copeland scroll compressor

[doormaster2008]

hi guys.dont know if anyone has had this problem with a scroll compressor.called out to wallcase with a zb21kce-pfj-551 single phase compressor.fitted suction guage,running but not pumping.switched off to check standing pressure.switched back on and the compressor started pumping.it worked for a week and did the same again.checked pressure switch settings with it being on pump down.ok.called out again last night and compressor would not start.switched off and called back this morning to take compressor details.switched it on and the compressor started up and worked.any ideas guys.thanks

[chemi-cool]

Starting gear? Capacitors, starting relay?

[monkey spanners]

It could be due to a momentery power cut that powers back up as the compressor is spinning backwards as it comes to a stop. It will keep running backwards till the power is turned off or it goes off on internal thermal safety.

It can be caused by poor power supply, faulty pressure switches or differentials set too low, or anything that cuases the power to go off for a fraction of a second. There may be an upgrade to the compressor electrics to include a start capacitor and relay or i have had good results with fitting a time delay into the control circuit to prevent short cycling.

[doormaster2008]

many thanks monkey spanners.will fit time delay as you suggest.cheers

[sendhilkmar]

I fully agree with monkey spanners. I faced simillar issue of reverse rotation due to sudden voltage drop (below the operating voltage range). Just verify the volatge fluctuation as well

[padraic]

as monkey spanners said.... power plays havoc with single phase scroll... if there is an issue with power or a problem of some sort it will go lock out and it will try and reset but when internal resets and will not reset start relay to bring on start capacitor... we found a delay timer helped but after a few years it got worse and stuck in a 3 phase... havent seen it since... i hate single phase srcolls there nothing but hassle
also check your pressure switch and settings.. keep it running within it design parameters and dont keep pumping it down to 0 or you will burn out your internal NRV and when it knocks off it will go in reverse hence the noise it makes hen it knocks off

[doormaster2008]

thanks again guys.cant believe they would fit a 3hp scroll on single phase either.suspect the pressure switch may be faulty but cant believe there is no time delay on it as standard.

[WeNeedUnions]

Check the side of the donk and see if it has a sticker I can't remember what Copland call it but basically what happens is if the donk gets to hot or pumps liquid they have some internal mechanism which opens valves inside which cause the donk to run 100% unloaded i.e doesnt pump many people in air con are not aware of it and condem the reversing valve when in truth it's the safety inside the donk.