Installation/ Owner Programming VariTrane Analog Electronic

Installation/OwnerProgramming

VariTrane™ AnalogElectronic Controls

VAV-SVX03A-ENNovember 2001

For use with:

Single-Duct Cooling & Reheat UnitsParallel & Series Fan-Powered UnitsLow-Height Parallel & Series Fan-Powered Units

VAV-SVX03A-EN 3

Contents

General InformationLiterature Contents ............................................................................................... 4Receiving and Handling ......................................................................................... 4

Unit InformationSingle-Duct Units ............................................................................................... 4-5Fan-powered Units ............................................................................................ 4-5

Analog ControlsGeneralElectonic Controls InstallationMinimum and Maximum Potentiometers AdjustmentsZone Sensor WiringLocation and Mounting

Sequence of OperationSingle-Duct Units .................................................................................................. 9Series Fan-powered ............................................................................................. 9Parallel Fan-powered ............................................................................................ 9

Control OptionsConstant-Volume ................................................................................................ 10Auto Dual Minimum ............................................................................................ 10

CalibrationTransducer Operation ..........................................................................................11Null Voltage ..........................................................................................................11Procedure for Maximum and Minimum Calibration ..............................................11Set Maximum Flow ..............................................................................................11Set Minimum Flow .............................................................................................. 12

No Dual Minimum .......................................................................................... 12Auto Dual Minimum ....................................................................................... 12

BalancingBalancing Procedure ........................................................................................... 13Adjustments (Set Maximum and Minimum Flows) .............................................. 13

Installation and WiringZone SensorZone Sensor Operation ....................................................................................... 15

TroubleshootingTools and Equipment ........................................................................................... 16System Check ..................................................................................................... 16Air Damper and Motor Check .............................................................................. 17Control Check ...................................................................................................... 17Zone Sensor Check ............................................................................................. 17Heater Contactor Check ...................................................................................... 17Fan Motor Check ................................................................................................. 17Circuit Board Check ............................................................................................. 17Transducer Check ................................................................................................ 18Triac Output Check .............................................................................................. 18Auto Dual Minimum Check .................................................................................. 18Electronic Zone Sensor Check ............................................................................. 19

4 VAV-SVX03A-EN

Literature ContentsThis manual describes the operation,calibration and set-up of VariTrane VAVSingle-Duct and Fan-powered unitswith Analog Electronic Controls.

Receiving and HandlingVariTrane units are shipped completelyassembled with the exception of filtersand accessories. Upon receiving,please inspect each unit and thecomponents for shipping damage.

GeneralInformation

After receiving the units, completethe following:

� Locate the nameplate and modelnumber and check that the correct unitshave been received.

� Inspect the control units and air dampercasing for dents or punctures.

� Verify that all options have beenincluded, such as filters, controls,heating coils, water valves, etc. Alsocheck that unit voltages agree with thebuilding parameters.

�Manually rotate the fan (if applicable) toassure that there are no obstructionswithin the housing.

� Claims for in-transit damage must befiled immediately with the deliverycarrier.

� For re-heat units, check the coil fins andmake sure the coils are not damaged.

� Locate and verify that the correct zonesensors are with the order. These willbe marked with an orange “AccessoriesEnclosed” label. Store in a secure placeuntil needed. Accessories lost at ajobsite are NOT covered by Trane’swarranty.

� If a discrepancy occurs between whatwas ordered and what is received,contact your local Trane representativeimmediately.

� Read the appropriate section in thismanual for installation procedures priorto actual starting of installation.

NOTICE:Warnings and Cautions appear at appropriate sections throughout this manual.Read these carefully.

— Indicates a potentially hazardous situation which, if notavoided, could result in death or serious injury.

— Indicates a potentially hazardous situation which, if notavoided, may result in minor or moderate injury.

— May also be used to alert reader to a situation that could resultin equipment or property only damage.

WARNINGWARNING

CAUTIONCAUTION

CAUTION:CAUTION:

VAV-SVX03A-EN 5

UnitInformation

Unit Type DescriptionAnalog Electronic VariTrane units use anelectronically-controlled air damper forprimary air modulation. The unit typesavailable are single-duct units (VCCF,VCWF, VCEF), series fan-powered units(VSCF, VSWF, VSEF), parallel fan-powered units, (VPCF, VPWF, VPEF) andlow-height fan-powered units (LSCF,LSWF, LSEF, LPCF, LPWF, LPEF).

Single-Duct Units

The basic unit consists of an air dampermounted in a sheet metal casing, whichis used to control the volume of airintroduced to the occupied zone. Theunit is designed to modulate eithercooling or heating air. The basic cooling-only unit can be equipped with reheatcoils located at the discharge of the unit.Standard choices include an electric coilwith up to three stages of heat or a hot-water coil.

Figure 1 – Typical Single-Duct Units

VCCF

VCWF

VCEF

Fan-Powered Units

VariTrane fan-powered units can beeither parallel or series, with or withoutre-heat. See Figure 2.

Note: Low-Height is similar to the seriesand parallel fan-powered units. Allseries and parallel references from thispoint on will also include Low-Heightunless noted.

