24479682 HVAC Handbook CARRIER Block Load v3 Manual

811-315 COPYRIGHT 1998 CARRIER CORPORATION PRINTED IN USA

BLOCK LOADUSER’S MANUAL

Copyright 1998 Carrier Corporation

Block Load

User’s Manual

Carrier Corporation

Software Systems Network

Manual Published.................................. 7/97

First Revision........................................ 4/98

Table of Contents

Block Load User’s Manual i

CHAPTER 1 GETTING STARTED

1.0 WHAT THIS CHAPTER CONTAINS ................................ ................................ ........................... 1-11.1 WHAT THE BLOCK LOAD PROGRAM DOES ................................ ................................ ......... 1-11.2 INSTALLING BLOCK LOAD................................ ................................ ................................ ....... 1-1

1.2.1 Check Hardware and System Requirements ......................................................................................... 1-21.2.2 Run SETUP.EXE ................................................................................................................................ 1-2

1.3 STARTING BLOCK LOAD ................................ ................................ ................................ .......... 1-21.3.1 Starting Block Load For The First Time .............................................................................................. 1-21.3.2 Navigating The Splash Screen............................................................................................................. 1-3

1.4 OVERVIEW OF PROGRAM OPERATION ................................ ................................ .................. 1-31.4.1 Preparing Your Data ........................................................................................................................... 1-31.4.2 Entering Your Data ............................................................................................................................. 1-31.4.3 Running HVAC Load Calculations...................................................................................................... 1-41.4.4 Analyzing Your Results....................................................................................................................... 1-4

1.5 ASSISTANCE WHILE YOU WORK ................................ ................................ ............................ 1-41.5.1 On-line HELP ..................................................................................................................................... 1-41.5.2 Block Load User’s Manual .................................................................................................................. 1-41.5.3 Local Carrier Sales Representative ...................................................................................................... 1-51.5.4 Technical Support Line ....................................................................................................................... 1-5

1.6 HOW TO LEARN MORE ABOUT THIS PROGRAM ................................ ................................ .. 1-51.6.1 Information on Program Operation...................................................................................................... 1-51.6.2 Information on Program Calculations .................................................................................................. 1-5

CHAPTER 2 MANAGING YOUR PROJECT DATA

2.0 WHAT THIS CHAPTER CONTAINS ................................ ................................ ........................... 2-12.1 BLOCK LOAD PROJECTS ................................ ................................ ................................ ........... 2-12.2 PROJECT DATA FILES................................ ................................ ................................ ................ 2-1

2.2.1 Project Registration Data File (PRJXX___.MDB)................................................................................ 2-12.2.2 User Configuration Data File (CFGXX___.MDB) ............................................................................... 2-12.2.3 Master Project Data File (BLK30___.MDB) ........................................................................................ 2-22.2.4 Individual Project Data File (BLK30PRJ.MDB)................................................................................... 2-2

2.3 THE FILE MENU ................................ ................................ ................................ .......................... 2-22.3.1 Starting New Projects .......................................................................................................................... 2-22.3.2 Opening Existing Projects ................................................................................................................... 2-22.3.3 Deleting Projects ................................................................................................................................. 2-32.3.4 Saving Projects.................................................................................................................................... 2-42.3.5 Making Project Notes .......................................................................................................................... 2-52.3.6 Controlling The Printed Page Margins ................................................................................................ 2-52.3.7 Selecting The Printer And Printing Options ........................................................................................ 2-62.3.8 Retrieving Project Data From Earlier Version Of Block Load .............................................................. 2-62.3.9 Archiving Project Data ........................................................................................................................ 2-72.3.10 Retrieving Project Data...................................................................................................................... 2-82.3.11 Compacting Project Data ................................................................................................................... 2-8

CHAPTER 3 NAVIGATING THE MAIN WINDOW

3.0 WHAT THIS CHAPTER CONTAINS ................................ ................................ ........................... 3-13.1 OVERVIEW OF THE MAIN WINDOW ................................ ................................ ....................... 3-1

3.1.1 Viewing Your Project Data.................................................................................................................. 3-13.1.2 Editing Your Project Data ................................................................................................................... 3-2

3.2 ADVANCED USER INTERFACE FEATURES ................................ ................................ ............ 3-23.2.1 Selecting A System.............................................................................................................................. 3-3

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ii Block Load User’s Manual

3.2.2 Adding New Systems........................................................................................................................... 3-33.2.3 Making A Copy Of A System .............................................................................................................. 3-33.2.4 Adding New Zones To A System......................................................................................................... 3-33.2.5 Attaching Zones To A System ............................................................................................................. 3-43.2.6 Moving Zones From One System To Another ...................................................................................... 3-43.2.7 Moving Zones To And From The Unattached Zones Region................................................................ 3-43.2.8 Making A Copy Of A Zone.................................................................................................................. 3-43.2.9 Removing Zones From A System......................................................................................................... 3-43.2.10 Removing Zones From The Unattached Zones Region....................................................................... 3-5

Chapter 4 DEFINING WEATHER DATA

4.0 INTRODUCTION................................ ................................ ................................ .......................... 4-14.1 OVERVIEW OF WEATHER DATA ................................ ................................ ............................. 4-14.2 EDITING WEATHER DATA ................................ ................................ ................................ ........ 4-1

4.2.1 The Edit City Form ............................................................................................................................. 4-14.2.2 Region Selection List........................................................................................................................... 4-24.2.3 State/Province Selection List ............................................................................................................... 4-24.2.4 City Selection List ............................................................................................................................... 4-34.2.5 Latitude Input Box............................................................................................................................... 4-34.2.6 Elevation Input Box............................................................................................................................. 4-34.2.7 Summer Dry Bulb Input Box ............................................................................................................... 4-34.2.8 Summer Wet Bulb Input Box............................................................................................................... 4-34.2.9 Daily Range Input Box ........................................................................................................................ 4-34.2.10 Winter Dry Bulb Input Box................................................................................................................ 4-34.2.11 Atmospheric Clearness Number Input Box ........................................................................................ 4-34.2.12 Data Source Text Box........................................................................................................................ 4-4

4.3 CHOOSING WEATHER DATA FOR THE DEFAULT PROJECT ................................ ............... 4-4

Chapter 5 ZONES

5.0 INTRODUCTION................................ ................................ ................................ .......................... 5-15.1 OVERVIEW OF ZONES ................................ ................................ ................................ ............... 5-1

5.1.1 Types Of Zones ................................................................................................................................... 5-15.1.2 Manipulating Zone Data...................................................................................................................... 5-1

5.2 THE ZONE MENU................................ ................................ ................................ ........................ 5-25.2.1 New Zone............................................................................................................................................ 5-25.2.2 Edit Zone ............................................................................................................................................ 5-25.2.3 Delete Zone ......................................................................................................................................... 5-25.2.4 Copy Zone........................................................................................................................................... 5-35.2.5 Move Zone .......................................................................................................................................... 5-35.2.6 Global Changes ................................................................................................................................... 5-3

5.3 THE NEW ZONE TOOLBAR BUTTON ................................ ................................ ....................... 5-45.4 THE ZONE INFORMATION FORM ................................ ................................ ............................ 5-5

5.4.1 Zone Data 1 Tab.................................................................................................................................. 5-65.4.2 Zone Data 2 Tab.................................................................................................................................. 5-75.4.3 Building Materials Tab........................................................................................................................ 5-95.4.4 Exposure Tab .................................................................................................................................... 5-125.4.5 Partitions Tab.................................................................................................................................... 5-14

Chapter 6 HVAC SYSTEMS

6.0 INTRODUCTION................................ ................................ ................................ .......................... 6-16.1 OVERVIEW OF HVAC SYSTEMS................................ ................................ ............................... 6-1

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Block Load User’s Manual iii

6.1.1 Types Of HVAC Systems..................................................................................................................... 6-16.1.2 Manipulating HVAC Systems.............................................................................................................. 6-2

6.2 THE SYSTEM MENU ................................ ................................ ................................ ................... 6-26.2.1 New System......................................................................................................................................... 6-26.2.2 Edit System ......................................................................................................................................... 6-26.2.3 Delete System...................................................................................................................................... 6-26.2.4 Copy System........................................................................................................................................ 6-2

6.3 THE NEW SYSTEM TOOLBAR BUTTON ................................ ................................ .................. 6-36.4 THE HVAC SYSTEM INFORMATION FORM ................................ ................................ ............ 6-3

6.4.1 HVAC System Data 1 Tab................................................................................................................... 6-36.4.2 HVAC System Data 2 Tab................................................................................................................... 6-76.4.3 Zones Tab............................................................................................................................................ 6-8

Chapter 7 REPORTS

7.0 INTRODUCTION................................ ................................ ................................ .......................... 7-17.1 OVERVIEW OF INPUT REPORTS ................................ ................................ .............................. 7-17.2 OVERVIEW OF OUTPUT REPORTS ................................ ................................ .......................... 7-17.3 SELECTING AN HVAC SYSTEM ................................ ................................ ............................... 7-27.4 CHOOSING THE CALCULATION TIMES ................................ ................................ .................. 7-27.5 SELECTING REPORTS................................ ................................ ................................ ................ 7-37.6 THE BLOCK LOAD REPORT FORM ................................ ................................ .......................... 7-4

7.6.1 Printing A Report ................................................................................................................................ 7-47.6.2 Paging Through A Report.................................................................................................................... 7-47.6.3 Selecting Other Reports....................................................................................................................... 7-47.6.4 Exiting The Report Form..................................................................................................................... 7-4

CHAPTER 8 COOLING DESIGN CALCULATIONS

8.0 INTRODUCTION................................ ................................ ................................ .......................... 8-18.1 ZONE COOLING LOAD CALCULATIONS ................................ ................................ ................. 8-18.2 COOLING COIL LOAD CALCULATIONS - SINGLE-ZONE SYSTEMS ................................ ... 8-28.3 COOLING ANALYSIS FOR MULTIPLE-ZONE SYSTEMS ................................ ...................... 8-11

CHAPTER 9 HEATING DESIGN CALCULATIONS

9.0 INTRODUCTION................................ ................................ ................................ .......................... 9-19.1 ZONE HEATING LOAD CALCULATIONS ................................ ................................ ................. 9-19.2 SIZING CALCULATIONS FOR WARM AIR HEATING SYSTEMS ................................ .......... 9-29.3 SIZING CALCULATIONS FOR HYDRONIC BASEBOARD HEATING SYSTEMS .................. 9-59.4 SIZING CALCULATIONS FOR ELECTRIC BASEBOARD HEATING SYSTEMS .................... 9-6

APPENDIX A INDEX

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iv Block Load User’s Manual

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Getting Started Chapter 1

Block Load 1-1

CHAPTER 1 GETTING STARTED

1.0 WHAT THIS CHAPTER CONTAINS

This chapter summarizes the basic information required to use the E20-II Block Load program. Thechapter explains what the program does, how to use the program to design HVAC systems, how tooperate the program and how to use this manual. This chapter takes 5 to 10 minutes to read. Programusers are strongly encouraged to read this chapter before using the program.

1.1 WHAT THE BLOCK LOAD PROGRAM DOES

Block Load is an engineering tool which helps HVAC engineers and designers size and select cooling andheating equipment. It calculates design cooling and heating loads for commercial buildings. It alsodetermines required sizes for terminals, fans, and cooling and heating equipment.

More than its name implies, Block Load is a fully featured load estimating program. In addition tocomputing "block" loads for buildings, the program can determine diversified zone loads and coil loads,all according to user specifications. Further, the program can easily analyze projects involving:

• One single-zone HVAC unit

• Several separate single-zone units

• Multiple-zone central air handler systems

• Constant volume equipment

• Variable volume systems

• DX or chilled water cooling coils

• Systems with warm air heating

• Systems with hydronic baseboard heating

• Systems with electric baseboard heating.

In all cases appropriate load and sizing information is provided as output.

1.2 INSTALLING BLOCK LOAD

You install Block Load on your computer using the Setup program. The Setup program installs all thefiles you need in order to run the Block Load program. Note: you cannot simply copy files from theBlock Load disks to your hard disk. You must run the Setup program to have all the Block Load filesinstalled in the appropriate directories on your hard disk.

To install Block Load, follow the steps outlined below.

Chapter 1 Getting Started

1-2 Block Load

1.2.1 Check Hardware and System RequirementsBefore you install Block Load, make sure that your computer meets the minimum requirements listedbelow. Do not proceed with Block Load installation if your computer does not meet the minimumrequirements.

System requirements for running Block Load include:

• Microsoft Windows 3.11 or later, or Microsoft Windows 95, or Microsoft Windows NT3.51 or later.

• 80386 or higher microprocessor.

• A hard disk with a minimum of 4 megabytes of available space.

• VGA or higher resolution monitor.

• 8 MB of RAM

• A mouse.

1.2.2 Run SETUP.EXEThis section describes how to run SETUP.EXE from drive A: of your computer. If you are installingBlock Load from a drive other than A:, simply substitute the actual drive letter for A: in theseinstructions.

To begin, insert Program Disk 1 into drive A:. From the File Menu of Windows Program Manager,choose the Run command, then type A:SETUP.

At this point, the install process will commence. At the beginning of the install process, you will be askedto specify the drive letter where you want Block Load installed. You may enter any valid hard disk drivedesignation available to your computer. If you enter an invalid hard disk drive letter, the Install programwill display a message stating “ Invalid Drive Specification “, You will have to answer OK then input thecorrect drive letter.

Continue to follow the directions on the screen. The Install program will prompt you to insert theremaining program disks as needed.

During installation, a “Carrier E20-II” group will be created, if one does not already exist. Within theCarrier E20-II group, a “Block Load” icon will be created.

At any point in the Install process, you may choose to stop the installation by pressing the Cancel button.If you press the Cancel button, the Block Load install will terminate, but will not remove any files alreadyinstalled. You are strongly encouraged to leave your system with the partial install until you canfinish it later. Do not attempt to remove any installed files or directories without first consulting CarrierSoftware Systems technical support.

1.3 STARTING BLOCK LOAD

To start the Block Load program, double-click on the Block Load icon in the Carrier E20-II group.

1.3.1 Starting Block Load For The First TimeThe first time you run Block Load, you will be prompted to enter your company name. The companyname will appear on all Block Load output reports.


Block Load 1-3

1.3.2 Navigating The Splash ScreenAt program startup, the Block Load splash screen is displayed. The splash screen contains three buttons:Help, Continue and Config. In order to proceed, you must push one of these buttons. Each is explainedbelow.

Help Button. Choose this button for an explanation of Block Load

Continue Button. Choose this button when you’re ready to begin using Block Load. This takes you tothe Block Load Main Window, and a new, default project (named Untitled) will be loaded. If you arestarting a new project, you may begin entering data into the Untitled project. If you want to work withan existing project, you can use the File:Open, File:Retrieve or File:Convert DOS Data file options toload an existing project, or you may select an existing project from the list of “most recently used”projects shown on the File Menu. Refer to Chapter 2 for more information on using the File Menu.

Config Button. Brings up the Data Storage Drive form. Here you select the drive to which yourBlock Load project data will be stored. The data drive does not need to be the same drive to which theBlock Load program was installed. For example, you may have installed Block Load on a network drive,but wish to store your Block Load project data on your local hard drive.

1.4 OVERVIEW OF PROGRAM OPERATION

This section briefly describes how to use Block Load to estimate cooling and heating loads, and to designHVAC systems. It explains basic operating principles for the program. Understanding these principles isone key to using Block Load efficiently.

More complete information is available in Chapters 2-9 of this manual.

1.4.1 Preparing Your DataBefore design load calculations can be performed, information about the building, its environment and itsHVAC system must be gathered. This work involves extracting data from building floor plans andspecifications, evaluating building usage, and studying basic HVAC system needs. Some of the specifictypes of information needed include:

• Climate data for the building site. This information may be easily obtained by pickinga city from Block Load’s weather database.

• Construction material data for walls, roofs, windows, floors and interior partitions.• Building size and layout data including wall, roof, window and floor areas, exposure

orientations and characteristics of external shading features.• Internal load characteristics for occupancy, lighting systems, office equipment,

appliances and machinery within the building.• HVAC system data concerning equipment and controls.

1.4.2 Entering Your DataOnce the required project information has been gathered and organized, Block Load can be used todetermine maximum cooling and heating loads for the building and to size the cooling and heatingequipment.

There are three basic steps in entering your project information into Block Load. Each is describedbelow.

Step 1: Enter Weather Data. First a city must be selected so that design temperature, humidityand solar radiation profiles can be computed. This weather data forms the basis for all cooling andheating load calculations. More information on this step is provided in Chapter 4.


1-4 Block Load

Step 2: Enter Zone Data. You must enter data for each of the zones in your building. A "zone"is a region of a building served by one thermostatic control. It is often convenient to think of azone as a room of your building, though a zone can be a group of several zones (or even the entirebuilding) or it can be only a portion of a room.

A zone is defined by its characteristics such as wall areas and properties, roof area and propertiesand the zone’s internal load characteristics. Refer to Chapter 5 for more detailed information onentering zone data.

Step 3: Enter HVAC System Data. The "HVAC System" is the equipment and controls used toprovide cooling and heating to your building. It includes such things as the supply fan, cooling andheating coils, thermostats, ventilation and exhaust dampers, and the controls that tie them together.

Chapter 6 provides further information on HVAC System input.

1.4.3 Running HVAC Load CalculationsOnce weather, zone and HVAC system data has been defined, design cooling and heating loads can becomputed, and the system can be sized.

Design cooling calculations are performed for a range of calculation months and hours. By default,Block Load calculates a full 24-hour design day for all twelve months. You have the option to limit thecalculations to any other range of months and hours.

Chapter 7 describes how to run load calculations in greater detail.

1.4.4 Analyzing Your ResultsOnce load and sizing calculations have been completed, Block Load’s reports can assist you in refiningyour HVAC system design and, ultimately, allow you to select proper cooling and heating equipmentfrom HVAC manufacturers’ product catalogs.

