varitrac changeover bypass vav (tracker system … catalog 060804...varitrac ™ changeover bypass...

VariTrac™

ChangeoverBypass VAV(Tracker System CB)

VAV-PRC003-ENJune 2004

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Contents

Introduction ............................................................. 4

Comfort Made Simple ................................................................ 4The Changeover Bypass VAV Comfort Advantage ....................... 4

VariTrac Product Enhancements ................................................. 4

Features and Benefits........................................... 5–12

Overview ................................................................................... 6Central Control Panel ................................................................. 7Optional Operator Display .......................................................... 7Communicating Bypass Controller ............................................. 8Tracker System Integration ......................................................... 8VariTrac Bypass Dampers ........................................................... 9VariTrac Zone Dampers ............................................................ 10Unit Control Module ................................................................ 10

Zone Sensors ...................................................................... 11–12

Application Considerations ................................ 13–24

Introduction .............................................................................. 13Zoning Considerations.............................................................. 13Effective Changeover Bypass VAV System Design ................ 14–19Pressure Dependent vs. Pressure Independent .......................... 20Local Reheat Capabilities Using VariTrane VAV Units ............. 20–21Bypass Damper Operation ........................................................ 22Building Pressure Control ......................................................... 23

Application Tip Summary.......................................................... 24

Selection Procedures ......................................... 25–28

VariTrac Dampers ................................................................ 25–26Service Model Numbers........................................................... 27

Typical Bill of Materials ............................................................. 28

Electrical Data and Connections ......................... 29–34

Specifications ................................................... 35–38

Acoustics.......................................................... 39–40

Dimensions and Weights .................................... 41–46

Glossary ........................................................... 47–48™ ® The following are trademarks orregistered trademarks of their respectivecompanies: Precedent, ReliaTel, Trace, Tracker,VariTrac, VariTrane, Voyager.

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Comfort Made SimpleTrane has a long history of innovativeleadership in variable air volume (VAV)technology. Trane introduced the:

• first fan-powered VAV unit

• first factory-commissioned DDCcontroller

• first preprogrammed VAV controllerdesigned specifically for VAVapplications

Trane is now the leading manufacturerof VAV terminal units and VAV-relatedproducts in the world.

The introduction of VariTrac™ in 1989brought VAV controls expertise into thechangeover bypass zoning market.

Trane is committed to continuousproduct improvement and nowintroduces a new generation of VariTraccontrols. This latest generation retainsthe functionality of the original VariTracsystem with exciting newenhancements, utilizing the best oftoday’s technology.

Figure 1. The VariTrac CCP maximizessystem efficiency and reliability bycoordinating the components of thechangeover-bypass system

Selected enhancements of the newVariTrac product are listed below.

• A new central control panel (CCP) withimproved system temperature andpressure control functions

• An optional touch-screen operatordisplay for the CCP with built-intime clock for easier system setup andcontrol

• A communicating bypass controllerallows duct pressure and ducttemperature to communicate to thesystem via a twisted shielded wire pair,thus eliminating costly “home-run”wiring

• The next generation UCM zonecontroller allows CO2 and occupancysensor inputs

• A digital display zone sensor forsimplified occupant control

VariTrac ProductEnhancements

Advanced Control Options

Some of the VariTrac intelligent systemcontrol features are listed below.

• CO2-based demand control ventilationresets the position of the HVAC unitventilation air damper when zone CO2levels rise

• Zone-based HVAC unit control operatesheating and cooling only when zonedemand exists

• Discharge air control to avoid extremesupply air conditions and maximizeequipment life and occupant comfort

• A simplified system-balancing processis available via PC software or thetouch-screen interface

• Global zone temperature setpoint limitssimplify startup, commissioning, andoperator control

Figure 2. The VariTrac CCP withoptional touch-screen interfacesimplifies system operation withintuitive icon-driven design

The Changeover BypassVAV Comfort Advantage

Packaged unitary systems offer apopular and cost-effective method ofsupplying conditioned air to lightcommercial buildings. These systemscommonly have a constant-volume fanwith a fixed outside air damper and asingle thermostat. While a constantvolume system may meet the overallthermal requirements of the space, onlya single thermostat is available. Thissystem may be insufficient in multiple-space applications with independentthermal load requirements.

Changeover bypass systems use thepracticality and cost effectiveness ofconstant volume unitary componentslike packaged rooftop units, splitsystems, or water-source heat pumps,and simply add dampers and a centralcontrol panel to coordinate thecomponents. This allows up to24 individual sensors (thermostats) forindependent temperature control.

Introduction

VAV-PRC003-EN 5

VariTrac ZoneDamper

Zone Sensor

HVACUnit

CommunicatingBypassController

VariTrac Central ControlPanel with touchscreeninterface

BypassDamper

VariTrac Central Control Panel (CCP)The CCP is the system level controller whichcoordinates and monitors VariTrac systemoperation, including HVAC system supplypressure and airflow, heating/cooling mode,

supply air temperature, all zone temperatures and setpoints,fan mode, economizer position (when paired with CO2demand controlled ventilation), time-of-day scheduling, zonegrouping logic, system override mode (after hoursoperation), and much more.

Bypass Damper w/ Wire and Quick ConnectA round or rectangular damper ductedbetween the HVAC supply and return ducts. Itis easily connected via a “quick-connector”

which provides quick and consistent field wiring. The bypassdamper is modulated by the CCP to maintain required systemstatic pressure.

Zone SensorZone sensors (sometimes referred to asthermostats) measure space temperature andreport it to the zone damper controller (UCM).

Five models are available to satisfy varied aesthetic andapplication preferences.

HVAC UnitVariTrac changeover bypass systemsoperate with Trane and non-Trane products,including split systems, packaged rooftopunits, and water-source heat pumps. Thesesystems are generically referred to as HVAC(heating, ventilating, and air conditioning)units. When combined with a Tranepackaged rooftop with ReliaTel™ controller,wiring, installation, and system startupefficiency is maximized by connecting with asimple twisted shielded wire pair.

Communicating Bypass ControllerA single enclosure with duct temperature sensor,static pressure sensor, and communicatingcontroller (UCM) which easily mounts on thesupply ductwork. The UCM provides power to

drive the bypass damper actuator.Rooftop

Split System

WSHP

Figure 3. VariTrac changeover-bypass VAV system components

5

Features andBenefits

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OverviewChangeover-bypass VAV is a comfortsystem developed for light commercialapplications. A changeover-bypass VAVsystem responds to changing coolingor heating requirements by varying thequantity or volume of air delivered toeach zone. Each zone has a thermostatfor individual comfort control. AnHVAC unit delivers a constant volumeof air to the system. As the volume ofair required by the zone changes,excess supply air is directed to thereturn duct via a bypass duct anddamper. (See Figure 3 for typicalsystem components.)

A changeover-bypass VAV systemcombines the comfort benefits of VAVwith the cost effectiveness andsimplicity of packaged, constant-volume unitary equipment.

How the System Works

A changeover-bypass VAV systemcommonly consists of an HVAC unitwith a constant-volume supply fan, anddirect-expansion (DX) cooling. Thiscombined system has the ability to“change” to the heating mode orcooling mode, depending on individualzone comfort requirements. A heatingcoil or a gas-fired heater and an outsideair damper are possible options.

A temperature sensor in each zonecommunicates information to anelectronic controller on the VAVterminal unit. The controller thenmodulates the zone damper open orclosed, supplying heating or cooling airto the zone.

The HVAC unit delivers a constantvolume of supply air to the system. Inorder to maintain duct static pressure, abypass duct and damper are requiredto bypass (detour) air not required inthe zones.

The VAV terminal unit controllercommunicates zone temperatureinformation to a central control panel(CCP). The CCP also gathersinformation from the system, includingduct static pressure and supply-airtemperature. The CCP determines zoneheating or cooling needs using voting(or polling) logic, then requests heatingor cooling from the HVAC unit. The CCPdirects the HVAC unit to provideventilation air to high-occupancy areas(demand control ventilation) or free-cooling when the outside airtemperature falls below thetemperature setpoint (economizercontrol).

Auto Changeover

“Auto changeover” refers to the abilityof the system to automatically changebetween the heating and coolingmodes.

In a changeover-bypass VAV system,the CCP determines whether the HVACunit should heat or cool by polling thetemperature of the individual zones. Itthen compares the zone temperaturesto the space temperature setpoints. Ifthe supply air does not meet the criteriafor the heat or cool mode called for, theCCP sends a signal to the HVAC unit tochange the system to the oppositemode.

VAV-PRC003-EN 7

Figure 6. VariTrac central control panelwith optional operator display


Central Control PanelThe VariTrac central control panel (CCP)serves as the central source ofcommunications and decisionmakingbetween the individual zones and theHVAC unit. The CCP determines systemheating and cooling modes andcoordinates the system supply airtemperature and static pressure tosatisfy building thermal loadconditions. Inputs to the CCP include24VAC power and communicationwiring to the zone dampers and bypasscontrol.

Binary inputs consist of priorityshutdown and occupied/unoccupiedmodes. Heating, cooling, and the HVACunit fan on split systems and non-TraneHVAC units can be controlled throughbinary outputs on an accessory relayboard. If a Trane rooftop air conditionerwith factory-installed electroniccontrols is used, the CCP can controlheating, cooling, and the fan with a two-wire communication link tied to aninterface board mounted in the rooftop.It can also display status informationfrom the electronic controller in therooftop. (See Figure 4.)

Optional Operator DisplayThe optional operator display is abacklit, liquid crystal display with touch-screen programming capability.

The operator can access system andzone status through the display andperform basic setup of zone VAV UCMsand CCP system operating parameters.The display allows an installer tocommission a VariTrac system withoutusing a PC. The operator display has aseven-day time clock for stand-alonescheduling capability.

Operator Display Feature Summary

• Backlit LCD touch-screen display foreasy operator interface

• Combination of icon- and menu-basednavigation provides intuitive operation

• Provides a level of control for the dailyoperator, and a second level forcommissioning and service

• Three levels of security are available toprotect system settings

• Seven-day time clock for stand-alone,time-of-day scheduling

CCP Feature Summary

• Communicates with up to 24 VAV unitcontrol modules (UCMs)

• Makes optimal heating and coolingdecisions based on setpoint andtemperature information received fromindividual zones

• Automatically calibrates all dampers,significantly reducing labor-intensiveand costly field calibration

• Windows-based PC software simplifiessetup and control

• Provides diagnostic information for allsystem components via the operatordisplay or PC software

• Provides status and diagnosticinformation for Trane HVAC unitsequipped with Trane ReliaTel or UCPelectronic controls

Figure 5. VariTrac central control panel

Figure 4. A screen representationfrom the central control panelillustrating system status

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Figure 8. Tracker System Architecture

Static Pressure Sensor

The static pressure sensor measuresduct static pressure and positions thebypass damper(s) to maintain the staticpressure setpoint.

Figure 7. Communicating bypasscontroller side view and 3-D view

Quick Connect

Minimizes field wiring labor andassures wiring consistency

Duct Temperature Sensor

The supply air temperature sensorallows the CCP to control heating andcooling stages to maintain the supplyair temperature. Supply airtemperature setpoints can be editedthrough the operator display orPC software.