The fan on a series unit runs continu-ously whenever the main air-handlerunit is in operation. There are variousoptions for starting the fan. The fan canbe started three ways: 1) remotely,2) by a duct-pressure switch, or 3) by acombination of both. The particular fancontrol method will vary from unit tounit, depending upon job needs.

Typically, the re-heat is off while the airdamper modulates primary air andresponds to zone temperature. If zonetemperature decreases to the pointwhere a decrease in primary air will notmaintain the desired temperature, there-heat will be activated to increase thetemperature of the discharge air.

On a parallel unit, the VariTrane airdamper delivers primary cooling air tothe unit outlet. When the spacetemperature decreases beyond airdamper control, the fan is turned on asthe first stage of heat. The fan delivers

Table 1 – Maximum Fan Motor Amperage (FLA)Fan HP 115 277 347 208Size VAC VAC VAC VAC

Series/Parallel 01 1/8 1.6 0.7 0.7 —Series/Parallel 02 1/8 1.6 0.7 0.7 —Series/Parallel 03 1/3 5.4 1.8 1.5 —Series/Parallel 04 1/3 5.4 1.8 1.5 —Series/Parallel 05 1/2 7.6 2.6 2.1 —Series/Parallel 06 1/2 — 3.8 3.8 6.3Series/Parallel 07 1 — 4.7 3.6 6.9

Low Height 08 1/8 4.7 1.76 1.52 —Low Height 09 2 x 1/8 2 x 2.1 2 x 0.79 2 x 0.62 —Low Height 10 2 x 1/8 2 x 4.7 2 x 1.76 2 x 1.52 —

plenum air from above the occupiedspace to the unit outlet, which is mixedwith primary air and delivered to theoccupied space.

Note: Either the fan, the air damper orboth can deliver airflow into theoccupied space. In order to preventprimary airflow from exiting throughthe fan when the fan is not running on aparallel unit, a back-draft damper isprovided. When the fan is not running,the efficiency of this system is thesame as a standard single duct VAVunit.

Typically, the control systems appliedto parallel units cause the air damperto close to zero or a minimum flowbefore the fan is activated. After thefan is activated, the heat will beactivated upon further reduction inzone temperature. Therefore, littleprimary air is mixed with theheated air.Fan-powered units are available withrectangular discharge connection only.Either straight flange or slip and driveis available with electric heat. Theelectric heater is mounted on thedischarge of the unit. Hot water coilsare connected to the plenum inlet onparallel units, and to the discharge ofseries units.

6 VAV-SVX03A-EN

Figure 2 – Typical Fan-Powered Units

UnitInformation

VSCF VSWF

VSEF

VPCF VPWF

VPEF

VAV-SVX03A-EN 7

GeneralElectronic control systems offerpressure-independent operation for useon all single-duct and fan-powered VAVunits (see Figure 3).

The electric air damper used with thiscontrol system has a stroke time (fromopen to close) of 90 seconds.

The pressure-independent system willcontrol room temperature by adjustingairflow into the space as a function ofzone temperature.

Figure 3 –Electronic Interface CircuitBoards

Electrical Data

INPUT:24 VAC, 50 VA maximumOUTPUT:1st Stage – 24 VAC, 10 VA magneticcontactors/12 VA mercury contactors2nd Stage – 24 VAC, 10 VA magneticcontactors/12 VA mercury contactors3rd Stage – 24 VAC, 10 VA magneticcontactors/12 VA mercury contactors

Cfm Requirements

Maximum Minimum Minimum HeatingControl Unit Cfm Flow Cfm Flow Cfm Flow Setting

Type Size Setting Setting (VCEF Only)4 38-225 0,38-225 45-2255 63-350 0,63-350 70-3506 73-500 0,73-500 100-500

Analog 8 134-900 0,134-900 180-900Electronic 10 215-1400 0,215-1400 280-1400

12 300-2000 0,300-2000 400-200014 408-2890 0,408-2890 578-289016 536-3790 0,536-3790 758-3790

24x16 1096-8000 0,1096-8000 1600-8000Notes:1. Minimum flow and maximum flow settings must have at least a 0.05 Delta P flow sensor signal difference.2. Flow rings are provided with all unit sizes.3. A minimum setting of zero is permissible, except for VCEF units.

AnalogControls

Electronic Controls InstallationCheck the wiring on the unit with the wiring diagram and wiring information label.Insure that all jumpers are to the proper location and that the actual unit wiringmatches the wiring diagram and wiring label information. See Figure 4.Units with electronic control options must use Trane zone sensors to be compatiblewith the unit circuitry. The analog zone sensor electronics are designedspecifically to operate with the Trane electronic controls; other zonesensors will not work properly with this unit. The Trane analog zone sensormust be used in conjunction with these electronic controls. Typically, fieldcontrols wiring include the following:

1. 24 VAC-powered connection to terminals TB1-1 and TB1-2. These are stab terminalsmarked one and two on the five-pole terminal strip located in the corner of thecircuit card.

2. Zone sensor connections are to TB1-3,4,5.3. Heater contact wiring is normally installed in the factory. Should field installation be

required, each wiring diagram shows the field alternate wiring requirements.

Hazardous Voltage!Disconnect all electric power, including remote disconnects before servicing. Followproper lockout/tagout procedures to ensure the power cannot be inadvertentlyenergized. Failure to disconnect power before servicing could result in death orserious injury.