Block Load’s output reports include central fan sizing information, central coil sizing information(including sensible and total capacity, entering and leaving air conditions), duct and terminal sizing data,and space heating capacities.

1.5 ASSISTANCE WHILE YOU WORK

If you need assistance with Block Load while you are running the program, there are several sources ofhelp for you. Each is outlined below.

1.5.1 On-line HELP

It is important when using Block Load to understand how the data that you enter will be used by theprogram. The fastest way to get this information is to use Block Load’s on-line Help system. BlockLoad provides context-sensitive help throughout the program. To get Help in any area of the program,simply press the F1 key; the Help system will appear on your screen with information pertinent to thedata you are entering.

1.5.2 Block Load User’s ManualYou are encouraged to become familiar with this manual. It contains a lot of useful information - often ofa more general nature - not contained in the on-line Help. Typically, you can find the answers to yourquestions in this manual within a few minutes of searching.


Block Load 1-5

1.5.3 Local Carrier Sales RepresentativeIf you haven’t been able to locate the information you need in the on-line Help system or the Block LoadUser’s Manual, you may want to call your local Carrier sales representative. In many cases, your BlockLoad questions can be answered by your local Carrier sales representative.

1.5.4 Technical Support Line

Carrier Software Systems provides a toll-free telephone technical support line to help you with yourBlock Load questions and problems. A staff of HVAC specialists are available to assist you duringnormal business hours (8:00am - 4:45pm ET, Monday through Friday). The toll-free technical supportnumber is 800/253-1794.

1.6 HOW TO LEARN MORE ABOUT THIS PROGRAM

The discussions in this chapter only provide an introduction to the Block Load Program. More detailedinformation on program operation is provided in the remainder of this User's Manual, and in otherpublications. These sources of information are described below:

1.6.1 Information on Program Operation1. Block Load User's Manual Chapter 2 describes the concept of projects and how they can be managed

in Block Load. Chapter 4 describes the Block Load user interface, and provides insight on how touse it most effectively.

2. Block Load User's Manual Chapters 4, 5, 6 and 7 describe how to work with the four basic steps inthe load calculation process. Chapter 4 describes how to define weather data; Chapter 5 discussesentry of zone data; Chapter 6 deals with HVAC system inputs; Chapter 7 describes the loadcalculation step and the generation of output reports.

1.6.2 Information on Program Calculations1. Block Load User's Manual Chapter 8 and 9 describe load and sizing procedures used for cooling and

heating systems.

2. The E20/TF Load Manual describes the transfer function load calculation procedures used in thisprogram in greater detail. Contact Carrier Software Systems technical support, or your local Carriersales representative to obtain a copy.

3. The E20-II Weather Data Guide discusses procedures used to calculate temperature, humidity andsolar radiation profiles. Contact Carrier Software Systems technical support, or your local Carriersales representative to obtain a copy.

4. The ASHRAE Handbook of Fundamentals (1993) provides general background material on theTransfer Function Methodology for load calculations.


1-6 Block Load


Block Load 2-1

CHAPTER 2 MANAGING YOUR PROJECT DATA


Block Load data is organized into projects. This chapter explains the concept of a project, where theBlock Load project data is stored, and explains the features built into Block Load to help you manage allof the data that make up your Block Load projects.

2.1 BLOCK LOAD PROJECTS

A project is a related collection of data (weather data, building physical characteristics, and HVACspecifications) which reside within the file structure of Block Load. This data makes up the informationneeded to calculate a building’s design cooling and heating loads, and to properly size the requiredHVAC equipment to maintain comfort in the building.

Other Carrier E20-II and Electronic Catalog programs written for Microsoft Windows® also deal withprojects. While Block Load maintains your Block Load project data separate from any project data youmay create in these other Carrier applications, Block Load is “aware” of these other projects. In somecases, it may be possible to ‘share’ some of this project data among the different applications. Forexample, if you create a project in Block Load named “New Office Complex”, it may be possible to passthe resulting equipment sizing output data to a Carrier equipment selection program (Rooftop Selection,for example) which has a project of the same name. Refer to the documentation for each Carrierapplication to determine if project data can be shared with other Carrier programs.

2.2 PROJECT DATA FILES

Block Load uses four standard files in managing your project data. This section documents the name,content and location of these files.

2.2.1 Project Registration Data File (PRJXX___.MDB)This file contains a list and description of all projects created by any Carrier E20-II or Electronic Catalogprogram written for Windows. It also cross-references each project with all of the Carrier programswhich have project data of the same name. The project registration data file is located in the ...\E20-II\ENVIRO directory.

For network installations, the “___” in PRJXX___.MDB is replaced by a three letters identifying thenetwork user.

2.2.2 User Configuration Data File (CFGXX___.MDB)This file contains user-configurable settings. These include a list of the most recently used projects, thedata storage drive letter, and whether projects are stored in English or SI Metric units. The userconfiguration data file is located in the ...\E20-II\ENVIRO directory.

Chapter 2 Managing Your Project Data

2-2 Block Load

For network installations, the “___” in CFGXX___.MDB is replaced by a three letters identifying thenetwork user.

2.2.3 Master Project Data File (BLK30___.MDB)This file contains the names of your Block Load projects, and the names of the directories in which theproject data is found (see section 2.2.4). This file is located in the ...\E20-II\BLK30\WORK directory.

For network installations, the “___” in BLK30___.MDB is replaced by a three letters identifying thenetwork user.

2.2.4 Individual Project Data File (BLK30PRJ.MDB)This file contains your Block Load project data. This includes weather data, zone data, HVAC data andall output data. This file is located in the ...\E20-II\BLK30\WORK\PJxxx directory, where ‘xxx’ is areference number (base 36) assigned to the project. Each project is assigned to its own Pjxxx directory.

2.3 THE FILE MENU

Most of Block Load’s data management features are built into the File Menu. The File Menu has optionsto create new projects (New), open existing projects (Open), delete projects (Delete), save projects(Save, Save As), archive projects (Archive), retrieve archived project data (Retrieve), recover projectdata from Block Load v2.1 (Convert DOS Data), clean up the project database (Compact), and addmiscellaneous notes to your project (Properties). In addition, it also has options for setting the printedpage margins (Page Setup), managing your printer resources (Print Setup), and contains a list of yourmost recently used projects for quick access. This section explains the purpose and use of each of theseoptions.

2.3.1 Starting New Projects

The New option is used to create (or start) a new project. When this option is chosen, a default project isloaded and displayed onscreen. The default project contains no systems or zones, but does contain adefault city [note: you can specify which city is used as the default by using the Save button on the EditCity form. For more details, refer to Chapter 4]. The name of the new project is initially set to“Untitled”. This name is displayed in the program’s title bar.

Before a new project is loaded, Block Load will verify that your current project has been saved. If it hasnot, you will be issued a warning, and given an opportunity to save that project.

2.3.2 Opening Existing Projects

The Open option is used to open an existing project. When this option is chosen, the Open Project formis displayed (see Figure 2.1).

The Open Project form contains a Project Name list box which is used to select the project to open.Beneath the Project Name text box is a list of all available projects which can be opened. To open aproject, click on the desired project from this list, then press the OK button in the upper right-hand cornerof the Open Project form.

The List Projects Of Type prompt - which appears at the bottom of the form - controls the list of projectsappearing beneath the Project Name text box. You may elect to display:

Managing Your Project Data Chapter 2

Block Load 2-3

• only those projects for which Block Load data exists (from the current version of BlockLoad).

• projects created by any other Carrier E20-II or Electronic Catalog program (RooftopSelection Program, for example).

• all projects created by all Carrier E20-II and Electronic Catalog programs.

Figure 2.1 Open Project Form.

2.3.3 Deleting ProjectsThe Delete option is used to delete projects from your current data drive which you no longer need. Thisis an important way of doing housecleaning on your computer hardware. When the Delete option ischosen, the Delete Project form is displayed (see Figure 2.2).


2-4 Block Load

Figure 2.2 Delete Project Form.

The Delete Project form contains a Project Name list box which is used to select the project to delete.Beneath the Project Name text box is a list of all available projects which can be deleted. To delete aproject, click on the desired project from this list, then press the OK button in the upper right-hand cornerof the Delete Project form.





If you choose to delete the currently-loaded project, Block Load will automatically create a new, defaultproject for you.

2.3.4 Saving ProjectsThe Save and Save As options are used to save your project to the current data storage drive. The Saveoption saves the current project under its current project name. The Save As option allows you to savethe current project under a new name. When the Save As... option is chosen, the Save Project As... formis displayed (see Figure 2.3).

Figure 2.3 Save Project As... Form.

The Save Project As… form contains a Project Name list box which is used to enter a name under whichthe current project will be stored. You may enter a name directly into the Project Name list box, or youmay choose to store your project in one of the existing projects listed beneath the Project Name text box.Up to 24 characters are allowed (embedded blanks are permissible). The project name must be unique(ie., you cannot have another project by the same name on the current data storage drive).



Block Load 2-5




If you choose to delete the currently-loaded project, Block Load will automatically create a new, defaultproject for you.

2.3.5 Making Project NotesThe Project Properties option allows you to save notes about the project that may not directly affect yourBlock Load data (see the example in Figure 2.4). The Project Properties form contains a ProjectDescription input box where your notes will be entered. This information is not used within the program,so its purpose is solely to record project-related information. It is not necessary to enter anything into theProject Description box.

Figure 2.4 Project Properties Form.

2.3.6 Controlling The Printed Page MarginsThe Page Setup option gives you control over the printed margins used when generating reports fromBlock Load. Figure 2.5


2-6 Block Load

Figure 2.5 Page Setup Form.

2.3.7 Selecting The Printer And Printing OptionsThe Print Setup option allows you standard Windows control over your printer. Refer to your Windowsdocumentation for information on how to use the Print and Print Setup forms.

2.3.8 Retrieving Project Data From Earlier Version Of Block LoadThe Convert DOS Data command converts a Block Load dataset from its DOS format (Block Loadv2.1) to the current program format. When the Convert DOS Data option is chosen, the Convert DOSData form is displayed (see Figure 2.6).

Use the Folders directory tree structure to locate the Block Load v2.1 data directory which contains thedata you wish to pull into Block Load For Windows. Double click on the directory.To convert your DOS data, do the following:

• Step 1: Use the Folders directory tree structure to locate the Block Load v2.1 datadirectory which contains the data you wish to pull into Block Load For Windows. Doubleclick on the directory

• Step 2: Highlight the file blk21sys.dat in the list box at the right of the form. Ifblk21sys.dat does not appear in the list box, then the folder identified in Step 1 does notcontain a valid Block Load v2.1 dataset.

• Step 3: Click the OK button.

The conversion will proceed to completion. All data will be loaded into a new, untitled project on theMain Window.


Block Load 2-7

Figure 2.6 Convert DOS Data Form.

2.3.9 Archiving Project DataThe Archive option is used to store your project data away for future use. When the Archive option ischosen, the Archive Project form is displayed. Use the Archive Project form to choose the project youwish to archive. The Archive Project form operates the same as the Open Project from (refer to Section2.3.2 for information on how to use this form).

Once you have selected a project to archive, the Archive prjname form will be displayed. This is shownin figure 2.7. Use this form to specify a file name for the archived dataset, and a folder in which to putthe file. You may choose to store the archived project onto a removable disk or onto a hard disk.

Archiving a project does not remove the project from the current data storage drive. If you wish to havethe project removed from the data storage drive, you must use the File:Delete option (see section 2.3.3).

Archived projects can be retrieved back into Block Load by using the File:Retrieve option (see section2.3.10).

Figure 2.7 Archive Prjname Form.


2-8 Block Load

2.3.10 Retrieving Project DataThe Retrieve option is used to restore Block Load data from an archived project dataset. The Retrieveoption can only be used on an archived dataset from Block Load v3. When the Retrieve option is chosen,the Retrieve Project form is displayed (see Figure 2.6). Use this form to specify the folder and file nameof the archived dataset that you wish to retrieve.

When you push the OK button, Block Load will retrieve your archived dataset and make it the currentproject.

Figure 2.6 Retrieve Project Form.

2.3.11 Compacting Project DataThe Compact option is used to compress a project dataset. This is important because the project datasettends to get filled with unused space as modifications to the project data are made. The Compact optionshrinks the size of the project dataset by removing all the unused space. When the Compact option ischosen, the Compact Project form is displayed (see Figure 2.7).

Figure 2.7 Compact Project Database Form.

Block Load 3-1

CHAPTER 3 NAVIGATING THE MAIN WINDOW


Most of your interaction with Block Load will occur in the Main window. It is here that you will performall your data entry and manipulation, and view all of your output results. The Main window has a richassortment of features for viewing and manipulating your project data. In order to get the most benefitfrom Block Load, it is important to understand how to navigate the Main window most efficiently. Thischapter explains all of the features and capabilities of the Main window.

3.1 OVERVIEW OF THE MAIN WINDOW

Figure 3.1 illustrates the appearance of the Main window. It consists of an all-white backgroundcontaining icons (pictures) representing your project data. A weather icon (a globe) represents yourweather data, HVAC system icons (air handlers) represent your HVAC systems, and zone icons (wallthermostats) represent your zones.

3.1.1 Viewing Your Project DataThe most obvious benefit of Block Load’s Main window is its ability to visually summarize your entireproject dataset. The weather icon lists the name of the city for which design weather is being used. Thename and number of HVAC system icons tells you what systems you’ve entered. And the zone iconscommunicate the number of zones in your project, and which HVAC systems are serving them.

When you first begin a project, the only icon on the Main window is the weather icon, indicating thatyour project has weather data (but no zone or HVAC system data). The weather icon is always locatedin the upper left-hand corner of the window. Icons for various zones and HVAC systems will appear asyou enter data for new zones and HVAC systems (refer to Chapters 5 and 6 for details on entering zoneand HVAC system data).

Each HVAC system that you enter into Block Load is represented by its own icon. Each HVAC systemicon is contained in a rectangular box, with the name of the system displayed beneath the icon. Eachrectangular “system” box is connected by a short vertical branch to the horizontal line extending from theweather icon. If your project contains more HVAC systems than can be displayed on the screen,horizontal scroll bars below the Main window allow you to view the remaining system icons. In additionto this, the dark arrow at the right-hand of the horizontal line is a visual clue that there are more systemswhich extend off the screen. Referring to Figure 3.1, the current project (named ISC1, as shown on thetitle bar) has systems named Base: Multiple Zone, Base: Single Zone, Solar and SZ: 100% vent_exhshown on the screen. The horizontal scroll bar and the horizontal arrow (pointing to the right) are visualindications that the project contains other systems.

Each zone that you enter is represented by its own zone icon. The zone icons are displayed vertically in arectangular box underneath the HVAC system icon which serves the zone. The zone’s name is listed tothe right of its icon. It is possible to have zones which are not “attached to” (ie., served by) an HVACsystem. These zone icons are displayed vertically in the area marked “Unattached Zones”, which islocated beneath the weather icon. If any system - or the unattached area - contains more zones than can

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3-2 Block Load

fit in its rectangular box, vertical scroll bars will appear at the right side of the box to allow you to viewthe remaining zones.

3.1.2 Editing Your Project DataThe Main window icons do more than just provide a picture of your project data. They also provide away for you to quickly access the data (to change it, or simply to look at it). This is done by double-clicking on the icon. For example, double-clicking on the weather icon will display the properties of thedesign weather data, and allow you to modify it. Double-clicking a zone icon will display the zone’sproperties, and allow you to change them. Double-clicking an HVAC system icon will display thesystem’s input properties, and will allow you to change them.

Figure 3.1 Main Window.

3.2 ADVANCED USER INTERFACE FEATURES

The Main window has features beyond just allowing you to view and edit your project data. It hasfeatures for easily moving zones from one HVAC system to another, or detaching zones from anysystems. This is particularly useful in helping determine the optimum zoning arrangement for a building.This section describes some of the advanced features of the Main window.

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3.2.1 Selecting A SystemBlock Load allows you to perform several operations on an HVAC system. You can print or edit itsinput data, create a copy of it, or run design load calculations on the HVAC system. Before performingany of these operations, you must first ‘select’ the system on which you want the operation performed.Selecting a system can be done through the Menu options (refer to Chapter 6), but the Main windowallows you a faster and easier way. To select an HVAC system from the Main window, single-click onthe HVAC system icon desired

In Block Load, only one system can be selected at a time. When you select a new system, the previously-selected system is automatically de-selected. The Main window provides a visual clue to indicate whichHVAC system is currently selected: the rectangular box surrounding the system and its attached zoneicons is drawn with thick, dark lines.

Note that you may often have situations where no system is currently selected.

3.2.2 Adding New SystemsThere are three ways to add a new system to your project:

1. Use the System:New System menu option.

2. Click the “Create a new system” button on the toolbar. The “Create A New System” button has apicture of a rectangular blue air handler with a white fan symbol inside of it.

3. Right click on an existing system icon. A pop-up menu will appear with an option to create a newsystem (New System). Choose this option.

When you choose any of these methods for creating a new system, a form displaying the defaultproperties of your new system will appear. When you press the OK button (you may change any of thesystem properties first), a system icon for your new system will appear on the Main Window.

3.2.3 Making A Copy Of A SystemTo make a copy of a system, right click on the icon of the system you want to copy. A pop-up menu willappear with an option to copy the system (Copy System). If you choose this option, Block Load willcreate a new system which is an identical copy of the selected system, except that the name will bemodified slightly (since you cannot have two systems with identical names). The new system will appearon the Main Window, and will have the same zones attached to it as the original system.

3.2.4 Adding New Zones To A SystemThere are three ways to add a new zone to a system:

1. Right click on the zone box beneath the system to which you want a zone added. A pop-up menuwill appear with an option to add a new zone (New).

2. Select the system to which you want to add a new zone (refer to section 3.2.1 for information onselecting a system). Choose the New option from the Zone Menu.

3. Click the “Create a new zone” button on the toolbar. The “Create A New Zone” button has apicture of a cube office on it.