Tracker System IntegrationThe VariTrac system can be fullyintegrated with the new family ofTracker building controls. A Trackerbuilding management system canmanage multiple VariTrac systems froma single control point.

Tracker System Summary

• Controls up to 10 VariTrac systemsfrom a single Tracker panel for easybuilding operation

• LCD touch-screen operator display orTracker PC software interface providessingle-point building management by alocal operator

• 365-day scheduling function and theflexibility of up to 10 schedules

• Assign all systems to a singleschedule, if desired, for simplifiedschedule changes

• Exception scheduling feature for easymanagement of vacations and holidays

• Automatically adjusts for daylightsavings time and leap year

• Remote communications capabilityvia modem for system programmingand control

Up to 24VariTrac orVariTraneDampers

Communicating BypassControllerThe communicating bypass controlleris a single control enclosure with thefollowing integrated devices included:

• integrated UCM board

• static pressure sensor

• discharge air temperature sensor

The communicating bypass controllerdirectly controls the bypass damperand communicates duct conditions tothe central control panel via a simpletwisted shielded wire pair.

Duct TemperatureSensor

Static PressureSensor

QuickConnect

VAV-PRC003-EN 9


VariTrac Bypass DampersBypass dampers are non-communicating VariTrac dampers andinclude an integrated fully-modulating24 VAC electric actuator.

Field wiring errors are reduced with aquick-connect harness that plugs intothe communicating bypass controller.

Dampers are nominally rated up to1800–2400 fpm at 1.75" of staticpressure, depending on size.

For damper performance information,see Table 2.

Round Bypass Damper Summary• Round bypass dampers are available

with inlet diameters 6, 8, 10, or 12 inches

• Heavy gage galvanized steel cylinderwith rolled bend for high structuralintegrity and corrosive resistance

• Metal-to-metal blade seal provides tightshutoff for low leakage

• Aerodynamic blade design provides aconstant torque for stable operation athigh velocity

• Factory-installed, direct-coupled, fully-modulating 24 VAC actuator

• Rated up to 2400 fpm at 1.75" of staticpressure

Rectangular Bypass Damper Summary

• Rectangular bypass dampers areavailable in sizes 14 x 12, 16 x 16,20 x 20, and 30 x 20 inches

• Formed heavy gage galvanized steelframe, mechanically joined with linkageconcealed in the side channel

• Air linkage is minimized with anopposed blade design with stainlesssteel side seals

• Damper casing is 16 inches long andconstructed of heavy gage galvanizedsheet metal with S cleats on the inletand outlet for easy installation

• Blades are six-inch nominal width,heavy gage galvanized steel

• A blade rotation stop feature preventsover-rotation of the blades in the fullyopen position

• Factory-installed, direct-coupled, fully-modulating 24 VAC actuator

• Rated up to 3000 fpm at 2" of staticpressure

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VariTrac Zone DampersVariTrac zone dampers are fully-modulating, pressure-dependent VAVdevices. The dampers control zonetemperature by varying the volume ofair flowing into a space. Each VariTracdamper has a control box with a VAVcontrol board and actuator enclosed.The dampers are designed to operate instatic pressures up to 1.75 in. wg.

Round Zone Damper

• Round dampers are available in 6, 8, 10,12, 14, and 16 inch diameters

• Heavy gage galvanized steel cylinderwith rolled bend for high structuralintegrity and corrosive resistance

• Metal-to-metal seal provides tightshutoff

• 90° blade rotation for a wide controlrange and stable operation

• Aerodynamic blade design providesconstant torque for stable operation athigh velocity

• Rated up to 2000 fpm at 1.75" of staticpressure

Rectangular Zone Damper

• Rectangular dampers are available insizes 8 x 12, 8 x 14, 8 x 16, 10 x 16,10 x 20, and 14 x 18 inches

• Heavy gage G90 galvanized steelframe assembled by a mechanicaljoining process

• Single-ply, heavy gage G90 galvanizedsteel blades

• Linkage has high impact ABS gears,and is 3" nominal diameter

• Factory-installed 24 VAC direct-coupledactuator

• Rated up to 2400 fpm at 2" of staticpressure

Figure 9. VariTrac rectangular and round zone dampers with UCMs

Unit Control ModuleA unit control module (UCM) is theindividual zone controller for theVariTrac air damper and is mounted oneach zone damper. The unit controllercontinually monitors the zonetemperature to maintain spacetemperature. The UCM varies thedamper position as needed to meetzone setpoints and communicatescurrent space requirements andsystem operating modes to the CCP.

The UCM can also control local heat.Local heat may be duct- or space-mounted, and can be staged electric,pulse-width modulating electric, andmodulating or two-position stagedhot water.

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Figure 10. DDC zone sensors Figure 11. DDC zone sensor with LCD

DDC Zone Sensor

The direct digital control (DDC) zonesensor is an uncomplicated, reliableelectro-mechanical room sensor. Noprogramming is required and mostsensors contain an internalcommunications jack.

Models are available with combinationsof features such as override (on-cancel)buttons and space-mounted setpoint.

Four sensor variations are available:

• Sensor only (no communications jack)

• Sensor with override buttons

• Sensor with temperature setpoint only

• Sensor with temperature setpoint andoverride buttons

DDC Zone Sensor with LCD

The DDC zone sensor with LCD (liquidcrystal display or digital) is compatiblewith VariTrane VAV and VariTraccontrollers.

Zone Sensors

Digital Zone Sensor Summary

• Displays setpoint adjustment and spacetemperature in °F or °C

• Simple, two-button control of spacesetpoint

• Setpoint control and room temperaturedisplay can be optionally disabled

• Includes button for timed override anda cancel feature for after-hours systemoperation

• An easily accessible communicationsjack is provided for Trane portable editterminal devices

• Nonvolatile memory stores lastprogrammed setpoints

• For field balancing, maximum andminimum airflow or position can beoverridden from the sensor

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Figure 14. Zone occupancy sensorFigure 12. Wall-mounted CO2 sensor

CO2 Sensor

Wall- and duct-mounted carbon dioxide(CO2) sensors are designed fordemand-controlled ventilation zoneapplications. The sensor is compatiblewith VariTrane VAV and VariTraccontrollers. The Trane CO2 sensorsmeasure carbon dioxide in parts-per-million (ppm) in occupied buildingspaces. Carbon dioxide measurementsare used to identify under-ventilatedbuilding zones. Outdoor airflowincreases beyond design ventilationrates if the CO2 exceeds specified levels.

CO2 Zone Sensor Summary

• Use with the UCM CO2 input fordemand control ventilation

• Silicone-based NDIR sensor technologyfor long-term stability

• Measurement range of 2000 ppm CO2input with an output of 0–10 Vdc

• Wall-mount transmitter is compact andaesthetic in appearance

• Optional zone return duct-mounttransmitter is available

Zone Occupancy Sensor

The energy-saving zone occupancysensor is ideal for zones havingintermittent use during the occupiedmode. The sensor sends a signal to theVAV controller upon detection ofmovement in the coverage area. TheVAV system then changes the zonefrom occupied standby mode tooccupied mode.

Occupancy Zone Sensor Summary

• Compatible with VariTrane VAV andVariTrac controllers

• Used with zone damper UCM forcontrolling the occupied standbyfunction

• Ceiling-mount PIR occupancy sensordetects motion over an adjustablerange up to 360 degrees

• Single detector covers up to 1200square feet. For areas larger than 1200square feet, multiple sensors can bewired in parallel

• Adjustable time delay avoids nuisancechange of state on loss of detection

• Adjustable sensitivity

• SPDT isolated contacts connect toUCM input

Figure 15. Auxiliary temperaturesensor

Figure 13. Duct-mounted CO2 sensor

Auxiliary Temperature Sensor

The auxiliary temperature sensor isused with any UCM damper control.The sensor allows the operator tomonitor duct temperature or airtemperature leaving a reheat device atthe zone damper. This sensor is usedfor automatic changeover of a UCMdamper when not using a CCP. Theauxiliary temperature sensor is ideal forremote monitoring and diagnosticsfrom the CCP operator display.

Auxiliary Temperature Sensor Summary

• Thermistor sensing element 10,000Ohms @ 77°F

• Wiring connection 8 feet, 18 awg

• Sleeving for wire leads is acrylic #5 awggrade C rated @ 155C

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ApplicationConsiderations

IntroductionThe VariTrac system is a changeover-bypass VAV system. One fan supplieseither warm air for heating or cool airfor cooling. It is typically applied insmall buildings which use unitaryheating/cooling air conditioners. Thesebuildings need the simplicity and lowcost of unitary equipment, but morethan one comfort control zone (onezone temperature sensor) for each airconditioner.

When is VariTrac a good HVAC systemchoice? To help answer this question,several important application conceptsand considerations are discussedbelow.

Zoning ConsiderationsConsider the following two questionswhen evaluating your HVAC systemdesign:

Will the building occupants becomfortable? A system designedwith a single-zone HVAC unit and onezone sensor provides comfort tooccupants near the zone sensor.However, occupants in perimeter areasor interior rooms may be too hot or toocold.

Will comfort be consistent fromroom to room and area by area? Abuilding is normally divided intothermal zones for increased comfortcontrol and energy savings. Eachthermal zone should have a dedicatedHVAC unit. For optimum comfort, eachthermal zone should be further dividedinto comfort zones.

Choosing the number and location ofthermal and comfort zones is critical inplanning an effective system. Somethings to consider in the designprocess include:

• Geographic location

• Orientation of the building to the sun

• Prevailing winds

• Wall construction (glass, insulation,building materials)

• Building layout, design, occupancy andoccupancy pattern throughout the dayand year

• Activities in each zone

Zoned unitary systems, such aschangeover-bypass VAV, divide thermalzones into smaller comfort zones. Eachcomfort zone has a damper and zonesensor that controls the amount ofheated or cooled air delivered to thezone. A central system controllermonitors the status of each zonedamper and zone sensor. The controllerthen makes the decision to heat or coolfor the HVAC unit.

Individual comfort zones served by acommon HVAC unit (part of the samethermal zone) can require heating andcooling at the same time. In achangeover-bypass VAV system, theunit alternately provides warm and coolair in an attempt to satisfy the needs ofall comfort zones. This is effective if thesimultaneous calls for heating andcooling exist for short time periodsonly. Wide temperature variations mayoccur if some comfort zones needheating for extended periods of timewhile others need cooling.

Some comfort zones require specialconsideration because of their use orlocation. An example is the foyer orreception area of an office building.These areas often have wide variationsin thermal load because of glass(relative to other areas of the building)and frequently-opened exterior doors.Another example is an interior storageroom with the need for ventilation butlittle or no heating or cooling. Thesezones can significantly influenceefficient operation and comfort levelsthroughout the building.

Preferably, areas such as these aredesigned as separate thermal zoneswith dedicated HVAC units. However,this may be impractical or costly.Instead, use fan-powered variable-volume terminal units, or units withlocal reheat.

