Trane CG-PRC007-EN manual Controls, 10, 15Ton

Page 31

Controls

(10, 15Ton)

 

 

 

 

ELECTRICAL CONTROL SYSTEM

The controls used on CGA 10 and 15-ton units are classified either as “safety” controls or “operational” controls. Brief descriptions of the specific safety and operating controls used in the CGA control scheme are provided in the following paragraphs.

Refer to the following control descriptions for control settings.

UNIT SAFETY CONTROLS

Low Pressure Cutout (LPC01, LPC02)

Mounted below the unit control box are two low pressure cutouts that open and stop compressor operation if the operating pressure drops below 38.5 + 1 psig.The cutout automatically resets when the pressure reaches 44.5 + 2 psig. The LPCO is a SPDT device. If it opens at low ambient start-up, it will energize ODF relay, stopping the outdoor fan(s) while the compressor remains energized through the LAST (Low Ambient Start Timer).

High Pressure Cutout (HPC01, HPC02)

These units have high pressure cutouts that open and stop compressor operation if the discharge pressure reaches 400 + 10 psig.The cutout automatically resets when pressure drops to 250 + 15 psig.

Reset Relays (RRS, RR2)

If the unit is shut down by the low pressure cutout (or high pressure cutout), the reset relay locks out the compressor contactor (CCS, CC2).This prevents the system from recycling until the condition that caused the low (or high) pressure cutout to trip is determined and corrected.

CAUTION:To prevent unit damage, do not reset the control circuit until the cause of the safety lockout is identified and corrected.

To reset RR1 and RR2, open and reclose the unit disconnect switch.

LowTemperature Cutout (LTC)

The LTC is designed to disable the unit if the leaving water temperature falls too low.The LTC’s remote sensing bulb is

mounted at the outlet end of the evaporator, where it monitors leaving water temperature.

During normal unit operation, if the low temperature cutout (LTC) senses a temperature falling to 36°F + 3.0°F, the LTC will open to interrupt compressor operation. (Manual reset is required.)

Motor Overloads

These units have internal compressor and condenser fan motor overloads. These overloads protect the motors from overcurrent and overheating conditions and automatically reset as soon as they cool sufficiently.

UNIT OPERATIONAL CONTROLS

WaterTemperatureThermostat (WTT)

System operation for 10 and 15-ton CGA units is governed by a two-stage water temperature thermostat (WTT).The remote sensing bulb of this device is factory-installed in a bulb well located on the evaporator water inlet; here, it monitors the temperature of the water returning to the evaporator.

Low Ambient StartTimer (LAST)

When one of the two timers energizes, the low pressure control is bypassed for four minutes, this allows time for suction pressure to build sufficiently for the low pressure cutout contacts to close.

Hot Gas BypassTimer, Solenoid (HGBT, HGBS)

The hot gas bypass option is factory- installed only, and is used in a chilled water system to keep the first stage compressor on-line during short no-load or light-load conditions.WhenWater TemperatureThermostat (WTT) first stage opens, 24-volt power is supplied to the Compressor Contactor (CC1) through Hot Gas BypassTimer (HGBT) pins one and four. Power is also applied from WTT-B to HGBT coil (fixed 30-minute time delay pickup) and to the Hot Gas Bypass Solenoid (HGBS) through HGBT pins eight and five. If first stage cooling remains satisfied for 30 minutes, HGBT will energize and shut down the compressor. If there is a call for cooling during HGBP mode, the unit will return to cooling mode.

The adjustable hot gas bypass valve is factory set at 70 psig.

Note: Hot gas bypass is available only on the lead compressor circuit.

Anti-Short CycleTimers (ASCT1,ASCT2)

An anti-short cycle timer is provided in each compressor control circuit to protect the compressors from starting too frequently.This can occur as a result of just over 0%, or just over 50% of the unit capacity, or because of sudden power outages of short duration. Whenever the contacts of the water temperature thermostat (WTT) open — or when there is a momentary power outage — the anti-short cycle timer will lock out compressor operation for three minutes.

Delay Between Compressors (DBC)

The delay between compressors prevents both compressors from starting at the same time by delaying compressor number two for 30 seconds.