When you choose either of these ways to add a new zone to the system, a form displaying the defaultproperties of a new zone will appear. When you press the OK button (you may change any of the zoneproperties first), a zone icon for your new zone will appear on the Main Window in the zone box attachedto the system.


3-4 Block Load

3.2.5 Attaching Zones To A SystemIn Block Load, you ‘attach’ a zone to a specific HVAC system to indicate that the zone will receiveconditioning from that system. Attaching zones to a system can be done on the HVAC SystemInformation form (see Chapter 6). However, it can be done more quickly and easily from the Mainwindow. To do this, drag the zone icon from its current position and drop it on the HVAC system iconto which you want it attached. Block Load will re-position the zone icon to the bottom of the zonesattached to the system.

In a similar fashion, you can detach a zone from a system by dragging the zone icon from beneath theHVAC system icon and dropping it on another system icon or in the ‘Unattached Zones’ area.

3.2.6 Moving Zones From One System To AnotherTo move a zone from one system to another, drag the zone icon from its currently attached system anddrop it onto the system icon to which it is to be attached. This is just a specific case of detaching and re-attaching a zone, as described in section 3.2.5.

3.2.7 Moving Zones To And From The Unattached Zones RegionIn general, the rules for moving zones to and from the Unattached Zones region are the same as for anysystem, with one exception: Block Load will not allow you to move a zone to the Unattached Zones areaif that zone is attached to any other system. If you attempt to do this, a warning message will appear,explaining that you cannot perform that operation, and ask if you want to remove the zone from thesystem where the original move was attempted.

For general rules on moving zones, refer to section 3.2.6.

3.2.8 Making A Copy Of A ZoneThere are two types of zone copies allowed in Block Load. It is very important to understand thedistinction between the two to avoid mistakes or possible loss of data.

1. You may attach the same zone to more than one system. In this case, there is only one zone, but itappears in multiple places. Changing the zone properties in any one of these places will changethe properties in all of the places where the zone is attached.

To attach a zone to more than one system, right click, drag and drop the zone icon in the zone boxof any other system. When you do this, a pop-up menu will appear with an option to attach thezone to the new system (Copy Here). If you choose this option, the zone will be attached to boththe original and destination systems.

2. You may create an identical - but unique - copy of a zone. Block Load will create a new zone withthe same properties as the original (except for the zone name). Since each zone is unique, changingthe properties of one zone doesn’t change the properties of the other.

To make a unique copy of a zone, right click and drag the zone icon to another system (or theUnattached Zones area). When you drop the zone icon on a system (or Unattached Zones area), apop-up menu will appear with an option for creating a new copy of this zone (New Zone Based OnOriginal). If you choose this option, the new zone (with a modified name) will appear.

You are permitted to drop the icon on the same system as the original. For example, referring toFigure 3.1, if you want to make a copy of East Zone, from the system Base: Multiple Zone, andkeep it in Base: Multiple Zone, then right click on East Zone, drag and drop it somewhere in thezone box for Base: Multiple Zone.

3.2.9 Removing Zones From A SystemThere are three ways to remove a zone from a system. They are:

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1. You may select the zone (by clicking on its icon), then use the Delete option on the Zone Menu.Note that the zone will not be deleted from your project. If the zone is not attached to any othersystem, then it will be automatically moved to the Unattached Zones area.

2. You can left drag the zone icon from your system and drop it in the Unattached Zones area.

3. You can select the zone (by clicking on its icon), then right click on it. A pop-up menu will ap pearwith an option to delete the zone (Delete). If you choose this option, the zone will be removed fromthat system. Note that the zone will not be deleted from your project. If the zone is not attached toany other system, then it will be automatically moved to the Unattached Zones area.

3.2.10 Removing Zones From The Unattached Zones RegionRemoving a zone from the Unattached Zones area deletes the zone from your project. There are twoways to remove a zone from the Unattached Zones area. They are:

1. You may select the zone (by clicking on its icon), then use the Delete option on the Zone Menu.Block Load will ask you to confirm that you want the zone permanently deleted from your project.

2. You can select the zone (by clicking on its icon), the n right click on it. A pop-up menu will appearwith an option to delete the zone (Delete). Block Load will ask you to confirm that you want thezone permanently deleted from your project.


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Block Load 4-1

Chapter 4 DEFINING WEATHER DATA

4.0 INTRODUCTION

This chapter describes how weather data can be manipulated for use in Block Load’s calculations. In thisstep the user specifies the design weather conditions for the building site. Separate sections in thischapter provide an overview of Editing City data and describe the use of various options on the Edit Cityscreen.

4.1 OVERVIEW OF WEATHER DATA

Weather data refers to the temperature, humidity and solar radiation conditions experienced by yourproject’s building and its HVAC system. Weather data has a significant effect on building loads andequipment operation. It therefore plays a key role in load estimating and HVAC system design work.

Block Load uses design weather data in its design cooling and heating load calculations. Design coolingweather data consists of design day (24-hour) profiles of temperature, humidity and solar radiation foreach month of the year. Design heating weather data consists only of a single winter design temperature.

A Block Load project dataset always includes weather data. When a project is first created, default datais assigned to it. This data cannot be deleted; it can only be changed.

4.2 EDITING WEATHER DATA

Weather data is changed by modifying the data on the Edit City form. You can reach the Edit City formby double-clicking on the globe icon on the Block Load Main window, or by selecting the Weather:Editoption from the Menu bar.

When you double-click on the globe icon in the Main window, or select the Weather:Edit option from theMenu bar, the Edit City form appears. This section describes the Edit City form, its contents and its uses.

4.2.1 The Edit City FormThe Edit City form is used to specify the location and design weather parameters for a Block Loadproject. Block Load uses the design weather parameters to generate all of the design weather data usedin its load estimating calculations, using a procedure outlined in the Weather Data Guide (Carrier Corp.,1989). Figure 4.1 shows the design weather parameters for Chicago, Illinois displayed on the Edit Cityform.

If the Block Load weather database contains a city matching your project location, then you may onlyneed to specify the correct region, state/province/country and city from the Region, State/Province andCity selection lists to specify the correct weather parameters (see sections 4.2.1 - 4.2.3). Otherwise, itmay be necessary to determine the correct weather parameters, and enter this data into the appropriateinput boxes on the Edit City form.

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The following sections describe each of the input fields on the Edit City form. After you have entered thecorrect data on the Edit City form, click the OK button to exit the form.

Figure 4.1 Edit City Form

4.2.2 Region Selection ListCities in the Block Load weather database are divided into geographical regions. The Region selectionlist, located at the top of the Edit City form, is used to select the geographic region in which the BlockLoad project is located.

Your first step in navigating the Edit City form should be to choose the correct region from the Regionselection list.

4.2.3 State/Province Selection ListCities in each geographic region are further subdivided into smaller groups by the state, province orcountry in which they are located. The State/Province selection list, located near the top of the Edit Cityform, contains the states, provinces or countries which comprise the region chosen in the Regionselection list.

If the Block Load weather database does not have any cities for a particular state, province or country,then that state, province or country will not appear in the State/Province list. If you do not find the state,province or country in the list, check to make sure that the proper region has been selected in the Regionlist.

Your second step in navigating the Edit City form should be to choose the correct state, province orcountry from the State/Province selection list.

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4.2.4 City Selection ListThe City selection list contains all the cities in the Block Load weather database which fall geographicallyinto the state, province or country selected in the State/Province list. Use this list to choose the citywhich most closely matches the weather pattern of the project location. Note that this is usually, but notalways, the city which is geographically closest to the project location.

Whenever you select a new city using the City drop-down list. Block Load automatically displays thedesign weather parameters for the new city. The Data Source parameter is always listed as “CarrierDefaults” whenever a new city is selected. This is to communicate that the design weather parametersdisplayed on the Edit City form come from the Block Load weather database.

4.2.5 Latitude Input BoxThe latitude for the city is used in solar radiation calculations. It has a direct effect on the direction andintensity of solar radiation throughout the year. Positive values are used for cities north of the equator.Negative values are for cities south of the equator.

4.2.6 Elevation Input BoxThe elevation for the city is required for air property and psychrometric calculations since the propertiesof air vary with altitude. Positive values indicate the distance above sea level. Negative values define thedistance below sea level.

4.2.7 Summer Dry Bulb Input BoxThis design temperature defines the warmest outdoor air temperature considered for cooling conditions.For U.S. and Canadian cities in Carrier's weather database, ASHRAE 1% values are used. This meansthe summer dry-bulb is exceeded in only 1% of the hours during summer months. This value is used toderive cooling design temperature profiles.

4.2.8 Summer Wet Bulb Input BoxThis is the average wet-bulb temperature coincident with the summer design dry-bulb. It is used ingenerating wet-bulb temperature profiles for cooling design days.

4.2.9 Daily Range Input BoxThis represents the difference between maximum and minimum temperatures on a typical cooling designday. It is used in deriving temperature profiles for cooling design days.

4.2.10 Winter Dry Bulb Input BoxThis design temperature defines the coldest outdoor air temperature considered for heating conditions.For U.S. and Canadian cities in Carrier's weather database, ASHRAE 99% values are used. This meansthe winter design temperature is exceeded in 99% of the hours during the winter (i.e. it is colder 1% ofthe time). The winter design value is used for heating design calculations, and is indirectly involved in thederivation of cooling design temperature profiles.

4.2.11 Atmospheric Clearness Number Input BoxThe atmospheric clearness number (ACN) is a factor used to correct clear sky solar radiation estimatesfor unusually clear or hazy conditions. Values typically range from 1.15 for very clear conditions, to 1.00for typical conditions, to 0.85 for very hazy conditions. For more information on this factor, please referto the E20-II Weather Data Guide or the ASHRAE Handbook of Fundamentals.

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4.2.12 Data Source Text BoxThe data source describes the source of the design weather parameters displayed on the Edit City form.Data from Block Load’s weather database is listed as “Carrier Default”. If you change any of the designparameters, the data source will be listed as “User Defined”.

4.3 CHOOSING WEATHER DATA FOR THE DEFAULT PROJECT

You can choose the weather data that will be loaded each time you start a new project (using theFile:New option). This is done by using the Save button located on the Edit City form.Whenever you push the Save button, Block Load saves the weather properties - shown on the form -with the default project data.

Block Load 5-1

Chapter 5 ZONES

5.0 INTRODUCTION

This chapter deals with Block Load zones. It describes what zones are, what they are used for, and howto enter zone information into Block Load. Section 5.1 provides an overview of zones. The remainingsections in the chapter describe the various zone features available in Block Load.

5.1 OVERVIEW OF ZONES

A zone is a region of a building which is served by one thermostat. It is sometimes helpful to think of azone as a room in a building, although the definition of a zone is much broader than this. A zone can be aportion of a room, a collection of several rooms, or even an entire building.

A zone is defined by its physical characteristics such as its floor area, wall areas and U-values, roof areaand U-value, window area, orientation (N, S, E, W, etc.), and internal loads. This data is used todetermine the cooling and heating loads in the zone.

5.1.1 Types of ZonesMany projects involve a single-zone HVAC unit. A small office building which needs packaged rooftopequipment may be such an example. For such projects, you’d only need to enter one zone into BlockLoad. Often the zone will represent the entire building.

For other projects, two or more single-zone HVAC units are used. Examples of these applicationsinclude the use of multiple rooftop units for a shopping center or single-story office building, or the use offan coil or water source heat pump units in hotels and larger office buildings. For these projects, separatezones might be defined for the individual stores in the shopping center, or the different portions of theoffice building or hotel.

Finally, some projects utilize a central air handler which provides conditioning to various regions of abuilding, each with its own thermostat. A variable air volume (VAV) system in a large office building is acommon example of this application. For this situation, separate zones would be defined for the variousregions in the building.

Block Load allows you to combine zones and equipment in various ways so that all these differentapplications can be properly analyzed.

5.1.2 Manipulating Zone DataBlock Load offers you several ways to manipulate your zone data. You can create a new zone, modifythe data for an existing zone, delete a zone, create a copy of a zone, print input data for a zone, attachand detach zones from HVAC systems, and make global changes to zone data.

There are three ways to access the zone data manipulation features in Block Load:

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• Chapter 3 described how to create new zones, modify existing zones, and attach/detachzones using the zone icons on the Main window.

• The Zone Menu has options for creating new zones, modifying existing zones, deletingzones, copying and moving zones, and making global changes to all zones. These optionswill be described fully later in this chapter.

• The toolbar has a New Zone button for creating new zones. Operation of the New Zonebutton will be described fully later in this chapter.

5.2 THE ZONE MENU

The Zone Menu has options for creating new zones, modifying existing zones, deleting zones, copyingand moving zones, and making global changes to all zones. Each of these options is described in thefollowing sections.

5.2.1 New ZoneThe Zone:New menu option allows you to create a new zone. When you select this option, the ZoneInformation form appears (see Figure 5.2). The Zone Information form allows you to describe thephysical characteristics of the zone. It initially contains default zone data. Refer to the section entitled“Zone Information Form” later in this chapter for complete details on the Zone Information form.

When you return from the Zone Information form, a new zone icon is added to the Main window withthe name you’ve assigned on the Zone Information form. The zone will be attached to the currentlyselected HVAC system automatically; if there was no currently selected HVAC system when the NewZone option was chosen, then the zone will be assigned to the “Unattached Zones”.

5.2.2 Edit ZoneThe Zone:Edit menu option allows you to modify existing zone data. This option is only available if youhave selected (highlighted) a zone on the Main Window; if no zone is selected, the Edit option will begrayed out.

When you select the Edit option, the Zone Information form appears. It contains the current zone datafor the selected zone. Refer to the section entitled “Zone Information Form” later in this chapter forcomplete details on the Zone Information form.

5.2.3 Delete ZoneThe Zone:Delete option is used to delete zones from your Block Load project. This option is onlyavailable if you have selected (highlighted) a zone on the Main Window; if no zone is selected, the Deleteoption will be grayed out.

The Delete option works in slightly different ways, depending on whether the zone you are trying todelete is attached to a system, or whether it is in the Unattached Zones area. Each case is discussedbelow:

Deleting a zone from a system. When you “delete” a zone from a system, the zone is un-attached fromthe system to which it was attached. However, the zone is not actually deleted from your project. If thezone is attached to any other system, then no other change is made to your project. If, however, the zoneis not attached to any other system, then the zone is moved to the Unattached Zones area. To removethe zone from your project, you must delete it from the Unattached Zones area.

Deleting a zone from the Unattached Zones area. When you delete a zone from the Unattached Zonesarea, you are asked to confirm that you want the zone permanently removed from the project. If you

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respond Yes, the zone is deleted from the project. If you say No, then the zone is left in the UnattachedZones area.

5.2.4 Copy ZoneThe Zone:Copy option is used to attach the selected zone to another system in your Block Load project,while keeping it attached to its current system(s). This option is only available if you have selected(highlighted) a zone on the Main Window; if no zone is selected, the Copy option will be grayed out.

When you select this option, the Copy Zone form appears. The Copy Zone form asks you to select thesystems to which you’d like the zone attached. When you press the Copy button, the zone will beattached to the chosen systems.

If the zone were originally attached to a system, the zone will remain attached to that system. If the zonewere originally in the Unattached Zones area, the zone will be removed from the Unattached Zones areaafter the copy process is completed (because the zone is no longer unattached).

5.2.5 Move ZoneThe Zone:Move option is used to un-attach a zone from its current system, and attach it to anothersystem. This option is only available if you have selected (highlighted) a zone on the Main Window; if nozone is selected, the Move option will be grayed out.

When you select this option, the Move Zone form appears. The Move Zone form provides a list box ofall systems in your project, and asks you to pick the system to which you want the zone attached.

When a zone move is executed, the zone will no longer be attached to its original system.

5.2.6 Global ChangesThe Zone:Global Changes option is used to make changes to many zones simultaneously. Rather thanmodifying zone data one space at a time, this option allows you to choose a category of data and a groupof zones, and then make changes for all zones in the group. This feature is useful when changingcommon attributes of a zone. Typically, it is used to change a single zone characteristic. For example,you may wish to examine the variation in cooling loads if you were to replace the building’s standarddouble-pane windows with low-e windows. Using the Global Changes option, you could - in one step -change the window glass factor (shade coefficient) for every zone in the building.

When you select the Global Changes option, the Global Zone Changes form appears (see Figure 5.1).This form allows you to choose which data item is to be changed and how it is to be changed. The formis divided into three general areas: Data Selection, Global Values and Make Changes To Zones. Each isdescribed below.

Data Selection. Located on the left-hand side of this form are listed the various data items which can beglobally changed. The items are grouped by category. For example, in the Wall Data category are threeitems which can be selected: wall U-value, wall weight and wall color.

Use this section to choose the data item that you want globally changed. Only one item can be selectedat a time. Notice that the information in the Global Values area (discussed below) of the form changes tomatch the data item you’ve chosen in Data Selection.

Global Values. Located beneath the Data Selection area. Use this area to specify what value you wantto assign to the data item chosen in the Data Selection area (see above). You have two choices aboutwhat data is changed.

• You can change the selected data item in all selected zones in your project. Check the boxin front of the Change All Values prompt, then enter the value for the data item in theinput box.

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• You can change only the data which matches a value that you specify. To do this, firstmake sure the Change All Values box is unchecked. In the Change To input box, enterthe value that you want the data changed to. In the remaining input box, enter the valueof the data item that you want replaced.

Figure 5.1 The Global Zone Changes Form

Make Changes To Zones. Located on the right-hand side of the form, this area is used to select thezones to which you want the global changes to apply. The global changes will apply only to those zoneswhich are highlighted in this area.

5.3 THE NEW ZONE TOOLBAR BUTTON

The New Zone button is located on the toolbar. The New Zone toolbar button behaves exactly as theZone: New menu option (see section 5.2.1).

The New Zone button allows you to create a new zone. When you push this button, the ZoneInformation form appears (see Figure 5.2). The Zone Information form allows you to enter a descriptionof the zone. It initially contains default zone data. Refer to the section entitled “Zone Information Form”later in this chapter for complete details on the Zone Information form.

