Reasons for system not pumping down

[Contactor]

hello

I have a job which is not pumping down, I think the solenoid is letting by.

The LP switch does cut the system off but then the pressure starts creeping up and cycles the LP on and off.

Would anyone care to expand on this, for example are there some units which aren't suitable for a pumpdown control system?

Thanks

[sedgy]

hi contactor,
it sounds like the solanoid is amiss,
valve off liquid valve, pump down strip down solinoid, fit new parts < which you took with you < fit new dryer, vac out liquid line and bobs your uncle, open liquid valve, test for leaks test operation of solinoid and fannys your aunt, sedgy,

[james10]

if you mean physically pumping down for service then as you say the solenoid valve is passing if you have a mechanical liquiid valve try closing that aswell valves passing are a pain in the proverbial butt either way if the pressure is rising then it's getting through the valves might be time to replace them or your oil is carring a lot of gas (just a thought)

[monkey spanners]

Its either the solenoid or the compressor head valves (note some scroll will not pump down to low suction pressures)

Pump it down by shutting the reciever, if then ok then check that there is no voltage to the coil when it should be shut, if not then try a new valve.

If it still won't pump down with the reciever shut then shut the suction valve and see if if will pump down, if not then turn comp off and see if pressure rises, if pressure rises still then (with comp off) shut discharge valve, if it now stops then comp if faulty. Note some rise is normal for scrolls when shutting off.

Jon :)

[lana]

Its either the solenoid or the compressor head valves (note some scroll will not pump down to low suction pressures)

Pump it down by shutting the reciever, if then ok then check that there is no voltage to the coil when it should be shut, if not then try a new valve.

If it still won't pump down with the reciever shut then shut the suction valve and see if if will pump down, if not then turn comp off and see if pressure rises, if pressure rises still then (with comp off) shut discharge valve, if it now stops then comp if faulty. Note some rise is normal for scrolls when shutting off.

Jon :)

I couldn't agree more.

I have the same problem with my home chiller right now. Faulty discharge valve.

Regards
LANA

[Contactor]

thank you

the solenoid is fitted upside down, would this be a problem, presumably not if they are sprung?

it's an alco 1/4 swaged with 240v coil

thanks

[Gingerair]

It shouldn't be fitted upside down, there may be some debris/swarf stuck in it causing it to pass..
Strip down inspect & if possible re-position as per manufacturers instructions..
Don't forget to take notice of which way round the internals of the valve are when you strip it, again check against manufctrs destructions..

Ginge :)

[monkey spanners]

Solenoids generally need the coil to be between 9 and 3 o'clock, but best is vertical at 12 o'clock. Never pointing down.

Also worth checking the flow, they will only shut tight one way.

Jon :)