WARNINGWARNING

8 VAV-SVX03A-EN

Circuit Board Damage!Before handling the circuit board,discharge any static electricity you mayhave accumulated by touching the unitcasing. Static charges produce voltageshigh enough to damage the electroniccomponents.

Location and Installation

A zone sensor in each control zoneshould be located in the most criticalarea of the zone. Sensors should not beinstalled in direct sunlight or in thearea’s supply air stream. Subdivision ofthe zone may be necessary for ad-equate control and comfort.Avoid installing zone sensors in areassubject to the following:

�Drafts or “dead spots” behind doors or corners.

�Hot or cold air ducts.

� Radiant heat from the sun orappliances.

� Concealed pipes or chimneys.

�Unheated or uncooled surfaces behindthe sensor such as outside walls.

�Air flows from adjacent zones orother units.

Figure 4 – Typical Analog ElectronicControl Wiring Diagram

Zone Sensor Wiring

Each unit must be controlled by a wall-or unit-mounted zone sensor which isdesigned specifically for use with a

WARNINGWARNING

solid-state circuit board that is providedby the factory.Two types of zone sensors are availablewith analog electronic controls. One hasthe thumbwheel visible, while the otheris hidden by the cover.

NOTE: Analog electronic zone sensorsare not interchangeable with DDCzone sensors.

The three wires required for the wallzone sensor to the terminal block are tobe furnished and completed bythe installer.If local codes require enclosedconductors, the zone sensor wiresshould be installed in conduit. Do notroute zone sensor wires in conduit with24-volt or any high-powered conductingwires. This will cause electrical noiseand result in erratic operation ofthe controls.

AnalogControls

CAUTION:CAUTION:

Hazardous Voltage!Disconnect all electric power, includingremote disconnects before servicing.Follow proper lockout/tagout proce-dures to ensure the power cannot beinadvertently energized. Failure todisconnect power before servicing couldresult in death or serious injury. Prior toreplacing the zone sensor, followwarning instructions above.

Avoid Wiring Errors!It is important to connect power and zone sensor control voltage wiring to the properterminals since improper connection will cause failure of the circuit board. To helpprevent errors, the 24 VAC power to circuit board zone sensor connectionsare labeled.

Minimum and MaximumPotentiometers Adjustments

The minimum and maximum flow (orposition) setpoints may require fieldsetting to obtain desired cfm settings.Refer to the calibration section of thismanual for proper adjustmentprocedures.On single-duct boxes where transform-ers are optional, the transformer mustbe NEC Class 2, energy-limiting, 24 VAC.Refer to electrical data for proper sizing.

CAUTION:CAUTION:

VAV-SVX03A-EN 9

Sequence ofOperation

Single-Duct UnitsThe air damper is controlled betweenminimum and maximum flow setpointsproportionally. When the zone tempera-ture is approximately 0.5°F above thesetpoint, the air damper will begin tomodulate to a maximum position,providing more cool air to the zone untilthe zone temperature reaches the zonesetpoint. Once satisfied, the air damperwill start to modulate to the minimumposition. When the zone temperature is0.5°F below the setpoint, the damperbegins to modulate to a minimumposition. When the damper is at thecooling minimum and the zone tem-perature is still below setpoint (cold), upto three stages of heat may be ener-gized on a reheat unit. The first stage isactivated at approximately 2°F belowthe setpoint, the second stage isactivated approximately 3°F below thesetpoint, and the third stage is activatedapproximately 4°F below the setpoint.

Series Fan-Powered UntisThe series fan-powered unit is aconstant volume, variable temperaturedevice. The fan is energized wheneverthe zone is occupied. It delivers designcfm regardless of the load. The airdamper controls primary air propor-tionally between minimum andmaximum flow setpoints. When thezone temperature is approximately0.5°F above setpoint, the air damperwill begin to modulate to a maximumposition, providing more cool air andless plenum air to the zone until thezone temperature reaches the zonesetpoint. When zone temperature is0.5°F below the setpoint, the damperbegins to modulate to its minimumposition, supplying less cold air andmore warm plenum air. When the airdamper is at minimum and zonetemperature is still below setpoint(cold), up to two additional stages ofelectric heat may be energized. On anelectric reheat unit, the first stage isactivated approximately 2°F below thesetpoint. The second stage is activatedapproximately 3°F below the setpoint.On Hot Water Reheat just one stage ofheat, in addition to the fan, will beactivated approximately 2°F belowthe setpoint.

Parallel Fan-Powered UnitsThe parallel fan-powered unit is avariable-volume, constant-temperaturedevice at high cooling loads and aconstant-volume, variable-temperaturedevice at low cooling and heating loads.The air damper controls primary airproportionally between minimum andmaximum flow setpoints. When thezone temperature is approximately0.5°F above setpoint, the air damperwill begin to modulate to a maximumposition, providing more cool air andless plenum air to the zone until thezone temperature reaches the zonesetpoint. When the zone temperature isapproximately 0.5°F below the setpoint,the damper will begin to modulate to aminimum position, reducing the coolingcapacity. If the cooling capacity isreduced and zone temperature is stillbelow the heating setpoint, the fan willbe energized at approximately 2°Fbelow the cooling setpoint acting as thefirst stage of heat. The second stage ofheat (electric or hot water) is activatedat approximately 3°F below the coolingsetpoint and the third stage (electric) isactivated at approximately 4°F belowthe cooling setpoint.

