Liquid Chillers Rev

8/14/2019 Liquid Chillers Rev

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J.ILANGUMARANJ.ILANGUMARAN


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Liquid Chilling SystemLiquid Chilling System

A liquid chilling system cools water, brine,A liquid chilling system cools water, brine,or other secondary coolant for airor other secondary coolant for airconditioning or refrigeration.conditioning or refrigeration.

The system may be either factory assembledThe system may be either factory assembledand wired or shipped in sections forand wired or shipped in sections forerection in the fielderection in the field


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Components of chillers (vapor compressionComponents of chillers (vapor compressionsystem)system)


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Chilled Water SystemChilled Water System

Air Handling unit Circulating Pumps

Condenser

Chiller - Pump Evaporator

Chiller

Chilled Water Headers


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Components of vapor compression systemComponents of vapor compression system


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Chilled Water SystemChilled Water SystemChilled Water SystemChilled Water SystemChilled Water SystemChilled Water SystemChilled Water SystemChilled Water System

Chiller Yard Pump

Room

HT

OT

PD

To Hotel Tower 450Dia

To Office Tower 400Dia

To Podium 250Dia


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Chiller YardChiller YardChiller YardChiller Yard


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Multiple Chiller SystemMultiple Chiller System

Parallel chilled water flowParallel chilled water flow

arrangementarrangement

Series water flow arrangementSeries water flow arrangement


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Parallel chilled water flow arrangement


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Series water flow arrangement


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Type Of ChillersType Of Chillers

Based OnBased On

Condensing MediaCondensing Media

Air cooledAir cooled

Water cooledWater cooled

Based onBased on

CompressorCompressor

ReciprocatingReciprocating


Screw CompressorScrew Compressor

CentrifugalCentrifugal



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Chiller packageChiller package

Hermetically sealed Compressor & Motor,Hermetically sealed Compressor & Motor,

Condenser, Expansion device & Evaporator, interCondenser, Expansion device & Evaporator, inter--connected to form refrigeration cycle withconnected to form refrigeration cycle with

Fully charged refrigerant.Fully charged refrigerant.

Safety & operational controls.Safety & operational controls.

Lubrication system.Lubrication system.

Operation monitoring devices.Operation monitoring devices.

Control panel duly wired.Control panel duly wired.

Starter with Disconnect switch duly wiredStarter with Disconnect switch duly wired


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ChillersChillers

AirAir--cooled Reciprocating Chiller ORcooled Reciprocating Chiller OR

Water cooled Reciprocating ChillerWater cooled Reciprocating Chiller

AirAir--cooled Screw Chiller OR Watercooled Screw Chiller OR Water

cooled Screw Chillercooled Screw ChillerAirAir--cooled Centrifugal Chiller ORcooled Centrifugal Chiller OR

Water cooled Centrifugal ChillerWater cooled Centrifugal Chiller


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Chiller with Reciprocating CompressorChiller with Reciprocating Compressor

1.1. Semi Hermetic Reciprocating compressorSemi Hermetic Reciprocating compressor

2.2. MufflerMuffler3.3. Fan & condenser coilFan & condenser coil

4.4. Filter drierFilter drier

5.5. Liquid Line sight glassLiquid Line sight glass

6.6. Moisture indicatorMoisture indicator7.7. Expansion valveExpansion valve

8.8. DxDx--EvaporatorEvaporator

9.9. Control PanelControl Panel

10.10. StarterStarter

11.11. ControlsControls


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Chiller with CentrifugalChiller with Centrifugal

CompressorCompressorSemi Hermetic Centrifugal compressorSemi Hermetic Centrifugal compressor

Fan & condenser coilFan & condenser coilLiq. Line sight glassLiq. Line sight glass

Moisture indicatorMoisture indicator

Fixed orifice assemblyFixed orifice assembly

Flooded EvaporatorFlooded Evaporator

External Lubrication systemExternal Lubrication system

External Capacity control systemExternal Capacity control system

Motor cooling systemMotor cooling system

Control PanelControl Panel

StarterStarter

ControlsControls


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Chiller with ScrewChiller with Screw

CompressorsCompressorsSemi Hermetic Screw compressorSemi Hermetic Screw compressor

Oil SeparatorOil SeparatorFan & condenser coilFan & condenser coil

Receiver/SubReceiver/Sub--cooling coilscooling coils

Filter drierFilter drier

Liq. Line sight glassLiq. Line sight glass

Moisture indicatorMoisture indicator

Expansion valveExpansion valve

DxDx--EvaporatorEvaporator

Lubrication systemLubrication system

Control PanelControl Panel

StarterStarter

ControlsControls


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Basis of DesignBasis of Design

The Chilled Water System has beenThe Chilled Water System has been

designed to produce the chilled waterdesigned to produce the chilled water

at following so as to achieve theat following so as to achieve the

comfort conditionscomfort conditionsby Air conditioningby Air conditioning

system at floors.system at floors.

Entering Chilled Water Temp. : 55Entering Chilled Water Temp. : 55FF

Leaving Chilled Water Temp.Leaving Chilled Water Temp. : 45: 45FF


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Variable Speed DriveVariable Speed Drive

All the chilled water pumps areAll the chilled water pumps are

provided with a microprocessor based,provided with a microprocessor based,

pulse width modulated, adjustablepulse width modulated, adjustable

frequency AC drive.frequency AC drive.

The drive controls AC motor.The drive controls AC motor.


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Chilled Water systemChilled Water system

OperationOperation-- LogicLogic

The whole system is automatic thruThe whole system is automatic thru

Building Management System to achieveBuilding Management System to achievethe specified conditions at floors.the specified conditions at floors.

Once temperature is achieved in conditionOnce temperature is achieved in condition

space the motorized 2space the motorized 2--way valve closesway valve closeswhich in turn increases the difference inwhich in turn increases the difference in

pressure between supply & Return pipes.pressure between supply & Return pipes.

Reduction in speed reduces the chilledReduction in speed reduces the chilled

water flow in the system and save thewater flow in the system and save the

energy.energy.


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Chilled Water system OperationChilled Water system Operation--

LogicLogic

Once load in condition space increases,Once load in condition space increases,two way valves opens thus reduces thetwo way valves opens thus reduces the

pressure difference between supply &pressure difference between supply &

return pipes.return pipes.

Increase in speed, increases the ChilledIncrease in speed, increases the Chilled

flow to meet the requirement of conditionflow to meet the requirement of condition

spacespace..


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PumpsPumps-- Automatic ShutdownAutomatic Shutdown

The VFD shuts down the pump shouldThe VFD shuts down the pump shouldany of the following happens:any of the following happens:

Over TemperatureOver Temperature

Motor OverloadMotor Overload

High Motor CurrentHigh Motor Current

Motor GroundMotor Ground


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Chiller principleChiller principle


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Reciprocating ChillersReciprocating Chillers


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Refrigeration cycleRefrigeration cycle


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RefrigerationCycleRefrigerationCycle

Motor Compressor

MeteringDevice

Condenser

T

0C

on

ditio

ne

dS

pace

Retu

rnair


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Reciprocating compressors


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Reciprocating CompressorReciprocating Compressor


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Semihermetic reciprocating compressorsSemihermetic reciprocating compressors


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Semihermetic reciprocating compressorsSemihermetic reciprocating compressors


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Thermostatic expansion valveThermostatic expansion valve


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Thermostatic expansion valveThermostatic expansion valve


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Returning discharge to suction


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Capacity controlCapacity control Controlling suction pressure by throttling;Controlling suction pressure by throttling;

Controlling discharge pressure;Controlling discharge pressure;

Returning discharge gas to suction;Returning discharge gas to suction;

Adding reexpansion volume;Adding reexpansion volume;

Changing the stroke;Changing the stroke;

Opening a cylinder discharge port to suction whileOpening a cylinder discharge port to suction whileclosing the port to discharge manifold;closing the port to discharge manifold;

