Demand Cooling

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Demand Cooling Components

 HEAD COOLING FAN

DEMAND COOLING MODULE

The reason a head cooling fan is used, for the purposes of removing as much heat as possible to keep the compressor from overheating because of extreme compression ratios.. NOTE: ( Copeland specs say discharge temperature should never go over 225 DEGREES) This is used in conjunction with liquid injection (Demand Cooling) Widely used used on R22 systems, but can still be used with new retrofitted refrigerants like 407a & 407f. NOTE: Sometimes you will find a breaker tripped for the compressor, so check the wiring on the head fan, some instances where the rack is 480 VAC you can experience a situation where the main breaker is tripped, due to the wiring on the head fan has rubbed out, so be sure to check this out as a possible source of a shorted wire, along with other troubleshooting practices.

Demand cooling module controls how and when liquid is injected into the compressor, this component HAS the same terminals as a SENTRONIC OFC 240-120-L-M-A. This module is also part of the control circuit for the particular compressor it is attached to.

https://opi.emersonclimate.com/CPID/GRAPHICS/Types/AEB/ae1287.pdf

INSIDE LOOK AT THE MODULE

LIQUID INJECTION VALVE BODY

What the module looks like on the inside.

This is the component used to inject liquid into the compressor. LIQUID REFRIGERANT comes in on the side to be BRAZED and goes out the FLARE NUT side. The FLARE NUT is what goes to the compressor body.

DEMAND COOLING SENSOR

HOW DEMAND COOLING WORKS

This sensor has an ohm value that is measured from  the module, to send power to the COIL on the valve body to open it. One end of the sensor goes into the discharge side of the head on the compressor, and the other end to the module.

Pictorial of how the refrigerant flows and how demand cooling works.

DEMAND COOLING SENSOR

DEMAND COOLING SENSOR 

This is a picture of a demand cooling sensor that had to be removed for cleaning, notice how it is blackened, this is caused by high compression ratio on an R22 compressor (Low Temp). The demand cooling module had tripped off, thus causing the compressor to not run.

This is the same demand cooling head sensor after it has been cleaned, lightly with sand paper. NOTE; When reinstalling the sensor be sure to use either leak lock or teflon tape.

      DEMAND COOLING MODULE           

What you see here is a demand cooling module, except this is for a scroll compressor same principal as any other demand cooling, and same troubleshooting teqniques.

 HEAD COOLING FAN

The reason a head cooling fan is used, for the purposes of removing as much heat as possible to keep the compressor from overheating because of extreme compression ratios.. NOTE: ( Copeland specs say discharge temperature should never go over 225 DEGREES) This is used in conjunction with liquid injection (Demand Cooling) Widely used used on R22 systems, but can still be used with new retrofitted refrigerants like 407a & 407f. NOTE: Sometimes you will find a breaker tripped for the compressor, so check the wiring on the head fan, some instances where the rack is 480 VAC you can experience a situation where the main breaker is tripped, due to the wiring on the head fan has rubbed out, so be sure to check this out as a possible source of a shorted wire, along with other troubleshooting practices.

DEMAND COOLING MODULE

Demand cooling module controls how and when liquid is injected into the compressor, this component HAS the same terminals as a SENTRONIC OFC 240-120-L-M-A. This module is also part of the control circuit for the particular compressor it is attached to.

https://opi.emersonclimate.com/CPID/GRAPHICS/Types/AEB/ae1287.pdf

INSIDE LOOK AT THE MODULE

What the module looks like on the inside.

LIQUID INJECTION VALVE BODY

This is the component used to inject liquid into the compressor. LIQUID REFRIGERANT comes in on the side to be BRAZED and goes out the FLARE NUT side. The FLARE NUT is what goes to the compressor body.

DEMAND COOLING SENSOR

This sensor has an ohm value that is measured from  the module, to send power to the COIL on the valve body to open it. One end of the sensor goes into the discharge side of the head on the compressor, and the other end to the module.

HOW DEMAND COOLING WORKS

Pictorial of how the refrigerant flows and how demand cooling works.

Demand Cooling Modules

Demand cooling is used mainly on LOW TEMP R22 COPELAND compressors. The compressor tends to get really hot on R22 LOW temp compressors because of the HIGH compression RATIO of the compressor. To get compression ratio you divide the suction pressure by the discharge pressure. On a R22 low temp compressor you can have 190-250 PSI DISCHARGE and 9-15 PSI suction. You can already see the huge difference. When a compressor gets hot it can coke your oil, another word for cooking it, which causes sludge. The demand cooling injects liquid refrigerant into the low side of the compressor to cool it. There will be a body head cooling fan on top of the compressor, which is designed to remove as much heat from the compressor as possible due to high compression ratios.

Demand Cooling Troubleshooting (COPELAND)

Troubleshooting DEMAND cooling is fairly easy. First of all if you find a compressor off, either by alarm or a RUN PROOF MONITOR alarm, start by using your meter to check for voltage at your various controls. OFC, LPC, HPC, and if they all check out, then move on to the demand cooling module. Check L and M and if there is voltage, then it is open. From there you can hit reset. Now remove the sensor from the BOTTOM side of the DEMAND cooling module. Take some thin wire and make a JUMPER. Put the jumper wire INTO where the sensor would go. When you do that the COIL on the VALVE body should energize. If it DOES, then the sensor in the head is probably carbonned up. At this point pump down the compressor as described on the compressors page. Front seat the suction and let it (COMPRESSOR), go off on LPC=LOW PRESSURE CONTROL. Turn compressor off, front seat discharge valve and pump discharge gas into rack or another compressor. Once compressor is at 0 PSI, remove sensor from compressor. You will notice more than likely it is BLACK and carboned up. Take some sand paper or sand cloth, same as what you use to clean copper fittings with, and polish it smooth and clean. Install back into compressor head, tighten up, open discharge valve FIRST then suction. Bring compressor back on and all should work good. If you JUMP the module (SENSOR PORT) out and the solenoid  DOES not energize, check for VOLTAGE at the COIL on the valve body. If there is voltage, then the solenoid is bad. If NO voltage, then MODULE is bad. NOTE: If you ever see a compressor that looks like a HUGE ice ball where the demand cooling solenoid/valve is and the other low temp compressors are running good, perhaps somewhere there is condensation on the end bell. If ONLY ONE COMPRESSOR is ICED up REALLY bad there is high probability the valve body stuck open on the DEMAND cooling valve body. When this happens it is advisable to change all three items; the module, sensor, and valve body. They generally come together in an all inclusive kit.

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