Introduction to Building Automation Systems (BAS) · Building Automation Systems zCentralized controls zChange scheduling for multiple HVAC units at same time zMonitor “health”

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Introduction to Building Automation Systems (BAS)

Ryan R. Hoger, LEED [email protected]


Building Automation Systems

Centralized controlsChange scheduling for multiple HVAC units at same timeMonitor “health” of equipmentInternet accessibleAlarming via text msg or emailCollect/trend dataIntegrate to lighting control or security system

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What is DDC?

DDC - Direct Digital Control of an HVAC system

A method of monitoring and controlling HVAC system performance by collecting, processing, and sending information using sensors, actuators, and microprocessors.

What is DDC?

DDC is the concept or theory of HVAC system control that uses digital controls

Physically, DDC encompasses all the devices used to implement this control method: a whole group of DDC controllers/microprocessors, actuators, sensors, and other devices.

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DDC - the Control Theoryinput-process-output cycle

What Is a Point?

A point is ANY input or output device used to control the overall or specific performance of equipment or output devices related to the equipment.

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Four Kinds of Points

Analog input - a sensor that monitors physical data, such as temperature, flow, or pressure.Discrete input - a sensor that monitors status. Momentary and maintained switches, ON-OFF equipment status, and digital pulses from flow and electric power meters are discrete inputs.Analog output - a physical action of a proportional device in the controlled equipment - e.g., actuator opens air damper from 20% to 40%, other dampers, valves, inlet guide vanes, etc.Discrete output - changes or maintains device status. Performs momentary or maintained switching for start/stop of pumps, fans, two-position dampers, and on/off control.

AI

DI

AO

DO

DDC: Actions and Reactions

Input sensors and status devices react to changes in conditions. Conditions include internal load, outside air temperature, and output actions.

Open cooling coil valve (output action). Supply air temperature sensor SAT detects (input reaction) decrease in temperature.

Output devices act based on sensor and status device reactions.

Ex. 1:

Ex. 2: Filters on an air handler get dirty (conditions). Air switch reacts by closing contact for “filter dirty” alarm.

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Control Point Identification Exercise

Sensor and Status Devices used as Input Points (Reactions)

Temperature– Thermistors– Resistance Temp. Detectors

(RTDs)– Transmitters

Pressure HumidityFlow (CFM, GPM)VoltageCurrent CO2

AI DI

Switch dry contact (open or closed)

– Airflow– Water– Differential pressure

High/low limit switch(alarm or normal)

– Freeze alarm– Smoke detectors

Wattmeter pulses (pulse initiator or counter)

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Devices used as Output Points (Actions)

Damper actuatorsModulating valvesVFD

AO DO Solenoid valvesRelays / contactorsAlarm signal

DDC: Closed Loop Control

Closed Loop Control is accomplished by the control signal being sent to the controlled device with constant feedback from the sensor/status device providing input to the controller.

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Closed Loop Control

Control algorithms

Configuration values

Time schedule data

Setpoint schedule data

Closed loop control is determined by:

Typical Control Algorithms

• Heating/cooling coil control• Humidification/dehumidification• Mixed air damper optimization• VAV fan control• VAV supply & return fan tracking• Indoor air quality• Generic PID control• Control point reset

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Typical Control Algorithms (cont’d)

• Time of day scheduling• Discrete device controlled as analog• Discrete interlock• Discrete staging• Proportional thermostat• Primary/secondary pump control• Night free cooling• Adaptable start/stop• Permissive interlock

Algorithm Type Used by Processor Determines Control Strategy

Proportional

Proportional-Integral

Proportional-Integral-Derivative

P

PI

PID

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What Is PID Control?

What it is: This type of control algorithm is based on value/amount (proportion), rate of change (integral), and error allowances (derivative). PID control calculates and sends commands for outputs based on all three types of information.Advantages: More precise than P and PI controls, PID wastes less energy based on more frequent feedback and quicker responses.

PID = Proportional-Integral-Derivative Control

Proportional Control (P)

What it is: Control algorithm based only on value/amount (proportion).

Disadvantages: Less precise than PID and PI control; cannot respond to error margins or time. Uses the most energy due to over- and under- outputs.

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Proportional-Integral Control (PI) & (PID)

What it is: Control algorithm based on value/amount (proportion), rate of change (integral). PID uses error allowances (derivative) as well. Advantages: More precise control and less energy used than proportional (P); minimum swings from setpoints.

