasing rather than decreasing mechanical cooling requirements. This article explains how these problems occur and how such problems can be diagnosed and corrected using HAP or the System Design Load Program.

Diagnosing the Problem. The peak coil load conditions described above represent snapshots of system operation for single points in time. While such snapshots are useful for identifying a problem, such as an unusual peak load time or an unusual sensible heat ratio, diagnosing the problem requires more detailed data. When diagnosing results it is often useful to generate 24-hour profiles of data to gain a broader view of operating behavior.

Figure 1 shows the 24-hour cooling coil load profiles for the system in this case study with and without an economizer. Data in the graph was obtained from the Hourly Air System Design Day Loads output. Figure 2 shows the 24-hour dry-bulb and wet-bulb profiles for the July design day. This data is for Chicago and was obtained from the Cooling Design Temperature Profiles output. In addition, the following outputs will be required to provide supporting data for our investigation:

• Air System Design Load Summary for July 0900. • Hourly Zone Design Day Loads for July

Figure 1 shows that the system with the economizer experiences an odd increase in cooling loads for 0700, 0800 and 0900. For the remainder of the day, coil loads for the systems with and without economizer have identical values.

To determine the cause of this behavior, let us focus on system behavior for 0900. The Air System Design Load Summary for the system with economizer shows that the ventilation and supply airflow rates are equal for this hour. Therefore, the outdoor air economizer is operating and is fully open. The Hourly Zone Design Day Loads output shows that the zone air is at 77.7 F and 44% RH for 0900. Using plenum load data from the Air System Design Load Summary the return air condition (after the plenum) can be computed. The return air condition is 80.2 F (26.8 C) dry-bulb, 63.7 F (17.6 C) wet-bulb. This equates to a specific humidity of 0.0091 lb/lb (kg/kg). The outdoor air condition for this hour is 79.8 F (26.6 C) dry-bulb, 70.0 F (21.1 C) wet-bulb for a specific humidity of 0.0138 lb/lb (kg/kg).

An integrated dry-bulb economizer activates whenever the return air dry-bulb is equal to or warmer than the outdoor air dry-bulb. Therefore, for July 0900 the economizer control should be activated. The economizer damper will modulate to the fully open position since it cannot eliminate mechanical cooling completely for this operating condition. While this will reduce the sensible cooling coil load by using outdoor air that is slightly cooler than return air, it introduces a large volume of outdoor air with high moisture content. As a result, the latent component of the cooling coil load soars. The increase in the latent load outweighs the reduction in the sensible coil load, and the ultimate result is a large increase in the total coil load.



This case illustrates the fact that at marginal conditions in which the outdoor air dry-bulb is only slightly cooler than the return air temperature, and outdoor air is relatively humid, integrated dry-bulb economizer control can increase rather than decrease system cooling coil loads. This case also illustrates one of the benefits of the system-based design approach used by HAP and the System Design Load Program. By considering specific components and controls in the design calculation, potential problems can be identified while the system is being designed

Correcting the Problem. There are several solutions to this problem:

• Use temperature cutoff limits on economizer operation. For example, if a cutoff of 75 F (23.9 C) is used, the economizer will not operate when the outdoor temperature is warmer than 75 F (29.3 C), even if the return air temperature exceeds the outdoor temperature. This cutoff helps to prevent economizer operation for marginal situations that lead to the problems discussed above. However, choosing a cutoff temperature, which will guarantee that all such problem conditions are avoided, is difficult and is highly application-dependent.

• Use an integrated enthalpy economizer control. With this control, return air enthalpy is compared with outdoor air enthalpy to determine when to activate the economizer. Because enthalpy accounts for the sensible and latent heat of air, the marginal conditions that lead to operating problems will be avoided.

• Use non-integrated control. This dry-bulb economizer control is only activated when the outdoor air is equal to or cooler than the supply air temperature. Since this control will not activate the economizer until all mechanical cooling can be eliminated, marginal situations involving partial free cooling are avoided. However, this solution sacrifices the large number of operating hours at warmer outdoor air temperatures for which an integrated economizer can reduce mechanical cooling demands.

Other Problem Situations. A similar sort of problem can occur for integrated enthalpy economizer controls used in hot, dry climates for marginal conditions. This type of control activates when the return air enthalpy is equal to or greater than the outdoor air enthalpy. In a hot, dry climate, it is possible for outdoor air enthalpy to be less than return air enthalpy; while at the same time the outdoor air dry-bulb is warmer than the return air dry-bulb. The enthalpy economizer will activate for such a condition, and will open fully. Outdoor air will eliminate the latent component of the cooling coil load, but can cause the sensible component to increase significantly.

The symptom of this problem in design load calculations is similar to that for integrated dry-bulb controls - a peak load at an unusual time of day. The problem can be diagnosed using the same procedures discussed for the dry-bulb economizer. And the solutions are similar: impose cutoff points for operation, or switch to a different type of control better suited for the climate.♦


Differences Between Peak Coil Load CFM, Max Block CFM, Sum of Peak Zone CFM In the cooling coil section of the HAP Air System Sizing Summary printout, three coil airflow rates are listed: (1) the coil airflow for the time when the maximum coil load occurs, and (2) the maximum block airflow rate and (3) sum of the peak zone CFM (L/s). When analyzing VAV systems, these three airflow rates can often differ. This article explains why. An accompanying article provides recommendations for selecting equipment in these situations.

In most cases, the coil airflow rates differ in VAV applications for one of the following two reasons:

• The peak cooling coil load and peak zone sensible load occur at different times, resulting in different coil airflow rates at these times.

• Due to the ASHRAE sizing methodology used by HAP, the two airflow rates are computed using slightly different considerations. This can introduce small differences between the two airflow values even if the coil load and zone sensible load peak at the same time.

Each reason will be explained separately below.

Differences Due to Timing of Peak Loads. The maximum airflow rate required for the supply fan and therefore for the central cooling coil depends on the cooling requirements in zones served by the air system. The individual component loads in the zones such as wall, roof, window, solar, lighting, people and equipment loads influence zone cooling requirements. These loads vary due to changes in outdoor air temperature, solar radiation and internal heat gains throughout the day.

While the maximum cooling coil load is influenced by these same zone cooling requirements, it is also influenced by extra heat gains introduced by outdoor ventilation air, fan heat, return plenum heat, and the latent components of the coil load.

Because extra factors influence the coil load, it is possible for the maximum coil load to occur at a different time than the peak zone sensible load occurs.

