short cycling compressor

[redgreeen]

i have a walk in freezer problem it is short cycling the head preesure is 150 psig the thermostat is new and is closed contacts the liquid line solenoid is energized yet the compressor is cycling the gauges read low side on at 15psig off at 3psig and it just keeps cycling off and on the head pressure gauge is at 150 psig i disconnected the condenser fans and the head pressure went up to 250 and also the suction pressure rose to 30 psig then the unit acted normal i reconnected condenser fans and the unit ran normal for a couple of days what did i do by doing this i have been told its a bad head master control but i dont understand if the head preesure is 150 psig at the service port that is after the reciever i dont get it can you help me

[sedgy]

hi red green,
giving us the psi , and not the gas you are on, dose not give us much to work on ,
your problems could be, low on gas faulty stat, over condencing< is there con, fan controle?< but could do with ambiant temp .room temp air on - air off just to start with ,

[barryjustin]

there could just be a shut valve somewhere that youv'ed missed by accident, hows the expansion device? not blocked?

[mikeref]

Redgreen, unit cycles on low pressure because of insufficient refrigerant flow or volume so by increasing head pressure, your forcing more volume through the circuit. sounds to me like expansion valve restriction.. mike.

[jpsmith1cm]

I'm with the others. Without a refrigerant type, I'm left mostly guessing.

Given the information that you've given us, though, I'd first look at a low charge condition.

Does the unit have a sightglass?

[barryjustin]

sounds like its on 507?

[FEISTY]

You didn't say when the problem started. Was the unit recently serviced? I would double check all service valves and make sure low side valves are not closed or partially shut down if you are taking low pressure control access from a takeoff that should be open at all times to read constant pressure. I did exactly that once myself. Had a multi-valve takeoff on a service valve port that was closed so far it just went up and down ....on and off. Hey.....we all miss something.