Changing compressor speed;Changing compressor speed;

Closing off cylinder inlet, andClosing off cylinder inlet, and

Holding the suction valve openHolding the suction valve open


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Factors Affecting the performance ofFactors Affecting the performance of

Refrigeration unitRefrigeration unit

Discharge pressureDischarge pressure

Out door air temperatureOut door air temperature

Air circulation thruAir circulation thru

condensercondenser

Condenser fins & tubeCondenser fins & tubeconditioncondition

Space between chillersSpace between chillers

Condenser fansCondenser fans

Excess refrigerantExcess refrigerant Evaporator pressureEvaporator pressure

Lack of refrigerantLack of refrigerant

Less water flowLess water flow

Erratic operation ofErratic operation of

Lubrication systemLubrication system

Low oil pressureLow oil pressure

Oil filter chokeOil filter choke

Quality & Accuracy ofQuality & Accuracy of

controls and Sensorscontrols and Sensors Calibration & settingCalibration & setting

Proper installationProper installation

Routine & preventiveRoutine & preventive

maintenancemaintenance

TimelyTimely

ProperlyProperly


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Factors Affecting theFactors Affecting the

performance ofperformance ofAir & water side systemAir & water side system

Air balancingAir balancing

Supply air flowSupply air flow

Return air flowReturn air flow

Grills and damperGrills and damper

adjustmentadjustment Fresh air flowFresh air flow

Dampers adjustmentDampers adjustment

AHU performanceAHU performance

Filters conditionFilters condition

Cooling coilCooling coil

Belts & pulleysBelts & pulleys

DampersDampers

Quality,Accuracy andQuality,Accuracy and

setting of Thermostats,setting of Thermostats,Humidistat and SensorsHumidistat and Sensors

Chilled water distributionChilled water distribution

StrainersStrainers

Flow control ValvesFlow control Valves

Pump performancePump performance

Chiller performanceChiller performance

Routine & preventiveRoutine & preventivemaintenancemaintenance


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Air Cooled CondenserAir Cooled Condenser


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E F


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DxDx EvaporatorEvaporator --Coil & FinsCoil & Fins

TypeType

DX E tDX E t Sh ll &T bSh ll &T b


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DX EvaporatorDX Evaporator--Shell &TubeShell &Tube

typetypeWater flow thru the shell.

Refrigerant is in tubes.

DX E aporatorDX Evaporator Shell &TubeShell &Tube


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DX EvaporatorDX Evaporator-- Shell &TubeShell &Tube

typetypeWater flow thru the shell

Refrigerant is in tubes

C i i lC iti l F t


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Critical FactorsCritical Factors

Shell & Tube EvaporatorsShell & Tube EvaporatorsQuality of watersQuality of waters

CleanedCleaned

Chemically treatedChemically treated

Velocity of water should not be higherVelocity of water should not be higher

than recommendedthan recommended Proper setting of Expansion valveProper setting of Expansion valve

Adequate water flowAdequate water flow

Proper installation of Sensors /ThermistorProper installation of Sensors /Thermistor


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Flooded EvaporatorsFlooded EvaporatorsIn flooded type evaporator aIn flooded type evaporator a

constant Refrigerant liquid level isconstant Refrigerant liquid level ismaintained.maintained.

A float valve / Level switches areA float valve / Level switches are

used as metering device to maintainused as metering device to maintainthe constant level.the constant level.

TypesTypes

Coil & Fins typeCoil & Fins typeShell & Tube typeShell & Tube type

Fl d d E tFlooded E aporator


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Coil & Fins typeCoil & Fins type

Fl d d E tFl d d E t


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Shell & Tube TypeShell & Tube Type

Orifice Assembly

Distributor

Tubes

From CondenserTo Compressor


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Metering DevicesMetering DevicesCapillary tubeCapillary tube

Fixed orifice typeFixed orifice type

Float valveFloat valve

Automatic expansion valveAutomatic expansion valveThermostatic expansion valveThermostatic expansion valve

Electronic expansion valveElectronic expansion valve


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Automatic expansion valveAutomatic expansion valveAutomatic expansion valveAutomatic expansion valveAutomatic expansion valveAutomatic expansion valveAutomatic expansion valveAutomatic expansion valve

It allows the flow ofIt allows the flow of

refrigerant torefrigerant tomaintain the constantmaintain the constant

pressure inpressure in

evaporator.evaporator.

It does not allow theIt does not allow therefrigerant flow torefrigerant flow to

maintain the Suctionmaintain the Suction

superheat.superheat.

Thermostatic ExpansionThermostatic Expansion


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Thermostatic ExpansionThermostatic Expansion

valvevalve


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Thermostatic Expansion valveThermostatic Expansion valve


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Electronic Expansion ValveElectronic Expansion Valve


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Sensing Bulb FixingSensing Bulb Fixing

Smaller diameter 1Smaller diameter 1Inch and belowInch and belowsuction linesuction line

Sensing bulb shouldSensing bulb should

be on topbe on topAbove 1 Inch dia,Above 1 Inch dia,

4 O4 O Clock Position.Clock Position.

Sensing Bulb shouldSensing Bulb shouldbe fully covered bybe fully covered byinsulating materialinsulating material..

dP i d i


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Protective devicesProtective devices

A highA high--pressure cutout.pressure cutout.HighHigh--temperature control devices to protect againsttemperature control devices to protect against

overheating and oil breakdown.overheating and oil breakdown.

Motor over temperature protective devicesMotor over temperature protective devices LowLow--pressure protection may be provided forpressure protection may be provided for

Suction gas and compressorSuction gas and compressor

Time delay, or lockouts with manual resets,Time delay, or lockouts with manual resets,prevents damage to both compressor motor andprevents damage to both compressor motor andcontactors from repetitive rapidcontactors from repetitive rapid--starting cyclesstarting cycles

Low voltage and phase loss or reversal protectionLow voltage and phase loss or reversal protection

is used on some systems. Phase reversalis used on some systems. Phase reversalprotection is used with multiprotection is used with multi--phase devices tophase devices toensure the proper direction of rotation.ensure the proper direction of rotation.

Suction line strainer.Suction line strainer.

Testing of Positive Displacement Refrigerant CompressorsTesting of Positive Displacement Refrigerant Compressors..


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g f p f g pg f p f g p

Compressor tests are of two types: the firstCompressor tests are of two types: the firstdetermines capacity, efficiency, sound level, motordetermines capacity, efficiency, sound level, motor

temperatures, etc.; the second predicts thetemperatures, etc.; the second predicts thereliability of the machine.reliability of the machine.

Standard rating conditions, which are usuallyStandard rating conditions, which are usuallyspecified by compressor manufacturers, includespecified by compressor manufacturers, includethe maximum possible compression ratio, thethe maximum possible compression ratio, themaximum operating pressure differential, themaximum operating pressure differential, themaximum permissible discharge pressure, and themaximum permissible discharge pressure, and the

maximum inlet and discharge temperaturemaximum inlet and discharge temperature Lubrication requirementsLubrication requirements

Power requirements for compressor startingPower requirements for compressor starting

Reciprocating ChillersReciprocating Chillers ControlsControls


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Discharge Pressure Control (High Pressure Control)Discharge Pressure Control (High Pressure Control)

Its function is to switch off the compressor, Once dischargeIts function is to switch off the compressor, Once dischargepressure exceeds the prepressure exceeds the pre--determineddetermined set pressureset pressure..

Set PointSet Point Cut outCut out -- 425 (+ or425 (+ or 6 ) Psig with R6 ) Psig with R--22 Refrigerant22 Refrigerant

Cut InCut In -- 320 (+ or320 (+ or 20) Psig20) Psig

Low Pressure Control (Depends upon Manufacturer)Low Pressure Control (Depends upon Manufacturer) Its function is to unload the compressor, once Suction /Its function is to unload the compressor, once Suction /

Evaporator pressure decreases to pre set pressure. Some timeEvaporator pressure decreases to pre set pressure. Some timeused to switch off the compressor.used to switch off the compressor.

