RT-DS-1November 1992First Printing

PackagedRooftopAir Conditioners

20 To 130-TonsC and E Style

Contents

Standard FeaturesŽ Trane 3-D™ scroll compressors (20-60

Ton)● Trane semi-hermetic ‘R’ compressors

(70-130 ton)Ž FC supply and exhaust fans● Factory run tested units and

components● Constant volume control● 14-gauge, single-piece construction

base railsŽ UL and CSA approval● Two-inch spring isolation (90-130 ton)● Meets ASTM B117 672 hour salt spray

test

Optional Features● Variable air volume control● FROSTAT™ coil frost protection (VAV

only)● Hot gas bypass● Statitrac™ direct building pressurization

controlŽ High capacity evaporator coil option● Double wall access doors● Double wall construction/perforated

double wall● Two-inch spring isolation (20-75 ton)● 90-95 percent bag filtersŽ 90-95 percent cartridge filters● Final filters● Barometric relief● 50 percent exhaust fans● 100 percent modulating exhaust● Extended casing● Frequency inverter terminal strip● Filter rack only (no filters)

● Inlet guide vanes on FC fans (VAV only)● Heating options: natural gas, electric or

hydronic● Copper evaporator/condenser coils● Heresite coated coilsŽ Dual electrical power connection● Horizontal discharge/return (cooling

only)● High efficiency motors● Oversized motors● High duct temperature thermostat● 0 F ambient● Economizer with low leak dampers● Ultra low leak economizer dampers● Night setback and remote control panel● Zone reset● ICS control module Tracer® Integration

Module (TIM)● Non-fused disconnectŽ Ventilation override sequences● Convenience outlet● Duplex controlŽ Single zone variable air volume controlŽ VariTrac interface● Fast morning warm-up● Roofcurbs● Special paint colors● Power supply monitoring● Pneumatic interfaceŽ Correction capacitors● U-frame motors

Features and Benefits 2

Model Number Description 6

General Data 8

Application Considerations 11

Selection Procedure 17

Performance Adjustment Factors 20

Performance Data 21

Electrical Data 62

Controls 64

Dimensional Data 66

Weights 72

Options 73

Features Summary 77

Mechanical Specifications 78

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Electrical Service SizingNote: To correctly size electrical servicewiring for. . .— SAHC, SXHC/E, SFHC/E, SSHC, and

SLHC units solve Equations 1 thru 4.— 200/230V SEHC units (dual-source-

power) solve Equations 1 thru 4 and9 thru 11.

— All other SEHC and SEHE units(single-source-power) solveEquations 1 thru 8.

Equation No. 1: Minimum CircuitAmpacity (MCA)

MCA = [1.25 x The largest of these:(Largest Compressor RLA ORLargest Motor FLA)]

+ Remaining Compressor RLA+ Remaining Supply Fan FLA+ Remaining Exhaust Fan FLA+ Total Condenser Fan FLA

Note: Round off the calculated MCAvalue to the nearest whole ampere. (Ifthe MCA value ends in “.5”, round itupward.)

Equation No. 2:Maximum Fuse Size (MFS)

Case A:Compressor is the largest loadMFS = (2.25 x Largest

Compressor RLA)+ Total Remaining Compressor RLA+ Total Supply Fan FLA+ Total Exhaust Fan FLA+ Total Condenser Fan FLA

Case B:Compressor is NOT the largest loadMFS = (4.0 x Largest Motor RLA)+ Total Compressor RLA+ Total Remaining Supply Fan FLA+ Total Remaining Exhaust Fan FLA+ Total Condenser Fan FLA

Note: Select the standard fuse ratingequal to MFS; or select the next lowerstandard fuse rating. (Standard fusesizes are taken from NEC 240-6.)

Equation No. 3:Recommended Dual-Element FuseSize (RDE)RDE = [1.5 x The larger of these:

(Largest Compressor RLA orLargest Motor FLA)]

+ Remaining Compressor RLA+ Total Remaining Supply Fan FLA+ Total Remaining Exhaust Fan FLA+ Total Condenser Fan FLA

Note: Select the standard fuse ratingequal to RDE; or select the next largerstandard fuse rating. However, the RDErating selected must not exceed theselected MFS rating. (Standard fusesizes are taken from NEC 240-6.)

Equation No. 4Disconnect Switch Size (DSS)DSS = 1.15 x(Total Compressor RLA+ Total Supply Fan FLA+ Total Exhaust Fan FLA+ Total Condenser Fan FLA)

Note: Select a disconnect switch sizethat is equal to or larger than the DSSvalue calculated.

All Single-Source-Power SEHC/E UnitsAfter solving Equations 1 thru 4, solveEquations 5 thru 8. Then compare the:— MCA values calculated in Equations

1 and 5;— MFS values calculated in Equations

2 and 6;— RDE values calculated in Equations 3

and 7; and,— DSS values calculated in Equations 4

and 8.

In each instance, use the largest valueof each pair to size the unit’s electricalservice.