10 VAV-SVX03A-EN

CONTROL OPTIONS

Constant Volume

With this feature, when jack J15 Pin A isconnected to Pin B, the electronics willcause the airflow to go to the maximumsetting and stay there. The influence ofthe thermostat is removed and maxi-mum flow is maintained at all times.The operation of the three reheat relaysis unaffected. Connecting Pins A and Bof jack J15 will only affect the signalwhich goes into the section of theelectronics which controls the airdamper movement. The maximumflow option is obtained by saturating thetemperature voltage signal so that themaximum limit is always sent on to thesection of the electronics, whichcompares the temperature voltage tothe flow voltage.

ControlOptions

Auto Dual Minimum

The auto dual minimum enables theunit to change the minimum automati-cally without an outside signal. Theminimum changes when the first stagerelay is activated. The electronics havebeen designed so that when jack J18Pins A and B are connected together,Minimum B (Potentiometer R69) willcontrol whenever the first relay stageactivated. Therefore, no matter whatminimum was in control before therelay stage was activated, after beingactivated, Minimum B (R69) will be thedetermining minimum flow. This optioncan be used effectively with fan-powered units where a minimum flowis set as the damper modulates andwhen the first stage comes on, the airdamper is then closed. In this manner,airflow to the space is never inter-rupted; however, the energy associatedwith maintaining a minimum airdamper airflow at all times is saved.

VAV-SVX03A-EN 11

The following tools are required toproperly adjust and calibrate theelectronic controls:� Digital voltmeter� 0-2 in. wg magnehelic gage (or inclined

manometer)� Tubing and fitting to connect gage to

flow ring tees (5/32" and 1/4" tubing).�Mechanical tools (screwdriver,

pliers, etc.)

Calibration

Null Voltage

The tolerance for the output voltage ofthe transducer with zero delta P signalfrom the flow ring is referred to as thenull voltage of the transducer. Thetransducer has three wires leadingfrom it to the control board. The wiresinclude a common (green wire), aninput (red wire), and an output (blackwire). The input (supply) voltage to thetransducer is 5 volts (+ .5). The accept-able voltage range of the output voltagewith zero flow (between black andgreen) can range from .100 volts to .400volts. To allow the controllers tocoordinate with the transducer voltage,internal calibration is necessary. Toaccomplish this, potentiometer R8 (zeroflow adjustment) is used. The flowvoltage signal should be 4.8 volts at testpoints #1 and #3 of the test pointterminals (next to R8) with zero delta Papplied. R8 is used to adjust the flowvoltage to 4.8 volts when zero delta P isapplied to the transducer. In thismanner, variability of the null point ofthe transducer is compensated for. Theimportance of this becomes evidentwhen minimum and maximum flowsare discussed.

PROCEDURE FORMAXIMUM AND MINIMUMCALIBRATION

Initialization

1. Monitor thermostat voltage and checkit by rotating the thermostat to fullheating and full cooling.

a. Connect a voltmeter to TB1-4 (+)and TB1-3 (-).

b. Rotate the thermostat fullyclockwise (full heating). Observethe voltage. It should be lessthan or equal to 5.4 volts DC.

c. Rotate the thermostat fullycounter-clockwise (full cooling);voltage should go up to 6.3 voltsDC or greater.

2. Set the min/max pots as follows:a. Rotate the max pot (R67) full

clockwise.b. Rotate min A (R68) full counter-

clockwisec. Rotate min B (R69) full counter-

clockwise

3. With both of the transducer ports opento ambient (0 delta P), read the outputvoltage at TP4. (Ground is either TP3,TB1-2, or TB1-3.) The value of the nulltransducer voltage output must bebetween 0.1 and 0.4 volts DC.Nominal is .250 volts DC.

4. Monitor TP1 (+) voltage (zero flowadjustment) and adjust R8 until 4.8volts DC + .010 volts is read at TP1.

Set Maximum Flow

Set the thermostat knob to the full-coolposition (fully counter-clockwise)thermostat voltage should go over 6.2VDC. Connect a pressure gage teed intothe high- and low-port flow ring of thetransducer and input the maximumdelta P. Refer to the flow vs. delta P charton the unit to obtain the proper delta Psignal desired. Adjust the max pot (R67)so that both the amber and green lightsare out, this indicates that equilibriumhas been established with the delta Pinput to the transducer.

Hazardous Voltage!Certain tests or calibration proceduresdescribed in this section may involveworking in close proximity to liveelectrical terminals. Only qualified andlicensed electrician or other properlytrained in electrical safety whenworking with live voltage shouldperform these procedures. Failure tofollow all electrical safety precautionswhen exposed to live terminal couldresult in death or serious injury.

WARNINGWARNING

Transducer Operation

This section discusses how airflowthrough the damper is transformed intoa voltage signal that can be used by thecontroller. The first transition from flowto voltage occurs at the Trane flow ring,where a delta P signal is generated as afunction of airflow through the unit. Thedelta P signal consists of a high-pressure signal from a total-pressuretap of the airflow ring and a low-pressure signal from the wake-pressure side of the flow ring.The transducer converts the pressuredifferential signal to an output voltage.The output of the transducer with noflow or zero delta P is .250 volts DC(+ .100). As flow increases, the delta Psignal increases; therefore, the outputvoltage of the transducer increases. Thegain of the transducer is 0.75 volts perinch of delta P.