Set PointSet Point Cut out 30 (+ orCut out 30 (+ or -- 5) Psig with R5) Psig with R--22 refrigerant.22 refrigerant.

Cut In 45 (+ orCut In 45 (+ or 5) Psig.5) Psig.



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Low Water Temperature ControlLow Water Temperature Control

Its function is to stop the refrigeration by stopping the compreIts function is to stop the refrigeration by stopping the compressor, oncessor, onceevaporator water temperature goes down below Set point so as toevaporator water temperature goes down below Set point so as to avoidavoidfreezing of water in the evaporator of chiller. Some time, it isfreezing of water in the evaporator of chiller. Some time, it is called ascalled as

AntiAnti--Freeze.Freeze.

Set Point 34 to 36Set Point 34 to 36 oo FF

Low Refrigerant Temperature ControlLow Refrigerant Temperature Control

It is used for not allowing the refrigerant temperature to go bIt is used for not allowing the refrigerant temperature to go below Setelow Setpoint, so as to avoid freezing of water and as well as loosing tpoint, so as to avoid freezing of water and as well as loosing theheefficiency of chiller.efficiency of chiller.

Flow ControlFlow Control

Its function is to ensure the adequate water flow through evapoIts function is to ensure the adequate water flow through evaporator.rator.Once flow decreases below set point, The switch will actuate andOnce flow decreases below set point, The switch will actuate and givegivealarm / stop signal to control panel, to avoid lower water tempealarm / stop signal to control panel, to avoid lower water temperature orrature orfreezing of water in evaporatorfreezing of water in evaporator



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Oil pressure differential switchOil pressure differential switch

It is used to ensure proper lubrication of bearingsIt is used to ensure proper lubrication of bearingsand other moving parts of compressor. To ensureand other moving parts of compressor. To ensureproper lubrication, a pressure difference is to beproper lubrication, a pressure difference is to bemaintained between oil pump pressure and crankmaintained between oil pump pressure and crankcase pressure. Once Differential pressure is lowercase pressure. Once Differential pressure is lower

than the preset differential pressure, It will actuatethan the preset differential pressure, It will actuateand alarm /stop the compressor operation.and alarm /stop the compressor operation.

Set pointSet point 6 to 10 Psig6 to 10 Psig-- DifferentialDifferential

Ground Current SafetyGround Current Safety

It opens on sensing a current to ground inIt opens on sensing a current to ground incompressor winding exceeds the 2.5 Amps.compressor winding exceeds the 2.5 Amps.



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In Adequate air flow thru condenserIn Adequate air flow thru condenser

Condensing Pressure will increase.Condensing Pressure will increase.

Load on compressor increases.Load on compressor increases.

Power consumption will increase.Power consumption will increase. Cooling capacity will reduce.Cooling capacity will reduce.

Leaving chilled water temperature will remain high.Leaving chilled water temperature will remain high.

Inadequate chilled water flow through evaporatorInadequate chilled water flow through evaporator Low suction pressure & Low evaporating temperature.Low suction pressure & Low evaporating temperature.

Liquid floodLiquid flood--back to compressor and may damageback to compressor and may damagecompressor discharge reeds (In Reciprocating compressor).compressor discharge reeds (In Reciprocating compressor).

May damage the Helical of screw compressor.May damage the Helical of screw compressor. Ice formation may occur and burst the evaporator.Ice formation may occur and burst the evaporator.

Cut out 30 (+ orCut out 30 (+ or -- 5) Psig with R5) Psig with R--22 refrigerant.22 refrigerant.

Cut In 45 (+ orCut In 45 (+ or 5) Psig.5) Psig.



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p gp g

NonNon-- Condensable gases in the systemCondensable gases in the system

Condensing Pressure will be high.Condensing Pressure will be high.

Load on compressor increases and compressorLoad on compressor increases and compressorwill be very hot.will be very hot.

Power consumption will be high.Power consumption will be high.

Cooling capacity will reduce.Cooling capacity will reduce.

Leaving chilled water temperature will remainLeaving chilled water temperature will remainhigh.high.

Poor cooling in conditioned space.Poor cooling in conditioned space.

Refrigerant ChargeRefrigerant Charge


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g gg g

Less chargeLess charge Compressor suction pressure will be low.Compressor suction pressure will be low.

Evaporator pressure and temperature will be low.Evaporator pressure and temperature will be low.

Heavy flashing and ice formation will occur at expansionHeavy flashing and ice formation will occur at expansionvalve, as a result lesser liquid refrigerant shall be availablevalve, as a result lesser liquid refrigerant shall be available

for actual refrigeration.for actual refrigeration.

BeingBeing low evaporator pressure & temperature, Any moisturelow evaporator pressure & temperature, Any moisture

present in refrigerant will freeze expansion valve orifice andpresent in refrigerant will freeze expansion valve orifice andrestrict the refrigerant flow.restrict the refrigerant flow.

Lower cooling capacity.Lower cooling capacity.

Over chargeOver charge

Higher head pressure and higher suction pressure.Higher head pressure and higher suction pressure. Load on compressor, will draw more current andLoad on compressor, will draw more current and

unnecessary High power consumption.unnecessary High power consumption.

Liquid flood back to compressor and can damage dischargeLiquid flood back to compressor and can damage dischargereeds.reeds.


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Centrifugal ChillersCentrifugal Chillers


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Working Of centrifugal Chiller


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(With Centrifugal Compressor(With Centrifugal Compressor))

Centrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal Chiller


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Centrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal ChillerCentrifugal Chiller

(Water Cooled)(Water Cooled)(Water Cooled)(Water Cooled)(Water Cooled)(Water Cooled)(Water Cooled)(Water Cooled)

Centrifugal CompressorCentrifugal Compressor

CondenserCondenser

--Shell & TubeShell & Tube

Orifice AssemblyOrifice Assembly--11

EconomizerEconomizer

Orifice AssemblyOrifice Assembly--22 Flooded EvaporatorFlooded Evaporator

Lubrication SystemLubrication System

Motor Cooling SystemMotor Cooling System Control PanelControl Panel

StarterStarter

ControlsControls


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CompressorCompressorCompressorCompressorCompressorCompressorCompressorCompressor


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CompressorCompressorCompressorCompressoreeee

Compressor &Compressor &

Motor casing.Motor casing. IIstst stage impellerstage impeller

IIIIndnd stage impellerstage impeller

Volute casingsVolute casings

Thrust bearingThrust bearing

Journal bearingsJournal bearings

High speed gearsHigh speed gearsassembly Inner oilassembly Inner oil

guardsguards

Gear spray nozzlesGear spray nozzles Motor stator & rotorMotor stator & rotor

Suction inlet guideSuction inlet guide

vane & actuatorvane & actuator

Orifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice Assembly


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Orifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice AssemblyOrifice Assembly

It is a assembly of twoIt is a assembly of twoplates having nos. ofplates having nos. of

orificesorifices

Liquid refrigerantLiquid refrigerant

pressure reduces whilepressure reduces while

passing thru it.passing thru it.

Refrigerant flowRefrigerant flow

controlled based oncontrolled based ondifferential pressuredifferential pressure..

Orifice

From Condenser To Evaporator


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This is a intermediate pressure chamber in whichThis is a intermediate pressure chamber in which

a intermediate pressure (Second stage suctiona intermediate pressure (Second stage suction

pressure) is maintained.pressure) is maintained.

The high pressure liquid refrigerant enters intoThe high pressure liquid refrigerant enters into

economizer through orifice plate assembly.Whileeconomizer through orifice plate assembly.While

liquid passing thru orifice assembly,a portion of itliquid passing thru orifice assembly,a portion of it

evaporates (flashes) by absorbing heat fromevaporates (flashes) by absorbing heat from

remaining liquid refrigerant and thus remainingremaining liquid refrigerant and thus remaining

liquid gets cooled.liquid gets cooled.

