Copland compressor oil switch tripping

[kothari]

The roof top cold room( 7 degree centigrade) condensing unit,having Copland compressor runs with R22.The differential oil pressure switch(make:PENN) trips frequently even though the oil level in the sump is enough.This seems to happens when the atmospheric temperature is low( -10 to-15 degree centigrade).
Seeking help to trouble shoot the situation.
Thanks,
Kothari

[Grizzly]

Check the crankcase heater as your oil could be affected by the low ambients?
Also Is this on Compressor start up that the oil diff switch fails.
It may not be any of the above and due to mechanical wear within the Compressor lowering the
Pressure diff across the switch.
Whats the switch diff set to?
Alternatively the switch could be faulty.
Check the above and also if necessary the Oil pressure.
Hope this helps?
Grizzlyhttp://www.refrigeration-engineer.com/forums/images/icons/icon14.gif

[Brian_UK]

What is the crankcase pressure and the oil pressure at start up and when running?

[kothari]

Oil pressure switch low setting is 9 psi.Compressor runs for few seconds and stop due to low oil pressure.
Thanks,
Kothari

[taz24]

Oil pressure switch low setting is 9 psi.Compressor runs for few seconds and stop due to low oil pressure.
Thanks,
Kothari


you need to measure the pressures.
Put a gauge on the crankcase (the suction port if it a single stage) and the put another gauge on the oil pump.

It does not matter what the pressure switch is set to, you need to know what the actual running pressures are.

Grizzly has it right.

Check the crankcase heater is working. Cold oil can have liquid saturated in it and that will cause wear on the comp.

I would drop the oil and check the crank case oil filter aswell they do tend to clog up with grot.

taz.

[Latte]

Aggree with whats being said, Check the crankcase heater. Do you know the history of the site. If you dont, first thing i would do after checking the heater is give the system the works, pump it down, drop the oil, clean the strainer, replace oil ,change drier, good vac (Preferably with a micron/torr gauge) and retry

Do you happen to know type/age of the oil

Regards

Fatboy

[Grizzly]

Kothari
One thing I forgot to mention although rare. Sometimes the Oil Pump drive dog can shear.
You definately have an oil pressure issue 6psi differential seems way to low.
Even when liquid refrigerant is present you normally get some oil pressure which then fades off!
What's the standing temp of the sump,
If you could tell us what comp it is would maybe help.
Has this just occured or has oil pressure fault reoccuring?
That should indicate "wear" to look!
Tell us more.
Steve.

[hendry]

yeah ... could we have some details on your lube oil?

by chance, you have a crankcase heater not operating as it should be?

otherwise you may have some foreign debris choking your oil filter/strainer which only give you alarm when its accumulated.

hope that helps ... cheers.

P/S: here, you go everywhere you start to hear Chinese New Year songs ...:)

[WVDM]

Oil Pressure On A Copeland Semi Should Never Be Anything Less Than 18psi Above Suction And Definately Too Much Liquid In Oil Will Tamper With The Viscosity Hence Oil Trips Normally 25-30psi Above Suction Is Good Obviously In Those Ambients The Liquid Migrates To The Compressor Check If Oil Is Very Foamy At Start Up :rolleyes:

[D.Evans]

The roof top cold room( 7 degree centigrade) condensing unit,having Copland compressor runs with R22.The differential oil pressure switch(make:PENN) trips frequently even though the oil level in the sump is enough.This seems to happens when the atmospheric temperature is low( -10 to-15 degree centigrade).
Seeking help to trouble shoot the situation.
Thanks,
Kothari

Are you sure the level you see in the sump is oil and not liquid refrigerant. Leave the unit off for awhile and see if that level disappears as any refrigerant is boiled off by the crankcase heaters. Do you have decent discharge superheat. Have you checked the oil sump strainer to see if it is clean.

[Grizzly]

Are you sure the level you see in the sump is oil and not liquid refrigerant. Leave the unit off for awhile and see if that level disappears as any refrigerant is boiled off by the crankcase heaters. Do you have decent discharge superheat. Have you checked the oil sump strainer to see if it is clean.
Guys CHECK THE DATE.
It would be nice if Kothari got back to us on this one. If only to satisfy our engineering curiosity.
Grizzly

[kothari]

Hi Guys,
I am able to overcome the re occurrences of tripping on oil pressure switch,as the Copland compressor heater was unable to heat enough to the sump oil at very low ambient.
Thanks for your input.
Kothari

[Grizzly]

Hi Guys,
I am able to overcome the re occurrences of tripping on oil pressure switch,as the Copland compressor heater was unable to heat enough to the sump oil at very low ambient.
Thanks for your input.
Kothari
So it was the crankcase heater after all.
Good news a least you have identified the cause of the problem.
You say the c/c heater is not man enough. I can't say for certain but most manufacturers have several heaters available at differant wattages.
Have you checked to see if a larger one is available.
If necessary post compressor details as I as sure one of the guys will be able to advise as to wether another is available.
I asume you wont be the first to experiance this type of extreme weather problem. Maybe dome sort of blanket heater around the sump would help, what does anyone else think?
Grizzly.http://www.refrigeration-engineer.com/forums/images/icons/icon14.gif
And by the way thanks for getting back to us.
Just thought if your crankcase heater goes off when
the Compressor Contactor energises (n/c auxillary on Comp Contactor). You could try having the c/c heater permanantly powered it might make a differance?

[kothari]

Hi Grizzly,
Thanks.You are absolutely right.I was thinking to insulate the heater which is located outside at bottom of the C.C. I kept the C/C heater permanently powered to seperate the liquid refrigerant.
Kothari

[mano]

Yeah . Liquid Migration right !
Pls. turn on crankcase heater for separated liq & oil
when system running.

[RAHUL JAIN]

The roof top cold room( 7 degree centigrade) condensing unit,having Copland compressor runs with R22.The differential oil pressure switch(make:PENN) trips frequently even though the oil level in the sump is enough.This seems to happens when the atmospheric temperature is low( -10 to-15 degree centigrade).
Seeking help to trouble shoot the situation.
Thanks,
Kothari

DEAR IT MAY BE U R SYSTEM IS HAVING MOISTURE (AIR) .

[ruvy frank]

check your pressure switch it could be faulty and check your crank case heaters they might be faulty bcoz its tripping when the temp drops hey

[techie]

does this compressor have sump heater cause that could be one of your problems and if so is it working properly then check to see if it wired right