I have a Norlake freezer that is making a loud noise from the compressor only when it first comes on after the defrost cycle. Customer says it has been happening for a long time.
Not knowing what compressor you have, (Danfoss SC do this) Either it is overcharged or the defrost system is not terminating at the correct time. Making the box to warm and forcing the compressor into overload. Also warming product every cycle. You never gave a model number, so I have no idea what machine you are talking about, the type of control, The defrost ternimation method.
The Model is Norlake CPF060DC-AThe compressor is a Copeland RS64C2E-CAV-101
I forgot to mention, if it has a copemetic compressor, it is mounted on springs. Sometimes the piping doesn't have the correct clearances for starting.and the tubing hits. They have a lot of starting torque.
Ok. You have a walk in with a top mounted condenser. That is getting to high of a suction pressure coming out of defrost.
Check for a solenoid valve on the liquid line just before the evaporator. This machine should have suction pressure control with a defrost timer to kick off the fans and solenoid so that the compressor pumps down the evaporator coil and keeps the compressor in it's working load range. If the compressor is left to start in overload for a extended period of time, it will take years off it's service life.
There manufacturers out there that like to cut corners. and are now starting to use Dixel controls on walk in's. They should still keep the liquid solenoid and suction control to save the compressor. Dixel should control the solenoid. not the compressor.
Alternately there are other ways to protect the compressor. Look for either a crankcase regulator valve on the condenser suction line or a expansion valve with a bypass tube and a pressure limiting charge like a Sporlan Z's. Like a SZP would have a tail pressure of 45 psi limit. If that is the design method, box has to be below 5 degrees when adjusting the TXV. Someone may have opened it up to much in set-up not knowing the effects of not waiting.
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