Evaporated refrigerant goes directly to 2nd stageEvaporated refrigerant goes directly to 2nd stage

impeller for recycling.impeller for recycling.


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Oil SumpOil Sump

Oil HeaterOil Heater

Sight glassSight glass

ThermometerThermometer

Submersible OilSubmersible OilPumpPump

Oil PressureOil Pressure

regulatorregulator

Oil cooling coilOil cooling coil

Oil Filter & IsolatingOil Filter & Isolatingvalvevalve

Oil by pass valvesOil by pass valves

Oil pipingOil piping

TemperatureTemperature

sensorssensors

Motor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling System


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Motor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling SystemMotor Cooling System

The hermetic motor are cooled by liquidThe hermetic motor are cooled by liquid

refrigerant.refrigerant.Liquid refrigerant enters the motor housing thruLiquid refrigerant enters the motor housing thru

an orifice and flows into a chamber surroundingan orifice and flows into a chamber surrounding

the stator.the stator.The refrigerant flows from this chamber thru theThe refrigerant flows from this chamber thru the

motor stator,thus cooling the stator and rotor.motor stator,thus cooling the stator and rotor.

Liquid refrigerant evaporates by absorbing heatLiquid refrigerant evaporates by absorbing heatfrom stator and rotor.from stator and rotor.

Finally Liquid & vapor mixture drain back toFinally Liquid & vapor mixture drain back to

evaporator thru bottom pipes.evaporator thru bottom pipes.

Electrical SystemElectrical SystemElectrical SystemElectrical SystemElectrical SystemElectrical SystemElectrical SystemElectrical System


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Starter panelStarter panel

SwitchesSwitches FusesFuses

TransformerTransformer

StarStar--Delta starter forDelta starter forcompressor motorcompressor motor

DOL / StarDOL / Star--DeltaDelta

starter for fansstarter for fansOverload relaysOverload relays

TimersTimers

ContractorsContractors

Control panelControl panel

Control switchControl switch Control TransformerControl Transformer

FusesFuses

RelaysRelays

Microprocessor modulesMicroprocessor modules

Unit control modulesUnit control modules

TimersTimers

AntiAnti--Recycle TimerRecycle Timer

Coast down TimerCoast down Timer

Safety switches (Outside)Safety switches (Outside)


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Flow SwitchesFlow SwitchesFlow SwitchesFlow SwitchesFlow SwitchesFlow SwitchesFlow SwitchesFlow Switches

It is a combination of Microprocessor andIt is a combination of Microprocessor and

Flow sensor.Flow sensor.Function is to give alarm or stop signal toFunction is to give alarm or stop signal to

chiller once flow reduces below set point.chiller once flow reduces below set point.

Setting in % (Minimum 50 %).Setting in % (Minimum 50 %).Shall give alarm signal to BMS at alarmShall give alarm signal to BMS at alarm

setting.setting.

Shall stop the chiller at stop setting.Shall stop the chiller at stop setting.Modulate Chiller capacity suit toModulate Chiller capacity suit to

temperature outlet.temperature outlet.


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Low Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out Switch


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Low Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLow Pressure cut out SwitchLo essu e cu ou S cLow Pressure cut out SwitchLow Pressure cut out SwitchLo essu e cu ou S c

It is a combination ofIt is a combination of

microprocessor and sensor.microprocessor and sensor.Some times it is a pressure switch.Some times it is a pressure switch.

The function is to give alarm / stopThe function is to give alarm / stop

signal to compressor once thesignal to compressor once theevaporator pressure reduces below theevaporator pressure reduces below theset point.set point.

Set pointSet pointCut out 2.0 bar (RCut out 2.0 bar (R--12 & R12 & R--134a)134a)

Cut in 2.3 to 2.4 barCut in 2.3 to 2.4 bar

Winding Temperature SensorsWinding Temperature SensorsWinding Temperature SensorsWinding Temperature SensorsWinding Temperature SensorsWinding Temperature SensorsWinding Temperature SensorsWinding Temperature Sensors


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It is a combination of microprocessor andIt is a combination of microprocessor andsensor.sensor.

A sensor sense the temperature and giveA sensor sense the temperature and givesignal to microprocessor.signal to microprocessor.

Microprocessor compares this signal withMicroprocessor compares this signal withset point and give out put command toset point and give out put command tostop the compressor if temperature isstop the compressor if temperature ishigher than set point.higher than set point.

Set point 265 deg F.Set point 265 deg F. Will Stop Motor once motor temperatureWill Stop Motor once motor temperature

rises to set point and will give alarm signalrises to set point and will give alarm signal

to BMS.to BMS.

Current LimiterCurrent LimiterCurrent LimiterCurrent LimiterCurrent LimiterCurrent LimiterCurrent LimiterCurrent Limiter


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e L ee L ee L ee L e

Its function is to limit the currentIts function is to limit the current

drawn by motor within set point.drawn by motor within set point. Set point 85Set point 85--95 % of full load95 % of full load

amperes.amperes.

It will unload the compressor byIt will unload the compressor byclosing the suction vane damper andclosing the suction vane damper andover ride all inputs / feed back for:over ride all inputs / feed back for:

Opening the vane dampers .Opening the vane dampers .

Increasing the load on compressorIncreasing the load on compressor

Critical FactorsCritical FactorsCritical FactorsCritical FactorsCritical FactorsCritical FactorsCritical FactorsCritical Factors(Evaporator)(Evaporator)(Evaporator)(Evaporator)(Evaporator)(Evaporator)(Evaporator)(Evaporator)


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Soft & Clean water.Soft & Clean water.

Cleaned tubes.Cleaned tubes.

Adequate chilled water flow.Adequate chilled water flow.

Adequate refrigerant flow.Adequate refrigerant flow.

Sensors are fitted properly.Sensors are fitted properly.

Application of Silicon grease orApplication of Silicon grease or

alternative heat transfer paste.alternative heat transfer paste.Chilled water temperatures as designed.Chilled water temperatures as designed.

Critical FactorsCritical FactorsCritical FactorsCritical FactorsCritical FactorsCritical FactorsCritical FactorsCritical Factors


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(Motor Cooling System)(Motor Cooling System)(Motor Cooling System)(Motor Cooling System)(Motor Cooling System)(Motor Cooling System)(Motor Cooling System)(Motor Cooling System)

Adequate liquid refrigerant flowAdequate liquid refrigerant flow

Strainer (Filter cum drier)Strainer (Filter cum drier) Adjustment of Service valvesAdjustment of Service valves

Design condenser pressureDesign condenser pressure

Design evaporator pressureDesign evaporator pressure

ProblemProblemProblemProblemProblemProblemProblemProblem

Higher motor temperatureHigher motor temperature


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System BalanceSystem Balance a)a)CompressorCompressor-- Able to pump refrigerant at same rate atAble to pump refrigerant at same rate atwhich liquid ref. vaporizes in evaporatorwhich liquid ref. vaporizes in evaporator

b)Condenserb)Condenser-- Able to reject heat from ref.at same rate atAble to reject heat from ref.at same rate atwhich ii picks up heat in evaporator and compressorwhich ii picks up heat in evaporator and compressor

c)Throttlingc)Throttlingdevicedevice-- Able to feed liquid ref.to evaporator atAble to feed liquid ref.to evaporator atsame rate at which the refrigerant is vaporized in thesame rate at which the refrigerant is vaporized in the

evaporatorevaporator Interconnecting liquid, suction and suction linesInterconnecting liquid, suction and suction lines-- capablecapable

of handling the same rate of flow of liquid ref, lowof handling the same rate of flow of liquid ref, low

pressure vapor and high pressure vapour with a minimumpressure vapor and high pressure vapour with a minimumof pressure dropof pressure drop

Capacity controlCapacity control


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p y

ReciprocatingReciprocating

compressorcompressorVariable speed motorVariable speed motor

Compressor cylinderCompressor cylinder

unloadingunloadingHotgasHotgas bypassbypass

Centrifugal compressorCentrifugal compressor

Guide vanes (inlet ofGuide vanes (inlet ofimpeller )impeller )

Screw compressorScrew compressor

Slide valve methodSlide valve methodLift valve methodLift valve method

LubricationLubrication


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Adequate Oil ChargeAdequate Oil Charge Manufacturer recommended oil should be used.Manufacturer recommended oil should be used.