In a VAV system, the coil airflow varies as zone cooling requirements vary. Therefore, if the peak cooling coil load and peak zone sensible load occur at different times, the coil airflow rates for the two times will differ. The following simple example illustrates how this situation can occur.

Example #1. Consider a 1-zone VAV system that serves an east-facing zone. Figure 1 shows 24-hour profiles for the total cooling coil load and the zone sensible load for this system. The zone has a large area of east-facing glass. Consequently, solar heat is the dominant load component and causes the peak zone sensible load to occur at 9 am.

The total cooling coil load in this example is strongly influenced by ventilation loads, which peak during the mid-afternoon hours. Since the outdoor air temperature is relatively cool at 9 am versus mid-afternoon, the peak coil load occurs at 2 pm rather than 9 am. When the peak zone sensible load occurs at 9 am, the zone requires 5154 CFM of supply air. When the cooling coil load peaks at 2 pm, the zone sensible load has dropped to approximately 80% of its peak value and the zone requires only 4100 CFM of supply air. For such a situation, HAP will report the following data on the Air System Sizing Summary output

Peak coil load occurs at: ............. Jul 1400 Coil CFM (L/s) at Jul 1400: ......... 4100 CFM (1935 L/s) Maximum block CFM (L/s): ......... 5154 CFM (2432 L/s) Sum of peak zone CFM (L/s)……5369 CFM (2534 L/s)

The Sum of the peak zone CFM (L/s) is useful for judging diversity in VAV systems and for sizing components for special periods when all VAV box dampers are full open at the same time.

Differences Due to Methodology. The ASHRAE design procedure, which utilizes the transfer function method and heat extraction techniques, requires a two-stage calculation:


1. First, zone sensible loads are computed assuming the zone is held exactly at the cooling thermostat set point 24 hours per day. Results from this analysis are used to determine peak zone airflow rates and the peak central coil airflow rate.

2. Second, the program simulates system operation. When doing so, it takes the zone loads calculated in the first stage and corrects them for the actual system operating conditions. These corrections account for the use of different thermostat setpoints during occupied and unoccupied periods or the shutdown of cooling during the unoccupied times, and for the existence of a throttling range for the thermostat. Considering these real-life system operating factors changes the thermal dynamics of the system, causing zone temperatures to vary within the thermostat throttling range and introducing pulldown load components at certain times of day.

The "Max block CFM (L/s)" is calculated in stage 1 and is therefore based on the idealized zone loads computed in this stage. The coil airflow at the peak coil load time is obtained from stage 2, and is therefore based on the corrected zone loads computed considering the actual system operating conditions. Because the two airflows are computed using slightly different considerations, differences between the two airflows often occur for VAV systems. The following example illustrates these method-based effects.


Example #2. Consider a VAV system that serves four zones. Hourly profiles of the total coil load and the zone sensible block load are shown in Figure 2. Here "block load" refers to the sum of the sensible loads for all four zones. The maximum zone sensible block load occurs at 5 pm in July. Based on this block load, the required coil airflow rate is 13269 CFM. The maximum cooling coil load also occurs at 5 pm in July. For this hour the coil airflow rate is 12355 CFM.

Therefore, on the Air System Sizing Summary, HAP will report:

Peak coil load occurs at .............. Jul 1700 Coil CFM (L/s) at Jul 1700 .......... 12355 CFM Max block CFM (L/s) ................... 13269 CFM

In this example, the 900 CFM (425 L/s) difference between airflows is due to the different considerations used to calculate the required fan airflow in stage 1 of the analysis, and the coil airflow during the system simulation in stage 2 of the analysis. Further investigation of the results showed that the zone air temperatures are close to 76 F (24.4 C), which is the upper limit of the thermostat throttling range for this example. For the initial zone loads calculated in stage 1 of the analysis, a thermostat setpoint of 75 F (23.9 C) was used. The difference in zone air temperatures used in the two calculations (75 F [23.9 C] versus 76 F [24.4 C]) and its effect on zone thermal dynamics ultimately results in lower coil airflow.

The important thing to recognize is that each airflow is computed for different purposes and therefore uses different considerations. The maximum coil airflow is derived as part of the zone and fan airflow sizing calculation, which considers idealized conditions. The coil airflow at the time of the peak coil load is derived as part of the cooling coil analysis. This analysis considers all of the operating factors of the system, most notably the interaction between the zone thermostats and the VAV box dampers, and between zone air temperature and room loads.


Further Information. Differences between maximum coil airflow rate and coil airflow rate for the peak coil load time can also occur for Multizone, Bypass Multizone and Dual Duct CAV systems, and for single-zone constant volume systems using fan cycling.

Selecting Equipment When Coil CFM (L/s) Differ The preceding article describes situations in which the maximum coil airflow rate differs from the airflow rate at the time of the peak cooling coil load. When this happens, a design engineer is faced with the dilemma of which airflow rate to use when selecting equipment. This article provides recommendations for dealing with this equipment selection situation.

Central Cooling Coils in VAV Systems. First, the packaged unit or the cooling coil for a built-up unit should be selected using the airflow at the time of the peak coil load [listed as "Coil CFM (L/s) at month/hour" in Table 1 below]. This airflow is obtained from the system simulation and corresponds to the total load, sensible load and entering and leaving temperature conditions in the table. Thus, in order to use consistent coil performance data for selection, the "Coil CFM (L/s) at month/hour" item must be utilized.

Second, use the fan motor BHP or fan motor kW data reported in the "Supply Fan Sizing Data" section of the Air System Sizing Summary to select the fan motor.

Third, verify that the selected fan can operate at the maximum fan airflow rate without exceeding its maximum RPM value. The maximum fan airflow is reported in two places on the Air System Sizing Summary. It appears in the "Central Cooling Coil Sizing Data " table as "Max block CFM (L/s).” It also appears in the "Supply Fan Sizing Data " table as "Actual max CFM (L/s)". The Sum of peak zone CFM (L/s) is provided for those who wish to take further precautions.

Finally, in certain applications, it may be necessary to use product literature to verify that excessive water carry-over will not occur when the coil experiences its maximum airflow rate.

Recommendations for Other System Types. Differences between the maximum coil airflow and the coil airflow at the peak coil load time can also occur for Multizone, Bypass Multizone, and Dual Duct CAV systems. For these systems, the cooling coil should be selected using the airflow at the peak coil load time. Make sure the coil will not have excessive water carryover when operating at maximum airflow. To select the fan, the maximum fan airflow should be used since the fan supplies air to both cold and hot decks. ¨

Table 1


How Ventilation Loads are Calculated in HAP Q. On the Air System Design Load Summary printout, the outdoor ventilation CFM and the corresponding design cooling and heating ventilation loads are listed. I have not been able to duplicate these load calculations by hand. Can you explain why?