Equation No. 5Minimum Circuit Ampacity (MCA)MCA = 1.25 X(Electric Heat Coil FLA+ Total Supply Fan FLA+ Total Exhaust Fan FLA)

Equation No. 6:Maximum Fuse Size (MFS)MFS = 1.25 X(Electric Heat Coil FLA+ Total Supply Fan FLA+ Total Exhaust Fan FLA)

Note: Select the standard fuse ratingequal to MFS; or select the next largerstandard fuse rating.

Equation No. 7:Recommended Dual-Element FuseSize (RDE)RDE = Electric Heat Coil FLA+ (1.5 x Largest Single Fan FLA)+ Total Remaining Supply Fan FLA+ Total Remaining Exhaust Fan FLA

Note: Select the standard fuse ratingequal to RDE; or select the next largerstandard fuse rating. However, the RDEsize selected must not exceed theselected M FS size!

Equation No. 8:Disconnect Switch Size (DSS)DSS = 1.15 x(Electric Heat Coil FLA+ Total Supply Fan FLA+ Total Exhaust Fan FLA)

Note: Select a disconnect switch sizethat is equal to or larger than the DSSvalue calculated.

Dual-Source-Power SEHC Units(200/230V Only):Solve Equations 1 thru 4 forrefrigeration-side MCA, MFS, RDE andDSS values.

Then, use Equations 9, 10 and 11 todetermine electric heat section MCA,MFS and DSS values.

Equation No. 9:Minimum Circuit Ampacity (MCA)MCA = 1.25 XElectric Heat Coil FLA

Equation No. 10:Maximum Fuse Size (MFS)MFS = 1.25 XElectric Heat Coil FLA

Note: Select a standard fuse ratingequal to MFS; or select the next largerstandard fuse rating.

Equation No. 11:Disconnect Switch Size (DSS)DSS = 1.15 xElectric Heat Coil FLA

Note: Select a disconnect switch sizethat is equal to or larger than the DSSvalue calculated.

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ElectricalData

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Sequence Of OperationShutoff VAV Rooftops

Temperature ControlsUnits are provided with a supply airtemperature sensor and HoneywellW7100 discharge air temperaturecontroller. The supply air temperaturesensor sends a continuous feedbacksignal to the W 7100 controller. Thissignal modulates the economizer andsequences the stages of mechanicalcooling in response to the supply airtemperature deviation from set point.

An optional zone air temperaturesensor is available which providescontinuous input to the W7100controller. The controller will reset thesupply air temperature upwards basedon a predetermined amount of resetwhich is adjustable from a remotepotentiometer,

The W7100 controller provides anti-short cycle protection by utilizing aminimum four minute time-delaybetween successive on and off stages.

CoolingOn units with economizer, a call forcooling will modulate the fresh airdampers open. The rate of economizermodulation is based on deviation of thedischarge temperature from set point,i.e., the further away from set point, thefaster the fresh air damper will open.First stage of cooling will be allowed tostart after the economizer reaches fullopen.

At outdoor air temperatures above theenthalpy control setting, mechanicalcooling only is used and the fresh airdampers remain at minimum position.

On units without economizer,mechanical cooling only is used tosatisfy the cooling requirements.

The inlet vanes will close when thesupply fan is shut down, except duringnight setback.

Night Setback/Morning WarmupStandard heating options are availableon shutoff/VAV units for use with nightsetback and/or morning warmupoperation only.

Night setback and morning warmupare operated through the time clockprovided in the remote panel with nightsetback. When the time clock switchesto night setback or morning warmupoperation, the outdoor air dampersclose and cooling is locked out. As thebuilding cools due to decreased load,the night setback thermostat energizes

Controls

the rooftop heating function (singlestage of heat provided on all units) andthe evaporator fan. The rooftop unitwill cycle through the evening asheating is required in the space. Whenthe time clock switches from nightsetback to daytime operation, allheating functions are locked out andnormal cooling operation begins.

Morning warmup is two-stage. Whennight setback terminates, the rooftopwill heat to stage 2 set point. Therooftop can “reheat” as many times asnecessary to maintain stage 2 set pointuntil stage 1 set point (typically 1 Fhigher than stage 2) is reached. At thispoint, the unit is released to daytimemode and cannot heat until the nextnight setback cycle.

When using the night setback/morningwarmup options in a heating/coolingrooftop, airflow must be maintainedthrough the rooftop unit. This can beaccomplished by electrically tying theVAV boxes to the rooftop time clock orby using changeover thermostats.Either of these methods will assureadequate airflow through the unit andsatisfactory heating of the building.

Inlet Vane ControlsVAV units ordered with supply fan inletvane controls (i.e., model no. digit 2.1includes “N”) are equipped with 2 staticpressure regulators that control theaction of inlet vane actuator(s).

