A CPR valve holds the compressor suction down -
And reduces the system capacity to whatever FLA the compressor can happily tolerate. Under higher-than-normal conditions - adjust the CPR valve to give you the highest suction pressure (at the compressor) that the compressor amps will allow.
The evap pressure just has to wait for the compressor to catch up. That's why the valve is there.
Will the compressor pump down well?
If so; you might want to try killing the evap fans and watch what happens. It's nice if you can stop just one or two fans and only reduce the evap loading - rather than eliminate it.
If it works OK without the fans - you just have to wait for it to pull down.
Also: some cheap freezers are barely equipped for holding-temp - let alone any pull-down capacity. Might take a day or two with the door locked to get down to temp.
BTW: The evap probably IS starving - even with the decent subcooling - because the high suction pressure is holding the TXV closed. Which it is supposed to be doing.
PHM
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Originally Posted by
freeeze43
Hi, have a walk-in freezer that wont drop below 20 deg.. cannot find any problems except for cpr valve, At suction service valve that is downstream of valve is at 19 psig,(r404a systemm,txv metering device),and service port on cpr valve is at 55 psig, Should it be adjustable at this service port on the upstream side which it wont, but i can adjust this pressure on the system suction port which is downstream and right next to compressor. is this valve stuck close and not allowing me to get my neccessary suction press.?? thanxs in advance.
also this is a water cooled cond,(waste) with a 252 psig head and 8 deg. subcooled with a 40 deg. temp. increase, suction press. taken at service port of cpr at 55psig and 22 deg. s.h. that wont go down by adjust txv. evapseems to be starved, full sightglass,new txv installed last month,,thankyou for any info on how these cpr valves would react if sticking partially closed,,
PHM
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When faced with the choice between changing one's mind, and proving that there is no need to do so, most tend to get busy on the proof.