Recommended quantity of oil should be charged.Recommended quantity of oil should be charged.

Lubricating oil container should never be left open.Lubricating oil container should never be left open. Excess ChargeExcess Charge

Can cause hydraulic knocking and damage the pistons.Can cause hydraulic knocking and damage the pistons.

It will be difficult to monitor the lubrication system.It will be difficult to monitor the lubrication system. Under ChargeUnder Charge

Oil pump will not be able to build up the pressure.Oil pump will not be able to build up the pressure.

Poor lubrication will damage the moving parts ofPoor lubrication will damage the moving parts ofcompressor.compressor.

Centrifugal ChillerCentrifugal ChillerControlsControls

Flow switches / Flow Sensor & Microprocessor CombinationFlow switches / Flow Sensor & Microprocessor Combination


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It is a combination of Microprocessor and Flow sensor.It is a combination of Microprocessor and Flow sensor. Function is to give alarm or stop signal to chiller once flow reFunction is to give alarm or stop signal to chiller once flow reducesduces

below set point.below set point.

Setting in % (Minimum 50 %).Setting in % (Minimum 50 %).

Shall give alarm signal to BMS at alarm setting.Shall give alarm signal to BMS at alarm setting.

Shall stop the chiller at stop setting.Shall stop the chiller at stop setting.

Modulate Chiller capacity suit to temperature outlet.Modulate Chiller capacity suit to temperature outlet.

Oil Differential Pressure SwitchOil Differential Pressure Switch

Its function is to stop chiller once differential pressure betweIts function is to stop chiller once differential pressure between oilen oilsupply and compressor casing reduces below the differential setsupply and compressor casing reduces below the differential set point.point.

Normally set at 1.0 bar to 1.5 bar differential.Normally set at 1.0 bar to 1.5 bar differential.

Shall give Alarm signal to BMS at Alarm setting.Shall give Alarm signal to BMS at Alarm setting.

Will stop Chiller if differential pressure below set poinWill stop Chiller if differential pressure below set pointt



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High Oil Temperature SensorHigh Oil Temperature Sensor It is a combination of microprocessor and sensor or some time itIt is a combination of microprocessor and sensor or some time it is ais a

Temperature switch.Temperature switch.

The function is to give alarm / stop signal to compressor once oThe function is to give alarm / stop signal to compressor once oilil

temperature increases above set point.temperature increases above set point. Set point 180Set point 18000 F.F.

Will give alarm signal to BMS on rising oil temperature above seWill give alarm signal to BMS on rising oil temperature above settpoint.point.

May stop compressor if control circuit is made accordingly.May stop compressor if control circuit is made accordingly. High Pressure ControlHigh Pressure Control

t is a combination of microprocessor and pressure sensor.t is a combination of microprocessor and pressure sensor.

In some Chillers, it is a Pressure switch.In some Chillers, it is a Pressure switch.

The function is to give alarm / stop signal to compressor onceThe function is to give alarm / stop signal to compressor once thethedischarge pressure increases to set point.discharge pressure increases to set point.

Set point 12.0 to 12.5 (RSet point 12.0 to 12.5 (R--12) and 15.0 (R12) and 15.0 (R--134a).134a).


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Chilled Water Temperature ControlChilled Water Temperature Control

It is a combination of Microprocessor and Temperature Sensor.It is a combination of Microprocessor and Temperature Sensor.

A sensor (installed in the outlet pipe of Evaporator) senses theA sensor (installed in the outlet pipe of Evaporator) senses the leaving chilledleaving chilled

water temperature and gives temperature signal to microprocessorwater temperature and gives temperature signal to microprocessor..

The Microprocessor compares this temperature signal with set temThe Microprocessor compares this temperature signal with set temperature.perature. According to difference, Microprocessor give output command to vAccording to difference, Microprocessor give output command to vane controlane control

modulating motor, either for closing or opening the vane to modmodulating motor, either for closing or opening the vane to modulate the flowulate the flowof refrigerant. Thus by it controls the capacity of Chiller.of refrigerant. Thus by it controls the capacity of Chiller.

Set Temperature generally 41 to 46Set Temperature generally 41 to 46

oo

FF Motor Winding Temperature SensorsMotor Winding Temperature Sensors

It is a combination of microprocessor and sensor.It is a combination of microprocessor and sensor.

A sensor sense the temperature and give signal to microprocessoA sensor sense the temperature and give signal to microprocessor.r.

Microprocessor compares this signal with set point and give outMicroprocessor compares this signal with set point and give out put commandput command

to stop the compressor if temperature is higher than set point.to stop the compressor if temperature is higher than set point.

Set point 265 deg F.Set point 265 deg F.

Will Stop Motor once motor temperature rises to set point andWill Stop Motor once motor temperature rises to set point and will give alarmwill give alarm

signal to BMSsignal to BMS


M t O L d P t tiM t O L d P t ti


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Motor Over Load ProtectionMotor Over Load Protection Its function is to protect compressor motor againstIts function is to protect compressor motor against

overloading.overloading.

Set point 95Set point 95--100 % full load Amperes.100 % full load Amperes.

It will stop compressor motor, once current drawn byIt will stop compressor motor, once current drawn bymotor increases to set point and remain for more than 30motor increases to set point and remain for more than 30--40 second.40 second.

Alarm signal will be given to BMS once it actuates.Alarm signal will be given to BMS once it actuates.

Current LimiterCurrent Limiter Its function is to limit the current drawn by motorIts function is to limit the current drawn by motorwithin set point.within set point.

Set point 80Set point 80--90 % of full load current.90 % of full load current.

It will unload the compressor by closing the suctionIt will unload the compressor by closing the suctionvane damper, and over ride all inputs for opening thevane damper, and over ride all inputs for opening thevane dampers for increasing the load on compressorvane dampers for increasing the load on compressor..


A ti RA ti R l Til Ti


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Anti ReAnti Re--cycle Timercycle Timer Its function is to ensure that chiller reIts function is to ensure that chiller re--start is not taking place before thestart is not taking place before the

Set time.Set time.

Once chiller stops either from controls or manually, It should nOnce chiller stops either from controls or manually, It should not take reot take re--start before a time recommended by manufacturer for the safety ostart before a time recommended by manufacturer for the safety off

Compressor & MotorCompressor & Motor.. Set time generally 15Set time generally 15 --20 Minutes.20 Minutes.

Coast Down TimerCoast Down Timer

Its function is to ensure that the Oil Pump is running for a cerIts function is to ensure that the Oil Pump is running for a certain periodtain period

even after chiller is given stop command either by controls or Meven after chiller is given stop command either by controls or Manualanualstop.stop.

As chiller has been given stop command either by controls or manAs chiller has been given stop command either by controls or manualualstop, The motor & impeller keeps rotating for some time due to istop, The motor & impeller keeps rotating for some time due to inertia.nertia.During this period, it is essential to provide lubrication to beDuring this period, it is essential to provide lubrication to bearing andaring and

rotating parts of Compressor & Motor.rotating parts of Compressor & Motor. Set time generally 3 minutesSet time generally 3 minutes (It is the time, Motor / Impeller takes in(It is the time, Motor / Impeller takes in

coming to idle condition after giving stop command).coming to idle condition after giving stop command).