A. On the Air System Design Load Summary report, the ventilation line item contains six separate values:

• The cooling ventilation CFM (L/s) • The cooling sensible ventilation load. • The cooling latent ventilation load. • The heating ventilation CFM (L/s) • The heating sensible ventilation load. • The heating latent ventilation load.

Equations and considerations involved in the calculation of these values are explained below. With this information, you should be able to duplicate computer calculations by hand.

Ventilation CFM (L/s). The cooling ventilation airflow rate is for the month and hour for the cooling data on this printout. A separate airflow is listed for the design heating condition. In certain types of systems, the cooling and heating values will differ. For example, in a VAV air system using proportional control for ventilation air, the outdoor ventilation airflow varies as a constant percentage of supply fan airflow. Because the supply fan airflow rates for design cooling and heating conditions differ, ventilation airflow rates will differ. It is important to use the appropriate ventilation CFM (L/s) when calculating ventilation loads by hand.

Cooling Sensible and Latent Loads. A ventilation load is the net heat gain or loss for the system due to outdoor ventilation air entering the system and exhaust air leaving the system. For conditions at sea level in which no direct exhaust is used, the common ventilation equations are:

Qvs = 1.08 Voa (Toa - Tex) Qvl = 4746.6 Voa (ωoa - ωex)

In SI Metric units, these equations are:

Qvs = 1.207 Voa (Toa - Tex) Qvl = 2946.7 Voa (ωoa - ωex)

where:

Qvs = Sensible ventilation load, BTU/hr or W. 1.08 = Product of air density, specific heat of air and a units conversion factor in

English Units. For sea level conditions. = (0.075 lb/cuft)(0.24 BTU/lb-F)(60 min/hr) 1.207 = Product of air density, specific heat of air and a units conversion factor in SI

Metric units. For sea level conditions. = (1.201 kg/m3)(1004.8 J/kg-K)(m3/1000 L) Voa = Outdoor ventilation airflow rate, CFM or L/s. Toa = Outdoor air temperature, F or C. Tex = Exhaust air temperature, F or C. Qvl = Latent ventilation load, BTU/hr or W. 4746.6 = Product of air density, heat of vaporization for water and a units conversion

factor. For sea level conditions. = (0.075 lb/cuft)(1054.8 BTU/lbm)(60 min/hr) 2946.7 = Product of air density, heat of vaporization for water and a units conversion

factor in SI Metric units. For sea level conditions. = (1.201 kg/m3)(2453.5 x 103 J/kg)(m3/1000 L) ωoa = Outdoor air specific humidity, lb/lb or kg/kg. ωex = Exhaust air specific humidity, lb/lb or kg/kg.


When solving these equations, be aware of the following:

• The air density value used by the program is adjusted for site elevation. Thus, for sites not located at sea level, factors other than 1.08, 1.207, 4746.6 and 2946.7 are used. Equations used to adjust air density for elevation are discussed in the program help system and the Design Load User's Manual for HAP.

• The value of Tex is sometimes difficult to determine. First, the zone air temperature is often not equal to the cooling setpoint. Instead, it varies within the thermostat throttling range. Both the System Psychrometrics and Hourly Zone Design Day Cooling Loads reports list zone temperatures. For multiple zone systems, the mixed temperature for air exiting the zones must be considered. The System Psychrometrics report lists this value for air mixed from all the zones.

• In addition, after leaving the zone, air temperature can be affected by plenum heat gains and losses, return fan heat gain, duct leakage and heat transfer in ventilation reclaim devices. The effect of these heat gains or losses is shown on the System Psychrometrics report, culminating in the calculation of the exhaust air temperature Tex.

• If direct exhaust air is used, air will be exhausted from the system at two or more different temperatures (e.g. air directly exhausted from the zone and air exhausted after picking up plenum and other heat gains). Equations used in this situation are discussed in program help system and in the Design Load User's Manual for HAP.

Design Heating Sensible Load. The basic equations used for the heating analysis are the same as for the cooling sensible analysis, but with one exception. The convention that a positive heating load represents a heat loss requires that the position of the temperature and humidity values in the equation be switched:

English Units: Qvs = 1.08 Voa (Tex - Toa)

Qvl = 4746.6 Voa (ωex - ωoa)

SI Metric Units: Qvs = 1.207 Voa (Tex - Toa)

Qvl = 2946.7 Voa (ωex - ωoa)

When solving these equations, be aware of the same considerations mentioned for cooling:

• Air density adjustment for altitude.

• Problems with determining Tex.

• Complications introduced by direct exhaust air.

As with cooling, the System Psychrometrics report lists the key temperature and humidity components used in these calculations. ♦


System Based Design Load Calculations In HAP, two of the important concepts in design load calculations involve the use of the ASHRAE heat extraction method and "system-based" sizing techniques. Both are concepts that have been used since HAP 3.0, but it is useful to review them since it is important to understand the principles and procedures involved as well as their effects on results. In this article the system sizing procedures used in HAP will be explained with emphasis on the roles heat extraction calculations and system-based sizing play.

Definitions. Before beginning, it will be useful to provide brief definitions of heat extraction and system-based sizing:

• Heat Extraction Procedures represent the second part of the two-step ASHRAE-endorsed transfer function load method. The first part is the basic transfer function calculation, which accounts for the transient nature of the processes that convert heat gains to cooling loads. Heat gains usually do not instantly become cooling loads, but rather involve a time delay due to heat storage. However, the loads calculated with the basic transfer function equations are based on the idealized assumption of a constant room temperature 24 hours per day. Heat extraction procedures are used to take the calculation one step further considering the effect of varying zone temperatures during the day (such as set-up or shutdown periods at night) and how air-conditioning systems and thermostat controls respond to load conditions. The most compelling reason to include heat extraction in design calculations is that they provide a way to obtain realistic, accurate estimates of pulldown loads.

• System-Based Design considers system specifics when sizing systems. Many load estimating programs deal with systems in a generic manner. Thermostat setpoints, supply air controls and fan characteristics are specified without being associated with a specific system control such as variable air volume (VAV) or constant air volume (CAV). However, different sizing procedures are needed for VAV and CAV. With a generic approach, it is up to the user to decide how to use program outputs to size a specific type of system. With HAP, sizing calculations and outputs are tailored to the system type specified by the user, thus making the results more accurate and easier to use.