Figure 16. System design affectsoccupancy comfort

Single Zone BuildingOne thermal and one comfort zone

Thermal Zoned BuildingMultiple thermal zones

each with one comfort zone

Thermal and Comfort Zoned Building

Multiple thermal zoneseach with multiple

comfort zones

Least

Most

En

erg

y S

avin

gs

• C

om

fort

• F

lexi

bili

ty

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Figure 17. Design process steps


Effective ChangeoverBypass VAV System Design

Unitary zoning systems feature lowfirst cost and quick, easy system designand equipment selection. The system issimple, but it is essential that keyelements are considered during thedesign process.

This section offers a system designsequence and discusses applicationconsiderations that, when followed,help avoid system control andoperational instabilities.

Suggested design steps for unitaryzoning systems are summarized inFigure 17.

Step 1. Define occupant comfort needs

The design process begins byconsidering the needs of buildingoccupants and intended building use.

What is the intended use of thebuilding? Is the building usageprimarily office space? Is there amanufacturing operation? Are thereareas that have special requirementssuch as computer or electronic rooms,video/television production, trainingfacilities, etc.?

What physical activity level isexpected of the occupants? Seatedoccupants require different indoortemperatures for comfort thancontinuously moving occupants. Anexample may be a building with a mixof office space and light assembly ormanufacturing.

Where will the occupants belocated and at what times? Payparticular attention to areas withintermittent use, such as conference,training, and lunchrooms.

How are the occupants expectedto dress? Give consideration to howthe building occupants will dress. Willthey dress in traditional business attire,such as long-sleeved shirts or blouses,ties, and jackets? Or, will they dress in

cooler, casual attire, such as golf shirts,light slacks, skirts, or shorts?

Gather as much usage information aspossible before designing a system.This can be challenging, particularlywhen finishing out tenant spaces.However, usage information is crucialto the selection of heating and coolingequipment, building zoning, and ductlayout.

Several publications provide guidancefor properly assessing indoor spacecomfort. An example is ASHRAE(American Society of Heating,Refrigerating and Air ConditioningEngineers) Standard 55, ThermalEnvironmental Conditions for HumanOccupancy. This standard specifies thecombinations of indoor spaceenvironments and personal factors(activity and clothing) that will producethermal environmental conditionsacceptable to 80 percent or more of theoccupants within a space. Standard 55addresses temperature, thermalradiation, humidity, and air speed.

ASHRAE Standard 62, Ventilation forAcceptable Indoor Air Quality, isanother source for occupant comfortand safety issues regarding indoor airquality. The standard recommends thatrelative humidity be maintainedbetween 30 and 60 percent. Thismaximizes comfort and reduces thepotential for microbial growth.

Step 2. Define the Thermal Zones

A thermal zone is an area with similarload profiles and occupant comfortrequirements. A thermal zone can be asingle room, an area, a group of roomsor an entire building. Defining thethermal zones within a building iscrucial to designing a comfortableindoor environment. Each thermal zoneis conditioned by a single heating and/or cooling unit. The load of the thermalzone determines the size of the heatingand cooling unit.

Step 1. Define Occupant Comfort Needs

Step 2. Define Thermal Zones

Step 4. Size Heating/ Cooling Equipment

Step 3. Determine Comfort Zones

Step 6. Design the Duct system

Step 5. Size Zone and Bypass Damper Units

Involves architect, engineer(s), and building owner

Involves engineers and contractors

Involves engineers, contractors, and building owner

Involves engineer(s) and contractors



Step 7. Air Diffuser Selection and Placement


VAV-PRC003-EN 15


Cost vs. Comfort

First cost can be reduced by limitingthe number of thermal zones.Unfortunately, this may impact thethermal flexibility of the system, andresult in zone comfort issues. Let’s takea closer look at this important systemdecision known as “thermal zoning.”

Characteristics of a building which caninfluence thermal load are:

• Orientation of the building (North,South, East, West)

• Amount and thermal resistance (R-value) of glass (walls, skylights, etc.)

• Expected occupancy within the area

• Interior partitions and doors

• Varying loads from equipment orprocesses

Let’s examine a few building examplesand discuss the zoning criteria of each.

Building Example 1 (See Figure 18.)

Consider an existing single-story officebuilding which is small, poorlyinsulated, with many large windowsand few interior partitions. On a clear,cool spring day, the entire building iscool in the morning so heating isrequired. By afternoon, however, thesouth side of the building beinginfluenced by the solar load, is warmand requires cooling. The north sideremains shaded and continues torequire heating. This situation results ina simultaneous requirement for heatingand cooling for extended periods. Dueto the varying loads throughout thebuilding, controlling the building as asingle thermal zone (with a single HVACunit) cannot satisfy the comfort needs

of all areas. It also is not a goodcandidate for a zoning system becauseof the simultaneous need for heatingand cooling.

A similar building with good insulationand fewer shaded windows, on theother hand, may be a good candidatefor a single thermal zone with individualcomfort zones. The reduction in wallglass reduces the solar effect on thebuilding resulting in all areas of thebuilding having similar load profilesthroughout the day. In this case, thebuilding has a single thermal zone andis a good candidate for one HVAC unit.Individual comfort zones (zonedampers) will be needed to assurecomfortable conditions throughout thezone.

Figure 18. Building Example 1 illustrates a small, poorly insulated office on the left, and improved design on the right.

Men'sRestroom

Women'sRestroom

ThermostatT

ShadedWindows

InsulatedWalls

Improved Design Elements• Multiple zone thermostats

• Shaded windows• Insulated walls

ThermostatTThermostatT

Men'sRestroom

Women'sRestroom

ThermostatT

Glass windowswith no shading Minimal wall

insulation

Poor Design Elements• One thermostat for space

• Glass windows with no shading• Minimal wall insulation

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Figure 19. Building Example 2illustrates a poorly insulated storedesign (above) and an improved design(below)

Building Example 2 (See Figure 19.)

Consider a strip mall in the spring or fallwith stores that face both east andwest. In the morning, the east side ofthe building gets full sun and warms upwhile the west side is shaded andrequires heating. In the afternoon, theeast side of the building may need heatand the west side cooling. Because ofthe thermal load variation throughoutthe day, this building will not remaincomfortable if designed with a singleheating and cooling unit.

On the other hand, comfort in thisbuilding could be improved by dividingthe building into two thermal zones(two HVAC units), one serving the eastexposure and the other serving thewest. Even with the two systems,individual occupant comfort is notnecessarily assured. Interiorpartitioning, varying schedules andnumber of occupants within thethermal zone will drive differingamounts of heating and cooling. Theissues related to comfort zoning areaddressed in the next section.

Step 3. Define the Comfort Zones

A primary criteria for defining a thermalzone is that it will not requiresimultaneous heating and cooling. AnHVAC unit with one fan is limited tosupplying either heating or cooling.Most applications with larger thermalzones however will have varyingthermal needs throughout the zone.These small variations can easily beaddressed by properly defining comfortzones.

A comfort zone is an area within athermal zone that is controlled by azone damper. The amount ofconditioned (heated or cooled) airentering the space varies. This is inresponse to a space thermostat.ASHRAE Standard 55 recommendslimiting indoor temperature variations.Temperature variations of less than 2°Fin 15 minutes or 4°F in an hour.Deviations from this recommendationwill cause discomfort in 80 percent ofthe occupants. Zoning systems cangreatly reduce temperature variationscaused by shifting occupancy and solarload conditions in large thermal zones.

JewelryStore

CoffeeShop

ElectronicsStore

ToyStore

ClothingStore

Pharmacy

OutsideDoors

N

Poor Design Elements• One thermostat for entire space

• One HVAC unit

JewelryStore

CoffeeShop

ElectronicsStore

ToyStore

ClothingStore

Pharmacy

OutsideDoors

N

Improved Design Elements• Two thermal zones

• Two HVAC units

VAV-PRC003-EN 17


Table 1. Diversity example

Calculating thermal zone diversity:

1. Determine the instantaneous peak(or block) load for the thermal zone.This information is output from loadanalysis software such as TraneTRACE® or manually calculated.

2. Calculate the sum of the peak loadsfor each of the comfort zones withinthe thermal zone.

3. The diversity factor is then calculatedby dividing the instantaneous peakload value by the sum of the peakloads.

The heating and cooling equipment willnever be called upon to provide morecapacity than was determined by theinstantaneous peak load value.Consequently, the equipment capacitycan be reduced by the diversity factor.

Step 4. Sizing HVAC Equipment

Once the building heating and coolingloads are known and the thermal zoneshave been determined, the heating andcooling equipment can be selected.Each thermal zone requires a separateheating and cooling unit. As discussedearlier, unitary zoning systems typicallyuse packaged DX rooftop units or DXsplit systems. These systems areoffered as heating and cooling units orheat pumps.

When selecting the heating and coolingunit for a thermal zone, load diversitywithin the zone should be considered tominimize equipment size and thereforereduce system first cost and operatingexpense. Load diversity is defined asthe ratio of the instantaneous peakloads (block load) to the sum of thepeak loads within the thermal zone. Inrecognizing load diversity, the designeracknowledges that all areas of thethermal zone will not require maximumcooling or heating at the same time.

While using diversity may reduce thesize of the HVAC unit, the zoneductwork, dampers, and diffusers mustbe sized for the individual zone peakloads. The main trunk duct may be sizedbased on the HVAC unit airflow.

DiversityFactor =

InstantaneousPeak Load

Sum of Peaks

Zone Time Peak LoadInterior 3 p.m. in mid-July 7.5 tonsNorth 5 p.m. in mid-July 3.0 tonsEast 9 a.m. in June 2.5 tonsSouth 4 p.m. in November 4.0 tonsWest 5 p.m. in September 2.5 tons

Sum of Peak Loads 19.5 tons

Note: The sum of blocks loads = 17.5 tonsand occurs at 5 p.m. in mid-July.

______19.5

Diversity = 17.5 = 90%

Figure 20. Diversity example

North Zone

East ZoneWest Zone Interior Zone

South Zone

Wedge ZoneBuilding Perimeter

GlassWindows

18 VAV-PRC003-EN


Step 5. Size Zone and BypassDamper Units

Sizing zone damper is relativelystraightforward. The volume of airflow(in cfm or L/s) for each comfort zoneshould be known from the loadanalysis. The designer must select theduct velocity to be used for the system.Recommended zone damper velocitiesare 1000 to 1600 feet per minute (fpm)when applied at the branch level.Sizing dampers in this range willminimize damper cost, reduce the riskof excessive noise, and ensureadequate zone modulation/temperaturecontrol.

Dampers located immediately adjacentto the zone or diffuser may need to besized at a lower velocity to avoid soundand airflow delivery issues.

Bypass dampers are typically sized for80 percent of HVAC unit airflow.Recommended velocities are 1600 to2000 fpm. Bypass dampers should belocated as close to the HVAC unit aspossible. (See Bypass DamperOperation for additional details.)

Note: VariTrac systems are designedfor HVAC unit static pressures up to1.75" w.c.