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When you return from the Zone Information form, a new zone icon is added to the Main window withthe name you’ve assigned on the Zone Information form. The zone will be attached to the currentlyselected HVAC system automatically; if there was no currently selected HVAC system when the NewZone option was chosen, then the zone will be assigned to the “Unattached Zones”.

Figure 5.2 The Zone Information Form (Zone Data 1 Tab)

5.4 THE ZONE INFORMATION FORM

The Zone Information form (shown in Figure 5.2) contains all the information needed to describe a zone.All entry of new zone data, and editing of existing zone data occurs on the Zone Information form. Theform is divided into several tabs. Each tab contains input boxes for a portion of the required zone data.For example, the Exposures tab contains input boxes for defining the wall and roof exposures and areasof a zone.

In addition to zone data input boxes, each tab contains an Information bar and a Parameter Limits bar.The Information bar serves as an automatic mini-Help system. As you move the cursor about the ZoneInformation form, it displays some useful, brief information about the data required in the input boxes.The Parameter Limits bar displays the allowable range of information which can be entered into an inputbox. For example, if the cursor is located on the Floor Area input box on the Zone Data 1 tab, theParameter Limits bar notes the minimum allowable floor area is 1.0 square foot (0.1 square meters); themaximum allowable floor area is 9,000,000 square feet (836,100 square meters).

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When you are finished entering zone data, click the OK button to save the data and return to the Mainwindow. You should review the zone data on each of the Zone Information form tabs before clicking theOK button.

If you wish to cancel any changes made to your zone data, click the Cancel button. Note that changescannot be canceled once you click OK.

The remainder of this section describes the zone data inputs on each of the Zone Information form tabs.

5.4.1 Zone Data 1 TabThe Zone Data 1 tab contains general zone data, and data to describe the lighting and other electric usagein the zone. Each data item is described below.

Zone Name. A reference name, up to 20 characters in length, is used to identify the zone. This nameappears on selection screens and on program printouts. The name may have embedded blanks andspecial characters.

Floor Area. This field is used to compute internal loads such as lighting and occupancy which aredefined on a per-unit-floor-area basis (per sqft or per sqm).

Building Weight. The overall weight of interior walls, floors and ceilings for the building plays amajor role in influencing how heat gains are converted into cooling loads. Heavy buildings tend toabsorb and store heat for longer periods than light buildings. Thus, there is more of a lag between thetime a heat gain occurs and the time it becomes an air-conditioning load. Building weight may beentered as "Light", "Medium" or "Heavy", or as an exact value in weight per unit floor area.Equivalencies for the light, medium and heavy categories are listed in Table 5.1.

TABLE 5.1 Wall, Roof and Building Weights

Weight (lb/sqft) Weight (kg/sqm)

Very Lt Light Medium Heavy Very Lt Light Medium Heavy

Walls 6.0 20.0 60.0 140.0 29.3 97.6 292.9 683.5

Roofs NA 10.0 30.0 55.0 NA 48.8 146.5 268.5

Building NA 30.0 70.0 130.0 NA 146.5 341.8 634.7

Lighting Usage. The lighting use in the zone can be specified in watts per unit floor area (W/ sqft orW/sqm) or in total watts. This input is the total of bulb wattage for all lights in the zone. To switchfrom one type of units to another use the drop down list.

Lighting Unoccupied Diversity Factor . The unoccupied diversity factor is the fraction of lightswhich are in use during the unoccupied equipment operation period. For example, a diversity factor of20% means that 20% of the lights are in use during the unoccupied period.

Because of the transient nature of lighting loads, lighting heat gains during one hour have an effect onloads during other hours of the day. Consequently, it is important to know the use pattern for lights forall 24 hours in the day. Further, in order to produce realistic load results, realistic diversity factorsmust be used.

Wattage Multiplier. The wattage multiplier describes the additional power required to operate aballast starter device for fluorescent lights. The actual lighting power draw is computed as fixturewatts times the wattage multiplier. When incandescent lights are used a wattage multiplier of 1.00should be entered.

Lighting Fixture Type. The proportions of convective and radiative heat transfer from lights will varydepending on the kind of lighting fixture used. This in turn affects the transient nature of loads due tolighting heat gain. In this program three lighting fixture types are offered:

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• Recessed, vented lighting fixtures,• Recessed, unvented lighting fixtures, or• Free-hanging lighting fixtures.

Other Electric Usage. Use of other electrical equipment such as computers, typewriters, vendingmachines, etc... is specified in either watts per unit floor area (W/ sqft or W/sqm) or in total watts. Toswitch from one type of units to the other, select from the drop down list.

Other Electric Unoccupied Diversity Factor . Defines the fraction of other electrical equipment inuse during the unoccupied equipment operation period. For example, a diversity factor of 10% meansthat 10% of the other electrical equipment is in use during the unoccupied period. For furtherinformation on the diversity factor and its importance, please refer to the discussion of the lightingdiversity factor.

5.4.2 Zone Data 2 TabFigure 5.3 illustrates Zone Data 2 tab. The Zone Data 2 tab contains information on the occupancy ofthe zone, its infiltration rate, details about basements or slab floors and other miscellaneous loads. Eachdata item is described below.

Occupancy. The number of people present in the zone is either specified directly or on the basis offloor area per person. To switch from one type of units to the other, use the drop down list.

People Unoccupied Diversity Factor . This factor defines the fraction of people present in the zoneduring the unoccupied equipment operation period. For example, a diversity factor of 5% means that5% of the total people are present during the unoccupied period.

Frequently this input is confusing to users because of the term "unoccupied". It is not meant to implythat no people are present. In this program the "unoccupied equipment operation" period refers to thehours when the equipment is off or in a set-up/set-back mode. For an office building, for example,cooling equipment typically operates to ventilate and cool the building during daytime working hours.At night, the equipment operates in set-up/set-back mode, only providing cooling or heating whennecessary. However, at night it is possible that custodial or security personnel are present. Hencepeople can be present in the building during the "unoccupied" period.

For further information on the importance of the diversity factor input, please refer to the discussion ofthe lighting diversity factor.

People Activity Level. Sensible and latent heat gains from people vary with the type of activity beingperformed in the zone. Five common activity levels are offered in the program. When one is chosen,the corresponding sensible and latent heat gains shown in Table 5.2 are used in load calculations.

If the values in Table 5.2 are not appropriate, the sixth activity level ("User-Defined") should be used.In this case sensible and latent heat gains are directly specified.

To change the activity level, select from the drop down list.

Sensible & Latent Heat Gains . If activity level six ("User-Defined") is selected, you are given theopportunity to specify people sensible and latent heat gains on a per person basis (BTU/h/person orW/person).

When any of the first five activity levels are selected, the standard heat gains for these levels aredisplayed on the input screen. In this case, these values may not be changed. Values can only bechanged by specifying the activity level as "User-Defined".

TABLE 5.2 People Activity Levels And Heat Gains

Sensible Latent Sensible Latent

Activity Level (Btu/hr-person) (Btu/hr-person) (W/person) (W/person)

Seated At Rest 230.0 120.0 67.4 35.2

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Office Work 245.0 205.0 71.8 60.1

Sedentary Work 280.0 270.0 82.1 79.1

Medium Work 295.0 455.0 86.5 133.4

Heavy Work 525.0 925.0 153.9 271.1

Figure 5.3 Zone Data 2 Tab

Miscellaneous Sensible & Latent Loads . Sensible and latent heat gains from other non-electricinternal sources can be considered using these inputs. Positive inputs indicate a heat gain; negativeinputs indicate a heat loss. Readers should note that miscellaneous internal loads are only consideredduring design cooling calculations. These inputs are useful for analyzing such things as the presence ofrefrigeration cases in supermarkets or the use of gas-fired kitchen equipment in restaurants.

Miscellaneous Load Unoccupied Diversity Factor . This factor defines the fraction of the specifiedmiscellaneous loads present during the unoccupied equipment operating period. A diversity factor of25%, for example, means that 25% of the heat gain is present during the unoccupied period.

While miscellaneous heat gains are assumed to become cooling loads instantly, the accumulation ofheat during a nighttime shutdown period can have a significant effect on pull down loads during thedaytime operating period. Hence, it is important to specify a realistic diversity factor in order to obtainreliable cooling load results.

Cooling & Heating Infiltration . Infiltration airflow may be specified as either an airflow per unitfloor area (CFM/sqft or L/s/sqm) or as a total airflow rate (CFM or L/s). To switch from one type of

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units to the other, use the drop down list. The cooling infiltration value is used for design cooling loadcalculations. The heating value is used for design heating load calculations.

Slab. Inputs are used to account for heat transmission losses through floors on grade, or throughfloors and walls below grade. These heat losses are only considered for design heating loadcalculations. The slab inputs have slightly different meanings for on-grade and below-grade cases.

For slabs on-grade:

• Slab Area is the area of the on-grade slab floor.

• Slab Perimeter is length of the perimeter of the on-grade slab floor.

• Slab Depth should be specified as zero for an on-grade slab.

For below-grade floors:

• Slab Area is the area of the below-grade basement floor.

• Slab Perimeter is the length of the perimeter of the below-grade basement floor.

• Slab Depth refers to the distance between the grade level and the top of the basementfloor surface. This input is used in conjunction with the slab perimeter to determinethe area of below-grade walls. The slab depth also influences rates of heat lossthrough the basement walls.

5.4.3 Building Materials TabFigure 5.4 illustrates the Bldg. Matl. tab. The Bldg. Matl. tab contains information on the thermalproperties of the walls, roofs and glass which are used in the zone construction. Also included on this tabis external shading dimensions. Each data item is described below.

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5-10 Block Load

Figure 5.4 Building Materials Tab

Wall U-Value. Wall U-values describe the overall insulating value of the wall assembly. U-values areused in transmission load calculations.

Wall Weight. The storage and transmission of heat by building walls depends partly on the weight ofthe wall. Wall weights may be specified as Very Light, Light, Medium or Heavy, or as an exact valueof the wall weight per unit surface area ( lb/sqft or kg/sqm). Equivalencies for the Very Light, Light,Medium and Heavy categories are shown in Table 5.1.

Wall Color. The color of the exterior wall surface affects the amount of solar energy absorbed by thewall. Colors are defined as Light, Medium or Dark. According to the ASHRAE Handbook ofFundamentals, the dark color specification should be used for all walls in industrial areas. The othercolor specifications should only be used when the designer is certain a wall will permanently remainlight or medium colored.

Roof U-Value. Roof U-values describe the overall insulating value of the roof assembly. U-values areused in transmission load calculations.

Roof Weight. The storage and transmission of heat by the roof depends partly on the weight of theroof assembly. Roof weights may be entered as Light, Medium or Heavy, or as an exact value of theroof weight per unit area (lb/sqft or kg/sqm). Equivalencies for the various weight categories are listedin Table 5.1.

Roof Color. The color of the exterior roof surface influences the amount of solar energy absorbed bythe roof. Colors are defined as Light, Medium or Dark. The ASHRAE Handbook of Fundamentalsrecommends that the dark specification be used for all roofs in industrial areas. The other color

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specifications should only be used when the designer is confident a roof will permanently remain lightor medium colored.

Glass U-Value. The glass U-value defines the insulating value of the window assembly. This U-valueis used in glass transmission load calculations.

Glass Factor. Defines how solar energy is transmitted through windows. In the ASHRAE Handbookthis factor is referred to as a "shading coefficient". The ASHRAE procedure for computing solar gainsevaluates solar energy transmission through a single pane of ordinary glass. The glass factor is used tocorrect solar gains for other types of glass such as double pane windows or reflective glass, or for theuse of internal shading devices. Chapter 27 of the ASHRAE Handbook of Fundamentals (1989)contains several tables of glass factors (shading coefficients) for various window designs.

Internal Shading. Plays a role in determining how soon a solar gain becomes a load. If internalshading devices such as curtains are used, a portion of the solar gain will be absorbed by the curtainand quickly convected to room air. If no shades are used, more of the solar energy will be absorbed byinterior floors and walls and will be convected to the air at a slower rate.

Readers should note that the "Internal Shading", "Glass Factor" and "Glass U-Value" inputs arerelated. If internal shades are specified, glass factors and U- values which are appropriate for theinternal shades should also be entered.

External Shading. Seven parameters are used to describe external shading features for windows in thezone. Five of these inputs deal with dimensions of overhangs, fins and reveals. External shadinginputs are discussed in the paragraphs below.

Window Height and Width. Used to describe the dimensions of one window aperture. For example,200 sqft of glass may be specified for the zone, but may consist of five windows, each 10 ft by 4 ft. Toperform external shading calculations, the dimensions of a single window aperture must be known. Itis assumed all windows associated with the external shading data have these dimensions. If this is notthe case, multiple glass types should be used, and separate shading types should be defined.

Reveal Depth. Defines the distance the glass pane is set into the wall of the building. Depth ismeasured from the wall surface to the outer surface of the glass.

Overhang Height. Defines the vertical distance between the top of the window aperture and thebottom of the overhang.

Overhang Extension. Defines the horizontal distance from the wall to the outer edge of the overhang.

Fin Separation. Defines the distance between the window aperture and the fin. It is assumed that finsare located on both sides of the window.

Fin Extension. Defines the distance from the wall to the outer edge of the fin.

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5-12 Block Load

Figure 5.5 Exposure Tab

5.4.4 Exposure TabFigure 5.5 illustrates the Exposure tab. The Exposure tab is used to describe the orientation of the zone,and its associated wall, roof and window areas. Each data item is described below.

Exposures. Defines the direction in which the exterior surface of the wall or roof faces. Block Loadoffers nine exposures. To enter a vertical wall, select from north, northeast, east, southeast, south,southwest, west and northwest. To enter a horizontal roof, choose the roof exposure.

Readers should note that only five exposures can be displayed on the screen at one time. To display theremaining exposures, use the slide bar at the bottom of the form.

Wall Type. Specify the wall or roof construction type. This refers to the Type 1, 2 or 3 wall or roofconstruction listed on the Bldg. Matl. tab. When you’ve chosen one of the eight principal exposures inthe Exposure input box, a summary of the three wall construction types will be displayed at the bottomof the form when the cursor is on the Wall Type input. If you’ve chosen the roof exposure, then thethree roof construction types will be displayed at the bottom of the form.

Gross Area. Wall and roof areas are entered on a gross area basis. This refers to the total surfacearea of the exposure, including the opaque surface (wall or roof) and the transparent surface (windowor skylight). During calculations, the program will automatically subtract glass areas from the grossareas to determine the net wall and roof areas.

Glass Type. Enter the glass type which applies to this exposure. This refers to the Type 1, 2 or 3glass construction listed on the Bldg. Matl. tab. When the cursor is on the Glass Type input box , thethree glass types are displayed at the bottom of the Exposure tab.

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Glass Area. The total glass surface area for each exposure must be defined. All glass areas for wallexposures are assumed to be vertical windows. The glass area input on the "Roof" line is used todefine horizontal skylight areas.

Shade Type. If the glass area listed above has any external shading, then enter the appropriate shadetype (1, 2 or 3) corresponding to the external shading data defined on the Bldg. Matl. tab. If noexternal shading is used, simply specify the shade type as zero. When the cursor is on the Shade Typeinput box, the three external shade types are displayed at the bottom of the Exposure tab.

Note that external shading is not considered for horizontal skylights, so only shade type values of zeroare permitted in this case.

5.4.5 Partitions TabFigure 5.6 illustrates the Partitions tab. Partitions refer to walls, floors or ceilings adjacent to anunconditioned region of the building. The Partitions tab is used to enter data for up to three partitions.Each data item is described below.

Net Area. Specify the surface area of the wall, floor or ceiling adjacent to the unconditioned region.

U-Value. The partition U-value describes the insulating value of the partition. This U-value is used intransmission load calculations.

Adjacent Region Temperature (Cooling). In order to compute heat transfer across the partition, thetemperature in the adjacent unconditioned region must be known. This input is used for design coolingcalculations only.

The temperature can be defined in two ways. The drop-down list to the right of the temperature inputbox allows you to choose whether to input the unconditioned space temperature directly, or define itbased on a percentage of the indoor-outdoor temperature difference.

A temperature input might be used when modeling a restaurant kitchen adjacent to a refrigeratedstoreroom in which the storeroom temperature is relatively constant.

A percentage input might be used to analyze offices adjacent to an unconditioned warehouse. In thiscase, the warehouse temperature might vary as a function of outdoor temperature. If for example a75% value is used, and the indoor and outdoor temperatures are 72 F and 92 F respectively, atemperature of 87 F in the adjacent region would be assumed when calculating partition heat gain.

Adjacent Region Temperature (Heating). This input is used to calculate heat transfer across thepartition for design heating load calculations. The same adjacent temperature and percentage inputoptions offered for the cooling input are offered for heating.

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Figure 5.6 Partitions Tab

Block Load 6-1

Chapter 6 HVAC SYSTEMS

6.0 INTRODUCTION

This chapter deals with HVAC systems. It describes what systems are, what they are used for, and howto enter system information into Block Load. Section 6.1 provides an overview of systems. Theremaining sections in the chapter describe the various system features in Block Load.

6.1 OVERVIEW OF HVAC SYSTEMS

An HVAC system is the airside equipment and controls used to provide cooling and heating to one ormore zones in a building. The system includes fans, thermostats, coils, ductwork, dampers, terminals,piping and controls which make up an air conditioning system.

HVAC system data is needed in order to perform design cooling and heating calculations. Thesecalculations determine how the system must be sized in order to satisfy peak cooling and heating loads ineach of the zones.

6.1.1 Types Of HVAC SystemsMany projects involve a single-zone HVAC unit. A small office building which needs packaged rooftopequipment may be such an example. For such projects, you’d only need to enter one HVAC system intoBlock Load. To this system, you would attach a single zone.

For other projects, two or more single-zone HVAC units are used. Examples of these applicationsinclude the use of multiple rooftop units for a shopping center or single-story office building. For theseprojects, separate HVAC systems might be defined for the individual stores in the shopping center, or thedifferent portions of the office building.