Exercise 1:Building Direct Digital Control on

a CV Air Handler

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Exercise 1: Base CV Air Handler Unit -No Controls

Exercise 1: AHU - DDC Control of

Start / Stop Scheduling

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Exercise 1: AHU - Add DDC

Damper

Exercise 1: AHU - Add DDC Cooling Coil

Control

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Exercise 1: AHU - Add DDC Outside Air reset and Enthalpy Control

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Control Point Summary for Base CV AHU

Exercise 2:Building Direct Digital Control on

a VAV Air Handler

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History

VAV systems came into favor for mid and large size facilities in the 1960s and 1970s

– Save energy– Improve comfort– Take advantage of building diversity– Cooling needed year round for true interior core zones

Sequence– Main AHU provides morning warm-up heat until RAT

setpoint is satisfied – all zones at 100% design airflow– AHU switches to 55°F discharge air controlled cooling –

zones modulate CFM to controls space temp– No AHU heat remainder of day – individual zone reheat or

baseboard as needed

Zoning Systems

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Single Zone Systems

ZC

ZONE 1

TMT TM TM

ZONE 2 ZONE 3 ZONE 4

ROOF

Heating/CoolingUnit

Heating/CoolingUnit

Heating/CoolingUnit

Heating/CoolingUnit

TM

Multiple Zone Systems

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To Build DDC on a VAV AHU, Start with DDC on a CV AHU...

* If using VFD, use two Variable Frequency Drives instead, but you will still need the same control points and HPS shown.

Exercise 2: Create a VAV AHU with Inlet Guide

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Typical DDC Items You Can Add as Optional Items:

• Filter Status (FLTS)

• FreezeStat (FRZ)

• Smoke Detector (SMK)

Exercise 2: VAV AHU with DDC Filter Status

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Exercise 2: VAV AHU with DDC FreezeStat

Exercise 2: VAV AHU with DDC Smoke Detector

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Control Point Summary for Base VAV AHU

DDC Controllers

Programmable controllers

Application Specific controllers

Factory integrated controllers

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Types of Direct Digital Control Networks

Interfaces to DDC

Interface - devices and software that work as a translator between a DDC system and the humans who operate it.

An interface is the operator’s window into a building’s operating systems and conditions.

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User Interface Benefits

• Allow more efficient system operation monitoring. You can look at what’s happening on all floors from the tenth floor if DDC network is peer-to-peer.

• Allow immediate diagnosis of HVAC units and controls, including changes, without physically being in front of the unit.

• Can provide reports (e.g., historical, consumable, run times, system activity) to be used as records of building operations.

• Can provide graphical representations of the controlled system.

User interfaces:

User Interface Types

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Interface Examples

Hand-held Connected to a DDC Controller

Interface Examples

PC Connected to a DDC Network

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Interface Examples

Web Server Connected to DDC Network

Web Interfaces

Standard web browser or WAP accessView system statusAccess schedules and setpointsTrending, alarming, reportingReal time interactive graphics

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FLOOR PLAN GRAPHICS

EQUIPMENT GRAPHICS

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EQUIPMENT GRAPHICS

FLEXIBLE SCHEDULING

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TRENDING

Internet Thermostats

Low cost alternative to BASDirect to EthernetNo PC software – uses standard web browserNo access feesText/email alerts

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Phone Apps for Thermostats

Information Transfer– Add new HVAC equipment to an existing Building

Management System

Common User InterfaceBuilding Integration

– Lighting, HVAC, Security, Fire & Life Safety– Enterprise Integration-Utilities, Financial

Integration

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Building Management Systems

PowerMetering

LightingSecurity

HVAC

Common Protocols

PTMODBUS®

PT

PT

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Interoperability

Interoperability is the ability of different devices from the same or different manufacturers to function accurately together.

Standard protocol - a set of guidelines for commands, inputs, and output encoding to create a universal language for all DDC devices. When the same standard protocol is used in DDC devices, interoperability is possible.

Gateways - devices added to DDC networks to make standard protocols available and interoperability possible.

Integration

BACnet

Standard protocol requirements for Building Automationand Control networking, created by ASHRAE to ensureinteroperability. BACnet uses software and a LANinterface to DDC to provide:

• Representation of all manufacturer devices’ internal functioning in a common, network-visible way.