PrePre--start Checksstart Checks

Check oil sump temperatureCheck oil sump temperature

Should beShould be 6060oo 7070oo CC

Start upStart up --ChillerChiller

Place system switch inPlace system switch in OFFOFF

positionposition Pl l h A O


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Should beShould be 6060oo -- 7070oo C.C.

Check oil levelCheck oil level

Should be visible 1/ 4 to 3/4 inShould be visible 1/ 4 to 3/4 in

lower glass.lower glass.

Check system pressureCheck system pressure

Should be below 8 Bar.Should be below 8 Bar.

Physical checkPhysical check -- CondenserCondenser

Check condenser fan and fanCheck condenser fan and fanbelts.belts.

Check chilled water flowCheck chilled water flow

Control panel reading (Control panel reading (

Microprocessor & Flow Sensor)Microprocessor & Flow Sensor)

Pressure drop methodPressure drop method

position.position. Place oil pump switch inPlace oil pump switch in AUTOAUTO

position.position.

Close the main disconnect switchClose the main disconnect switch(Make(Make ONON).).

Operate oil pump and fans onOperate oil pump and fans on

ManualManual to check operation.to check operation. Set the current limiterSet the current limiter %%

CurrentCurrent..

Suggest to setSuggest to set 75 to 80 %75 to 80 % initiallyinitiallyoror MinimumMinimum..

Set theSet the

Control TemperatureControl Temperature

atat

desired temperature.desired temperature.

Reset the safety controls or circuitReset the safety controls or circuitbreaker.breaker.

Place thePlace the Vane PositionVane Position switchswitchinin AutoAuto position.position.

Start Chiller by Putting the systemStart Chiller by Putting the systemswitch inswitch in ONON PositionPosition

Daily Operation Checks (Log Recommended by Manufacturer)

Parameter Normal operation Reading Actual Reading Actual reading

Ambient Condition DB & WB


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Chilled water Temperature Entering Leaving Temp Drop

Chilled water pressure Entering Leaving Pressure drop

Condenser Water Temperature Entering Leaving Temp. Rise

Condenser Water Pressure Entering Leaving Pressure drop

Evaporator Pressure

Discharge Pressure

oil pressureSupply to BearingsReturn from bearing

oil TemperatureSupply to BearingsReturn From bearing

Sump oil Temperature

% Vane opening

Amperes

Abnormal Sound or Noise

Maintenance (Weekly)Maintenance (Weekly)

Check Sump oil levelCheck Sump oil level Maintenance (Monthly)Maintenance (Monthly)

Perform weekly checksPerform weekly checks


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Check Sump oil level.Check Sump oil level. Oil should be visible inOil should be visible in

lower site glass.lower site glass.

Check liquid line siteCheck liquid line site

glasses.glasses. Check unit piping and coilsCheck unit piping and coils

for visible signs of leaks.for visible signs of leaks.

Listen and observe theListen and observe the

operation of the chiller foroperation of the chiller forusual sounds.usual sounds.

Check all operatingCheck all operatingpressure and temperaturepressure and temperature

againstagainst normal operatingnormal operatingcondition.condition.

Perform weekly checks.Perform weekly checks.

Check fan belt tension andCheck fan belt tension andwear.wear.

Check fan and fan motor forCheck fan and fan motor for

lubrication.lubrication. Check condenser condition,Check condenser condition,

If required clean the coil byIf required clean the coil by NUNU--coil/ calcoil/ cal--clean.clean.

Or follow individualOr follow individualmanufacturer recommendation.manufacturer recommendation.

Maintenance (Annual)Maintenance (Annual)

MechanicalMechanical

Perform weekly & monthlyPerform weekly & monthly ElectricalElectrical

Check physical condition ofCheck physical condition of


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Perform weekly & monthlyPerform weekly & monthlyinspection checks.inspection checks.

Clean the condenser coil byClean the condenser coil byrecommended chemical.recommended chemical.

Straighten the fins by NylonStraighten the fins by Nyloncomb.comb.

Change oil by approved oilChange oil by approved oilonly.only.

Be doubly sure about oilBe doubly sure about oil

quality and storage time.quality and storage time. Change oil filter.Change oil filter.

Check and change theCheck and change theliquid line filter of motorliquid line filter of motorcooling system.cooling system.

Clean the chilled water inletClean the chilled water inletstrainerstrainer

Check physical condition ofCheck physical condition ofthe components in starterthe components in starterpanel.panel.

Check physical conditionCheck physical condition

of all actuating components.of all actuating components. Terminal & Lugs condition.Terminal & Lugs condition.

Clean the contactor byClean the contactor byCommercial carbon tetraCommercial carbon tetrachloridechloride (CCL 100)(CCL 100) oror

equivalent.equivalent. Check for loose connection.Check for loose connection.

Check sensors.Check sensors.

Fill the conductive liquid inFill the conductive liquid in

thermothermo --well, if required.well, if required.

Periodic ChecksPeriodic Checks Leak checkLeak check

Purge operationPurge operation

System drynessSystem dryness L b i t l lL b i t l l

Inspection of starter contacts andInspection of starter contacts and

actionaction


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System drynessSystem dryness Lubricant levelLubricant level

Lubricant filter pressure dropLubricant filter pressure drop

Refrigerant quantity or levelRefrigerant quantity or levelSystemSystem pressures andpressures and

temperaturestemperatures Water flowsWater flows

Expansion valves operationExpansion valves operation

RegularlyRegularly Scheduled MaintenanceScheduled Maintenance

CondenserCondenser and lubricant coolerand lubricant coolercleaningcleaning

EvaporatorEvaporator cleaning on opencleaning on opensystemssystems

CalibratingCalibrating pressure, temperature,pressure, temperature,and flow controlsand flow controls

TighteningTightening wires and powerwires and power

connectionsconnections

actionaction Safety interlocksSafety interlocks Dielectric checking of hermetic andDielectric checking of hermetic and

open motorsopen motors Tightness of hot gas valveTightness of hot gas valve Lubricant filter and drier changeLubricant filter and drier change

AnalysisAnalysis of lubricant and refrigerantof lubricant and refrigerant Seal inspectionSeal inspection Partial or complete valve or bearingPartial or complete valve or bearing

inspection, as per manufacturerinspection, as per manufacturerssrecommendationsrecommendations

Vibration levelsVibration levels

Extended Maintenance ChecksExtended Maintenance ChecksCompressorCompressor guide vanes and linkageguide vanes and linkage

operation and wearoperation and wearEddyEddy current inspection of heatcurrent inspection of heat

exchanger tubesexchanger tubesCompressorCompressor teardown andteardown and

inspection of rotating componentsinspection of rotating components Other components asOther components as

recommended by manufacturerecommended by manufacture

Screw ChillersScrew Chillers


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Screw ChillersLiquid Chilling SystemLiquid Chilling System

A liquid chilling system cools water, brine,A liquid chilling system cools water, brine,or other secondary coolant for airor other secondary coolant for air

conditioning or refrigerationconditioning or refrigeration..

The system may be either factoryThe system may be either factoryassembled and wired or shipped inassembled and wired or shipped in

sections for erection in the field.sections for erection in the field.

Twin Screw Compressors


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Twin Screw Compressors

ComponentsComponents

of chillersof chillers


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Components of chillers Compressor (reciprocating, centrifugal orCompressor (reciprocating, centrifugal or

rotary),rotary),

Liquid cooler (evaporator),Liquid cooler (evaporator),

Condenser, a compressor drive, a liquidCondenser, a compressor drive, a liquid

refrigerant expansion or flowrefrigerant expansion or flow--controlcontroldevice, and a control center.device, and a control center.


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EconomizerEconomizerEconomizer is a separate vesselEconomizer is a separate vessel

containing the Electronic Expansioncontaining the Electronic Expansionvalve and a float valvevalve and a float valve

PurposesPurposes

It improves chiller capacity andIt improves chiller capacity andefficiencyefficiency

It provides compressor motor coolingIt provides compressor motor cooling


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Screw CompressorsScrew Compressors


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Both are conventionally used with fluidBoth are conventionally used with fluid

injection where sufficient fluid cools andinjection where sufficient fluid cools and

seals the compressorseals the compressor..