Definition of Abbreviations:

ASCT

—

Anti-Short CycleTimer

CC

—

Compressor Contactor

CWFIR

—

ChilledWater Flow

 

 

Interlock Relay

CWPS

—

ChilledWater Pump

 

 

Starter

DBC

—

Time Delay Between

 

 

Compressors

HGBT

—

Hot Gas BypassTimer

HPCO

—

High Pressure Cutout

LAST

—

Low Ambient Start

 

 

Timer

LPCO

—

Low Pressure Cutout

LTC

—

LowTemperature

 

 

Cutout

ODF

—

Outdoor Fan

RR

—

Reset Relay

SPDT

—

Single Pole, Double

 

 

Throw

WTT

—

WaterTemperature

 

 

Thermostat

CG-PRC007-EN

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Contents Air-Cooled Liquid Chillers 10, 15Tons 20-60Tons IntroductionContents 10-60Ton FeaturesBenefits Flexibility 10-15Ton20-60Ton Standard FeaturesOther Standard Features Optional FeaturesTracer control points for IntelliPak Chillers Enhanced ControlsLowTorqueVariation Proven DesignThroughTesting and ResearchTrane 3-D Scroll Compressor Simple Design with 70% Fewer PartsUnit Location General SettingThe UnitIsolation and Sound Emission ServicingProvide Sufficient Unit-to-Unit Clearance Walled Enclosure InstallationsProvideVertical Clearance Provide Lateral ClearanceHigh Ambient Operation Temperature ControllerLeaving SolutionTemperature range Low Ambient OperationSeries Operation SupplyWaterTemperature DropExample CGAFC50 with 100 gpm. Minimum LoopVolume = Gallon Minimum LoopVolume10, 15Ton Application Considerations20-60Ton Given Selection Procedure10, 15Tons Model Number Description20-60Tons Table GD-1 General Data 10-60Ton Units General Data∆ T Performance Adjustment FactorsWater Drop Pressure Performance Adjustment Factors Performance Adjustment Factors Table PD-1 10 Ton CGA PerformanceData 60 HZ Full LoadTable PD-3 20Ton CGAF-C20 20-25TonTable PD-4 25Ton CGAF-C25 Table PD-5- 30Ton CGAF-C30 30-40TonTable PD-6 40Ton CGAF-C40 Table PD-7- 50Ton CGAF-C50 50-60TonTable PD-8- 60Ton CGAF-C60 Data 50 HZ 10-30TonTable PD-17- 60Ton CGAF-C60 40-60TonTable PD-15 40Ton CGAF-C40 Table PD-16 50Ton CGAF-C50Table PD-18- Part Load Data,ARI Points 10-60Tons Part LoadTable PD-18 Part Load Data,ARI Points 10-60Tons Table PD-22 25Ton CGAF-C25 Table PD-19 10Ton CGA Table PD-20 15Ton CGA Table PD-21 20Ton CGAF-C20Table PD-25- 50Ton CGAF-C50 Table PD-24- 40Ton CGAF-C40Table PD-26- 60Ton CGAF-C60 Trane Integrated Comfort System Interface Required FeaturesInterface with Other Control Controls Systems10, 15Ton Controls10, 15 Ton Field Installed Head Pressure Control AccessoryTon Operation Customized Control Safety ControlsMonitoring and Diagnostics Controls 20-60 TonMain Menu of the Human Interface panel Standard Control Features20-60Ton Controls Interface Human Interface HI PanelOptional Control Features 4 analog outputs can be assigned to 5 binary outputs can be assignedOne binary output can be assigned to Load Definitions Electrical 10-60Ton Data 60 HZTable ED-1 Electrical Data Table ED-2 Electrical Data Electrical 10-60Ton Data 50 HZFigure DD-1 CGA-120B Unit Dimensions Dimensional 10Ton DataFigure DD-2 CGA-180B Unit Dimensions Dimensional 15Ton DataFigure DD-3 CGAF-C20 Unit Dimensions Dimensional 20Ton DataFigure DD-4 CGAF-C25 Unit Dimensions Dimensional 25Ton DataFigure DD-5 CGAF-C30 Unit Dimensions Dimensional 30Ton DataFigure DD-6 CGAF-C40 Unit Dimensions Dimensional 40Ton DataFigure DD-7 CGAF-C50 Unit Dimensions Dimensional 50Ton DataFigure DD-8- CGAF-C60 Unit Dimensions Dimensional 60Ton DataTable W-3 Cgaf Unit Weights lbs WeightsTableW-1 Approximate CornerWeights lbs 10-Ton Unit TableW-2 Approximate CornerWeights lbs 15-Ton UnitMechanical 10-15TonSpecifications Mechanical 20-60TonSpecifications Unit Mounted Disconnect Zone Sensor Chilled Solution ResetIce Building Compressor Current Sensing CSMCG-PRC007-EN Trane
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