Some projects utilize a central air handler which provides conditioning to various regions of a building,each with its own thermostat. A variable air volume (VAV) system in a large office building is a commonexample of this application. For this situation, a single HVAC system would be defined, to which wouldbe attached zones for the various regions in the building.

Finally, some projects involve many single-zone HVAC units which are similar. Examples of theseapplications include the use of fan coil or water source heat pump units in hotels and larger officebuildings. For projects of this type, you can designate that each zone attached to an HVAC systemrepresents a separate air handling unit. In this way, a single HVAC system can be defined whosecharacteristics represent one single fan coil or water source heat pump. The many zones attached to thesystem (representing the individual hotel rooms, for example) would be treated as though each has itsown HVAC unit. In effect, Block Load treats this one HVAC system as multiple HVAC units.

Block Load provides ways to combine zones and HVAC systems in various ways so that all thesedifferent applications can be properly analyzed.

Chapter 6 HVAC Systems

6-2 Block Load

6.1.2 Manipulating HVAC SystemsBlock Load offers you several ways to manipulate your HVAC system data. You can create a newsystem, modify the data for an existing system, delete a system, create a copy of a system, print input datafor a system, and attach and detach zones from the system.

There are three ways to access the system data manipulation features in Block Load:

• Chapter 3 describes how to create new systems, modify existing systems, andattach/detach zones from the system using the zone icons on the Main window.

• The System Menu has options for creating new systems, modifying existing systems,deleting systems, and copying systems. These options will be described fully later in thischapter.

• The toolbar has a New System button for creating new systems. Operation of the NewSystem button will be described fully later in this chapter.

6.2 THE SYSTEM MENU

The System Menu has options for creating new systems, modifying existing systems, deleting systems,and copying systems. Each of these options is described in the following sections.

6.2.1 New SystemThe System:New System menu option allows you to create a new system. When you select this option,the HVAC System Information form appears (see Figure 6.1). The HVAC System Information formallows you to enter a description of the system and attach zones to the system. It initially contains defaultsystem data. Refer to the section entitled “HVAC System Information Form” later in this chapter forcomplete details on the HVAC System Information form.

When you return from the HVAC System Information form, a new system icon is added to the Mainwindow with the name you’ve assigned on the HVAC System Information form. If you attached anyzones to the system on the form, those zone icons will be attached to the new system icon automatically.

6.2.2 Edit SystemThe System:Edit System menu option allows you to modify existing system data. This menu option isonly available if you have a system selected on the Main Window. When you select this option, theHVAC System Information form will appear. It contains the current system data for the selected system.Refer to the section entitled “HVAC System Information Form” later in this chapter for complete detailson the HVAC System Information form.

6.2.3 Delete SystemThe System: Delete System option is used to delete systems from your Block Load project. This menuoption is only available if you have a system selected on the Main Window. When you select this option,Block Load asks you to confirm that you want the selected system removed from the project. Note thatany zones attached to the system will not be deleted. If they are not attached to any other system , theywill be moved to the Unattached Zones area.

6.2.4 Copy SystemThe System: Copy System option is used to create a copy of any system in your Block Load project.When you select this option, Block Load creates a new system which is an exact copy of the original,except that the name is modified. If the original system had any zones attached, the new system will havethe same zones attached.

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To print the System Input report, press the Print button in the upper left-hand corner of the report screen,or choose the File:Print command. Refer to Chapter 7 for more details on the operation of the reportscreen.

6.3 THE NEW SYSTEM TOOLBAR BUTTON

The New System button is located on the toolbar. The New System toolbar button behaves exactly asthe System: New System menu option (see section 6.2.1).

The New System button allows you to create a new system. When you push this button, the HVACSystem Information form appears (see Figure 6.1). The HVAC System Information form allows you toenter a description of the system. It initially contains default system data. Refer to the section entitled“HVAC System Information Form” later in this chapter for complete details on the HVAC SystemInformation form.

When you return from the HVAC System Information form, a new system icon is added to the Mainwindow with the name you’ve assigned on the HVAC System Information form. If you attached anyzones to the system on the form, those zone icons will be attached to the new system icon automatically.

6.4 THE HVAC SYSTEM INFORMATION FORM

The HVAC System Information form (shown in Figure 6.1) contains all the information needed todescribe a system. All entry of new system data, and editing of existing system data occurs on the HVACSystem Information form. The form is divided into several tabs. Each tab contains input boxes for aportion of the required system data.

In addition to system data input boxes, each tab contains an Information bar and a Parameter Limits bar.The Information bar serves as an automatic mini-Help system. As you move the cursor about the HVACSystem Information form, it displays some useful, brief information about the data required in the inputboxes. The Parameter Limits bar displays the allowable range of information which can be entered intoan input box. For example, if the cursor is located on the System Name input box on the HVAC SystemData 1 tab, the Parameter Limits bar notes that you may enter up to 24 characters for the name.

When you are finished entering system data, click the OK button to save the data and return to the Mainwindow. [Note that the OK button is located on HVAC System Data 1 tab]. You should review thesystem data on each of the HVAC System Information form tabs before clicking the OK button.

If you wish to cancel any changes made to your system data, go to the HVAC System Data 1 tab andclick Cancel. Note that changes cannot be cancelled once you click OK.

The remainder of this section describes the system data inputs on each of the HVAC System Informationform tabs.

6.4.1 HVAC System Data 1 TabThe HVAC System Data 1 tab contains information about when the system operates, fan data, and supplyand ventilation air specifications. It is also where you can designate that each zone has its own HVACunit. Each data item is described below.

System Name. A reference name up to 24 characters in length is used to identify the system. Thisname appears on selection screens and program printouts.

System Type. The system type defines the capabilities of the HVAC system and how it providesconditioning. This input also influences how certain sizing calculations are performed. Seven systemtype options are offered:

• Cooling and Warm Air Heating


6-4 Block Load

• Cooling and Hydronic Heating

• Cooling and Electric Heating

• Cooling Only

• Warm Air Heating Only

• Hydronic Heating Only

• Electric Heating Only

Readers should note that hydronic heating refers to the use of hot water baseboard units. Electricheating refers to the use of electric baseboard units. For warm air heating, the heat source (electric,direct-fired, or hot water) does not need to be known.

Depending on the system type selected, various sizing calculations will be performed differently:

• For warm air heating systems, an airflow rate and supply temperature for heating willbe determined.

• For hydronic heating systems a baseboard unit hot water flow rate will be computed.

• For electric heating systems, the required baseboard heater wattage will be calculated.

• For systems which do both cooling and heating, ventilation airflow will be based onthe cooling sizing calculation.

• For a "Cooling and Warm Air Heating" system, the supply airflow rate is based oncooling sizing criteria. This supply airflow rate will also be used in design heatingcalculations.


Block Load 6-5

Figure 6.1 HVAC System Data 1 Tab

System Start Time & Duration . These two inputs define the "occupied" equipment operating period.During this period the equipment provides both ventilation and conditioning. This is referred to as the"occupied" period because it typically coincides with the times people are present in the building. Forthe remaining hours of the day, it is assumed the equipment operates in a set-up/set-back mode.Because fewer people or no people at all are present during set-up/set-back operation it is oftenreferred to as the "unoccupied period".

To define the occupied operating period, specify the hour the period begins, and the number of hours itlasts. A 24-hour clock format is used when defining start times. Hour 0000 corresponds to midnight,for example, 0100 corresponds to 1am, 0200 corresponds to 2am, etc ...

Sizing Specification: Supply . Supply air sizing calculations are based on this input. Sizing can bebased on:

• An airflow rate per unit floor area (CFM/sqft or L/s/sqm),

• A specified supply airflow rate (CFM or L/s), or

• A supply temperature.

If an airflow rate is defined, the program will calculate the required supply temperature. Likewise, if asupply temperature is entered, the program will determine the required airflow rate.

To change the type of units for the supply specification, select from the drop down list.

Whenever the current HVAC system provides cooling, this input pertains to the sizing of coolingsupply air. If the system type is "Warm Air Heating Only", this input defines the heating airflow sizingcriteria. Finally, if the system type is either " hydronic" or "electric" baseboard heating only, thissupply input is not used in sizing calculations.

It is also worth noting that when a cooling supply temperature is specified, it must be less than theoccupied cooling thermostat set-point. The parameter limits will change according to the thermostatsetpoint. The Max limit will be 5° F less then the setpoint. When a heating supply temperature isentered, it must be greater than the heating thermostat setpoint. The cooling setpoint must always behigher than the heating setpoint, even if you have specified a heating-only system.

Ventilation Air Sizing Specification. Ventilation air sizing calculations are based on this input.Sizing can be based on:

• An airflow per unit floor area (CFM/sqft or L/s/sqm),

• A specified ventilation airflow rate (CFM or L/s),

• A fixed percentage of the supply airflow rate, or

• An airflow per person value (CFM/person or L/s/person).

To change the type of units for the ventilation specification, select from the drop down list.

Whenever the current HVAC system provides cooling, this input defines how ventilation air for coolingwill be sized. If the system provides both cooling and heating, the ventilation airflow rate calculatedfor cooling will also be used for design heating calculations. Finally, for heating-only systems theventilation inputs are used specifically for heating sizing calculations.

Direct Exhaust Air Sizing Specification. "Direct exhaust" refers to air which is exhausted from azone rather than return to the central air handler through a return duct or plenum. Whether air isexhausted before or after the return plenum can have an important effect on the temperature rise in aplenum and the resulting cooling coil loads. Direct exhaust air sizing calculations can either be basedon:


6-6 Block Load

• A specified direct exhaust airflow rate (CFM or L/s/sqm), or

• A fixed percentage of the ventilation airflow rate.

Readers should note that this sizing input is only used for cooling load calculations.

Hot Water Delta-T. If hydronic baseboard heating is used, a delta-T value for water flowing throughthe heating coil must be specified. The required hot water flow rate is then calculated based on thissizing value and the design heating load. This input only appears when the "system type" inputspecifies that hydronic baseboard heating is used.

Fan Configuration. The air handling unit may have either a draw- thru or blow-thru configuration.For a draw-thru configuration, the cooling coil is located upstream of the fan. For blow- thru, thecooling coil is downstream of the fan.

This input is only used in cooling load calculations. The position of the cooling coil relative to the fanwill have an effect on the coil inlet and outlet temperatures. This in turn will influence the coilpsychrometrics.

Fan Static Pressure, Brakehorsepower or kW . In order to calculate fan heat gain, somecharacteristic of fan operation must be known. Because fan data is provided in various forms fordifferent types of equipment, users are provided with three alternatives. Users can specify the:

• Fan total static pressure (inches of water gage, or Pascals),

• Fan brakehorsepower, or

• Fan kW.

When total static pressure is used as the fan input, an assumed fan efficiency value of 54% is used inheat gain calculations. This is a typical efficiency and is a combined value for the motor, fan drive andfan mechanical efficiencies.

When brakehorsepower is used as the fan input, an assumed fan motor efficiency of 90% is used inheat gain calculations.

If these assumptions are not appropriate for a job, the fan kW input option should be utilized instead.

System Arrangement. Defines how the HVAC system and zone input data are to be combined duringload and sizing calculations. Two arrangement options are offered:

• All zones served by a common air handler.

• Each zone served by a separate air handler.

All Zones Served By A Common Air Handler. Block Load will treat this system as a single airhandler serving all attached zones. During load calculations, the HVAC system inputs and inputsfor all the zones selected will be put to use together. Required supply airflow rates will bedetermined for all zones involved, as well as for the central supply fan. The maximum centralcooling coil load will also be identified. Depending on the type of heating, either a central heatingcoil load will be determined for a warm air heating system, or baseboard loads will be computedfor each zone when hydronic or electric baseboard heating is used.

Each Zone Served By A Separate Air Handler. Block Load will treat this system as a series ofsingle-zone systems, each serving one of the attached zones. This is particularly useful inapplications such as hotels, where each room may have its own packaged air conditioner. Ratherthan force you to run load calculations for each single-zone unit separately, this option provides away to quickly run calculations for the entire project all at one time.

During load calculations, the HVAC system inputs will be used with each zone separately toperform load and sizing calculations. If, for example, the job involved 20 stores in a strip shoppingcenter, the program will generate separate load and sizing printouts for the 20 packaged units usedon the job. This feature allows you to complete calculations for a project quickly and efficiently.


Block Load 6-7

6.4.2 HVAC System Data 2 TabFigure 6.2 illustrates the HVAC System Data 2 tab. The HVAC System Data 2 tab contains thermostatsetpoint and return air plenum information. It is also where you can designate sensible, latent and heatingsafety factors. Each data item is described below.

Cooling Thermostat Setpoint(Occupied Period). This is the thermostat setpoint for cooling used forthe "occupied" equipment operation period.

Figure 6.2 HVAC System Data 2 Tab

Cooling Thermostat Setpoint (Unoccupied Period). This is the thermostat setpoint used for the"unoccupied" equipment operation period. Users may either enter the unoccupied setpoint temperatureor enter an [N] to specify that cooling is never provided during the unoccupied period. When a setpointtemperature is specified, it must be greater than or equal to the occupied cooling setpoint. Theprogram will not accept values less than the occupied setpoint.

While design cooling loads will never occur during the "unoccupied" period, cooling loads for all 24-hours in the day must be calculated in order to properly evaluate morning pulldown loads. Forexample, smaller pulldown loads would typically result when occupied and unoccupied setpoints of75/78 F are used compared to setpoints of 75/95 F.

Heating Thermostat Setpoint. For heating load calculations, the heating thermostat setpoint must bedefined. The heating setpoint must be less than or equal to the occupied cooling setpoint.

Cooling Coil Bypass Factor is used to evaluate dehumidification occurring at the cooling coil. Ingeneral, the bypass factor is a measure of the approach to the apparatus dewpoint (ADP) for airflowing through the coil.

Values of coil bypass factors are typically published in product literature. Note that somemanufacturers publish a "contact factor" rather than a bypass factor. The bypass factor is simply ( 1 -contact factor).


6-8 Block Load

Cooling Safety Factors (Sensible & Latent). The next two inputs are cooling safety factors. Indesign calculations, a factor is often introduced to provide a margin of safety. Separate safety factorsmay be specified for sensible and latent loads.

During calculations, zone cooling loads are increased by this safety amount before supply airflow andcooling coil computations are performed.

Heating Safety Factor. In design heating calculations, a factor is also often introduced to provide amargin of safety. During heating load calculations the zone heating loads are increased by this factorbefore airflow or baseboard sizing calculations are performed.

Is a Return Plenum Used? If a return plenum is used, a portion of the roof, lighting and wall loadsmay be removed by air flowing through the plenum. This reduces the room component of the load andcan have a significant effect on terminal sizing and system operation. When a plenum is specified,additional questions for roof, lighting and wall plenum loads will be displayed.

% of Roof Load to Plenum. When a plenum is used, a portion of the roof transmission load will becarried away by air flowing through the plenum. Therefore, only a portion of the total roof load willreach the zone. The portion of the roof load removed by plenum air is defined as a percentage of thetotal roof load.

% of Lighting Load to Plenum. A portion of the lighting load will also be removed by air flowingthrough the plenum. This typically happens when the lighting fixtures are recessed into the ceiling sothat plenum air flows directly over or through the fixture. Plenum heat gain from lights is estimated asa percentage of the total lighting heat gain.

% of Wall Load to Plenum. A portion of wall transmission loads may be removed by plenum air.The fraction of the wall load reaching the plenum can usually be estimated as the ratio of wall areaadjacent to the plenum divided by the total wall area.

6.4.3 Zones TabFigure 6.3 illustrates the Zones tab. The Zones tab contains a list of all zones in your project. It is usedto attach or detach zones from the HVAC system. Highlighted zones are attached, while all others arenot attached. To attach a previously-unattached zone, click on it; it will immediately become highlighted.To detach a previously-attached zone, click on it; it will immediately become un-highlighted.


Block Load 6-9

Figure 6.3 Zones Tab


6-10 Block Load


Block Load 7-1

Chapter 7 REPORTS

7.0 INTRODUCTION

This chapter describes the contents and operation of the Reports Menu. The Reports Menu allows youaccess to all of the input and output reports generated by Block Load. Reports contain the data inputsand results of the design cooling and heating load calculations performed by the program, including all ofthe information needed to properly select cooling and heating coils, fans and terminals.

There are two types of reports offered in Block Load: input reports and output reports. Input reportscontain only the project data that you have entered into the program. Output reports contain the resultsof cooling and heating load calculations which Block Load has performed on your project data.

This chapter will describe the various input and output reports available in Block Load, and how youaccess them.

7.1 OVERVIEW OF INPUT REPORTS

Block Load offers two input reports. They are:

Zone Input Report. The Zone Input Report contains all of the input data for a single zone. It is foundon the Zone:Zone Input Report option from the Reports Menu.

To generate a Zone Input Report, you must first select a zone on the Main Window. [If you do notselect a zone, the Zone Input Report option will be grayed out on the Reports Menu]. Then select theReports:Zone:Zone Input Report option. The Block Load Report form will display the Zone InputReport (refer to the Block Load Report Form section in this chapter for features of this report form).

System Input Report. The System Input Report contains all of the data for a single system. It is foundon the System:System Input Report option from the Reports Menu.

To generate a System Input Report, you must first select a system on the Main Window. [If you do notselect a system, the System Input Report option will be grayed out on the Reports Menu]. Then selectthe Reports:System:System Input Report option. The Block Load Report form will display the SystemInput Report (refer to the Block Load Report Form section in this chapter for features of this reportform).

7.2 OVERVIEW OF OUTPUT REPORTS

The purposes of Block Load are to compute design cooling and heating loads, and to size the HVACequipment which will maintain comfort conditions within your project’s building. The load and sizinginformation generated in Block Load is provided to you in a variety of reports.

There are three steps required to generate an output report. They are:

1. Select the HVAC system for which reports are to be generated.

Chapter 7 REPORTS

7-2 Block Load

2. Choose the calculation times.

3. Select the reports to view or print.

The following sections will cover each of these steps in greater detail.