Step 6. Designing the Duct System

Low pressure, low velocity airdistribution systems, such as zonedunitary systems, are usually designedusing the equal friction method.Although static regain is the ductdesign method of choice for mediumand high velocity variable air volumesystems, the added complexity isdifficult to justify with smaller unitarysystems. In addition, the low operatingvelocity of most unitary systems makesthe pressure available to “regain”, smalland inconsequential.

With the equal friction method, ductsare sized for a constant pressure lossper given length of duct and fitting(s).Where low noise levels are especiallycritical, the system velocity can bereduced by enlarging the entering andleaving ductwork, damper unit oradding duct liner. A characteristic of theequal friction method that must beconsidered however, is that there is nonatural provision for equalizingpressure drops in the branch sections.This results in each branch duct, andthus the damper units, having differententering static pressure and airflowcharacteristics.

A robust system and zone unitcontroller, like the Trane VariTracsystem, will compensate for systemstatic changes. The use of manual (orhand) balancing dampers in thebranches will also ensure that airflow isappropriately distributed to eachdiffuser. (See Figure 21.) The overalleffect is improved acoustical andsystem performance.

Figure 21. Hand balancing dampers

HandBalancingDamper

VariTracDamper

SupplyDuct

VAV-PRC003-EN 19


• When the average glass plus wall heatloss is less than 250 Btuh/linear foot,the slot diffuser may be located inthe center of the room with one ormore slots blowing toward theperimeter wall.

• With glass and wall heat loss between250 and 450 Btuh/linear foot, diffusersshould be positioned to blow towardthe window and the perimeter wall witha collision velocity of 75 to 150 fpm. Ifusing a continuous glass design,position diffusers every four feet.

• If heat loss exceeds 450 Btuh/linearfoot, radiation or floor mounted heatedair will be required to offset the highwall heat loss.

Step 7. Air Diffuser Selection andPlacement

Supply Diffusers

Many types of supply air diffusers areused in variable air volume systems.Performance, and ultimately spacecomfort, can vary greatly depending onthe diffuser selected. Althoughconstant-volume diffusers will provideair to the space at full cfm, as airvolume delivered to the spacedecreases, so does performance.Linear slot diffusers are recommendedfor most VAV systems.

Linear supply air slot diffusers aredesigned to properly mix variable airdelivery of both heated and cooled air.Linear slot diffusers supply conditionedair which “hugs” the ceiling rather than“dumps” air downward on theoccupants. This airflow characteristic isknown as the “coanda effect”. Thethrow and aspiration characteristics ofslot diffusers help to evenly distributethe air throughout the room or space.

Locate linear slot diffusers in the centerof the room with the discharge airpattern perpendicular to a perimeterwall. To maximize diffuserperformance, placement in which airdischarge patterns converge at rightangles should be avoided. (See Diffusersection of the VariTrane catalog (VAV-PRC008-EN) for additional diffuserplacement and performancerecommendations.)

The throw characteristics of diffusers iswell-documented. Slot diffusers shouldbe positioned so that the velocity of theair striking an obstruction (such as awall or column) is 75 feet per minute(fpm) or less. If airstreams from twodiffusers collide, the collision velocityshould not exceed 150 fpm. Highercollision velocities result inuncomfortable drafts in the lower levelsof the room.

In heating applications, linear slotdiffusers must be placed to offset heatloss and prevent downdraft problemsalong perimeter walls. The followingtechniques have been proven by testand experience:

Figure 22. Proper return diffuser orientation

Return Diffusers

Slot-style return diffusers offer someacoustical advantages over perforatedgrille styles. Perforated drop-in grillestypically offer little attenuation effectand thus allow sound in the plenum tobreak out into the occupied space. Thisis a problem in areas near the unitaryheating and cooling unit. Improvedceiling aesthetics is also an advantageof slot return diffusers in jobs whereslot supply diffusers are used. Withinthe occupied space, they blend with theslot supply diffusers.

A general rule of thumb is for the returnair openings to equal the total area ofthe supply openings. If the ceiling is nottight, such as a drop-in ceiling, thereturn openings can be reduced by upto 50% of the supply air openings.

To promote good air distribution, returndiffusers should be positioned tominimize supply air short-circuiting tothe return slot. The returns should beeither perpendicular to the supplyairflow or parallel and offset from thesupply diffusers.

20 VAV-PRC003-EN


Local Reheat CapabilitiesUsing VariTrane VAV Units

VariTrane pressure independent VAVunits are a simple way to upgrade thezone VAV capabilities on a VariTracsystem. The main advantage is theability to integrate units with either hotwater or electric reheat. Here areapplication examples where VAV unitsmay enhance your design:

Example 1

Series fan-powered VAV unitswork well in conference rooms andtraining rooms. Series fan-poweredunits supply constant air volume to thespace. This provides excellent airmovement in the space regardless ofthe internal load requirements. Hotwater or electric heat are integral to theunit and optionally available to temperthe air at partial load conditions.

Figure 24. Series fan-powered VAVterminal unit

Example 2

Parallel fan powered units withlocal heat applied help solveproblems in difficult areas to controllike lobbies and vestibules. The parallelfan provides local heat to an individualzone without relying on the main HVACunit’s heat or supply fan. This allowsgreater flexibility for mixing zones on aVariTrac system.

VariTrane units with integral electric orhot water heat are available as:

• single-duct

• parallel fan-powered

• series fan-powered

Figure 23. Single-duct VAV unit isavailable with integral electric or hotwater heat

Figure 25. Parallel fan-powered VAVterminal unit

Pressure Dependent vs.Pressure IndependentPressure-Dependent

A pressure-dependent VAV controlsequence uses the space temperaturesensor to directly control the positionof the zone damper. The actual airflowdelivered to the space is a by-product ofthis damper position and the staticpressure in the duct upstream of thezone damper.

Ventilation air is a fixed-damperposition and must be measured and setduring the commissioning process.

Pressure-Independent

A pressure-independent VAV controlscheme directly controls the actualvolume of primary air that flows to thespace. An airflow-measuring device inthe VAV terminal unit makes thispossible. The position of the modulatingdevice is not directly controlled and is aby-product of regulating the airflowthrough the unit. Because the airflowdelivered to the space is directlycontrolled, it is independent of inletstatic pressure.

VAV-PRC003-EN 21


Local Reheat CapabilitiesNon-VAV Options

The Trane VariTrac Zone Controller hasbuilt-in capabilities and logic to controla number of reheat sources. Theprevious page discussed how aVariTrane VAV unit with reheat cansolve application issues by providinglocal reheat.

Local Reheat

Let’s investigate a few other alternativeswhich will provide local reheat, andresult in exceptional zone temperaturecontrol.

Local reheat is particularly importantwhen an HVAC unit is in cooling mode.Cold air is delivered to all zoneswhether it is needed or not. Setting theminimum cooling position to zero maynot be practical based on ventilationand/or general airflow requirements. Inthis case, local reheat options whichcan be controlled by the standardVariTrac zone controller include:

• hydronic wall fin or convector unit witheither modulating or two positioncontrol. (See trane.com for a full line ofwall fin and convector products.)

• electric wall fin with multi-stage control

• duct-mounted electric heater withmulti-stage control

• duct-mounted hot water coil with eithermodulating or two-position control.(See trane.com for a full line of duct-mounted water coils.)

Figure 26. Trane hydronic wall fin

This is ideal for spaces with largewindows or perimeter heat losseswhich exceed 450 Btuh per linear foot.Trane wallfin is available with variousgrilles and paint options and can bepedestal or wall-mounted

Figure 27. Trane electric wall fin

22 VAV-PRC003-EN


Figure 28. Changeover bypass variable-air-volume system

Bypass Damper OperationWhen zone dampers modulate airflowto the spaces, static pressure changesin the supply duct system. Highpressure in a duct system createsexcessive noise and causes poorcomfort control. Low pressure resultsin insufficient airflow to the spaces.

The HVAC unit in a changeover bypasssystem is constant volume and doesnot modulate supply airflow.Changeover-bypass VAV systemssupport variable-air-volume operationin the zones by using a bypass ductwith a motorized damper and apressure-sensing device.

As duct pressure rises above the staticpressure setpoint, the bypass damperbegins to open. Conversely, when staticpressure falls below the static pressuresetpoint, the bypass damper begins toclose until the static pressure setpointis reached. The optimal static pressuresetpoint is automatically determinedupon system calibration.

Proper operation requiresconsideration of all aspects of bypassdesign and location. The bypassdampers and ductwork should be sizedand located according to the followinggeneral recommendations:

Avoid turbulence by locating thebypass two to three equivalent ductdiameters downstream of the HVACunit discharge.

Locate the static pressure and supplyair sensors in the main supply ductupstream of the bypass.

Locate the bypass before the zonedampers (as close to the HVAC unit aspossible) to avoid comfort or noiseissues.

Size the bypass damper to maintain theminimum required airflow through theHVAC unit (usually 80 percent of thetotal design cfm)

Provide adequate access for servicingthe damper.

Supply Air Duct

ReturnAir Duct

Ductwork

BypassDamper

ReturnAir Duct

HHeating and

RooftopMicro Control

Static Pressureand SupplyTemperature Sensors

VAV-PRC003-EN 23


Building Pressure ControlComfortable, efficient buildingoperation requires that the air pressureinside the building be slightly higherthan the atmospheric pressure outsideof the building. That is, the building is ata “positive” pressure with respect tothe outside environment. If the indoorpressure is too low (negative), thedoors may be hard to open and cold airmay leak in through constructioncracks, causing drafts and cold floors.On the other hand, if the indoorpressure is too high, the doors maystand open and the supply air flow tothe zones may decrease, decreasingcomfort.

Fixed Outside Air Dampers

Achieving appropriate buildingpressure is simple in a system with aconstant volume supply fan and fixedoutdoor air damper. To maintain aslightly positive building pressure, sizethe exhaust fans to remove slightlyless air than is introduced through theoutdoor air damper.

Outside Economizer or Demand-Controlled Ventilation Systems

If the system resets the quantity ofoutdoor air in response to occupancydemands (demand-controlledventilation), or uses an outdoor aireconomizer, undesirable changes inbuilding pressure may result. As thequantity of outdoor air intake varies,the system must exhaust a similarquantity of air to avoid over or underpressurizing the building.

When using an economizer in achangeover-bypass VAV system underlow cooling load conditions (reducedairflow to the zones), the bypassdamper opens to maintain the staticpressure setpoint and airflow throughthe supply fan. As the outside airdamper opens to provide economizercooling, the return air damper closes.In buildings with a ceiling plenumreturn, the bypass air dumps into theceiling plenum since it can no longerreturn to the fan. The plenum pressurerises and plenum air enters the zonesthrough the return air grilles.

In buildings that have a ducted return tothe fan, bypass air pressurizes thereturn air duct. As the return air ductpressure rises, the air flows out of thebuilding through the barometric reliefdamper in the rooftop unit. Excessbypass air flows into the zones throughthe return air grilles.

Using the following suggestions willhelp maintain building pressurizationcontrol:

• Use an exhaust fan with a modulatedexhaust damper to remove air from thereturn air plenum or duct. Energize theexhaust fan as the outside air damperopens beyond the minimum position.Sense building static and maintainbuilding air pressure at a slightlypositive level by modulating theexhaust damper position.