Sizing Overview. In HAP, sizing calculations are performed for all system types using the following three-step procedure:

• Size Zone Airflows. Zones are dealt with separately to determine peak sensible loads and required airflow rates.

• Size Supply Fan Airflow. Zone airflow requirements are then combined to determine the maximum supply fan airflow requirement.

• Size Coils. Given user specifications of air system characteristics plus the calculated zone and fan sizing data, the program simulates operation of the system for design cooling conditions each month. A simulation is also performed for the design heating condition. Coil loads resulting from these simulations are inspected to identify the maximum load for each coil in the system. These are reported on program outputs.

In the paragraphs below, each of these steps will be discussed in detail.


Step 1: Zone Airflow Sizing. The goal of this step is to identify the maximum sensible load and maximum airflow rate for each zone in the system. To do this the program deals with each zone separately. Using space and zone input data and ASHRAE transfer function procedures; the program calculates heat gains for all heat sources in a zone and converts the heat gains to "cooling loads". Per ASHRAE procedures, these cooling loads are based on the assumption that cooling equipment operates 24 hours per day and that the zone is maintained exactly at the cooling thermostat setpoint. Thus, these cooling loads are idealized unless the system will actually operate this way. This simplifying assumption will be compensated for later during the coil simulations using the heat extraction procedure.

After calculating loads for all design cooling months specified, the program searches the data to identify the maximum zone sensible cooling load. For a given supply air temperature, the program calculates the required airflow rate to satisfy this load.

Results of the zone airflow sizing analysis appear on the Zone Sizing Summary report. Zone sensible loads from this analysis also appear on the Air System Design Load Summary, Zone Design Load Summary and Hourly Zone Design Day Loads reports. On these reports, the cooling loads are interchangeably referred to as "zone load" and "zone sensible.”

Step 2: Fan Airflow Sizing. The goal of this sizing step is to determine the maximum airflow requirement for the central supply fan. This is the first calculation in which system-based sizing is involved. For a CAV system, the program adds peak CFMs (L/s) for all zones to determine the required supply fan airflow. For VAV systems, the program identifies the peak coincident CFM (L/s). This is done by first using zone sensible load data from the previous step to determine require airflow rates for each hour of the day. Hourly airflow requirements for each zone are then added together to build a fan airflow profile. Finally, the program searches this profile to find the maximum airflow rate.


Figure 1 illustrates this calculation for a VAV system. Zone airflow rates are shown in this figure for an east-facing zone and a west-facing zone. For each hour, the sum of east and west zone airflow rates is the required fan airflow rate. In Figure 1, the east zone peaks at 0900 with a 6252 CFM (2950 L/s) requirement, the west zone peaks at 1700 with a 6989 CFM (3298 L/s) requirement, and the supply fan peaks at 1600 with a 10213 CFM (4820 L/s) requirement. Note that this VAV fan airflow is 23% less than the 13241 CFM (6248 L/s) that would be required for a CAV system. Because a VAV system can take advantage of load diversity, its design airflow can often be less than the sum of peak zone CFMs (L/s). When a VAV air system is specified in HAP, the system-based sizing procedure automatically considers this.

Step 3: Coil Sizing Calculations. The goal of the final sizing step is to determine maximum loads for all coils in the air system. Performing detailed simulations of air system operation for each design cooling month and the design heating condition does this. Air system input data, the airflow rates and zone sensible load profiles calculated in steps 1 and 2, and ASHRAE heat extraction procedures are used to perform these simulations. Simulations are specific to the type of system being dealt with and consider all system components and controls specified.

The zone sensible load profiles calculated in step 1 are the basis for system simulations. As noted earlier, these load profiles were calculated assuming 24-hour equipment operation and a constant zone temperature equal to the occupied cooling thermostat setpoint. Consequently, these load profiles must be adjusted using the ASHRAE heat extraction equations if cooling equipment is operated for less than 24 hours, if an unoccupied period set-up temperature is used, if cooling equipment is shut down during the unoccupied period and if a thermostat throttling range other than 0 F (-17.8 C) is used. The heat extraction calculations yield the amount of heat the air conditioning system must remove each hour to maintain the zone in the thermostat throttling range. Once zone heat extraction rates have been computed, this data serves as the basis for calculations of airflow rates, temperatures and humidity at all points in the air system. Finally, these results allow loads for coils in the system to be determined. For example, the cooling coil inlet and outlet dry-bulb temperatures and the coil airflow rate are used to calculate the sensible coil load.

Figure 2 provides sample results from a design simulation for a single-zone CAV air system. The figure provides a useful comparison between zone sensible loads, heat extraction rates (called "zone conditioning") and sensible and total cooling coil loads.

The "zone sensible" load profile represents sensible cooling loads assuming 24-hour equipment operation and a constant 75 F (23.9 C) zone air temperature. The "zone conditioning" profile represents heat extracted from the zone during the 6am-7pm operating period (from 8pm to 5am the cooling system is off). During this operating cycle, the zone air temperature varies within in the 75 F (23.9 C) - 78 F (25.5 C) throttling range during the 6am-7pm operating period, and floats at higher temperatures during the nighttime shutdown period. Heat extraction method estimates of zone air temperature are shown in Figure 3. As a result of this behavior, extra load is imposed on the air conditioning equipment to pull down the zone air temperature and to remove heat that has accumulated in the building mass during the nighttime period. This pulldown load is the principal reason for differences between the zone sensible and zone conditioning profiles in Figure 2. Note that these differences are most significant at the start of the operating period, but also continue throughout the 13-hour operating period.

The coil sensible profile in Figure 2 represents the sensible heat that must be removed at the central cooling coil. In addition to providing enough sensible cooling to meet zone-conditioning demands, the coil must also provide cooling to offset fan heat gain, sensible ventilation load and the portion of plenum heat gains that returns to the coil. These factors cause the coil sensible profile in Figure 2 to exceed than the zone conditioning profile for all hours. Finally, the total coil load profile in Figure 2 represents total heat removal at the cooling coil. The difference between the total and sensible coil profiles is the latent cooling provided by the coil.


Results from the coil sizing analysis are reported on the Air System Sizing Summary. Zone conditioning and coil load data are also provided on the Air System Design Load Summary and Hourly Air System Design Day Loads reports. Zone temperatures and zone conditioning are listed on Hourly Zone Design Day Loads reports.