12 VAV-SVX03A-EN

Calibration

Set Minimum Flow(s)

In this section, two procedures forsetting minimums will be discussed.No Dual Minimum

Adjust the thermostat knob to the full-heat position (full clockwise). Monitorthe delta P of the transducer with apressure gage (high port first and lowport). Refer to the calibration label onthe side of the unit, which relates CFMto delta P. Adjust R68 (minimum A) sothat both the red and green lights areout at the desired minimum flow delta P.If the minimum setting is to be zero flow,then leave the minimum pot (R68) fullcounter-clockwise so that the red lightremains on even when no delta P is

applied to the transducer. This willensure that the unit will always go toclosed when minimum is desired.Auto Dual Minimum

Place jumper on J18-A to B.The heating minimum is the minimumat which the damper is controlled towhen the fan on a fan-powered unit isactivated or when the first relay isactivated on a reheat unit.

Set the thermostat to the full-heatposition (full clockwise).

Adjust minimum potentiometer R69(Minimum B) to desired heatingminimum. If this setting is to be zero,leave the potentiometer fully counter-

clockwise so that the amber lightremains on with no delta P applied tothe transducer.

Remove the jumper from J18-A to J18-B. This puts the unit into the modewhere minimum A is now in control(cooling minimum).

Adjust R68 (Minimum A) when bothlights are off when the condition issatisfactory. If zero minimum is desired,leave pot R68 full counter-clockwise sothat the amber light is on continuouslywith zero delta P applied to thetransducer.

Replace J18 jumper.

VAV-SVX03A-EN 13

Balancing

The following tools are required toproperly adjust and calibrate theelectronic controls:� Digital voltmeter� 0 to 2 in. wg magnehelic gage� Tubing and fitting to connect gage to

flow ring tees.�Mechanical tools i.e. screwdriver,

pliers, etc.

Balancing Procedure1. Check the 24-volts AC supply voltage

to the circuit card, terminals TB1-1 toTB1-2. Acceptable range =21.6 to 26.4 volts AC.

2. Check the 12-volts DC power supply ofthe circuit card terminals TB1-5 (+) toTB1-3 (-). Acceptable range = 11.6 to12.4 volts DC.

3. Install the magnehelic gage toobserve delta P. When connecting tothe test tees, be careful not to createan excessively low pressure on thetransducer (when used). The followingprocedure should be followed:

a. Remove low-pressure cap fromtest tee.

b. Remove high-pressure capfrom test tee.

c. Connect gage to high-pressure side.

d. Connect gage to low-pressure side.

Adjustments (Set Maximum andMinimum Flows)

To set minimum and maximum flows tothe desired setting, refer to thecalibration section.

14 VAV-SVX03A-EN

The general layout of the analog circuitboard is shown in Figure 5. The layout ofthe circuit card shows the physicallocation of each item. Basic connectionsare as follows (see Figure 4, page 7):Figure 5 – Analog Electronic Controller

Installationand Wiring

1. Power is connected to TB1-1 and TB1-2. The power requirement is 24 voltsAC (+ 10%).

2. The zone sensor is connected toterminals TB1-3, 4, and 5. It is veryimportant not to connect power tothese terminals, since applying powerto the wrong terminal will destroy thecard.

3. The motor is connected via jack J1.4. The transducer (pressure-

independent) is connected at jack J3.5. Reheat stages (or fan on fan-powered

units) are connected at jacks J7 (24VAC), J9, J10, and J11.

6. Various options to cause changes tothe operation of unit are input atjack J15.

7. There are various adjustments on thecircuit card as discussed in detail in theCalibration section.

a. Maximum flow (or position)adjustment is R67. Turningclockwise increases themaximum flow.

b. There are two minimum flowadjustments labeled R68 andR69. Turning clockwiseincreases the minimum flow.

c. There is a zero-flow adjustmentused in initial calibration and set-up of the circuit card. This is R8.

8. There are four test points for theconvenience of servicing in the field.These test points include:

� TP4: Transducer output� TP1: Flow voltage (null calibration)� TP2: Temperature voltage� TP3: A common to make application of

clip leads easy.

VAV-SVX03A-EN 15

Zone Sensor Operation

This section explains how the zonesensor operates.Temperature is sensed using athermistor. The thermistor changesresistance with a change intemperature. The resistance of athermistor decreases as temperatureincreases. By using a voltage dividercircuit, the deviation from the roomsetpoint is determined.

1. 12-volts DC is supplied from TB1-5 onthe circuit card to terminal 1 on thezone sensor.