• Use an exhaust fan with no exhaustdamper. Energize the exhaust fan whenthe outdoor air damper opens beyond25 percent to remove excess outside airfrom the building. This method is usedwith some rooftop units and iseffective, affordable, and easy to install.

• Use a back draft damper to preventairflow to the return air plenum orgrilles. When bypass airflowpressurizes the return duct, the backdraft damper closes. Pressure in theHVAC unit return air inlet rises, causingthe rooftop barometric relief damper toopen. This method is less effectivebecause the rooftop barometric reliefdamper is sized for a portion of the totalairflow, not 100 percent of airflow whichmay be seen in economizer mode. Asthe economizer drives to the maximumposition, the building usually becomesover-pressurized.

Figure 29. Changeover bypass with an economizer. Without proper buildingpressurization, bypass air may be forced out of the return duct.

OutdoorAir Damper

Economizer Fan

Bypass

ReturnDamper

ReturnOpening

24 VAV-PRC003-EN

Application Tip Summary

Tip 1. Use comfort zones

Units serving thermal zones canprovide greater comfort by dividing thethermal zones into “comfort zones”using a changeover-bypass-VAVsystem.

Tip 2. Create thermal zones

Create thermal zones which minimizesimultaneous heating and coolingrequirements. This will avoidunnecessary changeover of the systemand maximize comfort. As an example,a computer room would be a poorcandidate for one comfort zone of achangeover-bypass-VAV systembecause it will rarely, if ever, requireheating.

Tip 3. Use local heat

Zones which vary thermally byrequiring more heat than the otherzones or require heat when the HVACunit is in cooling mode should use localheat. Local heat in the form of VariTraneVAV units with electric or hot waterheat, or wallfin, or convectors, or duct-mounted coils. The standard VariTraccontroller is capable of controlling theheat based on zone temperaturedemands.

Tip 4. Place dampers properly

The bypass damper should be ductedbetween the supply and the return ofthe unit as close to the unit as possible,and should be sized to handle 80% ofthe total system CFM.

Tip 5. Control building pressure

It may be necessary to provide amodulating means to control buildingpressure, especially when economizersor demand-controlled ventilation areused in conjunction with a changeover-bypass-VAV system.

Tip 6. Use fan-powered VAV boxes

Consider using fan-powered VAV boxesto provide local heat or to enhancecomfort levels in some of your zones.Conference rooms, or zones with highwall heat loss are ideal for either seriesor parallel units.


VAV-PRC003-EN 25

Zone Damper Selection Procedures

Refer to the sizing chart in Table 2 forzone dampers. Follow down the firstcolumn in the table for the desiredvelocity. Then follow across for the cfm(air volume) of a given VariTrac damperbased on that velocity.

Note: If the cfm exceeds the damperrange, increase the damper size.

Minimum airflow damper positionshould be set to10 percent in heating orcooling when a zone duct temperaturesensor is used for stand-alone control.In addition, when controlling duct-mounted electric reheat coils, coolingminimum airflow should meet theheating unit manufacturer’s guidelines.(See Application Considerations,Maximum System Effectiveness formore details.)

Bypass Damper Selection Procedures

To determine the cfm capacity requiredfor a bypass damper, calculate80 percent of the cfm capacity ofthe heating/cooling unit.

Example: If the rooftop capacity is 1200cfm, the bypass damper should besized for 1200 x .8 = 960 cfm.

To determine the size of the damper,locate the recommended velocity andcfm for the bypass damper.

Since a 10" round bypass damper at1800 fpm provides 980 cfm, a 10"damper at 960 cfm would be slightlyless than 1800 fpm, but still within the1600 to 2000 fpm recommendedvelocity. A 10" bypass damper isselected.

SelectionProcedures

VariTrac dampers are typically installedon VariTrac changeover bypass variableair volume (VAV) systems. VariTrac isideal when applied to buildings whichuse unitary HVAC units. The damperunits have controls, which vary airvolume and maintain appropriate ductstatic pressure in the system to makesure that all zones receive the rightamount of airflow.

Trane offers four VariTrac dampers:

• Round zone dampers with DDCcontrols

• Rectangular zone dampers with DDCcontrols

• Round bypass dampers

• Rectangular bypass dampers

Figure 30. Round and rectangular zone and bypass dampers

VariTrac Dampers

26 VAV-PRC003-EN

SelectionProcedures

Notes:1. Recommended velocity for zone dampers is between 1000 and 1600 fpm. Use

good standard design practices (such as location of duct).2. Recommended velocity for bypass damper is between 1600 and 2000 fpm.

Table 2. Damper sizing charts

Round Zone DamperCapacity (cfm), Dimensions, and Weights

Size 6" 8" 10" 12" 14" 16"

600 120 210 330 470 640 840

800 160 280 435 630 855 1115

1000 200 350 545 785 1070 1395

1200 235 420 655 940 1280 1675

1400 275 490 765 1100 1500 1955

1600 315 560 875 1255 1710 2235

Length 12" 12" 16" 16" 20" 20"

Ship Wt 11 lbs 12 lbs 17 lbs 18 lbs 27 lbs 31 lbs

Re

com

me

nd

ed

Velo

city

(fpm

)

Size 8 x 12 8 x 14 8 x 16 10 x 16 10 x 20 14 x 18

600 398 464 531 663 829 1045

800 531 619 707 884 1105 1393

1000 663 774 884 1105 1382 1741

1200 796 928 1061 1326 1658 2089

1400 928 1083 1238 1547 1934 2437

1600 1061 1238 1415 1769 2211 2785

Blades 2 2 2 3 3 4

Ship Wt 8 lbs 10 lbs 12 lbs 14 lbs 16 lbs 18 lbs

Velo

city

(fpm

)

Rectangular Zone DamperCapacity (cfm), Dimensions, Blades, and Weights

Re

com

me

nd

ed

Size 14 x 12 16 x 16 20 x 20 30 x 20

600 696 1061 1658 2487

800 928 1415 2211 3316

1000 1161 1769 2763 4145

1200 1393 2122 3316 4974

1400 1625 2476 3869 5803

1600 1857 2830 4421 6632

1800 2089 3183 4974 7461

2000 2321 3537 5527 8290

Blades 2 3 3 3

Ship Wt 16 lbs 21 lbs 29 lbs 40 lbs

Re

com

me

nd

ed

Rectangular Bypass DamperCapacity (cfm), Dimensions, Blades, and Weights

Velo

city

(fpm

)

Size 6" 8" 10" 12"

600 120 210 330 470

800 160 280 435 630

1000 200 350 545 785

1200 235 420 655 940

1400 275 490 765 1100

1600 315 560 875 1255

1800 350 630 980 1415

2000 390 700 1090 1570

Length 12" 12" 16" 16"

Ship Wt 11 lbs 12 lbs 17 lbs 18 lbs

Re

com

me

nd

ed

Round Bypass DamperCapacity (cfm), Dimensions, Blades, and Weights

Velo

city

(fpm

)

VAV-PRC003-EN 27

Digits 1, 2, 3, 4 – Product Type

VADA = VariTrac Air Damper

VARA = Rectangular Air Damper

Digits 5, 6 – VariTrac Damper Size

06 = 6" Damper

08 = 8" Damper

10 = 10" Damper

12 = 12" Damper

14 = 14" Damper

16 = 16" Damper

1R = 14 x 12 bypass damper




5R = 8 x 12 zone damper





AR = 14 x 18 zone damper

Digit 7 – Controls (all factory downloadedand verified)

A = Bypass with actuator

B = Damper only control (Changeover)

C = Damper plus up to 3 stages ofElectric

D = Damper plus 1-stage Normally-open hot water

E = Damper plus 1-stage Normally-closed hot water

F = Not used

G = No controls (Actuator Only)

H = Not used

J = Bypass for rectangular damperwith actuator

Digits 8, 9, 10, 11

00P0 = Design sequence

SelectionProcedures

Service Model Numbers

V A D A 0 6 A 0 0 P 0

1 2 3 4 5 6 7 8 9 10 11

28 VAV-PRC003-EN

A & J

BC

D

EF

G

HFigure 31. Typicalcomponents in achangeover-bypassVAV system

Table 3. Typical VariTracchangeover-bypass VAVsystem components

SelectionProcedures

Typical Bill of Materials

Device Name Function in System Number Required

A Central control panelw/optional operator display

Controls the HVAC system and provides localoperator interface

One per HVAC unit/VariTrac system(thermal zone)

Communicating bypasscontroller

Sends supply duct temperature and pressure tothe central control panel

One per VariTrac system

Bypass damper(s) Supply air duct volume control to maintainappropriate static pressure in the duct

One or two per system as needed tobypass from supply to returnairstream

D VariTrac dampers Varies air volume to the space to control comfort One per comfort zone

Zone sensors Sends space temperature and setpointinformation to the zone damper controller

One per comfort zone (DDC sensorw/ LCD requires 4 VA)

CCP power supply 24V power for the central control panel The CCP must have a dedicated 24Vpower supply

G Zone damper power supply(s) 24V power for the zone dampers Power supplies may be shared; eachzone requires 10VA (plus the load ofoptional outputs)

H Trane rooftop communicationsinterface

Allows the CCP and Trane rooftop controller tocommunicate with each other via simple twistedshielded wire pair

One per controlled Trane rooftopwith ReliaTel controller

Optional relay board Provides 24V control of any non-communicatingHVAC unit

One per controlled non-communicating HVAC unit

B

C

J

F

E

VAV-PRC003-EN 29

24 VacLine voltage

Comm5link

Comm5link

Comm5 UCMTracker

Splice

AA

BB

Twisted pair, shielded wireper Trane specifications

Shield termination

Earth ground

Contact points

TransfTT ormer

Termination resistor

Shield ground

=

=

=

=

=

=

=

Termination Board TB2

Figure note=

Comm4link

Comm4link

Comm4 UCMComm4 UCM

Splice

-

+

-

+

Legend Figure Notes:

1 All customer wiring must be in accordance with national, state, and local electrical codes.

2 Trane recommends a dedicated transformer for 24 Vac power.

3 Do not apply voltage to the priority shutdown and occupancy inputs.

4 Example of Comm5 communication link wiring. See product-specific literature for Comm5 wire connection details.

Electrical Dataand Connections

Figure 32. Central control panel field wiring

30 VAV-PRC003-EN


Figure 34. Typical relay board wiring

Figure 33. Relay board wiring

1

3

2

9

12

15

R

5

13

4

8

10

11

14

6

7

TB1

Relay Board TB2

cR

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Y1

Y2

W1

W2/

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UX

NO

NC

NO

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SE

D

24 VAC CLASS 2 COOL UNIT

24 VAC CLASS 2 HEAT UNIT

COOL 1

COOL 2

HEAT 1

HEAT 2

SUPPLY FAN

SPARE OUTSIDE AIRHEAT/COOL

OR ICS

2 HEAT/2COOL HEAT PUMP

REV VALVE

AUX HEAT

COMP 2

COMP 1

HVAC Unit24V Terminal Strip

R

G

Y1

Y2

W1

W2

Relay Board TB2

1

3

2

R

5

4

6

7

TB1

cR

hG

Y1

Y2

W1

W2/

0

VAV-PRC003-EN 31


Figure 35. UCM Comm Link Wiring

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TB

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Por

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+ VO

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1 10 11 12 13 14 1598765432

+ –

J3R GBK

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AC

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VG

ND

ZO

NE

BIP

GN

DG

ND

TB3–6

A/C

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SE

T

J1

J10

TB1–1

TB2–6

TB3–1

TB3–2

TB3–3

TB3–5

J11

J9

J7

J8

TB2–2

TB2–3

TB2–5

TB2–4

TB2–1

++

+–

––

1

PRESS

1

D.D

.C.\U

.C.M

.C

ON

TR

OL

BO

AR

D

TB4–1

TB1–2

Com

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Sen

sor/

Byp

ass

Con

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Ass

embl

y A

ddre

ss #

33

AD

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SS

WIT

CH

COMM 5COMM 4

Spl

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2

Spl

ice

To Z

one

Dam

pers

3 th

roug

h 24

J3

SG

RN

YE

L

AC

T24

VG

ND

ZO

NE

BIP

GN

DG

ND

TB3–6

A/C

O2

SE

T

J1

J10

TB1–1

TB2–6

TB3–1

TB3–2

TB3–3

TB3–5

J11

J9

J7

J8

TB2–2

TB2–3

TB2–5

TB2–4

TB2–1

++

+–

––

1

PRESS

1

D.D

.C.\U

.C.M

.C

ON

TR

OL

BO

AR

D

TB4–1

TB1–2

AD

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SG

RN

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L

AC

T24

VG

ND

ZO

NE

BIP

GN

DG

ND

TB3–6

A/C

O2

SE

T

J1

J10

TB1–1

TB2–6

TB3–1

TB3–2

TB3–3

TB3–5

J11

J9

J7

J8

TB2–2

TB2–3

TB2–5

TB2–4

TB2–1

++

+–

––

1

PRESS

1

D.D

.C.\U

.C.M

.C

ON

TR

OL

BO

AR

D

TB4–1

TB1–2

AD

DR

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and

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32 VAV-PRC003-EN


Figure 36. Communicating bypass controller wiring

CW

ACTUATOR

HOT

CLOSE

CCW OPEN

COM

SPARECONNECTOR

ACTUATOR

TB

1–1

STATICPRESSURE

PORT

W–HOT

BIP

BK–OPEN

2.2. 24VAC

24VGNDACT

R–CLOSE

TB

1–2

TB

4–1

1

TO NEC CLASS 224V TRANSFORMER

LOAD 8 VA(WITHOUT ACTUATOR){

HIGH

D.D.C.\U.C.M.CONTROL BOARD

PRESSURETRANSDUCER

ADDRESSSWITCH

COMMUNICATING SENSOR/BYPASSCONTROL BOX

AIR SUPPLY TEMP SENSOR

SHIELDEDTWISTED PAIR

COMMUNICATIONSWIRING

D.D.C.\U.C.M.CONTROL BOARD

MALE PLUG ENDLOCATED ON DDC\UCM

CONTROL BOARD

FEMALE PLUG ENDOF BYPASS SENSOR

ASSEMBLY CABLE

{

TB

2–3

TB

2–4

TB

2–5

J8

TB

2–6

J11

J10

J9 J7 J1J1

YEL GRN

TB

2–2

TB

2–1

TB

3–1 S

PR

ES

S

TB

2–6

TB

3–2

TB

3–6

TB

3–5

TB

3–3

GNDA/CO2SETGNDZONE

J3

1

VOUT

+++ –– –

–

R

BK

G

+

OU

T

OU

T

ININ

ACT

WH

RBK

VAV-PRC003-EN 33


Figure 37. UCM Wiring

24 VAC 60 HZNEC CLASS–2

CONTROL CIRCUIT

8.

W

GW

R

DAMPERACTUATOR

WIRING

D.D.C. \ U.CM.CONTROL BOARD

D.D.C. \ U.CM.CONTROL BOARD

ADDRESSSWITCH

SHIELDEDTWISTED PAIR

COMMUNICATIONSWIRING

}

}J1

1

PRES

S

TB2–

1

TB2–

2

TB2–

3

TB2–

4

TB2–

5

TB2–

6 S

TB3–

6

TB3–

5

TB3–

3

TB3–

2

TB3–

1

TB1–

1

TB1–

2

TB4–

1

J7 J8J9J10

A/CO2SETGNDZONE

J1

1

J3

24VGNDBIPACT

GRNYEL

GND

– –+–++

1

7.

9.

OUT

OUT

IN IN }6.

6.

OPTIONAL FIELD INSTALLEDOPTIONAL FIELD INSTALLEDAUX TEMP SENSORAUX TEMP SENSOR

OPTIONAL FIELD INSTALLEDOPTIONAL FIELD INSTALLEDCO2 SENSORCO2 SENSOR

OPTIONAL FIELD INSTALLEDOPTIONAL FIELD INSTALLEDONON–OFF WATER VALVEOFF WATER VALVE

OPTIONAL FIELD INSTALLEDOPTIONAL FIELD INSTALLEDPROPORTIONAL WATER VALVEPROPORTIONAL WATER VALVE

5.

OPTIONAL FIELD INSTALLEDOPTIONAL FIELD INSTALLEDOCCUPANCY SENSOROCCUPANCY SENSOR

R (HOT)

O (COMMON)GR (NC CONTACT)BK (RETURN)

Y

(TB4–1) BIP(TB1–1) 24VAC

NOT CONNECTED

(TB1–1) 24VAC(TB1–2) GND

ON–OFFWATER VALVE

24VAC12 VA MAX

PROP. WATERVALV

24VAC12 VA MAX

TO J8

TO J8

TO J9

TO J9

TO J10

OPTIONAL FIELD INSTALLEDOPTIONAL FIELD INSTALLEDELECTRIC HEATERELECTRIC HEATER

TO J11

TO J8

TO J9

TO J10

HOT

1ST STG.2ND STG.

3RD STG.HEATER STAGECONTACTOR(S)24 VAC, 12 VA

MAX/COIL

R (OPEN)

BK (CLOSE)

W (HOT)

CO2SENSOR

24V

V

+0

OUT

GND

WAL

LM

OUNT

ED

DUCT

MOU

NTED

(TB3–5) A/CO2

(TB3–6) GND

(TB1–1) 24V

TB3–6TB3–5

TB1–1

22 1 3 211

TB3TB2TB1

TB2–6

TB2–5TB3–3

TB3–2TB3–1

TB1–2

DIGITALZONE SENSOR

OPTIONAL FIELDINSTALLED DIGITAL ZONE SENSOR

OPTIONAL FIELDINSTALLED DIGITAL ZONE SENSOR

ZONE SENSORW/ COMM. JACKREMOTE MTD.

TB2–6TB2–5

TB3–1

TB3–2TB3–3

4.

45 23

3.

1

1.

2. ¼" quick connect required for all field connection.

3. Zone sensor terminals 4 and 5 require shielded twisted pair wiring for communications jack equipped zone sensor options

4. No additional wiring required for night setback override (on/cancel).

5. The optional binary input connects between TB4–1 (BIP) and 24VAC (HOT) from transformer. The binary input can be reconfigured as an occupancy input via the communications interface.

6. As shipped, the aux input is configured as an AUX input. The AUX input can be reconfigured as a CO2 sensor input viathe communications interface.

7. S terminal not to be used with this applications.

8. If unit mounted transformer is not provided, polarity from unit to unit must be maintained to prevent permanent damageto control board. If one leg of 24VAC supply is grounded, then ground leg must be connected to TB1–2.

9. Shields of communication wiring should be tied together and insulated.

NOTES:

Factory WiringField WiringOptional or Alternate Wiring

34 VAV-PRC003-EN


Digital SensorTerminal Connection Chart

Sensor UCMField Wire

Color Code

TB1–1 TB1–1

TB2–1

TB1–2

TB2–6

TB2–2

TB2–5

TB3–1

TB3–3

TB3–1

TB2–3

TB3–2

TB1–2

TB3–2

Digital SensorBoard

TB1–1

TB3–1

TB2–1

GND

24V–2–2

–2

–2

–2Temperature

Signal Common

Setpoint

Communications+ (High)

Communications– (Low)

1

OptionalField Mounted

Aux. Temp. Sensor

J11

ACT

ADDRESSSWITCH D.D.C.\U.C.M.

CONTROL BOARD

J8J7J9J10

TB

1–1

TB

1–2

TB

4–1

PR

ES

S

TB

2–1

TB

2–2

TB

2–3

TB

2–4

TB

2–5

TB

2–6

TB

3–6

TB

3–5

TB

3–3

TB

3–2

TB

3–1

1

J3

S

GNDA/CO2SETGNDZONE

GRNYEL

J1

GNDBIP

–+–+ –+

1

24V

Figure 38. DDC zone sensor with LCD

Figure 39. DDC zone sensor wiring

J11

ACT

ADDRESSSWITCH D.D.C.\U.C.M.

CONTROL BOARD

J8J7J9J10

TB

1–1

TB

1–2

TB

4–1

PR

ES

S

TB

2–1

TB

2–2

TB

2–3

TB

2–4

TB

2–5

TB

2–6

TB

3–6

TB

3–5

TB

3–3

TB

3–2

TB

3–1

1

J3

S

GNDA/CO2SETGNDZONE

GRNYEL

J1

GNDBIP

–+–+ –+

1

24V

OptionalField Mounted

Aux. Temp. Sensor

1

2

Mechanical SensorTerminal Connection Chart

Sensor UCMField Wire

Color Code

TB1–1 TB3–1

TB1–4

TB3–2

TB1–5

TB2–5

TB2–6

TB1–2

1

2

Figure Notes:

Shield must be spliced with othercommunication link shields

Shield must be cut back and tapedat sensor.

Temperature

Signal Common

Setpoint

Communications (Optional)+ (High)

Communications (Optional)– (Low)

TB1–1

–4

–3

–2

–5CommunicationsJack

AdjustableSetpoint Option

Night SetbackOverride Option

Comm 1

Cooler

Warmer

Sensor

ON

PB1

VAV-PRC003-EN 35

Table 4. Zone sensor options

Specifications

Figure 40. VariTrac DDC zonesensors

Number ofZone Sensor Options Required Wires1

Sensor only (no communications jack available) 2Sensor with adjustable setpoint 3Sensor with night setback override and cancel buttons 2Sensor with adjustable setpoint and night setbackoverride and cancel buttons 3Sensor with digital display and adjustable setpoint andnight setback override and cancel buttons 52

Notes:1Most sensors have a communication jack available as an option. If these jacks are used, they must bewired to the UCM using an approved two-conductor, shielded cable. The communication jacks do notneed to be wired for the system to operate properly.

2Three wires are required for sensor connections. Two wires are required for 24-Vac power connection.