Inlet vane assemblies installed on thesupply fan inlets regulate fan capacityand limit horsepower at lower systemair requirements. When in any positionother than full open, the vanes prespinintake air in the same direction assupply fan rotation. As the vanesapproach the full-closed position, theamount of “spin” induced by the vanesincreases at the same time that intakeairflow and fan horsepower diminish.

The field-adjustable static pressureregulators (1S22 and 1S23) are factory-installed in the unit control panel togovern the supply fan inlet vaneactuators. These controls monitor ductstatic pressure (rather than atmosphericpressure) via a factory-installedpressure-sensing tube in the supplyfanboard, and then modulate the inletvane actuators accordingly to maintainthe optimal rooftop discharge static.

FROSTAT™ Suction LineTemperature SensingThe FROSTAT system eliminates hotgas bypass and adds a suction linesurface temperature switch near theTXV bulb location to shut the coolingoff when coil frosting conditions occur.The supply fans are not shut off andwill de-ice the coil. Timers prevent thecompressor from rapid cycling.

The following flow chart describes theoperation of FROSTAT suction linetemperature sensing in large VAVrooftop units

Economizer CycleNote that the economizer is onlyallowed to function freely if ambientconditions are below the factory-setcontrol range of enthalpy switch 3S20.

If outside air is not suitable for“economizing”, the fresh air dampersdrive to the minimum open position. (Apotentiometer located on top of theeconomizer actuator cover establishesthe minimum damper position.)

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Controls

Sequence Of OperationTemperature ControlsA 20-volt dc regulated power supply isprovided to the thermostat. Acontinuous signal of 1 to 16 volts dc isreturned to the Honeywell MasterEnergy Controller (W973) by thethermostat. This signal is monitored bythe controller to determine actual zoneheating and cooling requirements. Thecontroller will then, according to thevoltage value received, operate thenecessary mechanical componentsthrough relay stages which aresensitive to the zone signal.

The control system provides two tofour stages of mechanical refrigeration,depending upon tonnage and either ofthe following:

Ž Three stages of electric heat.● Two stages of gas heat.

CoolingOn those units with an economizercycle, outdoor air is used to providenatural cooling at outdoor enthalpybelow the setting on the enthalpycontrol (approximately 70 F at 55percent relative humidity). Mechanicalcooling is available to aid theeconomizer cycle at any ambientcondition.

During economizer operation, thecontroller modulates the outdoor andreturn air dampers between theminimum and full open settings tosatisfy cooling requirements. If coolingdemands cannot be met by the fullopen outdoor air dampers, mechanicalcooling is activated (first and secondstages if necessary). The outdoor airdampers remain open to takeadvantage of free natural cooling.However, due to the temperaturesensing ability of the unit dischargesensor, the outdoor air dampers willbegin to close at a discharge airtemperature (off the evaporator coil) of62 F. The outdoor air dampers will goto the minimum position at a dischargetemperature of 50 F. This feature istermed positive modulating low limit.

At outdoor air temperatures above theenthalpy control setting, mechanicalcooling only is used and the outdoor airdampers remain at minimum position.

If the unit does not include aneconomizer cycle, mechanical coolingonly is used to satisfy coolingrequirements. Outdoor air dampersmay be set manually for a maximum of25 percent outdoor air, if rooftop isequipped with 0 to 25 percent manualfresh air damper.

Heating

Gas-Fired HeatingUpon a call for heating, the masterenergy controller closes the first stageheating contacts beginning the firingsequence. First, the heat exchangercombustion blower begins operation.Upon positive proving of combustionairflow, a prepurge cycle is executed.Then the ignition sequence takes place.

If ignition is not proven, the ignitiontransformer is de-energized. After atime delay another prepurge cycletakes place followed by anotherattempt to ignite. If ignition fails asecond time, the cycle repeats on 235and 350 MBh modules. 500, 850 and1000 MBh modules, the heatingsection, will be shut down and lockedout until manually reset at the unit.

As additional heat is required, themaster energy controller will close thesecond stage heating contacts andeither the second stage of the gasvalve or a second stage gas valve willopen depending on heat module size.

During heating operation, an electronicflame safety control providescontinuous flame supervision. Ifcombustion should become unstablefor any reason, heating willautomatically shut down. After oneminute, another 60 second prepurgeand ignition cycle begins.

As the heating requirement is satisfied,the master energy controller will openthe second stage heating relay de-energizing the second stage of heat.When the requirement is fully satisfied,the first stage contacts are opened de-energizing the first stage of heat.

The specific sequence of operation ofthe gas heat will depend on the size ofthe heat exchanger.

Electric HeatingThe three stages of electric heat will besequenced on the zone demand signalfrom the room thermostat. The zonesignal is relayed to the master energycontroller and the stages aresequenced based on load demand.

Steam or Hot Water HeatingUpon a call for heat, the master energycontroller will close the heating contactfeeding a varying voltage signal to thevalve actuator. The valve will modulateto meet building demand as indicatedby the voltage signal. When heating issatisfied, the heating relay will be de-energized, stopping the signal to thevalve actuator. The valve will modulateclosed.

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