Implication: Performance-Based Coil Estimate. While it is useful to understand the sizing procedures used in HAP, it is even more important to recognize the implications of the procedures. The most significant of these is that the system simulation technique used yields a "performance-based" estimate of peak coil loads. By this, we mean that the calculation considers all system controls and operating variables. Perhaps most important among these is the variation of zone temperature.

As noted earlier, zone temperature will vary during the unoccupied set-up or shutdown period, and within the thermostat throttling range during the occupied period. In Figure 3, for example, zone temperatures lie toward the upper end of the 3 F (-16.1) thermostat throttling range during the 13-hour occupied operating period. This is not necessarily always the case. If unoccupied cooling at a set-up temperature was provided, or 24-hour cooling was provided, the pulldown load component would be less severe or eliminated altogether and zone temperatures would tend to lie closer to the bottom of the throttling range.

These temperature variations may or may not be desired by the designer. On one hand, some designers wish to consider actual operating characteristics in the calculation, including zone temperature variations, and are therefore comfortable with a performance-based calculation. Others may want to use idealized conditions with the zone temperature fixed exactly at a single setpoint temperature.



While the performance-based nature of the coil simulations cannot be eliminated completely, using a throttling range of 0.1 F (-17.7 C) can minimize it. Note that a finite throttling range is required by the heat extraction method. Without it, the analysis cannot be performed and pulldown loads cannot be computed; 0.1 F (-17.7 C) is the minimum allowed by the program. Using this throttling range will have an effect both on the zone conditioning and cooling coil loads calculated, as well as the estimates of zone temperatures. Results from the single-zone CAV example for both 3 F (-16.1 C) and 0.1 F (-17.7 C) throttling ranges are shown in Figures 4 and 5. Use of the 0.1 F (-17.7 C) throttling range results in a peak cooling coil load that is 4% larger than the 3 F (-16.1 C) throttling range case. It also results in estimated zone temperatures closer to the 75 F (23.9 C) cooling setpoint as shown in Figure 5.

Thus, system based design using the heat extraction method offers powerful, sophisticated capabilities to user. But to successfully use the heat extraction method, a designer must understand the procedure and its implications.


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APPENDIX “D”Technical White Papers


Appendix “D” The Benefits of System-Based Design


Introduction In 1993 Carrier incorporated system-based design features in its Hourly Analysis Program (HAP) software. At the time, system-based design was a new concept that allowed the computer to do a more complete and accurate job of sizing equipment than the traditional load estimating approach. Ten years later, this approach still yields significant benefits to HVAC system designers because of the productivity advantage it offers. And even today it still serves to differentiate HAP from other load estimating and system design software on the market. This paper explains system-based design and its benefits. First the paper discusses how traditional system design methods work and the shortcomings of the traditional approach. Next, the concept of system-based design is explained, and the benefits it offers are explored. How Traditional System Design Methods Work Many computer programs used for HVAC system design are based on a traditional approach that manual methods use. First, the engineer inputs weather data, information about the building construction, internal loads and layout, and HVAC sizing parameters. The latter includes such things as thermostat setpoints, the required supply temperature and the required outdoor air ventilation rate. Using this data the program then: • Computes zone sensible cooling loads for all zones for a series of design cooling months. • Identifies the maximum zone sensible load for each zone in order to calculate required zone

airflow rates and the required supply fan airflow rate. • Calculates central cooling coil loads for the months being considered in order to identify the

maximum cooling coil load. • If the system also provides heating, calculations are performed to determine the maximum

heating coil load. This procedure yields data useful for sizing terminal diffusers, the supply fan, the central cooling coil, and the central heating coil.

Shortcomings of the Traditional Approach It is important to note the traditional approach does not explicitly consider the type of HVAC system being designed. This approach is acceptable when designing simple CAV or VAV systems. However, when an HVAC system with special features, components or aspects of operation is involved, the traditional approach has two important flaws. First, it leaves a gap between what the engineer needs to design the system fully, and what the program provides as sizing data. Different types of HVAC systems contain different components which each need to be sized. Further, different types of HVAC systems require different sizing procedures. Therefore defining the system type is necessary to determine the components to be sized and the procedures to be used. The following examples illustrate this point: • A single zone CAV system requires that the supply diffusers, supply fan and the central

cooling and heating coils be sized. The supply fan airflow is equal to the required airflow for the single zone.

• A VAV Reheat system serving multiple zones requires that supply diffusers, the supply fan,

the central cooling coil and the terminal reheat coils be sized. The supply fan is sized for the


diversified peak airflow to zones, rather than the sum of zone airflows. The terminal reheat coils are sized using a procedure that is different from sizing a central heating coil.

• A VAV Fan Powered Mixing Box system serving multiple zones requires that supply diffusers,

mixing box terminals, the supply fan and the central cooling coil be sized. Unlike other systems, the terminal equipment for this system includes both a fan and a reheat coil, both of which must be sized. Sizing procedures differ slightly depending on whether a series mixing box or parallel mixing box terminal is used.

• A 2-Fan Dual Duct VAV system serving multiple zones requires that supply diffusers, mixing

box terminals, the cold deck supply fan, the hot deck supply fan, the cold deck cooling coil and the hot deck heating coil all be sized. This system contains a unique configuration of components not found in other systems. Procedures tailored to this type of system must be used to properly size the equipment.

The second problem with the traditional approach involves accuracy. If the traditional approach is used to size a system such as series Fan-Powered Mixing Box or 2-Fan Dual Duct, additional hand calculations will be required to size components not addressed by the calculation. These additional hand calculations make the design more difficult, more time consuming and prone to error. In more complex situations, sizing is often approximated to save time. Thus, the traditional approach plus hand calculations is often less accurate than a computerized approach that considers system type and does a complete job.

System-Based Design and How It Works The system-based design approach considers the unique features of the HVAC system being designed and then tailors the load estimating and sizing procedures to that system. It can therefore provide specific, accurate sizing information for each component of the system. If a Series Fan Powered Mixing Box system is being designed, for example, the system-based approach will provide the information necessary to size the terminal mixing boxes, their fans and heating coils. It will also consider the special operating features of the system to determine accurate primary supply fan and primary cooling coil sizes. In this way sizing methods and output data are customized to each specific system type. By providing system-specific sizing data, the system-based design approach can bridge the gap between what an engineer needs and what a computerized system design program provides. How It Works. The information a designer must supply to initiate the design process is similar to the traditional approach. The engineer must: • Input weather data. • Input building construction, internal heat gain and layout information. • Define the HVAC system. In addition to thermostat setpoints and sizing criteria, the engineer

specifies exactly what type of HVAC system is involved and its attributes. For example, it could be VAV Reheat, VAV with baseboard heat, Series Fan Powered Mixing Box, Dual Duct VAV, etc...