2. The zone sensor output signal isconnected from terminal 2 of the zonesensor to TB1-4 on the circuit card.

3. A common (ground) is supplied fromTB1-3 on the circuit card to terminal 3on the zone sensor. At setpoint, theinput to the circuit card is 6 voltsmeasured across terminals 2 and 3.Therefore, with 12 volts input betweenterminals 1 and 3, the voltage dropacross the thermistor will equal thevoltage drop between terminal 2 and

ZoneSensor

terminal 3. With the voltages being equal, the room temperature is consideredsatisfied and all output relays are de-energized. If the temperature in the zone goesup, the resistance of the thermistor will go down, causing a voltage increase, whichwill drive the air damper open. Conversely, if the room temperature goes down, thethermistor resistance goes up, causing a decrease in the output signal, which willdrive the air damper to minimum and energize the relay output. To determine thesetpoint, the setpoint potentiometer is moved, changing the resistance betweenterminals 2 and 3. By changing the setpoint potentiometer, the temperature at whichthe output signal equals 6 volts will be changed. Therefore, the setpoint potentiometermoves the setpoint up and down.

Degrees Fahrenheit Thermistor Nominal Resistance (Ohms)

65 407066 396067 385068 375069 366070 358071 350072 342073 333074 325075 317076 308077 300078 294079 287080 2810

16 VAV-SVX03A-EN

Symptom Probable Cause Recommended Action

Fan not running Faulty connection Check wiring diagrams and inspect all connections.

Incorrect voltage input Compare actual voltage with supply requirement.

Faulty fan motor Check motor and power to the fan motor. If power is present and fan does not run, replace the motor.Fan motor noise Incorrect voltage input Compare actual voltage input with supply requirement.

Loose fan wheel Adjust and tighten fan wheelLow cfm to unit Supply fan not providing Adjust supply fan speed. Check for proper rotation.

adequate cfm

Leaky duct work Repair leak.

Dirty Filters Replace air filtersImproper cfm to zone Debris is jamming valve Clear valve damper travel.

Damage to valve casing Repair casing or replace valve.

Improper wiring Check unit diagrams for correct connection.

Faulty circuit board Check and replace if necessary.

Faulty valve motor Check and replace if necessary.

cfm setting incorrect Recalibrate circuit board.Incorrect air temperature Incorrect wiring to reheat coil Check and replace if necessary. Compare wiring with diagram on unit.delivered to the zone

Faulty zone sensor Check for correct zone sensor resistance.

Faulty circuit board Recalibrate and replace if necessary.

Incorrect supply air temperature Check leaving air temperature from air handling unit.Coils do not engage on Faulty relay or Triac Check for voltage to heating coil and relay(s). Verify supply voltage matches coil voltage.Call for heat

Board not calibrated Calibrate.Room temperature differs Erratic zone sensor Check zone sensor voltage 12-volts DC between terminals 1 and 3. Check DC voltage at zone sensorfrom reading on zone terminal 2 and 3 (6 volts DC). Turn zone sensor to full heating voltage; it should be equal to or lessSensor (PI) than 5.4 volts DC. Turn zone sensor to full cooling voltage should be equal to or greater than 6.5 volts

DC. If DC voltage is not attainable, replace the zone sensor.

Zone sensor miscalibrated. Check calibration of zone sensor. See also calibration section.

Troubleshooting

Tools and EquipmentWhen repairing a VariTrane product (analog control), it is important to have the necessary tools and instruments.

1. 0-2" magnehelic gauge with fittings for two ¼" outside diameter (OD) tubing2. Voltmeter3. Four jumper leads4. Small screwdriver 1/8" blade

Hazardous Voltage!Certain tests or calibration procedures described in this section may involve working in close proximity to live electrical terminals.Only qualified and licensed electrician or other properly trained in electrical safety when working with live voltage shouldperform these procedures. Failure to follow all electrical safety precautions when exposed to live terminal could result in deathor serious injury.

WARNINGWARNING

VAV-SVX03A-EN 17

System CheckImproper room control may be causedby areas other than the VAV boxes.Before replacing the air damper orcontrol box, make sure that the entiresystem is operating properly and issupplying sufficient air to the damper.Complete the following checks.

1. Look for obvious leaks in the ductsystem. Assure that sufficient staticpressure is present at the airDamper.

2. Inspect the supply fan and VAV fanfilters. Clean or replace, if necessary.

3. Check zone sensor location, outsidewall, appliances, direct sunlight or thesupply air stream may be artificiallyheating or cooling the zone sensor.

4. Evaluate diffuser should have 15" offlat ceiling surface on either side of theslot to assure proper air distribution.Check that airflow from grills ordiffusers is properly balanced.

5. For accurate flow control, there mustbe at least two duct diameters ofstraight ductwork before the airdamper inlet. Electric coils require fourfeet of straight ductwork downstreamof the coil.

6. Compare voltage requirements, asspecified on the side of unit with actualvoltage supplied to the unit. Thecontrol voltage requirement is24-volts AC + 10%.

Troubleshooting

Air Damper and Motor CheckIf problems occur with damper actua-tion, perform the following steps:

1. Visually inspect the damper for loosegaskets, casing damage, or restrictionto damper travel.

2. Be sure that there is proper voltagesupplied by checking for 24 volts atterminal 1 and 2 on the circuit board.Acceptable voltage range is 21.6 to26.4-volts AC.

3. To open the damper, apply 24-volts ACto the white and green wires on themotor plug coming from the actuator.The drive takes a maximum of 90seconds to fully open.

4. To close the damper, apply 24-volts ACto the white and red wires on themotor plug coming from the actuator.

5. If the motor fails to operate from adirect 24-volts AC power source, andthere is neither binding norobstructions, then the actuator isdefective and should be replaced.