36 VAV-PRC003-EN

Table 5. VariTrac control panel specifications

Specifications

Table 6. UCM damper specifications

Figure 41. VariTrac central controlpanel components

Figure 42. VariTrac UCM rounddamper

Power Requirements 20–30 Vac, 60 Hz, single-phase, 30 VA minimum. Class 2 transformerrequired.

Operating Environment 32°–122°F (0°–50°C), 10–90% relative humidity, non-condensingStorage Environment -40°F–122°F (-40°–85°C), 5–95% relative humidity, non-condensingControl Enclosure NEMA 1 resin enclosure, plenum ratedMounting Mount directly on wall surface or mount on recessed 4" x 4"

(101.6 mm x 101.6 mm) conduit box.Weight 2.5 lbs. (1.13 kg)Communication Link Wiring Communication link wiring must be Level 4 22-AWG twisted shielded

pair wire with stranded tinned copper conductors. Maximum total wirelength is 3,500 ft (1066.8 m). Wire must meet Trane specifications.

Binary Input Voltage (provided by VariTrac CCP): 10–14 VdcCurrent (provided by VariTrac CCP): 10–14 mANote: Only “dry” contacts may be attached to binary inputs.

UL Approval The VariTrac Central Control Panel is UL approved.Memory Backup Upon a power loss, all operator-edited data stored in the VariTrac Central

Control Panel is maintained permanently.

Power Requirements 20–30 Vac, 60Hz, single-phase 10 VA minimum (plus load of optional heatoutputs). Class 2 transformer required.

Operating Environment 32°–120°F (0°–49°C). 10–90% relative humidity, non-condensingStorage Environment -50°–200°F (-46°–93°C). 5–95% relative humidity, non-condensingControl Enclosure NEMA 1 metal enclosure, plenum ratedCommunication Link Wiring Communication link wiring must be Level 4 22-AWG twisted shielded

pair wire with stranded tinned copper conductors. Maximum total wire is3,500 ft (1066.8 m). Wire must meet Trane specifications.

VAV-PRC003-EN 37

Table 8. Zone occupancy sensor specifications

Table 7. Communicating bypass control assembly specifications

Specifications

Figure 43. Communicating bypasscontroller

Figure 44. Zone occupancy sensor

Ideal for zones with intermittentoccupancy like conference rooms).When occupied, the zone reverts tounoccupied setpoints to save energy.

Power Requirements 20–30 Vac, 60Hz, single-phase 15 VA minimum. Class 2 transformerrequired.

Operating Environment 32°–120°F (0°–49°C). 10–90% relative humidity, non-condensingStorage Environment -50°–200°F (-46°–93°C). 5–95% relative humidity, non-condensingControl Enclosure NEMA 1 metal enclosure, plenum ratedCommunication Link Wiring Communication link wiring must be Level 4 22-AWG twisted shielded

pair wire with stranded tinned copper conductors. Maximum total wire is3,500 ft (1066.8 m). Wire must meet Trane specifications.

Power Supply 24 Vac or 24 Vdc, ±10%Maximum VA Load 0.88 VA @ 24 Vac, 0.722 VA @ 24 VdcIsolated Relay Rating 1 A @ 24 Vac or 24 VdcOperating Temperature 32°–131°F (0°–55°C)Storage Temperature -22°–176°F (-30°–80°C)Humidity Range 0–95% non-condensingEffective Coverage Area 1200 sq. ft (365.8 m)Effective Coverage Radius 22 ft (6.7 m)Housing Material ABS plastic

38 VAV-PRC003-EN

Table 10. CO2 sensor specifications

Table 9. Digital zone sensor specifications

Specifications

Figure 45. DDC zone sensor withdigital display

Figure 46. CO2 duct sensor

Figure 47. CO2 wall sensor

Thermistor Resistance Rating 10kW at 77° (25°C)Accuracy at 77°F (25°C) 0.4°F (0.2°C)Setpoint Resistance Rating 500 Ohms at 70°F (21.2°F)Display Zone Temperature Range 40°–99°F (10° to 35°C)Display Setpoint Range 50°–90°F (10° to 32°C)Operating Temperature 0°–120°F (–18° to 49°C)Storage Temperature –20°–130°F (–29° to 54°C)Humidity Range 5–95% non-condensingPower Supply 24 VACMaximum VA Load 4 VAHousing Material Rigid vinyl

Duct Wall

Dimensions 3 1/8" × 3 1/8" × 7 3/4" 4 1/4" × 3 1/8" × 1 7/16"Operating Temperature 23°–113°F (–5°–45°C) 59°–95°F (15°–35°C)Accuracy at 77°F (25°C) < ± (30 ppm CO2 + 3% of reading) < ± (40 ppm CO2 + 3% of reading)Measuring Range 0-2000 parts per million (ppm)Recommended Calibration Interval 5 yearsResponse Time 1 minute (0–63%)Storage Temperature –4°–158°F (–20°–70°C)Humidity Range 0 to 85% relative humidity (RH)Output Signal (jumper selectable) 4-20 mA, 0-20 mA, 0-10 VDCResolution of Analog Outputs 10 ppm CO2

Power Supply Nominal 24 VACPower Consumption <5 VAHousing Material ABS plastic

VAV-PRC003-EN 39

Acoustics are tricky to define forspecific jobsites. To provide anacoustical overview of a typical officesystem with mineral glass fiberdropped ceiling, ARI standard 885-98has generated the transfer functions inTable 11.

Sound power data was collected inaccordance with ARI Standard 880.Applying the transfer function forsound reduction due to officefurnishings, materials, etc. generatedthe NC data which follows. This is areference document only provided toaddress general acoustical issues.What you will find is that the sound inthe occupied spaces generated by theVariTrac dampers is minimal whencompared to the main HVAC unitsound generation.

Acoustics

Some general ideas to minimizeacoustical issues:

• pay close attention to location of theHVAC unit. This will typically set theoverall acoustical quality of your job.

• locate VariTrac dampers outside theoccupied space.

• internally lined ductwork can be used toreduce the discharge sound generatedby the HVAC unit.

• install flex duct with minimal sagging,and turns.

• locate balancing dampers as far fromthe diffuser as possible to limit airbornenoise.

Note: VariTrac dampers do not carry theARI seal.

Table 11. Acoustical transfer functions

Table 12. Radiated sound data

NC Based on 885-98 Mineral TileSize Radiated NC Size

6 in. 33 4708 in. 26 84010 in. 25 131012 in. 26 188514 in. 29 214016 in. 21 2515

NC based on maximum rated airflowconditions.

ARI 885-98 Discharge TransferFunction Assumptions

Octave Band2 3 4 5 6 7

Small Box -24 -28 -39 -53 -59 -40(<300 cfm)Medium Box -27 -29 240 -51 -53 -39(<300–700 cfm)Large Box -29 -30 -41 -51 -52 -39(>700 cfm)

Note: Add to terminal unit sound power todetermine discharge sound pressure in the space.

ARI 885-98 Radiated TransferFunction Assumptions

Octave Band2 3 4 5 6 7

Type 2 Mineral -18 -19 -20 -26 -31 -36Fiber Insulation

40 VAV-PRC003-EN

Acoustics

Table 13. Discharge sound data

Note: NC data based on ARI 885-98 Acoustical transfer functions in Table 11.

DischargeSize CFM ISP NC

6 in. 375 0.25 —6 in. 375 0.5 —6 in. 375 1 186 in. 375 2 226 in. 300 0.256 in. 300 0.5 —6 in. 300 1 —6 in. 300 2 196 in. 225 0.25 —6 in. 225 0.5 —6 in. 225 1 —6 in. 225 2 166 in. 150 0.25 —6 in. 150 0.5 —6 in. 150 1 —6 in. 150 2 166 in. 75 0.25 —6 in. 75 0.5 —6 in. 75 1 —6 in. 75 2 166 in. 38 0.25 —6 in. 38 0.5 —6 in. 38 1 —6 in. 38 2 158 in. 656 0.25 —8 in. 656 0.5 168 in. 656 1 248 in. 656 2 308 in. 525 0.25 —8 in. 525 0.5 —8 in. 525 1 208 in. 525 2 258 in. 394 0.25 —8 in. 394 0.5 —8 in. 394 1 168 in. 394 2 228 in. 263 0.25 —8 in. 263 0.5 —8 in. 263 1 —8 in. 263 2 238 in. 131 0.25 —8 in. 131 0.5 —8 in. 131 1 158 in. 131 2 248 in. 66 0.25 —8 in. 66 0.5 —8 in. 66 1 —8 in. 66 2 20


10 in. 1031 0.25 —10 in. 1031 0.5 1510 in. 1031 1 2110 in. 1031 2 2710 in. 825 0.25 —10 in. 825 0.5 —10 in. 825 1 1710 in. 825 2 2210 in. 619 0.25 —10 in. 619 0.5 —10 in. 619 1 —10 in. 619 2 2010 in. 413 0.25 —10 in. 413 0.5 —10 in. 413 1 —10 in. 413 2 1910 in. 206 0.25 —10 in. 206 0.5 —10 in. 206 1 —10 in. 206 2 1910 in. 103 0.25 —10 in. 103 0.5 —10 in. 103 1 —10 in. 103 2 1812 in. 1500 0.25 —12 in. 1500 0.5 1512 in. 1500 1 2112 in. 1500 2 2912 in. 1200 0.25 —12 in. 1200 0.5 —12 in. 1200 1 1712 in. 1200 2 2512 in. 900 0.25 —12 in. 900 0.5 —12 in. 900 1 —12 in. 900 2 2212 in. 600 0.25 —12 in. 600 0.5 —12 in. 600 1 —12 in. 600 2 2112 in. 300 0.25 —12 in. 300 0.5 —12 in. 300 1 —12 in. 300 2 2012 in. 150 0.25 —12 in. 150 0.5 —12 in. 150 1 —12 in. 150 2 19


14 in. 2000 0.25 —14 in. 2000 0.5 1714 in. 2000 1 2414 in. 2000 2 3014 in. 1600 0.25 —14 in. 1600 0.5 —14 in. 1600 1 1914 in. 1600 2 2614 in. 1200 0.25 —14 in. 1200 0.5 —14 in. 1200 1 1514 in. 1200 2 2314 in. 800 0.25 —14 in. 800 0.5 —14 in. 800 1 —14 in. 800 2 23

14 in. 400 0.25 —14 in. 400 0.5 —14 in. 400 1 —14 in. 400 2 2314 in. 200 0.25 —14 in. 200 0.5 —14 in. 200 1 —14 in. 200 2 2016 in. 2625 0.25 —16 in. 2625 0.5 1716 in. 2625 1 2516 in. 2625 2 32

16 in. 2100 0.25 —16 in. 2100 0.5 —16 in. 2100 1 2316 in. 2100 2 2916 in. 1575 0.25 —16 in. 1575 0.5 —16 in. 1575 1 2216 in. 1575 2 2716 in. 1050 0.25 —16 in. 1050 0.5 —16 in. 1050 1 —16 in. 1050 2 2216 in. 525 0.25 —16 in. 525 0.5 —16 in. 525 1 —16 in. 525 2 2316 in. 263 0.25 —16 in. 263 0.5 —16 in. 263 1 —16 in. 263 2 23

VAV-PRC003-EN 41

Dimensions and Weights

Figure 48. Central control panel dimensions

Note:1. Central control panel weight is 2.5 lbs.

