Crankcase pressure regulator

Question: I had a service call on a R-502 reach-in freezer. It was a pump down system with a remote condensing unit located on the roof of the building. It had a crankcase pressure regulator on the suction line at the condensing unit.

What is it about this application that requires a CPR? Or do you think it is needed there at all?

-David Chapman, Upper Marlboro, MD

Answer: Your letter does not say anything about what type defrost this freezer has. If this system pumps down before defrost I would say it is possible the CPR is not required. When the compressor is just stopped by the time clock, the CPR could be required.

The only way to determine if a CPR is required is to check the compressor amperage right after a defrost cycle. When the amperage exceeds the compressor RLA rating, the CPR is there to limit the suction pressure to keep the compressor from tripping off on its motor protector.

-Frank Latuda, Alco