Control Check

Zone Sensor CheckTo troubleshoot the zone sensor, makesure that 24 volts are available at thecontrol unit board and then completethe following procedure:

1. Move the zone sensor to full cooling.The damper should open completely.If the action is reverse, check theproper zone sensor connection.

2. Rotate the zone sensor knob to fullheat. This should cause the damper toclose and fan to come on. When theroom setpoint is above the actualroom temperature, stages of heat willbe energized, if enabled.

3. If the zone sensor does not operate atall, check the wiring from the board tothe sensor. Reference the zonesensor section.

4. Check DC voltage at zone sensorterminals 2 and 3 (6-volts DC). Turnthe zone sensor to full heating voltage;it should be equal to or less than5.4-volts DC. Turn the zone sensor tofull cooling; voltage should be equal toor greater than 6.5-volts DC.

Heater Contactor CheckTo troubleshoot heater contacts on unitswith electric reheat, complete thefollowing procedure:

1. Disconnect power source.

Hazardous Voltage!Certain tests or calibration proceduresdescribed in this section may involveworking in close proximity to liveelectrical terminals. Only qualified andlicensed electrician or other properlytrained in electrical safety whenworking with live voltage shouldperform these procedures. Failure tofollow all electrical safety precautionswhen exposed to live terminal couldresult in death or serious injury.

WARNINGWARNING

Hazardous Voltage!Disconnect all electric power, includingremote disconnects before servicing.Follow proper lockout/tagout proceduresto ensure the power cannot be inadvert-ently energized. Failure to disconnectpower before servicing could result indeath or serious injury.

WARNINGWARNING


WARNINGWARNING

1. Disconnect power source and removezone sensor wires 3, 4, and 5. Be sureto mark the wires so that they will becorrectly replaced.

2. Reconnect power to the unit. Thedamper should move to its minimumor fully closed position.

3. Jumper terminals 4 and 5. The greenLED should light. This should cause thedamper to move fully open or to itsmaximum flow setting.

4. Disconnect the jumper from terminals4 and 5.

5. Jumper terminals 3 and 4. The amberLED should light. The damper shouldclose to minimum and the relays (orreheat) should energize.

6. Remove Jumper terminals 3 and 4.7. If everything operates correctly,

disconnect power and reconnect allwires. Check the air damper or zonesensor for further trouble analysis.

2. Disconnect wires from the contactor.3. Connect an ohmmeter to the contacts.4. Apply 24 volts (from independent

power supply) to the coil of relays.Check for contact closure. If thecontact does not close, replacethe contactors.

18 VAV-SVX03A-EN

Troubleshooting

Fan Motor CheckTo troubleshoot the fan motor, completethe following procedure:

1. Disconnect the power, check all wiringdiagrams provided on the unit.

2. Turn the power back on. Operate thezone sensor to see if the propervoltage is being supplied to the motorrelay. If the motor does not start, checkthe capacitor and fan motor.

3. Check the motor relay by attaching avoltmeter across the 24-volt coil of therelay. For parallel fan-powered,operate the zone sensor to energizethe fan and confirm the voltage to therelay is turned on. Check for supplyvoltage between the common and hotside of the relay.

4. Attach a Voltmeter to the whitecommon wire on the terminal blockand the blue, black or red wires fromthe fan motor. If line voltage is present,check for fan obstruction.

5. With the power off, spin the fan wheel.If it does not run freely, check shaftalignment or housing clearances.

Circuit Board Check1. Remove the control box cover. Inspect

all wiring and compare with the labelon the control box cover. The labelalso indicates jumper connections.Make sure that all wiring and jumpersare connected exactly as shown onthe diagram.

2. Measure the voltage a terminalsTB1 –1 (+) and TB1 –2 (-) on the circuitboard. The voltage reading should be24-volts AC +/- 10%.

3. Measure the voltage at terminal TB1-5(+) and TB1-3 (-) on the circuit board.Voltage reading should be 12-voltsDC + 10% tolerance. This voltage isthe output power for the zone sensor.If these voltage readings are notshown, it could indicate adefective board.

4. If 12-volts DC is present, rotate thezone sensor thumbwheel and checkfor voltage change across zone sensorterminals 2 and 3.

5. Adjust the minimum fully counter-clockwise and the maximumfully clockwise.

6. Verify the amber and green lightschange when rotating thethumbwheel.

7. If any step does not work,replacement of the board may benecessary. If all steps work, proceedwith further component checks.

Transducer Check1. Disconnect the tubing to the flow

sensor, remove the low-pressure linefirst, then the high side. Transducerdamage may result if procedure isnot followed.

2. Attach the voltmeter to terminals TP4(+) and ground, B1-2 or 3, or TP3.Voltage on these terminals should bebetween .1- to .4-volts DC; the ideal is.254 volts DC.

Triac Output Check1. Make sure that the zone sensor

operation is correct and, if applicable,which zone sensor is under control.Refer to prior sections for step-by-stepprocedures.

2. Remove all connections from J9, J10,and J11. In addition, remove J19 if it isa series fan-power unit.

3. Set the zone sensor to the fullcooling position.

4. Place a 500-1000 ohm resistorbetween the connectors J7 and J9and measure the voltage betweenthese points. It should be less than 10volts AC.

