Pump-down problems!

[dannyk]

Hi everyone, new to this site and hope you can help me out. I have a problem with a maneurope compressor r404 which serves a walk in freezer.
Problem is when it pumps down, solenoid closes and compressor pumps down to around 8psi when LP switch knocks off unit, then pressure begins to rise quite fast to around 60 psi (suction) and unit cuts back in, and this process goes on and on. Would you say this was a solenoid problem or a compressor problem? What simple tests could i do to determine this? Thanks in advance.

[monkey spanners]

Hi Danny,

Could be either, fit your gauges on the suction and discharge valves on the compressor.
With the solenoid open shut the reciever valve and pump the unit down. After it has pumped all the liquid into the reciever does the pressure still keep rising?

If not, make sure solenoid is shut, and open reciever valve, if pressure now rises it looks like its a duff solenoid (you may see frost forming after it)

If the pressure keeps rising after the pumping down, it points to compressor problem, discharge check valve if its a scroll compressor (not familair with maneurop scrolls), oil seperator float/solenoid.
With the power off shut the dicharge valve, does this stop the pressure rising? if so thats how its getting in.

Basically you need to find out how the refrigerant is getting into the compressor, either through the suction due to duff solenoid, or through the discharge through duff discharge valves or external check valve if fitted, or possibly oil sepreator if fitted.

Jon :)

[dannyk]

Thats great jon, thanks for the advice, will check it 2moro, much appreciated!!

[coolhibby1875]

if the room has a ball valve close that which elimanates the solenoid vavle but i would bet any money its the compressor i come across this all the time with maneuropes, it plays ahvoc with defrost as the contactor for heaters go through the aux on the comp contactor.

[cadwaladr]

what happens if you close suction valve,is the evaporator badly frozen?

[dannyk]

It turned out to be the compressor, thanks for the advice, could that affect the performance of the system? Defrosted the coil, system hits -10, sight glass just full, suction at 18psi, discharge at 175psi, once it hits -10 it starts frosting back on suction and struggles to get any colder, any ideas?

[cadwaladr]

have you replaced the compressor yet?

[dannyk]

no, but have ordered it for thursday, freezer is still full of stock and customer has nowhere to put it so need to get it another 5 degrees colder at least, if possible. Soon as it reaches -10 the coil and suction start to ice up quite bad, do u think the pressures seem about right?

[cadwaladr]

no, but have ordered it for thursday, freezer is still full of stock and customer has nowhere to put it so need to get it another 5 degrees colder at least, if possible. Soon as it reaches -10 the coil and suction start to ice up quite bad, do u think the pressures seem about right?what is the air temperature onto the condensor,are you sure the evaps clear and fans all running ,sometimes fans [paddle]in airflow of the other,is the water getting away [via drain]completely after defrost.

[dannyk]

air temp onto condensor is around 5 degrees, condensor is inside but has a hole cut in the wall, evap is completley clear, had electric heaters defrost it all, evap is single fan and is working correctly.

[Brian_UK]

I wonder whether you could improve the liquid flow by blocking the condenser to raise the pressure (just in the short term).

[dannyk]

Thanks brian, will give that a try!

[cadwaladr]

good call brian