Screw compressors have the capability toScrew compressors have the capability to

operate at pressure ratios above 20:1operate at pressure ratios above 20:1

single stage.single stage.

The capacity range currently available isThe capacity range currently available is

from 20 to 1300 tonsfrom 20 to 1300 tons


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Single Screw Compressor


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Sequence of CompressionSequence of Compression


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SSuctionuction

CompressionCompression

DDischargeischarge

Compressor rotationCompressor rotation


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Compressor rotationCompressor rotationCompressor rotation in ScrewCompressor rotation in Screw

compressor is extremely importantcompressor is extremely importantOperation in the opposite direction, evenOperation in the opposite direction, even

momentarily, can cause serious rotormomentarily, can cause serious rotor

damage and must be avoideddamage and must be avoided

Mechanical FeaturesMechanical Features


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RotorsRotors

The screw rotor is normally made of castThe screw rotor is normally made of castironiron and the mating gate rotors are madeand the mating gate rotors are made

from an engineered plastic.from an engineered plastic.

The inherent lubricating quality of the plastic,The inherent lubricating quality of the plastic,as well as its compliant nature, allow theas well as its compliant nature, allow the

singlesingle--screw compressor to achieve closescrew compressor to achieve close

clearances with conventional manufacturingclearances with conventional manufacturing

practice.practice.

Mechanical FeaturesMechanical Features


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RotorsRotors

BearingsBearings EconomizersEconomizers

Economizers


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Hermetic CompressorsHermetic Compressors


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Hermetic screw compressors areHermetic screw compressors arecommercially available through 200 tons ofcommercially available through 200 tons of

refrigeration effect using Rrefrigeration effect using R--22. The hermetic22. The hermetic

motors can operate under discharge, suction,motors can operate under discharge, suction,

or intermediate pressure. Motor cooling canor intermediate pressure. Motor cooling canbe with gas, oil, and/or liquid refrigerant. Oilbe with gas, oil, and/or liquid refrigerant. Oil

separation for these types of compressorsseparation for these types of compressors

may be accomplished either with anmay be accomplished either with an

integrated oil separator or with a separatelyintegrated oil separator or with a separatelymounted oil separator in the systemmounted oil separator in the system..

Capacity ControlCapacity Control


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All positiveAll positive--displacement compressors, bothdisplacement compressors, both

speed modulation and suction throttling can bespeed modulation and suction throttling can be

used. Ideal capacity modulation for anyused. Ideal capacity modulation for anycompressor includescompressor includes

Continuous modulation from 100% to less thanContinuous modulation from 100% to less than

10%,10%,

Good partGood part--load efficiencyload efficiency

Unloaded startingUnloaded starting

Unchanged reliabilityUnchanged reliability

TwinTwin--screw compressorsscrew compressors


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Twin screw is the common designation forTwin screw is the common designation fordouble helical rotary screw compressors.double helical rotary screw compressors.

A twinA twin--screw compressor consists of twoscrew compressor consists of twomating helically grooved rotorsmating helically grooved rotors--malemale(lobes) and female (flutes or gullies) in a(lobes) and female (flutes or gullies) in a

stationary housing with inlet and outletstationary housing with inlet and outletgas ports.gas ports.

The flow of gas in the rotors is mainly inThe flow of gas in the rotors is mainly inan axial directionan axial direction

Sequence of Compression Process inSequence of Compression Process in

Twin Screw CompressorTwin Screw Compressor


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SuctionSuction

CompressionCompression DischargeDischarge

LubricantLubricant

b i i l d b f h f ll i h d


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Lubricant is cooled by one of the following methodsLubricant is cooled by one of the following methods

WaterWater--cooled using condenser water, evaporative condensercooled using condenser water, evaporative condenser

sump water, chilled water, or a separate watersump water, chilled water, or a separate water-- or glycolor glycol--toto--air cooling loopair cooling loop

AirAir--cooled using a lubricantcooled using a lubricant--toto--air heat exchangerair heat exchanger

RefrigerantRefrigerant--cooled (where lubricant cooling load is low)cooled (where lubricant cooling load is low)

Liquid injection into the compressorLiquid injection into the compressor Condensed refrigerant liquid thermal recirculationCondensed refrigerant liquid thermal recirculation

(thermosyphon), where appropriate, compressor head(thermosyphon), where appropriate, compressor head

pressure is availablepressure is available

Oil separatorsOil separators


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Efficient lubricant separators areEfficient lubricant separators are

required. The types and efficienciesrequired. The types and efficienciesof these separators vary according toof these separators vary according to

refrigerant and application. Fieldrefrigerant and application. Field

built systems requires better built systems requires betterseparation than complete factoryseparation than complete factory--

built systemsbuilt systems


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MotorComp

Control

Air cooled condenser

SCREW.CH.FLOW CYCLE


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Oil separator

Oil cooler

StrainerOil pump

Control

Evaporator

Filter coreReceiver

MotorComp

control


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Oil separator

oil cooler

strainer

oil pump

oil filtersGauge

Gaugecontrol

CAPACITY CONTROL

LUBRICATION SYSTEM

Capacities and Types AvailableCapacities and Types Available

Screw compressor liquid chillers are available as factoryScrew compressor liquid chillers are available as factory


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Screw compressor liquid chillers are available as factoryScrew compressor liquid chillers are available as factory--

packaged units from about 30 to 1250 Tons.packaged units from about 30 to 1250 Tons.

The following types of liquid chillers are generally used for aiThe following types of liquid chillers are generally used for airrconditioning:conditioning:

Up to 25 tonsUp to 25 tons Reciprocating or scrollReciprocating or scroll

25 to 80 tons25 to 80 tons Screw, reciprocating, or scrollScrew, reciprocating, or scroll

80 to 450 tons80 to 450 tons Screw, reciprocating, or centrifugalScrew, reciprocating, or centrifugal 200 to 1000 tons200 to 1000 tons Screw or centrifugalScrew or centrifugal

Above 1000 tonsAbove 1000 tons CentrifugalCentrifugal

Safety controlsSafety controls


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Lubricant failure switch,Lubricant failure switch, High discharge pressure cutout,High discharge pressure cutout,

Low suction pressure switch,Low suction pressure switch,

Cooler flow switch,Cooler flow switch,

High lubricant and discharge temperature cutout,High lubricant and discharge temperature cutout,

Hermetic motor inherent protection,Hermetic motor inherent protection,

Lubricant pump and compressor motor overloads,Lubricant pump and compressor motor overloads,

andand

Low lubricant temperature (flood back/dilutionLow lubricant temperature (flood back/dilutionprotection).protection).


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Starting of Screw compressorStarting of Screw compressor

The current limit relay protects against motorThe current limit relay protects against motor


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The current limit relay protects against motorThe current limit relay protects against motoroverload from higher than normal condensingoverload from higher than normal condensing

temperatures or lowtemperatures or low--voltage and also allows avoltage and also allows ademand limit to be set, if desired. An antire cycledemand limit to be set, if desired. An antire cycletimer is used to prevent overly frequenttimer is used to prevent overly frequentrecycling. Lubricant sump heaters are energizedrecycling. Lubricant sump heaters are energizedduring the off cycle. A hot gas capacity control isduring the off cycle. A hot gas capacity control isoptionally available and prevents automaticoptionally available and prevents automaticrecycling at norecycling at no--load conditions such as is oftenload conditions such as is oftenrequired in process liquid chilling. A suction torequired in process liquid chilling. A suction todischarge starting bypass sometimes aids startingdischarge starting bypass sometimes aids starting

and allows the use of standard starting torqueand allows the use of standard starting torquemotors.motors.

