I'm continously getting "cant pump down" alarms on Circuit B. The alarm is more of an alert it doesnt shut the machine down. I discovered this on a pm when I went into alarm history. Anyway this particuliar unit uses the exv for pumpdown, I confirmed proper operation of exv. My thoughts are that there is some internal problem with compressor, because even when calling for cooling this circuit doesnt have the capacity that circuit A has. Circuit A holds the load at 50 percent while circuit B cant hold the load at 100 percent. beside my suction pressure being a little high about 73psi and my subcooling being a little low about 5 degrees everything else appears normal.
My question is does anyone have any info on these Mcquay scews that I could trouble shoot the compressor further???
Pump down problems
I haven't worked on the ALS line, but I do remember having problems on other McQuay units that would not pump down because the liquid line solenoids would not close off tight enough-so it wouldn't hit the low pressure cut off. It wouldn't go into a critical alarm and shut down, but it would show fault.
als don't close solenoid's on pump down,they close exv,liq.injection solenoid stay's open to keep gates cool and lubricated.they are open when ever compressor is energized.check filter drier for metal and gates.