Next, the system-based design computer program calculates loads and sizes system components:


1. Zone Load Calculation. The program first calculates hourly zone sensible cooling loads for all zones for the design cooling months being considered.

2. Zone Airflow Sizing. The program then identifies maximum zone sensible loads in order to

determine required zone supply airflow rates and required central fan airflow rates. For some systems, such as fan powered mixing box systems, special aspects of system operation may influence the required airflow rates.

3. System Simulation. Once system airflows have been determined, the program simulates the

hour-by-hour operation of the HVAC system and all its components to determine loads for all coils in the system. This mathematical simulation considers the interplay of component operation for the specific system being studied. Simulations are performed for the range of design cooling months specified by the designer and for the heating design condition.

4. Coil Sizing. Finally, the program searches results of system simulation to determine

maximum required size for each component coil in the system. Benefits of System-Based Design The major benefit of the system-based design approach, of course, is that it gives the engineer exactly what is needed to design a system. Specific sizing data is provided instead of raw material for further hand calculations. The result is increased productivity for the designer because the computer is being put to work more effectively. The computer does a complete job of system sizing, not a partial job. A related benefit is that the system-based approach does a more accurate and therefore reliable job of generating sizing data. This is because sizing calculations consider the specific operating nature of the system, not the features of a simple, generic system. Further, the approach can evaluate more operating conditions than can be checked by hand, so that the approach is more thorough and comprehensive. Finally, because detailed, dynamic system simulations are part of this approach, the method can potentially be used to investigate the effect on sizing of such devices and controls as: • Outdoor air ventilation energy recovery devices. • Outdoor air economizers. • Active dehumidification and humidification controls. • Night-time free cooling controls. Previously, such controls have only been evaluated in energy analysis simulations to determine effects on operating costs. But each can also have an effect on sizing which in turn can have a significant effect the first cost of the system.

CONCLUSION Even though the concept is no longer brand new, system-based design still represents a promising advance in the field of HVAC system design. It offers improvements in productivity and accuracy, and opens new avenues of investigation to the designer in the pursuit of the optimal design. Look for it when choosing your HVAC design tools.


The Benefits of 8760 Hour by Hour Building Energy Analysis


Introduction As energy costs rise, building owners are becoming increasingly interested in operating costs and energy efficiency. As a result, building energy analysis (BEA) is becoming an important tool in the HVAC design field. Currently many BEA tools are available to engineers. Most are in the form of computer programs and employ a variety of methods with different benefits. Among these, BEA tools such as Carrier's HAP program that use the 8760 hour-by-hour method can offer the greatest benefits because they yield highly accurate, sophisticated system comparisons. This article will discuss the benefits of 8760 hour building energy analysis by first explaining the basics of building energy analysis and the requirements for high quality BEA system comparisons. Then, major BEA methods will be evaluated with special emphasis on the benefits of 8760 hour-by-hour versus reduced hour-by-hour methods.

What Is Building Energy Analysis? Building energy analysis is the technique of estimating energy use and operating costs for a building and its energy consuming systems. In our industry, particular emphasis is placed on the energy use of a building's HVAC systems. The purpose of BEA is to compare the energy use and operating costs of alternate system designs in order to choose the optimal design. The analysis mathematically simulates the thermal performance of the building to determine cooling and heating loads. It then mathematically simulates the performance of HVAC equipment in response to these loads to determine energy use over the course of a year. Finally, energy data is used to calculate operating costs.

Requirements for High Quality Results. Successful building energy analysis relies on considering as many of the physical factors

influencing building loads and equipment performance as possible. The ultimate result of the analysis is a predicted operating cost. An accurate cost prediction relies on energy use data, which in turn relies on equipment simulations, which must be based on building load predictions, all of which must be accurate. Concisely stated, high quality results can be obtained when the analysis considers: 1. The Range and Timing of Weather

Conditions. Varying levels of temperature, humidity and solar radiation during the year influence building loads and equipment performance. In each geographical location conditions range from hot to cold, wet to dry and sunny to cloudy in different ways. Considering the actual ranges of these conditions and when they occur on a daily, monthly and yearly basis is crucial to producing accurate energy use results.

2. The Hourly and Daily Variation in

Internal Loads. Patterns of building use involving occupancy, lighting and equipment operation can change significantly from one day to the next. Considering these use patterns in their correct day-to-day sequence is important in generating accurate load data.

3. The Dynamic Nature of Building Heat

Transfer. The process of converting heat gains and losses to cooling and heating loads is a transient rather than a steady-state process. Heat gains occurring during one hour often affect loads over a number of succeeding hours. Consequently, it is important to consider accurate sequences of heat gains occurring during the day. In addition, because weather conditions and building use profiles vary from day to day, sequences of heat gains can affect loads from one day to the next.

4. The Response and Performance of

HVAC Equipment. How controls, systems and equipment respond to demands for cooling and heating in a building, and the factors that affect part-


load performance of the equipment must be considered to yield accurate equipment energy use data.

5. The Details Of How Utilities Charge

For Energy Use. Often prices for energy vary by season and time of day. Further, charges are often made for peak energy usage. As a result, the analysis must not only be able to produce accurate estimates of how much energy is used, but must also accurately determine when during the day energy is used.

Evaluation of BEA Methods A wide variety of building energy analysis methods are currently available to HVAC engineers and range from simple to sophisticated. The simplest methods involve the largest number of simplifying assumptions and therefore tend to be the least accurate. The most sophisticated methods involve the fewest assumptions and thus can provide the most accurate results. Generally, BEA methods are divided into three categories: a) Single Measure Methods (example:

Equivalent Full Load Hours) b) Simplified Multiple Measure Methods

(example: Bin Method) c) Detailed Multiple Measure Method

(example: Hour by Hour) While methods in the first two categories serve a useful role in providing quick, preliminary energy estimates, the simplifications they involve impair their accuracy. Each will be briefly discussed below. The main focus of the following discussions, however, will be the different hour by hour methods contained in the third category. Single Measure Methods These methods involve one calculation of annual or seasonal energy use. The Degree-Day Method, for example, computes energy use by combining one degree-day weather value with a load value and an efficiency value to obtain seasonal or annual energy use. Similarly, the Equivalent Full Load Hour Method combines full load capacity, full load

efficiency and equivalent full load hours to obtain annual energy use. In both cases, this level of simplicity is achieved by using such sweeping assumptions that the accuracy and reliability of these methods are very limited. Simplified Multiple Measure Methods These methods involve calculations of energy use at several different conditions. With the Bin Method, for example, energy use is computed at a series of outdoor air dry-bulb conditions. Results are then weighted according to the number of hours each dry-bulb condition is expected to occur to determine annual energy use. For example, the temperature 47 F would be used to represent the range of conditions between 45 F and 50 F, referred to as a "bin". Building loads and equipment energy use would first be calculated for the 47 F bin. Next, energy results would be multiplied the number of hours per year temperatures are expected to occur between 45 F and 50 F to determine annual energy use for that bin. Similar calculations would then be repeated for all other temperature bins for the local climate and would be summed to determine overall annual energy use. While the Bin Method provides a vast improvement in sophistication over single measure methods, it has a fatal flaw. This flaw is that it must decouple weather conditions, loads and system operation from time. For example, hours in the 47 F bin, when the outdoor dry-bulb is between 45 F and 50 F, occur at a variety of times of day and night, days of the week and months of the year. Because a single calculation is performed to represent energy use for all these different times it is difficult or even impossible to accurately: a) Link solar radiation and humidity

conditions to the bin. b) Consider hourly and daily variations in

internal loads. c) Consider the transient hour to hour and

day to day thermal performance of the building.


d) Predict time-of-day energy use and peak demands.

Inevitably averaging assumptions must be made to shoehorn all these considerations into the framework of the bin analysis. And these assumptions impair accuracy. While the Bin Method is useful for simple, preliminary estimates of energy use and operating cost, it cannot provide the level of accuracy and sophistication offered by the detailed multiple measure methods.

Detailed Multiple Measure Methods These methods perform energy calculations on an hour-by-hour basis. As a result, they have the potential to satisfy all the requirements listed earlier for high quality energy analysis results. There is, however, a certain amount of variation among different detailed multiple measure methods, leading some methods to meet the accuracy requirements better than others. Within the detailed multiple measure category are two major sub-categories worth discussing: a) The Reduced Hour-By-Hour Method b) The 8760 Hour-By-Hour Method.

Reduced Hour-By-Hour Method: How & Why? This method typically uses one 24-hour profile of average weather conditions per month. Energy simulations are performed for this average profile and results are then multiplied by the number of days in the month to obtain monthly energy totals. Upon this basic foundation, different reduced hour-by-hour methods make various improvements to enhance the accuracy of results: a) Some methods analyze building

operation for a typical Weekday, Saturday and Sunday each month since building use profiles differ significantly between these days. One average

weather profile is still used for all three typical day simulations each month.

b) Some methods also analyze equipment

operation for a hot and cold day each month in an attempt to improve estimates of peak electrical demand.

c) Some methods simulate building

operation for one 7-day week each month to try to account for day-to-day building dynamics. However, a one average weather profile is still used for all 7 days of the simulation.

The fundamental principle of this method is that building and equipment performance on hotter and colder than normal days each month averages out so that monthly energy use can be accurately predicted by simulating a small group of days using average weather conditions. The method offers the benefits of reduced calculation time and more moderate demands on computer memory and hard disk storage space. 8760 Hour-By-Hour Method: How and Why? This method simulates building and equipment performance for all 8,760 hours in the year using the proper sequence of days and actual weather data. No weighting of results or simplifications are necessary. The fundamental principle is that the way to produce the most accurate energy and operating cost estimates is to mimic the real-time operating experience of a building over the course of a year. All the requirements listed earlier for high quality energy analysis results can be met with this approach. The actual weather data accounts for the range and timing of weather conditions in great detail. Further, the hourly and daily variation of building occupancy, lighting and equipment use can be easily accounted for. In addition, the full year simulation tracks the dynamic hour-to-hour and day-to-day thermal behavior of the building, and the response of HVAC equipment to this behavior. The ultimate result is high-quality data that can be utilized to produce accurate,


detailed data about the quantity and timing of energy use. Both are requirements for accurate operating cost estimates.

Comparison of Reduced and 8760 Hour-By-Hour Methods While the Reduced Hour-By-Hour method often provides accurate results, the 8760 Hour-By-Hour method can consistently provide superior accuracy and reliability. Among the reasons why, five stand out: 1. Better Estimates of Monthly Energy

Use. One of the flaws in the fundamental principle of the reduced hour-by-hour method is that it relies on building and HVAC system behavior being "continuous" and "linear" during the month. Often these requirements are not met and this adversely affects accuracy "Continuous" is a mathematical term that in this context refers to a consistent mode of operation (it does not refer to constant 24-hour operation of equipment). For example, during a summer month HVAC system operation is continuous when cooling is consistently done on all days whether hot, cool or average weather conditions prevail. In this situation simulation of system performance for one 24-hour average weather profile has the best chance of approximating the total energy use for a month. However, system operation is often not "continuous" during a month, especially during intermediate seasons. For example, during an autumn month, cooling may be done on warmer than average days, economizer operation may occur on average days, and heating may occur on cooler than normal days. A simulation of one average day for such a month may indicate little or no cooling and heating because it does not consider the warmer and colder than average conditions. In moderate climates this problem can become severe when the only time heating occurs is on colder than average winter

days. Because only average winter weather is considered, most or all of the heating duty for the year may be missed by an average-day simulation approach. Finally, "linear" behavior is a requirement for averaging to be accurate. For example, if cooling loads are 20% larger when the temperature is 15 F warmer than average, and 20% smaller when the temperature is 15 F cooler than average, cooling loads are linearly proportional to outdoor temperature. Averaging of the warm day and cool day loads will result in loads similar to those produced by simulating only the average weather day. However, loads depend on more than just outdoor temperature. Solar radiation, internal loads and hour-to-hour and day-to-day dynamic behavior also affect loads and often result in non-linear behavior. Another example involves cooling equipment. If equipment input kW decreases 8% for every 10% drop in part-load ratio, input kW and load are linearly proportional. If this relationship holds true, simulation of equipment performance for one average day per month has the best chance of accurately approximating equipment performance on the collection of hot, average and cool days during the month. Unfortunately, the performance of equipment is often non-linear due to part-load, entering condenser temperature and other performance factors. Consequently, the accuracy of the average day approach can be degraded when equipment behavior is non-linear. The 8760-hour method avoids these problems by simulating building and equipment operation for the entire month. Actual weather data used by the simulation consists of a collection of days, all with different combinations of temperature, humidity and sunshine. Figures 1 and 2 provide an example of this kind of data for the month of September in Chicago. Figure 1 demonstrates the way dry-bulb temperatures can vary during a month. The dotted lines in this figure are the upper and lower limits of the average temperature profile for the month that would be used by


the reduced hour-by-hour method. Comparison of the average and actual data shows a significant number of hours outside the range of conditions considered by the average day simulation approach.