• A common command set for device services.• Common encoding of commands, understandable by

all devices and interfaces adhering to the protocol.

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Fire Systems

Security Systems Energy Lighting

And More

FacilityManagement

CFO

MODBUS

LEGACY

XML SQL

HTTP HTML

WAP

ODBC SNMP

JDBC FTP

SMTP

Open SystemFramework

Enterprise

HVAC Systems

MaintenanceMaintenance

Typical Questions

Q: What part of the control system is done by the HVAC designer? What is done by the installing contractor? Do most HVAC engineers actually do control system work or is that done by specialty contractors?A: Depends on the project

– A good designer lays out the control system as an integral part of the mechanical system, including:

Sequence of operationFront-end/user interface details

– The details of hardware, software, and cabling should be left to the contractor since every manufacturer’s system is different

– Unfortunately, most designers rely on manufacturers to write project specs, or worse, contractors to design in the field as they install

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Typical Questions

Q: How does one select the type, number, and position of sensors? (i.e. measure temp in a room or in the supply duct? Where in the room or duct do the sensors go? How many go in each room?)A: Depends on the project

– Best to measure what you want to control – usually space tempMount between 4 and 5 ft high, out of direct sunlight, and in the return air pathOne sensor per controllable piece of equipment is best – usually one per room

– Many exceptions for specialty systems and/or install cost compromises

Typical Questions

Q: How does one go about determining the coefficients of a P, PI, or PID controller and tune the system once it has been installed?A: Practice and Patience

– Zero out the derivative term – HVAC equipment and building systems react too slowly for it to matter

– Tune the proportional term first, then worry about integral term– Make small changes and monitor– Use a dynamic graph

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Typical Questions

Q: Where can one go to get more information and training?A:

– Iowa Energy Center / Iowa State Universitywww.ddc-online.org

– ASHRAE Learning Institutehttp://www.ashrae.org/education/page/1809

– Continental Automated Buildings Association - www.caba.org– www.automatedbuildings.com– BACnet - www.bacnet.org

Case Study – Conrad Hotel

352 HVAC units– 311 guestrooms

Added DDC controlsOccupancy sensors

– Entrance door & motion

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Energy Savings Estimation Tools

Utility Rebates for ControlsUtility Rebates for Controls

• Programmable Thermostat• Nicor Gas or NIPSCO Gas – $50• Peoples Gas or North Shore Gas – $80• Wisconsin Focus on Energy – $100 per RTU

• Economizer Controls• ComEd – $40 per ton• Wisconsin Focus on Energy – $250 per RTU

• CO2-based DCV• ComEd – $0.03 per ft2• DCEO – $0.28 to 0.40 per ft2• Peoples Gas or North Shore Gas – double custom• NIPSCO Gas – $0.15 per ft2• Wisconsin Focus on Energy – $0.05/CFM supply• Wisconsin Focus on Energy – $350 per RTU

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• Boiler Reset Control• Nicor Gas – $0.50 per MBH• Peoples Gas or North Shore Gas – $500• NIPSCO Gas – $0.35 per MBH• Wisconsin Focus on Energy – $75/controller

• DDC Controls• ComEd – $0.20 per ft2• DCEO – $0.20 to 0.40 per ft2

• Variable Frequency Drives (VFDs)• ComEd – $60 per Hp• DCEO – $92 per Hp• NIPSCO Electric - $40 per Hp• Wisconsin Focus on Energy – $50 per Hp

• Hotel Guest Room Energy Mgmt System• ComEd – $25 to 65 per unit

• Kitchen Exhaust Demand Control Ventilation• ComEd – $350 per Hp

• Custom Incentives (based on annual savings)

• ComEd – $0.06 to 0.07 per kWh• Nicor Gas – $0.75 to 1.00 per therm• Peoples Gas or North Shore Gas – $1.00 per therm• DCEO – $0.12/kWh and $3.00/therm• NIPSCO – $0.09/kWh and $0.60/therm


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Thanks for Coming!

and Special Thanks to those who allowed me to use their graphics…

Thanks for Coming!

and Special Thanks to those who allowed me to use their graphics…



Documents

Introduction to Building Automation Systems (BAS) · Building Automation Systems zCentralized controls zChange scheduling for multiple HVAC units at same time zMonitor “health”