7.3 SELECTING AN HVAC SYSTEM

In order to calculate load or generate reports, you must first choose an HVAC system for which reportsare to be generated. The Main Window allows you a fast and easy way to select a system. To select anHVAC system from the Main window, simply single-click on the HVAC system icon desired. Refer toChapter 3 for more details on selecting systems.

In Block Load, only one system can be selected at a time. When you select a new system, the previously-selected system is automatically de-selected. The Main Window provides a visual clue to indicate whichHVAC system is currently selected. The box surrounding the selected system icon and attached zones isdrawn with thick, dark lines.

Note that you can have situations where no system is currently selected.

7.4 CHOOSING THE CALCULATION TIMES

By default, Block Load will calculate loads for an entire 24-hour design day for each month of the year.By doing so, you are guaranteed that Block Load can identify the peak load conditions within yourbuilding.

However, there may be times when you do not wish to have Block Load “wasting time” performingcalculations for months or hours which are of no consequence to you. For example, you may know forcertain that none of your zones or the HVAC system peak in winter months such as December, Januaryor February. In these cases, you may wish to exclude those months from Block Load’s calculations.

The Reports:Calculation Parameters menu option is used to set the months and hours for which you wantcalculations run. When this option is chosen, the Calculation Parameters form appears (see Figure 7.1).Each of the required inputs is explained below. The Options:Display Calculation Times menu item can beused to display the currently chosen calculation months and hours on the Main Window.

REPORTS Chapter 7

Block Load 7-3

Figure 7.1 Calculation Parameters Form

First Month and Last Month. These inputs are used to specify the months for which the designcooling calculations will be performed. Months are chosen to ensure that times of year when maximumcooling loads occur are included in the calculations. To be absolutely sure maximum loads areidentified, all months should be selected (eg., select January as the First Month, and December as theLast Month). However, based on prior experience, you may be able to select a smaller range ofmonths and still be sure that peak loads have been identified. At a minimum. it is best to include arange of months encompassing the times when maximum solar gains on the different buildingexposures occur, and the times when maximum outdoor temperatures occur.

Month selections are made by touching the First Month or Last Month drop down boxes, then selectingthe month you desire.

First Hour and Last Hour. Cooling load calculations can also be performed for any group ofconsecutive hours during the day. This group is defined by specifying the first and last hours in thegroup. Hours are specified using a 24-hour clock convention. Hour 0000 corresponds to midnight,0100 corresponds to 1am, 0200 corresponds to 2am, etc ...

Hour selections are made by selecting the appropriate times from the First Hour and Last Hour dropdown lists.

7.5 SELECTING REPORTS

Results from the load and sizing calculations can be displayed or printed from the Reports menu. Whenyou select an output report from the Reports Menu, Block Load will automatically determine whetherload calculations need to be performed (if the calculations have previously been run, then they will notneed to be run again). Each output report listed on the Reports Menu is described below.System:System Sizing Summary. The standard program output provides all load and sizing datanecessary to select cooling and heating equipment for the job. This includes cooling sizing data such asthe required supply temperature and airflow rates, coil loads and coil operating conditions. Heatingsizing data describes maximum loads, and required airflow rates, hot water flow rates or baseboardwattages depending on the type of heating used. In addition, useful check figures are also provided.

Chapter 7 REPORTS

7-4 Block Load

System:Detailed System Load Report. This printout provides a component-by-component breakdownof loads for the month and hour in which the maximum cooling coil load occurs. Component loads arealso provided for the design heating condition. This printout is typically used when detailed informationabout a job is required for troubleshooting or documentation purposes.

System:Design Psychrometric Process. The psychrometric output is a graphical report which plots theair conditioning processes for the entire HVAC system on a psychrometric chart. When you select thisoutput, the Psychrometric Graph form is displayed. This form allows you to customize the psychrometricgraph a great deal. In order to access the customizability features of this form, right-click anywherewithin the graph area. A menu will appear, containing all of the customizability options allowed.

Zone:Detailed Zone Load Report. This printout provides a listing of component loads for each zoneserved by the HVAC system. Load data is printed for the month and hour in which the maximumsensible load for each zone occurs. A one page printout is generated for each zone involved. Typically,this printout is generated when very detailed information about a job is needed for troubleshooting ordocumentation purposes.

Weather:Design Temperature Report. This output contains a table of the design weather parameters(which are project inputs), and a table of design drybulb and wetbulb temperatures for a selected month.In addition, a graph of the drybulb and wetbulb temperature profiles is contained in the report.

Weather:Design Solar Report. This output contains a table of the design weather parameters (whichare project inputs), and a table of the maximum solar heat gains on each of the principal exposures foreach month of the year.

7.6 THE BLOCK LOAD REPORT FORM

All reports, except for the Psychrometric Graph, are displayed on the Block Load Report form. Thisform has several useful features, documented below.

7.6.1 Printing A ReportThe Block Load Report form provides two ways to print the currently displayed report. You can selectthe File:Print option or simply press the Print button located at the top of the form.

7.6.2 Paging Through A ReportFour buttons - located in the lower left-hand corner of the form - allow you an easy and convenient wayto quickly go to the previous page of the report, the next page, the first page or the last page. A pagecounter separating the buttons lets you know which page of the report you are viewing.

7.6.3 Selecting Other ReportsThe Reports list is located at the top of the Block Load Report form. This allows you a quick way toaccess other available reports. For example, if you are viewing one of the output reports, the Reports listcontains the names of all the other input and output reports offered in Block Load. Choosing any ofthese reports will immediately display that report on the form.

7.6.4 Exiting The Report FormBlock Load offers you three ways to close the Block Load Report form. You may:

• press the Exit button at the top of the form.

• press the “Close” button (the “X” in the upper right-hand corner of the form).

• select the File:Exit menu option.

Block Load 8-1

CHAPTER 8 COOLING DESIGN CALCULATIONS

8.0 INTRODUCTION

This chapter describes design load calculations and equipment sizing procedures for cooling systems.

Maximum cooling loads are determined using an hour-by-hour calculation approach. Loads for a numberof hours specified are examined. Maximum cooling loads are identified from among this group of hoursand are then used to size the cooling system.

Cooling analyses for single-zone and multiple-zone systems differ slightly. For single-zone HVACsystems, the analysis involves two stages:

1. Zone Load Calculations. First, zone sensible loads are computed for the months and hoursspecified by the user. A "zone load" is the amount of heat which must be removed in order tomaintain zone air at the cooling setpoint temperature.

2. Cooling Coil Load Calculations. Next, system operation is analyzed in order to determine thesystem airflow rate and the sensible and latent cooling coil loads. Airflows and coil loads aredetermined for all the months and hours specified.

The sensible and latent coil loads can then be combined to determine the total cooling coil load. Themaximum coil load is identified from among all the months and hours considered. Sections 8.1 and 8.2describe these calculations for single-zone systems in more detail.

Calculations for multiple-zone systems are discussed in section 8.3.

8.1 ZONE COOLING LOAD CALCULATIONS

In the first step in the analysis zone sensible cooling loads are calculated. A zone load is the amount ofheat which must be removed from a zone in order to maintain zone air at the cooling setpointtemperature. This load is the sum of a number of transmission, infiltration, solar and internal loadcomponents:

Qs = [ Qw + Qg + Qr + Qp + Qslr + Qlt + Qpe + Qoe + Qms + Qi ] [ 1 + Fss/100 ] .... (Eqn 8-1)

where:

Qs = Zone sensible load (BTU/hr or W).

Qw = Wall transmission load (BTU/hr or W).

Qg = Glass transmission load (BTU/hr or W).

Qr = Roof transmission load (BTU/hr or W).

Qp = Partition transmission load (BTU/hr or W).

Qslr = Solar load (BTU/hr or W).

Qlt = Lighting load (BTU/hr or W).

Chapter 8 COOLING DESIGN CALCULATIONS

8-2 Block Load

Qpe = People sensible load (BTU/hr or W).

Qoe = Other electrical load (BTU/hr or W).

Qms = Miscellaneous sensible load (BTU/hr or W).

Qi = Sensible infiltration load (BTU/hr or W).

Fss = Sensible cooling safety factor (%).

In this program, zone loads are computed using the Transfer Function methodology. This proceduretakes into account the transient heat transfer characteristics of all component loads in the building.Currently, Transfer Functions are recommended by ASHRAE as the preferred means of computinghourly loads. These calculations are described in full detail in the E20/TF Load Manual.

Finally, you should note that a "zone load" is different from a "coil load". A coil load is the amount ofheat removed at the cooling coil. Heat removed at the coil is a combination of heat removed from thezone plus fan and ventilation heat gains, plus portions of the plenum heat gains. Coil load calculations aredescribed in the next section.

8.2 COOLING COIL LOAD CALCULATIONS - SINGLE-ZONE SYSTEMS

In the second step of the process, system operation is analyzed in order to determine cooling coil loads.In this procedure airflow rates, dry-bulb temperatures and humidities at all key points in the system arecomputed. The ultimate goal is to determine the coil inlet and outlet conditions so that the coil load canbe calculated. Coil loads are determined for a number of hours and the maximum coil load among thesehours is then identified.

This analysis is performed in two parts. The first involves a sensible analysis of the system which leads toa calculation of the sensible cooling coil load. In the second part, system humidities are determined inorder to compute the latent cooling coil load.

Step-by-step procedures for both the sensible and latent system analyses are described in remainder ofthis section.

A. SENSIBLE ANALYSIS1. Calculate Supply Air Characteristics. First, the zone sensible load is used to determine either the

supply airflow rate or the supply temperature. Different calculations are required depending onwhich supply characteristic the user defined during HVAC system inputs.

a. Supply Airflow Rate Defined as CFM (L/s) or CFM/ sqft (L/s/sqm). In this case thespecified airflow rate will be used for all hourly cooling coil load calculations. For each hour,a required supply air temperature is computed by solving equation 8-2 for Ts.

Qs = pa Vs Cpa Fu (Tc - Ts) .... (Eqn 8-2)

where:

Qs = Zone sensible load (BTU/hr or W).

pa = Density of air. Value is adjusted for site elevation.

= psl Pba / Psl

Vs = System supply airflow rate (CFM or L/s). For the case in which supply air isspecified as CFM/sqft (L/s/sqm) this value is multiplied by the total floor areaserved by the HVAC system to obtain the system CFM.

Cpa = Specific heat for air (.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

COOLING DESIGN CALCULATIONS Chapter 8

Block Load 8-3

Fu = Units conversion factor.

= (60 min)/hr for English units.

= m3/(1000 L) for S.I. Metric units.

Tc = Cooling thermostat setpoint temperature (F or C).

Ts = Supply air temperature (F or C).

psl = Density of air for standard sea level conditions (0.075 lbm/ft3 or 1.201 kg/m3).

Pba = Standard atmospheric pressure at site elevation ( psia or kPa).

= 14.696 (1 - 6.87535x10-6E)5.2561 for English units.

= 101.3 (1 - 2.25569x10-5E)5.2561 for Metric units.

Psl = Standard atmospheric pressure at sea level (14.696 psia or 101.3 kPa).

E = Site elevation (feet or meters above sea level).

b. Supply Temperature Defined. In this case the temperature will be used for all hourly coolingcoil load calculations. For each hour the required supply airflow rate is computed by solvingEquation 8-2 for Vs.

2. Calculate Supply Fan Heat Gain. Based on the system supply air flow rate, the fan heat gain canbe computed next. Fan heat gain is due to friction between air and the fan blades, energy added tothe air by compression, energy lost in the fan drive mechanism, and energy losses in the fan motor.Depending on data supplied by the user, fan heat gain is calculated in one of three different ways:

a. If a total static pressure is defined for the fan, heat gain is determined using the equation:

Qf = Ffu Vs Tsp / nf .... (Eqn 8-3)

where:

Qf = Fan heat gain (BTU/hr or W).

Vs = Supply airflow rate (CFM or L/s).

Tsp = Total static pressure across fan (in wg or Pa).

nf = Combined fan drive, mechanical and motor efficiency (dimensionless). A value of0.54 (i.e. 54%) is assumed.

Ffu = Units conversion factor.

= .4003 for English units.

= (62.3 lbm water/cuft)(ft/12 in)(60 min/hr)(.001285 BTU/ft- lb)

= m3/(1000 L) for Metric units.

b. If a fan brakehorsepower is specified by the user, heat gain is computed using the equation:

Qf = Ffu BHP / nm .... (Eqn 8-4)

where:



= 2544.3 for English units.

= (745.7 W/hp)(3.412 BTU/hr/W)


8-4 Block Load

= 745.7 W/hp for Metric units.

BHP = Fan brakehorsepower specified by user.

nm = Fan motor efficiency (dimensionless). A value of 0.90 (i.e. 90%) is assumed.

c. Finally, if fan kW is directly specified by the user, heat gain is computed using the equation:

Qf = Ffu Pf .... (Eqn 8-5)

where:



= 3412 (BTU/hr)/kW for English units.

= 1000 W/kW for Metric units.

Pf = Fan kW specified by user.

3. Calculate Coil Outlet Temperature. Based on the values computed thus far, a coil outlettemperature can be determined next. The coil outlet temperature will be used later to compute thecoil sensible load. Two different calculation procedures are used depending on whether the supplyfan configuration is blow-thru or draw-thru:

a. Blow-Thru Fans. For this fan configuration, the coil outlet temperature, Tco is equal to thesupply air temperature, Ts.

b. Draw-Thru Fans. For this configuration, the coil outlet temperature is lower than the supplytemperature due to fan heat gain. The coil outlet temperature is computed using the equation:

Tco = Ts - Qf / (pa Cpa Vs Fu) .... (Eqn 8-6)

where:

Tco = Coil outlet temperature (F or C).


Qf = Supply fan heat gain (BTU/hr or W).

pa = Air density (lb/ft3 or kg/m3). Values are adjusted for elevation.

Cpa = Specific heat of air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vs = System supply airflow rate (CFM or L/s).


= 60 min/hr for English units.


4. Calculate Ventilation Airflow Rate. This and the following four steps are used to determine thecooling coil inlet temperature. This process involves working forward from the point air exits fromthe zone to the point where air enters the cooling coil, solving for airflow rates and temperatures ateach point along the way.

First the ventilation airflow rate must be determined. Airflow is calculated in four different waysdepending on how the user has defined ventilation air:

a. When the ventilation air per unit floor area (CFM/ sqft or L/s/sqm) has been specified, theairflow rate is calculated as:


Block Load 8-5

Vv = Vvf Atot .... (Eqn 8-7)

where:

Vv = Ventilation airflow rate (CFM or L/s).

Vvf = Ventilation airflow per unit floor area (CFM/ sqft or L/s/sqm).

Atot = Total floor area served by system (sqft or sqm).

b. When the ventilation airflow rate (CFM or L/s) is directly specified, no calculation isnecessary.

c. When ventilation is specified as a percentage of the supply airflow rate, airflow is calculatedas:

Vv = Vs Fv/100 .... (Eqn 8-8)

where:


Vs = Supply airflow rate (CFM or L/s)

Fv = Percentage value specified by user (%).

d. Finally, when ventilation is specified on an airflow per person basis (CFM/person orL/s/person), the airflow is calculated as:

Vv = Vvp P .... (Eqn 8-9)

where:


Vvp = Ventilation airflow rate per person (CFM/person or L/s/person).

P = Total number of people occupying zone served by the HVAC system at maximumoccupancy.

It is important to note that in some unusual situations, the ventilation airflow rate computed will belarger than the system supply airflow rate. This could occur when a fixed ventilation rate (CFM orL/s) and a supply air temperature are defined. For this combination of inputs, it is possible therequired supply airflow rate that is calculated will be less than the ventilation airflow specified.

When this happens, the supply airflow rate is increased to equal the ventilation airflow rate. Thisis done because it is assumed ventilation rates must be maintained to conform to codes. After thesupply airflow rate has been adjusted, steps 1 through 3 in the sensible analysis procedure must berepeated. Further, in order to maintain the specified supply air temperature, reheat will be requireddownstream of the cooling coil.

5. Calculate Direct Exhaust Airflow Rates. In some cases, air may be directly exhausted from thezone before it enters the return duct or plenum. This airflow rate is determined in two differentways depending on the user's HVAC system inputs:

a. When the direct exhaust air is defined as a total airflow (CFM o r L/s), no calculations arenecessary.

b. When direct exhaust is specified as a percentage of the ventilation airflow, the direct exhaustairflow is computed using:

Vde = Vv Fde/100 .... (Eqn 8-10)

where:


8-6 Block Load


Vde = Direct exhaust airflow rate (CFM or L/s).

Fde = Direct exhaust percentage value specified by user (%).

6. Calculate Return Airflow Rate. Next, knowing the direct exhaust airflow rate, the return airflowrate can be calculated using the equation:

Vr = Vs - Vde .... (Eqn 8-11)

where:

Vr = Return airflow rate (CFM or L/s).



7. Calculate Return Air Temperature. If a return air plenum is used, portions of the roof, wall andlighting loads may be carried away by air flowing through the plenum. To calculate thetemperature of air after it has passed through the plenum, the following equation is used:

Tr = Tc + Qp / (pa Cpa Vr Fu) .... (Eqn 8-12)

where:

Tr = Temperature of air after it has passed through the return plenum (F or C).


Qp = Total sensible plenum load (BTU/hr or W).

pa = Air density (lb/ft3 or kg/m3). Values are adjusted for elevation.

Cpa = Heat capacity for air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vr = Return airflow rate (CFM or L/s).




Note: If no return plenum is used, the return air temperature is assumed to be equal to the zone airtemperature.

8. Calculate Mixed Air Temperature. Next, the air temperature resulting from the mixture of returnair and outdoor ventilation air can be computed:

Tmix = [Vv Ta + (Vs - Vv) Tr] / Vs .... (Eqn 8-13)

where:

Tmix = Mixed air temperature (F or C).


Ta = Outdoor air temperature (F or C).


Tr = Return air temperature (F or C).