Figure 1. Chicago Weather / September Dry Bulbs

Figure 2. Chicago Weather / September Solar

Likewise, Figure 2 demonstrates the variation of solar radiation profiles during the month. The dotted line indicates the maximum solar flux in the average day profile used by the reduced hour-by-hour method. Once again, there are many conditions with greater sunshine and less sunshine than considered by the average day approach. More importantly, comparison of the peaks and valleys in Figures 1 and 2 shows that hot days are not always sunny, and cool days are not always cloudy. The diverse collection of hot, cold, sunny, cloudy and in between conditions shown in these figures illustrates the complex nature of actual weather data and provides evidence that building loads will not be a simple linear function of outdoor air temperature. By considering a diverse collection of weather conditions each month, the 8760 hour method produces a diverse, realistic set of cooling and heating loads for the month.

Further, because a full month of days are simulated, the appropriate factors influencing equipment performance are considered. There is no reliance on the assumption of "continuous" or "linear" behavior, and the estimates of monthly energy use can be highly accurate. 2. Higher Quality System Comparisons. The issues discussed under item (1) affect not only the accuracy of monthly energy estimates, but also the quality of system comparisons. This is because many of the system design alternatives commonly considered exhibit behavior that is both discontinuous and non-linear. "Discontinuous" refers to inconsistent operation. That is, operation that starts and stops rather than continuing for all operating conditions during a month. "Non-linear" refers to the fact that there is often not a simple proportional relationship between load or outdoor temperature and equipment performance, as discussed in item (1). A comparison of air handling systems with and without a non-integrated outdoor air economizer provides a good illustration of this problem. With this type of economizer control, economizer dampers open when outdoor air temperature drops below the supply air temperature. The system can then immediately use outdoor air for free cooling; mechanical cooling can be turned off. For this example, assume the supply air temperature is 57 F and that we are simulating system operation for the weather data shown in Figure 1. The dotted lines in this figure indicate the upper and lower limits of an average temperature profile for the month. Because this average profile ranges between 58 F and 75 F, a simulation using the reduced hour-by-hour approach would never find a condition when the economizer dampers opened during September; free cooling would never be available. However, with the 8760 hour method, the use of actual temperature profiles for the month result in 119 hours during 13 days when temperatures drop below 57 F. If cooling loads exist during these times, the economizer would operate to provide free


cooling. Therefore, because an economizer exhibits discontinuous operation, turning on and off at specific conditions, the reduced hour-by-hour approach may not be able to successfully account for its operation. In our example the reduced hour-by-hour method would underestimate the benefit of the economizer. Similar situations can exist for other system components and controls that involve discontinuous, on/off behavior. Examples include ventilation heat reclaim, supply air reset, humidity control, cooling tower fan cycling, and loading and unloading of chiller networks as well as many others. 3. More Accurate Load Histories. The fact that the 8760 hour method simulates building thermal performance day to day for the entire year means it can correctly account for day to day dynamic load behavior. This results in more accurate load profiles, which ultimately lead to more accurate energy use predictions. For example, on a Monday morning in the summer, pulldown loads tend to be larger than on other days of the week due to the heat accumulated by the building mass during the weekend. In addition to resulting in larger cooling loads, these conditions can sometimes set the monthly electric demand. In reduced hour-by-hour methods that do not simulate a full week of operation, each day is simulated separately from all other days. Consequently, day to day building dynamics cannot be considered, and the building load histories are more simplistic. In those reduced hour-by-hour methods that do simulate a 7-day sequence each month, results tend to be unrealistic since the same average weather profile is used for all 7 days. 4. Higher Quality Time Of Use Energy

Data. Because of the diverse weather conditions and operating conditions, and because of the dynamic nature of building heat transfer, 8760 hour methods can produce energy use data that not only accurately defines how

much energy is used, but when during the day and week the energy is used. When energy prices vary with time of day, accuracy of the timing of energy use is critical for producing accurate operating cost data. 5. More Accurate Estimates of Peak

Demand. Finally, by considering the full range of weather and operating conditions experienced by a building during a month, the 8760 hour method is able to produce more accurate estimates of peak energy demand. When utility rates include a demand charge component, a significant part of the energy cost can be due to the peak energy use rather than the quantity of energy used. Many reduced hour-by-hour methods must determine demands from average day simulations which tend to underestimate demand values. Those methods that add consideration of hot and cold day weather profiles can provide an improvement in demand estimates. However, it is important to recognize that demand will be dependant on more than just the outdoor air temperature. Solar radiation, internal loads, building use profiles and day to day building dynamics also play an important role. The 8760-hour method is the only method that can simultaneously consider all these factors. Thus, while the Reduced Hour-By-Hour Method considers many of the factors required for high-quality energy estimates, certain aspects of the method are flawed and can limit the accuracy of the method. Because the 8760 hour method uses a more detailed, comprehensive approach to building simulation, it can consistently overcome these problems to provide accurate, reliable energy estimates.

Conclusion This article has discussed the important benefits of the 8760 hour-by-hour building energy analysis method. This method is certainly not new. Computer programs using this method have been available for nearly three decades. However, because many of these programs were developed on mainframe computers as research tools, the


programs, and by association, the 8760 hour method itself acquired a reputation of being complicated, difficult and impractical to use. It is important to note that these are problems with the implementation of the 8760 hour method, not with the method itself. If the 8760 hour method is implemented in a well-designed, well-documented microcomputer program, the 8760 hour method can be as easy to learn and use as reduced hour-by-hour methods. In developing Carrier's Hourly Analysis Program we have put two decades worth of experience in the HVAC software field to work to produce an 8760 hour energy analysis tool that is both powerful and easy to use. The resulting program maximizes the benefits of the 8760 hour method while minimizing or even eliminating costs traditionally associated with use of this method.

224 HAP V 4.4 Advanced Training Seminar Copyright Carrier Corp. © 2006

Notes

HAP V 4.4 Advanced Training Seminar 225 Copyright Carrier Corp. © 2008

HAP V 4.4 Advanced Training Seminar 226 Copyright Carrier Corp. © 2008

© Carrier Corporation P.O. Box 4808, Bldg. TR-4, Room 400A

Syracuse, NY 13221 Phone: 800.253.1794 • Fax: 315.432.6844 eMail: [email protected]

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