Front view Side view

8.75 in.(22.38 cm)

2.75 in.(6.99 cm)

10.25 in.(26.04 cm)

Top view

Bottom view

42 VAV-PRC003-EN

Figure 49. Communicating bypass control dimensions


Mounting holesSee back view for dimensions

4 1/4"

1 15/16"

3 5/16"Side View

6 3/4"

5"

3 3/8"

3 7/8"4 5/16"

1.00" 1.00"

0.300"

Back View

Notes:

7/8" knockout1/2" conduitCustomer entry

Weight 3 1/4 lbsOperating Temp 32˚ to 140˚Humidity 5 to 95% (non-condensing)Mounting Method Metal screws

Duct StaticPressure Sensor

Duct TempSensor

VAV-PRC003-EN 43

Figure 50. Round zone and bypass damper dimensions


Airflow

Controls Area8.875"

2.125"

4.375"

0.50"

6.625"

C

Airflow

A

B DIA

3.625"

2.00"

Center of Bead Duct Temp Sensor (Optional)N/A on Bypass Control

DamperSize A WeightNominal

CFMCB

6"

16"

14"

12"

10"

8"

6.375"

16.375"

14.375"

12.375"

10.375"

8.375"

300

20.00"

20.00"

16.00"

16.00"

12.00"

12.00"

21.125"

19.125"

17.125"

15.125"

13.125"

11.125"

2000

1600

1100

800

500

12 lbs

11 lbs

9 lbs

8 lbs

7 lbs

6 lbs

44 VAV-PRC003-EN

Figure 51. Rectangular zone damper dimensions


H

6.00" Ref.

Slip & DriveConnection

Seam

16.00" Ref.

Dimensions

W H

12.00"

14.00"

16.00"

16.00"

20.00"

18.00"

8.00"

8.00"

8.00"

10.00"

10.00"

14.00"

Damper Frame DataFrame

Blades

Blade PinGear

16-gage galvanized steel16-gage galvanized steelAll blades are 3.19" nominal widthand 8" maximumABS plastic3/8" rolled steel, zinc plated

W

VAV-PRC003-EN 45


Figure 52 Rectangular bypass damper dimensions

Factory InstalledCable Provided

Actuator

Air Flow Y

5"

Damper Frame DataFrame

LinkageBlade Pin

Blade PinExtension

Bearings

Blade Seals

Side SealsCableWeight

Blades

13 gage galvanized steel

16 gage galvanized steel; blades are6" nominal width and 8" maximum

1/8" rolled steel, zinc plated3/8" square steel, zinc plated

7/16" diameter, 7" longIncluded with all dampers

Self-lubricating acetol

None

None10"

Seam

Seam

16" Ref

X

5"

Hub

Actuator Dimensions

1.0"

1.2" 1¾"

3.5"1.3"

Dimensions

X Y

14" 12"

16"

20"

16"

20"

30" 20"

Wiring Actuator CCP

Red

White

Black

CCW

COM

CW

Close

Com

Open

46 VAV-PRC003-EN

R

UNOCC SETPOINT OVERRIDE

˚C˚F

MAX

CANCEL

ON

4.5

2.8

1.1

1.0

4.25"

1.44"3.125"

Figure 54. CO2 Sensor dimensions


Figure 53. Occupancy Sensor

Figure 55. Digital Zone Sensor

3.60"

1.90"

2.50"

Front View

SideView

VAV-PRC003-EN 47

Glossary

ABS gears – Gears formed of alightweight plastic known for itstoughness, impact strength, anddimensional stability.

Back draft damper – A one-wayairflow damper in a parallel fanpowered unit prevents primary flowfrom exiting the plenem inlet.

Binary input – A two-position signalindicating on/off status.

Binary output – A control output thatis either on or off.

Built-in time clock – The occupancytimer included in the CCP operatordisplay.

Bypass damper – The motorizeddamper ducted between the systemsupply and return ducts used tocontrol static pressure in changeoverbypass VAV systems.

Central control panel (CCP) – Thesystem level control device in a Tranechangeover bypass or delivered VAVsystem that gathers data from zonecontrollers and operates the HVAC unitto maintain the correct air flow andtemperature.

Changeover-bypass VAV – A controlthat provides variable air volumefunctionality to a constant volume airhandling system.

CO2 sensor – An analog sensor thatdetects and measures carbon dioxidesensor to determine occupancy level.

Commissioning – The process ofstarting up and verifying correctoperation of a building system.

Conditioned air – Air that is heated,cooled, humidified, or dehumidified tomaintain comfort in an interior space.

Constant volume – An airdistribution system that varies thetemperature of a fixed volume of air tomaintain space comfort.

Delivered VAV – A self configuringsystem providing true pressureindependent VAV control to smallerbuilding applications. Delivered VAVrequires a CCP with operator display, a

Commercial Voyager VAV rooftop unitand VariTrane VAV boxes.

Demand control ventilation – Amethod of maintaining indoor airquality through intelligent ventilationbased on occupancy. The quantity ofventilation is controlled based onindoor CO2 levels, which correlate tooccupancy levels. Demand controlledventilation saves money by reducingventilation during periods of lowoccupancy.

Direct-expansion (DX) – When therefrigerant in the system is eithercondensed or evaporated directly bythe medium being heated or cooled.

Discharge air (DA) – Air dischargedfrom the air handler into the ducts.

Discharge air control – An airhandling system that provides fixedtemperature air (either fixed or variablevolume). Other control devices vary theactual volume of air delivered to thespace to maintain occupant comfort.

Economizer – A damper arrangementand automatic control system thatallows a heating, ventilation and airconditioning (HVAC) system to supplyup to 100 percent outside air to satisfycooling demands, even if additionalmechanical cooling is required

Exception schedule – A one timeonly time of day schedule in a systemthat is removed automatically after use

Free cooling – Outdoor air introducedto a system under correct conditions toprovided cooling to a space. Also seealso “Economizer”

HVAC Unit – An air moving devicethat conditions air. An HVAC unit mayprovide cooling, or heating and cooling.Typical HVAC units include packagedrooftop units, split systems, and watersource heat pumps.

LCD – Liquid crystal display

NDIR – Non-dispersive infraredtechnology

Negative pressure – The conditionthat exists when more air is exhaustedfrom a space than is supplied.

Non-volatile memory – Systemmemory that retains programming withno battery or capacitor back uprequired

Normally closed (NC) – Electricalcontacts that are closed (current flows)in the de-energized condition

Normally open (NO) – Electricalcontacts that are open (no currentflows) in the de-energized condition

Occupancy sensor – A binary sensorthat transmits a signal upon detectionof movement in the coverage area

Outdoor air (OA) – This is fresh airdrawn in to provide space ventilation.Also see ‘Ventilation air”

Outdoor air damper – The damperthat draws fresh air into the air handlingsystem for ventilation. Also referred toas the ventilation or fresh air damper

Override – A manual or automaticaction taken to bypass normaloperation

Packaged unitary system – An airhandling system with all the majorcomponents contained in a singlecabinet or installed in a single location

PIR – Passive infrared sensingtechnology (used in occupancy andmotion detection sensors)

Polling – The method a VariTrac CCPuses to determine the need for heatingor cooling from the air handling systemby examining the zone requirements

Positive pressure – The condition thatexists when more air is supplied to aspace than is exhausted.

Pressure-dependent VAV control –A VAV unit with airflow quantitydependent upon static pressure. Thereis no zone flow sensor in pressuredependent VAV boxes.

Pressure-independent VAVcontrol – A VAV unit with airflowquantity independent of duct staticpressure. Actual airflow to the space ismeasured and controlled by an airflowsensor in the pressure independentVAV box.

48 VAV-PRC003-EN

Glossary

Priority shutdown – An immediateshutdown of the fan and heating orcooling stages in a VariTrac changeoverbypass or Delivered VAV systemcaused by either the loss of criticalsystem information or an externalpriority shutdown input

Pulse-width modulating reheat –Reheat that operates duct mountedelectric coils on a 0-100% duty cycle inresponse to increased space heatingdemand.

Reheat device – A source of heatlocated downstream from a controldevice such as a VAV box to add heat toair entering a space to provideoccupant comfort

ReliaTel (RTRM) – The latestgeneration Trane factory mountedunitary controller.

Return air (RA) – Air returned to theair handler from the conditioned space,to be reconditioned.

Setpoint – The desired roomtemperature to be achieved andmaintained by an HVAC system.

Setpoint limit – An electronic ormanual constraint imposed on asetpoint to prevent misadjustment

SPDT – A relay with of one set ofnormally-open, normally-closedcontacts

Staged electric reheat – Reheat thatoperates one or more duct mountedelectric coils in a series in response toincreased space heating demand.

Staged (or perimeter) hot waterreheat – Reheat that operates duct-mounted hot water or space-mountedelectric or hot water reheat coils inresponse to increased space heatingdemand

Static pressure – The differencebetween the air pressure on the insideof the duct and outside of the duct.Static pressure is an indicator of howmuch pressure the fans are creatingand how effective they will be atdistributing the supply air through theducts.

Supply air (SA) – air which blows outof the air handler into the ducts. Seealso “Discharge air (DA)”

Terminal unit – HVAC equipment thatprovides comfort directly to a space.

Thermal requirements – The heatingor cooling load requirements for aspecific area or space in a building.Care must be taken to not control areaswith different thermal requirementsfrom one air handling system

Touch-screen operator display –The LCD panel mounted onto a VariTracCCP to allow direct user interface andtime of day programming for thesystem

Unit control module UCM – A Tranemicroelectronic circuit board thatcontrols individual HVAC equipment.May link to an Integrated ComfortSystem

Unitary – one or more factory-madeassemblies which normally include anevaporator or cooling coil, an airmoving device, and a compressor andcondenser combination

Variable air volume (VAV) – an airhandling system that varies the volume(amount) of constant temperature air toa space to control comfort

VariTrac – The Trane changeoverbypass VAV system

VariTrane – The Trane pressureindependent VAV box

VAV box – The damper or air valve(plus associated controller) thatcontrols the zone air volume in a VAVsystem. Also see “Variable air volume”

Ventilation air – The outdoor airdrawn into the HVAC unit to providefresh air to the space. Also see“Outdoor air (OA)”

Voting – See “Polling”

Zone sensor – The device thatmeasures a variable (usuallytemperature) in a space and sends it toa controller. Commonly referred to as athermostat.

VAV-PRC003-EN 49

50 VAV-PRC003-EN

VAV-PRC003-EN 51

TraneA business of American Standard Companieswww.trane.com

For more information contact your local district officeor email us at [email protected]

Literature Order Number VAV-PRC003-EN

File Number PL-TD-VAV-000-PRC003-EN-0604

Supersedes VAV-DS-12

Stocking Location La Crosse

Trane has a policy of continuous product and product data improvement and reserves the right to changedesign and specifications without notice.

varitrac changeover bypass vav (tracker system … catalog 060804...varitrac ™ changeover bypass...

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