9. Calculate Coil Inlet Temperature. At this point, the coil inlet temperature can be computed.Different calculations are required depending on the supply fan configuration:


Block Load 8-7

a. Draw-Thru Fans. The coil inlet temperature is equal to the mixed air temperature in this case,so no calculation is necessary.

b. Blow-Thru Fans. In this case, fan heat gain must be considered so the inlet temperature iscomputed as:

Tci = Tmix + Qf / (pa Cpa Vs Fu) .... (Eqn 8-14).

where:

Tci = Cooling coil inlet temperature (F or C).

Tmix = Mixed air temperature (F or C).


pa = Air density (lb/ft3 or kg/m3). Values are adjusted for altitude.

Cpa = Heat capacity of air (0.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).


Fu = Unit conversion factor.



10. Calculate Sensible Cooling Coil Load. Finally, we're ready to compute the sensible cooling coilload:

Qcs = pa Cpa Vs Fu (Tci - Tco) .... (Eqn 8-15).

where:

Qcs = Sensible cooling coil load (BTU/hr or W).







Tci = Coil inlet temperature (F or C).


11. Calculate Sensible Ventilation Load. Based on the previous calculations, the sensible ventilationload can also be determined at this point. This calculation is performed differently for cases inwhich direct exhaust air is used and is not used. For the case in which no direct exhaust air isused:

Qvs = pa Cpa Vv Fu (Ta - Tr) .... (Eqn 8-16)

where:

Qvs = Sensible ventilation load.




8-8 Block Load





Ta = Outdoor air temperature (F or C).

Tr = Return air temperature (F or C).

For the case in which air is directly exhausted from the zone before it flows through areturn air duct or plenum:

Qvs = pa Cpa Vde Fu (Ta - Tc) + pa Cpa (Vv-Vde) Fu (Ta - Tr) .... (Eqn 8-17)

where:

Qvs = Sensible ventilation load (BTU/hr or W).


Tc = Cooling thermostat setpoint (F or C).

B. LATENT ANALYSISThe latent system analysis is somewhat more complicated than the sensible analysis. This is due to theinter-dependence of humidities throughout the system. Background information and a description of thegeneral approach to the latent analysis are provided in the following paragraphs. Afterward, the step-by-step calculation procedure is described.

BACKGROUND INFORMATIONHumidity calculations are frequently a source of confusion among designers. This confusion seems toresult from differences between the way humidity was analyzed in older hand-calculation approaches andthe way it is analyzed in computer programs. Typically in the older hand-methods a room relativehumidity was assumed (usually around 50%) and was then used as the starting point for calculations.

It is important to recognize, however, that this assumed room RH is an approximation. For manyapplications the true room RH is within 5 to 10 percentage points of 50%, so only small to moderateerrors are introduced by the RH assumption. For other applications, the true room RH deviates fartherfrom 50% and therefore, the RH assumption introduces larger errors.

Rather than rely on an assumed room RH which leads to errors of varying magnitude, Carrier's loadestimating computer programs perform the rigorous calculations necessary to determine the truehumidities present in the system. This analysis procedure yields more accurate latent coil load resultsthan previous hand-calculation approximations.

GENERAL APPROACHBefore humidity calculations begin, a sensible load analysis for the air conditioning system must becompleted. This analysis defines the airflow rates and dry-bulb temperatures at all points in the system.

Next, the basic humidity equations for the system are formulated. There are five separate equations asshown below. These define the latent ventilation load (Eqn 8-18), the latent coil load (Eqn 8-19), thezone latent load (Eqns 8-20 and 8-21), and the relationship between the bypass factor and coil humidities(Eqn 8-22).

Qvl = paVvhfgFu(wa-wz) ... (Eqn 8-18)


Block Load 8-9

Qcl = paVshfgFu(wci-wco) ... (Eqn 8-19)

Qzl = [Ql+paVihfgFu(wa-wz)](Msl) ... (Eqn 8-20)

Qzl = paVshfgFu(wz-wco) ... (Eqn 8-21)

BF = (wco-wadp)/(wci-wadp) ... (Eqn 8-22)

= (Tco-Tadp)/(Tci-Tadp)

where:

BF = Cooling coil bypass factor (dimensionless).

Fsl = Latent cooling safety factor (%).

Fu = Units correction factor.



hfg = Heat of vaporization for water (1054.8 BTU/ lbm or 2.4535 x 106 J/kg).

Msl = Latent cooling safety multiplier.

= (1 + Fsl/100)

Qcl = Latent cooling coil load (BTU/hr or W).

Ql = Internal latent heat gains due to people and miscellaneous internal sources(BTU/hr or W).

Qvl = Latent ventilation load (BTU/hr or W).

Qzl = Latent zone load (BTU/hr or W).

Tci = Coil inlet temperature (F or C).


Vi = Zone infiltration airflow rate (CFM or L/s).



wa = Outdoor air specific humidity (lb/lb or kg/kg).

wadp = Specific humidity corresponding to apparatus dewpoint for coil (lb/lb or kg/kg).

wci = Specific humidity at coil inlet (lb/lb or kg/kg).

wco = Specific humidity at coil outlet (lb/lb or kg/kg).

wz = Zone specific humidity (lb/lb or kg/kg).

pa = Density of air (lb/ft3 or kg/m3). Values adjusted for site el evation.

To solve for the system humidities, a moisture balance for the system must be formulated. Because thetotal moisture added to and removed from the system must be equal for steady-state conditions, we knowthat:

Qvl - Qcl + Qzl = 0 ... (Eqn 8-23)

Using equations 8-18, 8-19 and 8-20 from above we can rewrite equation 8-23 as :


8-10 Block Load

Vswci - Vswco + (ViMsl+Vv)wz = QlMsl/pahfgFu + (Vv+ViMsl)wa ... (Eqn 8-24)

This single equation contains three unknowns (wco, wci, wz) which reveals an important fact - that allsystem humidities are interdependent. The room humidity is influenced by the supply air provided withhumidity wco; the coil outlet humidity is influenced by the coil inlet humidity; the coil inlet humidity isinfluenced by return air with humidity wz. Thus, no single humidity can be calculated directly. Becauseof this, the only way to solve the problem is to develop a set of three equations containing the threeunknowns and then solve the equations simultaneously.

Equation 8-24 serves as the first of the three equations required. To obtain a second equation, we can setEquations 8-20 and 8-21 equal to one another since both are expressions of the zone latent load, Qzl:

[Ql + paVihfgFu(wa-wz)](Msl) = paVshfgFu(wz-wco)

This equation can be rewritten as:

-Vswco + (Vs + ViMsl) wz = QlMsl/(pahfgFu) + waViMsl ... (Eqn 8-25)

To obtain the third equation, we can use Equation 8-22. Because the coil inlet and outlet dry-bulbtemperatures are already known from a sensible analysis of the system, the apparatus dewpointtemperature, Tadp, can be computed. Further, because the apparatus dewpoint is a saturated condition,the corresponding specific humidity, wadp, can be easily determined. Then Equation 8-22 can berewritten as:

(BF)wci - wco = wadp(BF - 1) ... (Eqn 8-26)

Finally, with the set of equations 8-24, 8-25 and 8-26, we have a system of three equations and threeunknowns and the equations can be solved simultaneously to determine wci, wco and wz.

First, simultaneous solution of the three equations yields the following expression for wz:

wz = [waVvBF+QlMsl/(pahfgFu)+waViMsl+wadpVs(1-BF)] / [(ViMsl+Vs - (Vs-Vv)BF ] ... (Eqn 8-27)

Once wz is known, it can be used in Equation 8-25 to solve for wco:

wco = [-QlMsl/(pahfgFu)-waViMsl+(Vs+ViMsl)wz]/Vs ... (Eqn 8-28)

Finally, wz and wco can be used in Equation 8-24 to solve for wci:

wci = [QlMsl/(pahfgFu) + (Vv+ViMsl)wa + Vswco - (ViMsl+Vv)wz ] / Vs ... (Eqn 8-29)

From this discussion it is evident that calculation of true system humidities involves a fair amount ofmathematics and several complicated equations. This is probably why the procedure was never used inolder hand-calculation methods. Using a computer, however, it is no trouble to perform the rigorousanalysis in order to determine the correct humidity values.

The procedure for using these equations to complete the latent system analysis is outlined in the followingparagraphs.

STEP-BY-STEP LATENT SYSTEM ANALYSIS PROCEDURE1. Compute Total Internal Latent Heat Gain. The first step is to add up all the internal latent heat

gains from people and miscellaneous sources for the zone served by the system. This quantity isreferred to as Ql in the humidity equations.

2. Compute Room Humidity. Next, Equation 8-27 is solved to determine the room specific humid ity,wz.

3. Compute Coil Outlet Humidity. Then solve Equation 8-28 for the coil outlet specific humidity,wco.

4. Compute Coil Inlet Humidity. Solve Equation 8-29 for the coil inlet specific humidity, wci.


Block Load 8-11

5. Calculate Latent Cooling Coil Load. Once the coil inlet and outlet humidities are known, the latentcooling coil load can be determined using Equation 8-19.

6. Calculate Latent Ventilation Load. At this point, the latent component of the ventilation load canalso be computed using Equation 8-18.

7. Calculate Resulting Room Relative Humidity. Finally, the resulting relative humidity can also bedetermined. The relative humidity is determined using standard psychrometric equations with theknown values of the zone cooling setpoint temperature, Tc, and the zone specific humidity, wz.

8.3 COOLING ANALYSIS FOR MULTIPLE-ZONE SYSTEMS

Cooling analyses for multiple-zone central air handler systems are slightly more complicated than single-zone analyses. The multiple-zone calculation procedure includes three stages:

1. Zone Load Calculations. Zone sensible loads are computed for all zones in the system for allmonths and hours specified.

2. Zone Airflow Calculations. Next, required airflow quantities for the zones served by the HVACsystem are determined.

3. Cooling Coil Load Calculations. Finally, system operation is analyzed to determine the systemairflow rate and the sensible and latent cooling coil loads for all months and hours specified.

Sensible and latent coil loads are then combined to obtain the total coil load. The maximum coil load isidentified from among all the months and hours considered.

Step-by-step details for these calculations are provided in the remainder of this section.

A. ZONE LOAD CALCULATIONSZone sensible cooling loads are computed using the same procedure described for single-zone systems(section 8.1). The only difference is that loads are computed separately for each zone served by thesystem. The total of sensible loads for all zones served by the system is also calculated for each hour.

B. ZONE AIRFLOW CALCULATIONSNext, the required zone airflow rates are calculated. These computations take one of three formsdepending upon the supply air characteristic specified.

1. Given a specified supply airflow per unit floor area (CFM/ sqft or L/s/sqm), zone airflow quantitiesare computed as shown in Equation 8-30. Note that these airflows are not related to a specificsystem supply temperature, or even to the zone loads. The airflow rates are therefore ofquestionable use for multiple-zone HVAC systems.

Vsz = Vsf Az .... (Eqn 8-30)

where:

Vsz = Zone supply airflow rate (CFM or L/s).

Vsf = Supply flow rate per unit floor area (CFM/sqft or L/(s-sqm)).

Az = Zone floor area (sqft or sqm).

2. If a total supply airflow rate is specified for the system, the zone supply air flow rates aredetermined using zone sensible load ratios:

Vsz = Vs (Qsz / Qs) .... (Eqn 8-31)

where:


8-12 Block Load


Vs = System supply airflow rate defined by user (CFM or L/s).

Qsz = Zone sensible load, calculated for hour when maximum cooling coil load occurs(BTU/h or W).

Qs = Sum of zone sensible loads for all zones, calculated for hour when maximumcooling coil load occurs (BTU/h or W).

Note that this calculation relies partly on data for the month and hour during which the maximumcooling coil load occurs. Therefore, the zone supply airflow rates cannot be determined in this caseuntil after the cooling coil load analysis has been completed.

3. Finally, given the supply temperature, the zone supply flow rate is computed by solving thefollowing equation for Vsz.

Qsz = pa Vsz Cpa Fu (Tc - Ts) .... (Eqn 8-32)

where:

Qsz = Maximum zone sensible cooling load (BTU/hr or W).

pa = Density of air (lb/ft3 or kg/m3). Value is adjusted for site elevation.



Fu = Units conversion factor:





C. COOLING COIL LOAD CALCULATIONS - SENSIBLE ANALYSIS1. Calculate Supply Air Characteristics. First, the total zone sensible load is used to determine either

the supply airflow rate or the supply temperature. Different calculations are required depending onwhich supply characteristic has been defined by the user.

a. Supply Airflow Rate Defined as CFM (L/s) or CFM/ sqft (L/s/sqm). In this case, the samespecified airflow rate will be used for all hourly cooling load calculations. For each hour, arequired supply temperature will be computed by solving Equation 8-5. This approach isappropriate for the analysis of constant volume multiple-zone HVAC systems.

b. Supply Temperature Defined. In this case the specified temperature will be used for all hourlyload calculations. For each hour, the required supply airflow rate will be computed usingEquation 8-5. This approach is appropriate for the analysis of variable volume multiple-zoneHVAC systems.

For the remaining steps in the sensible analysis procedure:

2. Calculate Supply Fan Heat Gain.

3. Calculate Coil Outlet Temperature.

4. Calculate Ventilation Airflow Rate.

5. Calculate Direct Exhaust Airflow Rate.


Block Load 8-13

6. Calculate Return Airflow Rate.

7. Calculate Return Air Temperature.

8. Calculate Mixed Air Temperature.

9. Calculate Coil Inlet Temperature.

10. Calculate Sensible Cooling Coil Load.

11. Calculate Sensible Ventilation Load.

All calculations are the same as for single-zone systems. In these calculations zone sensible and plenumloads represent the total for all zones served by the system.

D. COOLING COIL LOAD CALCULATIONS - LATENT ANALYSISThe same latent cooling load analysis described for single-zone systems is used for multiple-zone systems.The only difference is that the internal latent heat gain, Ql, and the infiltration airflow rate, Vi, representtotals for all zones served by the HVAC system rather than the total for a single zone.


8-14 Block Load


Block Load 9-1

CHAPTER 9 HEATING DESIGN CALCULATIONS

9.0 INTRODUCTION

This chapter describes design load calculations and equipment sizing procedures for heating systems.

A "design-point" analysis technique is used to determine design heating loads. With this technique, loadsare analyzed assuming outdoor air is at the winter design temperature. The traditional heating designprocedure is to consider only transmission and infiltration components when computing the zone heatingload. Further, only zone and ventilation loads are considered when determining the total heating coilload. Readers should note that the heating design condition is not associated with any particular monthor hour.

In this program, heating analyses involve two stages:

1. Zone Load Calculations. First, zone loads are computed. A "zone load" is the amount of heatwhich must be added in order to maintain zone air at the heating thermostat setpoint.

2. Coil Load and Sizing Calculations. Next system sizing and heating coil load calculations areperformed. For a warm air system, the required supply airflow characteristics are determinedalong with the resulting heating coil load. For hydronic baseboard systems, required hot waterflow rates are computed. For electric baseboard systems, required baseboard wattages arecalculated.

Zone load calculations are described in section 9.1 below. Sizing of warm air, hydronic baseboard andelectric baseboard systems are each dealt with in the remaining sections in the chapter. Readers shouldnote that in these discussions heating loads are presented as positive numbers in order to simplify thediscussions and avoid confusion.

9.1 ZONE HEATING LOAD CALCULATIONS

The first step in the analysis involves calculating zone heating loads. This procedure is repeated for allzones served by the HVAC system.

A zone load is the amount of heat which must be added in order to maintain zone air at a desiredtemperature. This load is the sum of a number of transmission and infiltration components:

Qzh = [Qw + Qr + Qg + Qp + Qi](1+Fsh/100) ... (Eqn 9-1)

where:

Qzh = Zone design heating load (BTU/hr or W).

Qw = Wall transmission load (BTU/hr or W).

Qr = Roof transmission load (BTU/hr or W).

Qg = Glass transmission load (BTU/hr or W).

Qp = Transmission load for partitions adjacent to u nconditioned areas (BTU/hr or W).

Chapter 9 HEATING DESIGN CALCULATIONS

9-2 Block Load

Qi = Infiltration load (BTU/hr or W).

Fsh = Heating safety factor (%).

All transmission load calculations are performed using a simple (UAdelta-T) equation. The infiltrationload is computed using the equation:

Qi = paCpaViFu(Th - Ta) ... (Eqn 9-2)

where:

Qi = Heating infiltration load (BTU/hr or W).

pa = Density of air (lb/ft3 or kg/m3). Values are adjusted for site elevation. SeeChapter 9 for details.


Vi = Heating infiltration airflow rate (CFM or L/s).

Fu = Units conversion factor:



Th = Heating thermostat setpoint temperature (F or C).

Ta = Outdoor air temperature for winter design condi tion (F or C).

Zone heating load calculations are described in greater detail in the E20/TF Load Manual.

9.2 SIZING CALCULATIONS FOR WARM AIR HEATING SYSTEMS

In a warm air heating system, a central heating coil and supply fan are used to provide warm air to eachzone served by the system. Sizing procedures for warm air heating systems vary slightly depending onwhether the equipment provides both cooling and heating, or heating only. Procedures for each case aredocumented below.

WARM AIR HEATING -- COOLING & HEATING SYSTEMAt the start of this procedure several basic load and sizing values are known:

Qs = Sum of zone heating loads, for all zones served by the HVAC system (BTU/hr orW).

Vs = Supply airflow rate (CFM or L/s). This value was determined duri ng coolingsizing calculations. See Chapter 8 for details. Because the system provides bothcooling and heating, the same supply airflow rate used for cooling is also used forheating.

Vv = Ventilation airflow rate (CFM or L/s). This value was also dete rmined duringcooling sizing calculations. See Chapter 8 for details. Since the system providesboth cooling and heating, the same ventilation airflow rate will be present for bothmodes of operation.

Using this data, the sizing procedure is as follows:

1. Calculate Required Heating Supply Temperature.

Ts = Qs / (paCpaVsFu) + Th ... (Eqn 9-3)

where:

HEATING DESIGN CALCULATIONS Chapter 9

Block Load 9-3

Ts = Heating supply temperature (F or C).

