Copeland 50HP Compressor (Low Oil Fault)

[Mr Cilltech]

I have a problem with a copeland compressor, cutting out on low oil pressure often. i carried out the following tests:-

1) clean sump oil strainer
2) check oil pump pressure ( suction 32psig and oil pump pressure 75psig)
3) check crankcase heater operation which was normal( no liquid feedback)
4) normal oil level on the compressor sight glass (normally half)

compressor have a sentronic oil sensing controller with a sensor connected on the oil pump. i have check the operation of the controller as follows:-

contact on the sensor closes when compressor running ( basically normal oil pressure)

contact opens when compressor stops. if the disconnect the sensor cable the contacts are open and the red indicator on the controller lights up indicating low oil pressure and once reconnected with 120 secs the green light ups ( normal oil pressure).

compressor stops if the leave cables disconnected for more than 120 secs. So basically i have tested everything but problem keeps coming often.

plz help.

[setrad7791]

Hi there.. Firstly check the oil pressure and monitor it during running, if the sentronic drops out and you have maintained correct oil pressure then the sentronic is faulty.. I have had a fare amount of experience with the sentronic oil saftey device on commercial fishing vessel's and have found them to be unreliable! my advice is to replace with a danfoss oil failure. Hope this helps!

[Eeram]

Hi Mr Chilltech

setrad7791 is right. Watch the suction pressure and oil pressure while the compressor is running, but especially check the sump pressure of the compressor with the oil pump pressure.

Sometimes if the compressor has worn rings or journals it could affect the oil pump pressure.

Is this a new compressor?

[Redhot]

Hey mate, depending on the wiring of the control and compressor circuit have found a faulty / intermitant time delay on compressor contactor will cause oil fault, is the compressor part winding?

Cheers redhot

[Mr Cilltech]

thanx for ur response.

this is not a new compressor. i have monitor the suction and oil pump pressure on start up and during operation, its all normal.

There is no wiring issue as the sentronics mains is wired on normally open contact of the contactor so the sentronic only comes ON when the contactor energises. there is no delay on power feed.

this compressor is on a rack system at a process plant, the operation of the plant is from monday to friday. so during the weekend the compressors stage out and according to the data we have 99% of the time the fault occurs on monday morning when the process starts.

there is something happening during this loading of compressor after cold start, which i cannot figure it out.

[absrbrtek]

I have had intermitant oil pump failures in rare instances. I can only remember seeing it 3 times in 30 years. A real PITA to troubleshoot. You just needed to be lucky and be there when it happens. You need to be onsite when they start the process up on Monday morning.

Is this sentronic wired with 3 or 4 wires? I have also seen the 3 wire setup feeding back thru the control circuit causing false failures while the system was off?

Could the compressor be stalling during startup after sitting for awhile?

[setrad7791]

My advice.. change the oil failure with a danfoss or mechanical oil failure, it's a small outlay to determine if the problem is with the oil control... I can almost be certain it will fix the problem!
also make sure you check oil pressure with your gauge fitted to the sump... just incase you have a blocked suction strainer at the service valve!

[Eeram]

Is the compressor on a pumpdown during standstill over weekends? If not, liquid can floodback to the compressor on Monday morning startup, even with an operational crankcase heater!

Remember, refrigerant likes to stay at the coldest place in the system, the evaporator.

[sonnyshores]

I had this problem with a walk-in freezer. The fix was to replace the 3PH contactor , one of the legs was holding in at heavy amp. draw then openning letting the compressor run on two PHs causing the oil presure switch to set a fault. The cooling fan on the compressor is running off of two legs, which weaken the third. Hope this helps