Starting of Screw compressorStarting of Screw compressor

Some units are equipped with electronicSome units are equipped with electronic


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Some units are equipped with electronicSome units are equipped with electronicregulators specially developed for theregulators specially developed for the

screw compressorscrew compressor These regulators include PI controlThese regulators include PI control

(Proportional(Proportional--Integrating) of the leavingIntegrating) of the leaving

brine temperature and such functions as brine temperature and such functions asautomatic/manual control, capacityautomatic/manual control, capacityindication, time circuits to preventindication, time circuits to preventfrequent recycling and to bypass thefrequent recycling and to bypass the

lubricant pressure cutout during startup,lubricant pressure cutout during startup,switch for unloaded starting, etc.switch for unloaded starting, etc.

Inspection or change outInspection or change out

timetabletimetable


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Shaft seals 1.5 to 4 yr InspectShaft seals 1.5 to 4 yr Inspect

Hydraulic cylinder seals 1.5 to 4 yrHydraulic cylinder seals 1.5 to 4 yr

ReplaceReplace

Thrust bearings 4.0 to 6 yrThrust bearings 4.0 to 6 yr

Shaft bearings 7 to 10 yr InspectShaft bearings 7 to 10 yr Inspect

Check preload via shaft end play every 6Check preload via shaft end play every 6months and replace as requiredmonths and replace as required

Capacity Slide ValveCapacity Slide Valve


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A slide valve for capacity control is a valveA slide valve for capacity control is a valve

with sliding action parallel to the rotorwith sliding action parallel to the rotor bores. They are placed within or close to bores. They are placed within or close to

the highthe high--pressure cusp region, face one orpressure cusp region, face one or

both rotor bores, and bypass a variable both rotor bores, and bypass a variableportion of the trapped gas charge back toportion of the trapped gas charge back to

suction, depending on their positionsuction, depending on their position

Capacity Lift ValveCapacity Lift Valve

Capacity lift valves or plug valves areCapacity lift valves or plug valves are


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Capacity lift valves or plug valves areCapacity lift valves or plug valves aremovable plugs in one or both rotormovable plugs in one or both rotor

bores (with radial or axial lifting bores (with radial or axial liftingaction) that regulate the actual startaction) that regulate the actual startof compression. These valves controlof compression. These valves control

capacity in a finite number of steps,capacity in a finite number of steps,rather than by the infinite control ofrather than by the infinite control ofa conventional slide valvea conventional slide valve

Chiller NumberChiller Number

NomenclatureNomenclature


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ExampleExample

0 6 N A 11 2 3 S 6 E A0 6 N A 11 2 3 S 6 E A

First three digits are the basic modelFirst three digits are the basic model 06N06N

Fourth digitFourth digit AA for Airfor Air--cooledcooledWW for Waterfor Water--cooledcooled

Fifth digit Type of RefrigerantFifth digit Type of Refrigerant 11for refrigerant 134afor refrigerant 134a

Sixth, Seventh and Eighth digits Compressor displacementSixth, Seventh and Eighth digits Compressor displacement

Ninth digit Electrical characteristicsNinth digit Electrical characteristics

Tenth digit Electrical FrequencyTenth digit Electrical Frequency

Eleventh digit Type of motor coolingEleventh digit Type of motor cooling EE forfor

economizedeconomized NN noneconomizednoneconomized

Twelfth digit PackagingTwelfth digit Packaging AA standard packagingstandard packaging BB

service packagingservice packaging

HVAC controlsHVAC controls

Automatic HVAC control systems are designed toAutomatic HVAC control systems are designed tomaintain temperature, humidity, pressure, flow,maintain temperature, humidity, pressure, flow,power lighting levels and safe levels of indoorpower lighting levels and safe levels of indoor


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power, lighting levels, and safe levels of indoorpower, lighting levels, and safe levels of indoorcontaminantscontaminants

Automatic control primarily modulates, stages, orAutomatic control primarily modulates, stages, orsequences mechanical and electrical equipmentsequences mechanical and electrical equipmentto meet load requirements and provide safeto meet load requirements and provide safe

operation of the equipment.operation of the equipment. It can use digital, pneumatic, mechanical,It can use digital, pneumatic, mechanical,

electrical, and electric control devises, andelectrical, and electric control devises, and

implies that human intervention is limited inimplies that human intervention is limited instarting and stopping equipment and adjustingstarting and stopping equipment and adjustingcontrol set points.control set points.


The sensor measuresThe sensor measures A controller can be inA controller can be in


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the controlled variablethe controlled variable

and transmits values toand transmits values tothe controllerthe controller

The controller comparesThe controller comparesthe value of thethe value of the

controlled variable withcontrolled variable withthe set point andthe set point andgenerates a signal to thegenerates a signal to the

controlled device forcontrolled device forcorrective action.corrective action.

the form of hardwarethe form of hardware

or software.or software.Thermostats,Thermostats,humidistat, andhumidistat, andpressure controls arepressure controls areexamples of hardwareexamples of hardwarecontrollers. Digitalcontrollers. Digitalalgorithms arealgorithms are

examples of softwareexamples of softwarecontrollers.controllers.


The set point is the desiredThe set point is the desired


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value of the controlledvalue of the controlled

variable.variable. The controller seeks toThe controller seeks to

maintain this set point.maintain this set point.

The controlled device reactsThe controlled device reactsto signals received from theto signals received from thecontroller to vary the flow ofcontroller to vary the flow ofthe control agentthe control agent

The controlledThe controlled

device may be adevice may be avalve, damper,valve, damper,heating element, or aheating element, or a

motor driving amotor driving apump or a fan.pump or a fan.


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ValvesValvesValvesValves

A singleA single--seated valve isseated valve isdesigned for tightdesigned for tight

A threeA three--way mixingway mixingvalve has two inlet andvalve has two inlet and


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designed for tightdesigned for tightshutoffshutoff

A doubleA double--sealed orsealed orbalanced valve isbalanced valve is

designed so that thedesigned so that the

media pressure actingmedia pressure actingagainst the valve disc isagainst the valve disc isessentially balanced,essentially balanced,reducing the operatorreducing the operator

force requiredforce required

valve has two inlet andvalve has two inlet and

one outlet connectionsone outlet connectionsand a doubleand a double--faced discfaced discoperating between twooperating between twoseatsseats

A threeA three--way divertingway divertingvalve has one inlet andvalve has one inlet andtwo outlet connectionstwo outlet connections

and two separate discsand two separate discsand seatsand seats


A thermistor is aA thermistor is ad hi d h

Preprogrammed controlPreprogrammed controlti k fiti k fi


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semiconductor thatsemiconductor that

changes electricalchanges electricalresistance withresistance withtemperature. It has atemperature. It has anegative temperaturenegative temperature

coefficient; i.e., thecoefficient; i.e., theresistance decreases as theresistance decreases as thetemperature increasestemperature increases

routines, known as firmware,routines, known as firmware,are typically stored inare typically stored inpermanent memory such aspermanent memory such asEEPROM (electronicallyEEPROM (electronicallyerasable programmable readerasable programmable readonly memory). To preventonly memory). To preventunauthorized alteration, theunauthorized alteration, theoperator can modify parametersoperator can modify parameterssuch as set points, limits, andsuch as set points, limits, andminimum off times within theminimum off times within the

control routines, but thecontrol routines, but theprogram logic cannot beprogram logic cannot bechanged without replacing thechanged without replacing thememory chips.memory chips.


DampersDampers Indoor Air QualityIndoor Air Quality


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DampersDampers

Humidity SensorsHumidity Sensors

Pressure TransmittersPressure Transmitters andand

transducerstransducers

Flow Rate SensorsFlow Rate Sensors

TransducersTransducers

Indoor Air QualityIndoor Air Quality

SensorsSensors Digital ControllersDigital Controllers

ThermostatsThermostats

PI ControllersPI Controllers

Liquid Chillers Rev

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