Qs = Sum of zone heating loads, for all zones served by the HVAC system (BTU/hr orW).

pa = Air density (lb/ft3 or kg/m3). Values are adjusted for site elevation.

Cpa = Heat capacity of air (.24 BTU/(lbm-F) or 1004.832 J/(kg-K)).

Vs = Supply air flow rate (CFM or L/s).




Th = Heating thermostat setpoint (F or C).

2. Calculate Ventilation Load.

Qv = paCpaVvFu(Th - Ta) ... (Eqn 9-4)

where:

Qv = Heating ventilation load (BTU/hr or W).








Ta = Outdoor air temperature at winter design condition (F or C).

3. Compute Heating Coil Load.

Qhc = Qs + Qv ... (Eqn 9-5)

where:

Qhc = Heating coil load (BTU/hr or W).

Qs = Sum of zone heating loads for all zones served by the HVAC system (BTU/hr orW).

Qv = Heating ventilation load (BTU/hr or W).

WARM AIR HEATING -- HEATING ONLY SYSTEMAt the start of this procedure two basic quantities are known. One quantity is:

Qs = Sum of zone sensible heating loads, for all zones served by the HVAC system (BTU/hr or W).

The other is either of the following two items, depending on the user's supply air specification:

Vs = Heating supply airflow rate (CFM or L/s). This value may be directly specifiedby the user, or entered in terms of CFM/sqft (L/s/sqm). In the latter case, the


9-4 Block Load

supply airflow rate is determined by multiplying the CFM/ sqft (L/s/sqm) value bythe total floor area served by the heating system.

Ts = Heating supply air temperature (F or C).

Using this data, the sizing procedure is as follows:

1. Calculate Required Supply Airflow Rate or Temperature. If a supply airflow rate has beenspecified by the user, equation 9-6 is solved to determine Ts. If a supply temperature has beenspecified, equation 9-6 is solved to determine Vs.

Qs = paCpaVsFu(Ts - Th) ... (Eqn 9-6)

where:

Qs = Sum of zone heating loads for all zones served by the HVAC system (BTU/hr orW).




Fu = Conversion factor to provide load in proper units.



Ts = Heating supply air temperature (F or C).


2. Calculate Ventilation Airflow Rate. The ventilation airflow rate is computed in one of four waysdepending on user specifications:

a. When the ventilation air per unit floor area (CFM/ sqft or L/s/sqm) has been specified, theairflow rate is calculated as:

Vv = Vvf Atot .... (Eqn 9-7)

where:


Vvf = Ventilation airflow per unit floor area (CFM/ sqft or L/s/sqm).

Atot = Total floor area in zones served by system ( sqft or sqm).

b. When the ventilation airflow rate (CFM or L/s) is directly specified, no calculation isnecessary.

c. When ventilation is specified as a percentage of the supply airflow rate, airflow is calculatedas:

Vv = Vs Fv/100 .... (Eqn 9-8)

where:


Vs = Supply airflow rate (CFM or L/s)

Fv = Percentage value specified by user (%).


Block Load 9-5

d. Finally, when ventilation is specified on an airflow per person basis (CFM/person orL/s/person), the airflow is calculated as:

Vv = Vvp P .... (Eqn 9-9)

where:


Vvp = Ventilation airflow rate per person (CFM/person or L/s/person).

P = Total number of people occupying zones served by the HVAC system atmaximum occupancy.

Note that if the ventilation airflow rate is greater than the calculated supply airflow rate, the supplyflow rate will be increased to equal the ventilation flow rate. A new supply temperature will thenbe determined using Equation 9-6. The reason for this adjustment is that it is assumed ventilationmust be maintained for code requirements.

3. Calculate Ventilation Load. Next, the ventilation load is computed using Equation 9-4.

4. Calculate Heating Coil Load. Finally, the design heating coil load is derived using Equation 9-5.

9.3 SIZING CALCULATIONS FOR HYDRONIC BASEBOARD HEATING SYSTEMS

For a hydronic heating system it is assumed heat is provided via hot water baseboard units. If the systemalso provides ventilation air, a separate hot water coil will be sized to heat ventilation air to the heatingthermostat setpoint.

At the start of this analysis, the following values are known:


deltaTw = Temperature drop for water flowing through baseboard heating coil (F or K).

Steps in the sizing procedure for this system are described below:

1. Calculate Required Hot Water Flow Rates for Zone Baseboards. For each zone included in theHVAC system, a required baseboard hot water flow rate is determined:

Vw = Qzh / (pwCpwFwudeltaTw) ... (Eqn 9-10)

where:

Vw = Hot water flow rate for zone baseboard unit (gallons/min or L/s).

Qzh = Design heating load for zone (BTU/hr or W).

pw = Density of water (62.0 lbm/ft3 or 993.1 kg/m3). Conditions for water at 100 F(37.8 C) are used.

Cpw = Specific heat of water (1.0 BTU/(lbm-F) or 4186.8 J/(kg-K)).

Fwu = Units conversion factor.

= (60 min/hr)(.13668 ft3/gal) for English units.



2. Determine Ventilation Airflow Rate. If the HVAC system provides both cooling and heating, thenthe ventilation airflow rate defined during cooling sizing calculations will be used for heating. Fora heating-only system, ventilation air is computed in one of four ways, depending on user-


9-6 Block Load

specifications. Refer to section 9.2 for details on this calculation. Readers should note that ifventilation air is specified as a "% of supply air" for a heating-only system, a zero airflow will beused for ventilation. This is because no supply airflow exists.

3. Calculate Ventilation Load. Next, the ventilation heating load is computed using Equation 9-4.

4. Calculate Hot Water Flow Rate for Ventilation Coil. The required water flow rate for a coil whichheats ventilation air from the outdoor temperature to the heating setpoint temperature is computedas:

Vw = Qv / (pwCpwFwudeltaTw) ... (Eqn 9-11)

where:

Vw = Hot water flow rate for ventilation coil (gallons/minute or L/s).

Qv = Ventilation heating load (BTU/hr or W).

pw = Density of water (62.0 lbm/ft3 or 993.1 kg/m3). Conditions for water a t 100 F(37.8 C) are used.

Cpw = Specific heat of water (1.0 BTU/(lbm-F) or 4186.8 J/(kg-K)).

Fwu = Units conversion factor.

= (60 min/hr)(.13668 ft3/gal) for English units.



5. Compute Totals. Finally, the total heating load is computed using the zone heating loads and theventilation heating load. The required total hot water flow rate is determined using the zone flowrates and the flow rate for the ventilation coil.

9.4 SIZING CALCULATIONS FOR ELECTRIC BASEBOARD HEATING SYSTEMS

For an electric heating system it is assumed heat is provided via electric baseboard units. If the systemalso provides ventilation air, a separate electric heating coil will be sized to heat ventilation air to theheating thermostat setpoint.

At the start of this analysis, the following value is known:


Steps in the sizing procedure for this system are described below:

1. Calculate Required Wattages For Zone Baseboards. For each zone included in the HVAC system,a required baseboard wattage is determined:

Pbb = Qzh Feu ... (Eqn 9-12)

where:

Pbb = Required wattage for zone baseboard heating unit (Watts).

Qzh = Design heating load for zone (BTU/hr or W).

Feu = Units conversion factor:

= 0.2930711 (W)/(BTU/hr) for English units.

= 1.0 for Metric units.


Block Load 9-7

2. Determine Ventilation Airflow Rate. If the HVAC system provides both cooling and heating, thenthe ventilation airflow rate defined during cooling sizing calculations will be used for heating. Fora heating-only system, ventilation air is computed in one of four ways, depending on user-specifications. Refer to section 9.2 for details on this calculation. Readers should note that ifventilation air is specified as a "% of supply air" for a heating-only system, a zero airflow will beused for ventilation. This is because no supply airflow exists.

3. Calculate Ventilation Load. Next, the ventilation heating load is computed using Equation 9-4.

4. Calculate Wattage for Ventilation Coil. The required wattage for a coil which heats ventilation airfrom the outdoor temperature to the heating setpoint is computed as:

Pva = Qv Feu ... (Eqn 9-12)

where:

Pva = Required wattage for ventilation coil (Watts).

Qv = Ventilation heating load for zone (BTU/hr or W).

Feu = Units conversion factor:

= 0.2930711 (W)/(BTU/hr) for English units.

= 1.0 for Metric units.

5. Compute Totals. Finally, the total heating load is computed using the zone heating loads and theventilation heating load.


9-8 Block Load


Block Load A-1

APPENDIX A INDEXActivity Level ................................ ..5-7

Atmospheric Clearness Number .......4-3

Building Weight............................... 5-6

ButtonConfig................................ .......1-2, 1-3Continue................................ ....1-2, 1-3Help................................ ..........1-2, 1-3New System .............................. 6-2, 6-3New Zone................................ ..5-2, 5-4Print................................ ..........7-4

Calculation Parameters .................... 7-2

Calculation Times .......................... 7-1, 7-2choosing................................ ....7-2first hour ................................ ...7-2first month................................ .7-2last hour ................................ ....7-2last month ................................ .7-2

Daily Range................................ .....4-3

Data Source................................ .....4-4

Elevation ................................ .........4-3

Equipmentcooling ................................ ......1-1heating ................................ ......1-1sizing ................................ ........1-1, 2-1, 8-1, 9-1

Exposure ................................ .........5-11, 5-12

External Shading............................ 5-10fin extension .............................. 5-10fin separation............................. 5-10overhang extension .................... 5-10overhang height ......................... 5-10reveal depth............................... 5-9type................................ ...........5-12window height ........................... 5-10window width ............................ 5-10

Index Appendix A

A-2 Block Load

File Menu ................................ .......2-2Archive option........................... 2-2, 2-6Compact option ......................... 2-2, 2-8Convert DOS Data option..........1-3, 2-2, 2-6Delete option ............................. 2-2, 2-3, 2-6New option................................ 2-2Open option............................... 1-3, 2-2, 2-3, 2-6Page Setup option...................... 2-2, 2-5Print Setup option...................... 2-2, 2-5Properties option ....................... 2-2, 2-4Retrieve option .......................... 1-3, 2-2, 2-7Save As option .......................... 2-2, 2-4Save option ............................... 2-2, 2-4

Floor Area ................................ .......5-5, 5-6

FormArchive Project.......................... 2-6Block Load Report .................... 7-1, 7-4Calculation Parameters .............. 7-2Compact Project ........................ 2-8Convert DOS Data .................... 2-6Copy Zone ................................ 5-3Data Storage Drive .................... 1-3Delete Project ............................ 2-3Edit City ................................ ...2-2, 4-1 thru 4-4Global Zone Changes ................ 5-3HVAC System Information........6-2 thru 6-8Move Zone................................ 5-3Open Project ............................. 2-2, 2-3Page Setup ................................ 2-5Print................................ ..........2-5Print Setup ................................ 2-5Project Properties ...................... 2-4Retrieve Project ......................... 2-7Save Project As ......................... 2-4Zone Information....................... 5-2 thru 5-5

Glassarea................................ ...........5-9, 5-12external shade type .................... 5-10, 5-12factor ................................ ........5-10internal shading ......................... 5-10type................................ ...........5-10, 5-12U-value ................................ .....5-10

HELPbutton................................ ........ see Button, Helpon-line................................ .......1-4

HVAC System ................................ 6-1 thru 6-9arrangement .............................. 6-6, 6-7

Appendix A Index

Block Load A-3

attaching zones .......................... 3-1, 3-3 thru 3-5, 5-1 thru 5-4, 6-1, 6-2, 6-3, 6-8cooling coil bypass factor ..........6-7cooling safety factor .................. 6-7cooling thermostat setpoint ........6-7copying ................................ .....3-2, 3-3, 6-1, 6-2creating ................................ .....3-3, 6-1 thru 6-3definition ................................ ...6-1deleting ................................ .....6-1, 6-2design................................ ........1-3direct exhaust sizing spec...........6-5duration................................ .....6-4, 6-5entering system data .................. 1-4, 6-3fan brakehorsepower.................. 6-6fan configuration ....................... 6-6fan kW................................ ......6-6fan static pressure...................... 6-6heating safety factor .................. 6-8heating thermostat setpoint.........6-7hot water delta-T ....................... 6-5icon................................ ...........3-1 thru 3-4, 6-2, 6-3, 7-1modifying................................ ..6-1 thru 6-3name ................................ .........6-3overview................................ ....6-1, 6-2printing ................................ .....7-1return plenum ............................ 6-8selecting ................................ ....3-2, 3-3, 6-2, 7-1start time ................................ ...6-4, 6-5supply air sizing specification ....6-5type................................ ...........6-1, 6-3, 6-4vent air sizing specification ........6-5

Infiltration ................................ ......5-8cooling ................................ ......5-8heating ................................ ......5-8

Information bar................................ 5-5, 6-3

SETUP.EXE ................................ ...1-2

Installation, system requirements ......1-2

Latitude................................ ...........4-3

Lighting................................ ..........5-6fixture type................................ 5-6unoccupied diversity factor ........5-6usage................................ .........5-6wattage multiplier ...................... 5-6

Loadcalculations ............................... 8-1, 8-2, 9-1, 9-2coil................................ ............ 1-1, 8-1, 8-2, 8-11 thru 8-13, 9-1, 9-3, 9-5design cooling............................ 1-1, 2-1, 4-1design heating............................ 1-1, 2-1, 4-1, 9-1, 9-5diversified zone.......................... 1-1

Index Appendix A

A-4 Block Load

estimating................................ ..1-1, 1-3glass transmission...................... 8-1, 9-1infiltration ................................ .8-2, 9-1, 9-2latent................................ .........8-1, 8-2, 8-9 thru 8-11, 8-13lighting................................ ......8-1maximum cooling ...................... 8-1miscellaneous ............................ 8-2other electric.............................. 8-2partition transmission ................ 8-1, 9-1people ................................ .......8-2roof transmission ....................... 8-1, 9-1sensible ................................ .....8-1, 8-2, 8-7 thru 8-9, 8-11, 8-12, 9-3solar................................ ..........8-1wall transmission....................... 8-1, 9-1ventilation ................................ .8-8, 8-9, 8-11, 8-13, 9-3, 9-5 thru 9-7zone ................................ ..........8-1, 8-2, 8-9 thru 8-12, 9-1 thru 9-6

Main window................................ ..1-3, 4-1, 5-1, 5-2, 6-2, 6-3, 7-1, 7-3advanced features ...................... 3-2 thru 3-5appearance ................................ 3-1, 3-2navigating ................................ .3-1 thru 3-5

Miscellaneous Load ........................ 5-8latent load ................................ .5-8sensible load.............................. 5-8unoccupied diversity factor ........5-8

Other Electric ................................ 5-6, 5-7unoccupied diversity factor ........5-7usage................................ .........5-6

Parameter Limits bar ....................... 5-5, 6-3

Partition ................................ .........5-12, 5-13adjacent region temperature .......5-12definition ................................ ...5-12net area ................................ .....5-12tab ................................ ............ 5-12U-value ................................ .....5-12

Peopleactivity level .............................. 5-7latent heat gain .......................... 5-7occupancy ................................ .5-7sensible heat gain....................... 5-7unoccupied diversity factor ........5-7

Projectdata files ................................ ...2-1, 2-2data storage drive ...................... 1-3definition ................................ ...2-1editing project data .................... 3-1managing................................ ...1-5,2-1 thru 2-8

Appendix A Index

Block Load A-5

viewing project data................... 3-1

Reports................................ ...........7-1 thru 7-4Design Solar.............................. 7-3Design Temperature .................. 7-3Detailed System Loads .............. 7-3Detailed Zone Loads .................. 7-3printing ................................ .....7-4Psychrometric Graph ................. 7-3selecting ................................ ....7-1, 7-3System Input ............................. 7-1System Sizing Summary ............ 7-3Zone Input................................ .7-1

Roofarea................................ ...........5-12color................................ ..........5-10type................................ ...........5-11U-value ................................ .....5-10weight ................................ .......5-10

Skylight................................ ...........5-12

Slab................................ ................. 5-8, 5-9

Splash Screen ................................ ..1-2

Summer Dry Bulb............................ 4-3

Summer Wet Bulb ........................... 4-3

System ................................ ............ see HVAC SystemCopy System option................... 3-3, 6-2Delete System option ................. 6-2Edit System option .................... 6-2New System option.................... 6-2, 6-3System Menu ............................ 6-2, 6-3

Technical Support............................ 1-4, 1-5

Terminals ................................ ........1-1

Units, English and SI Metric ............ 2-1, 2-3, 2-8

Wallarea................................ ...........5-12color................................ ..........5-10type................................ ...........5-11U-value ................................ .....5-10weight ................................ .......5-10

Weatherdefinition ................................ ...4-1design weather parameters .........4-1, 4-3cooling design day ..................... 4-1, 4-3

Index Appendix A

A-6 Block Load

entering weather data ................. 1-3, 4-1 thru 4-3heating design day ..................... 4-1, 4-3icon................................ ...........3-1, 4-1overview................................ ....4-1printing ................................ .....4-4

Winter Dry Bulb.............................. 4-3

Zoneattaching to a system ................. 3-3 thru 3-5, 5-1 thru 5-3, 6-8creating new .............................. 5-1, 5-2definition ................................ ...1-3, 5-1editing ................................ .......5-1, 5-2entering zone data...................... 1-3global changes ........................... 5-1 thru 5-4icon................................ ...........3-1, 3-3, 5-1 thru 5-3, 6-2, 6-3name ................................ .........5-6overview................................ ....5-1, 5-2types ................................ .........5-1Unattached Zones area............... 3-1, 3-4, 3-5, 5-2 thru 5-4

Zone Menu ................................ .....5-2 thru 5-4Copy Zone option ...................... 5-3Delete Zone option..................... 3-4, 3-5, 5-2Edit Zone option ........................ 5-2Global Changes option............... 5-3, 5-4Move Zone option ..................... 5-3New Zone option ....................... 3-3, 5-2

Documents

24479682 HVAC Handbook CARRIER Block Load v3 Manual