5. Slowly increase the zone sensorsetting from full cooling to heating. At aposition on the zone sensor near roomtemperature, Triac #1, which connectsJ7 to J9 should close. Next, Triac 2,which connects J7 to J10, shouldenergize and finally Triac 3, whichconnects J7 to J11, should energize.When the zone sensor is rotated to thefull heating position, a voltage checkshould show that contact closuresbetween J7 and J9, J7 and J10, andJ7 and J11 have been made (closed).

6. If continuity is not present at all stages,replace the board.

Auto Dual Minimum CheckA digital voltmeter will be required tomake the voltage checks described inthis procedure. Note the followingdifferences in labeling of adjustmentpotentiometer described in the follow-ing steps:CircuitBoardLabel

R8 Null Voltage CalibrationR67 Max FlowR68 Min Flow AR69 Min Flow B

1. Refer to calibration setup steps 1through 4. Make changes as describedin the following steps:

2. Rotate the zone sensor to the full coolposition. The green LED should beilluminated on the circuit board andvoltage present at terminals J1-3 toJ1-1. The voltage at terminal TP2 toground should be 5.9 volts DCor higher.


WARNINGWARNING

3. Connect the voltmeter to terminalsTP1 (+) and ground. Voltage at theseterminals should be 4.78 to 4.82 voltsDC. If the voltage at these terminals islower or greater than the specifiedtolerance, this could be the cause fornot obtaining correct minimum ormaximum flow. This causes thecontroller to not operate within thespecified minimum and maximumvalues, even with the minimumpotentiometer fully counter-clockwise.Adjust R8 for 4.8 volts DC.

4. Reconnect the air valve actuator anddrive to maximum position. Voltageshould increase on TP4 to TP3.

5. If voltage does not increase, verifywith a magnehelic that the delta Pis increasing.

6. Replace the transducer if delta Pincreases and voltage doesnot change.

Note: A faulty transducer will cause theair damper to function improperly.

VAV-SVX03A-EN 19

3. Slowly rotate the zone sensor until theamber LED on the circuit boardilluminates. Voltage at terminal TP2 toground should be approximately3.2 volts DC.

4. Continue rotating the zone sensor untilthe first stage of heat energizes. Thiscan be determined by voltage acrossterminals J7 to J9. At this point, thegreen LED on the circuit board shouldilluminate. Voltage at terminal TP2 toground should be 3.9 volts DC orhigher. R68 should be in control.

5. Now adjust the zone sensor so that theoutput voltage at terminals 2 and 3 is6.0 volts DC, +.01 volts DC, -.01volts DC.

6. Compare the actual zone sensor to theindicated setpoint on the dial of thezone sensor. If the two readings arewithin 3°F of each other, then the zonesensor is within standard calibrationtolerance. Calibration procedures aredescribed in the Calibration Section inthis manual.

7. Note position of R69. Rotatepotentiometer R69 clockwise andcounter-clockwise while watching theamber and green LED’s to make surethat the control is now with minimumpotentiometer R69.

8. Return R69 to its original position.

Electronic Zone SensorCheck

Note: The following checkout procedureswill be used when power is applied tothe electronic zone sensor.

1. Room temperature must be between65°F and 80°F. Make sure also thatplacement of the zone sensor issatisfactory. It should not be located indirect sunlight, on cold or hot wallsurfaces, etc. A zone sensor or otheraccurate temperature measuringdevice should be installed next to thezone sensor. It is preferable to mountthe temperature sensing elementunder the zone sensor cover next tothe thermistor of the zone sensor. (theThermistor is a small electronictemperature sensing deviceimbedded in a glob of siliconecement.)

2. Remove the zone sensor cover.3. Attach a volt meter to terminals 2 (+)

and terminal 3 (-).4. Record temperature in zone. It should

be between 65°F and 80°F.

Troubleshooting

5. Check the voltage a terminals 2 (+)and terminal 3 (-). If the zonetemperature and the zone sensorsetpoint are at equilibrium, the voltageat this point should be 6.00-volts DC.

6. Rotate the zone sensor to the full-heating position. Allow five minutes forthe zone sensor to equalize setpoint.The voltage on terminals 2 and 3should drop to 5.5-volts DC or less.

7. Rotate the zone sensor to the fullcooling position. The voltage onterminals 2 and 3 should rise to6.3-volts DC or higher.

Jack Numbering Designationsfor Analog Control BoardsJack Function

J1 MotorJ3 TransducerJ9 Stage 1 ContactJ10 Stage 2 ContactJ11 Stage 3 ContactJ15 Drive MAX (constant volume)J18 Auto Dual MinimumJ19 Output OverrideTB1 Field Connections: Power and Zone

Sensor

The Trane CompanyAn American Standard Companywww.trane.com

For more information contactyour local district office ofe-mail us at [email protected]

Literature Order Number VAV-SVX03A-EN

File Number SL-TD-VAV-000-SBX03A-EN-1101

Supersedes New

Stocking Location La Crosse

Since The Trane Company has a policy of continuous product and product data improvement, it reserves the rightto change design specifications without notice.Only qualified technicians should perform the installation and servicing of equipment referred to in thispublication.

Installation/ Owner Programming VariTrane Analog Electronic

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