View Full Version : Oil pressure problem

27-02-2012, 02:32 PM
Hello friends, I have a rack system R22 ***** with 4 copeland semi h ermatic compressor ( 5 HP each ) my question is what should the oil pressure be ? I have 2 compressor that are running around 80 psi. And 2 that are running around 58 psi. What should the minimum oil pressure be and the maxium be ? Thanks for your help

27-02-2012, 02:55 PM

Is the system dual temp / dual pressure?

Oil pressure is dependant on suction pressure.

The oil pump pumps the oil under pressure above the crank case pressure (suction pressure).

The actual pressure for the oil is about 2 bar (30 psi) above suction pressure but can be as
much as 3, 4 or even 5 bar above the crank case pressure (suction pressure).

Do the comps have oil differential switches fitted?

If they do not have switches fitted then any oil pressure will be ok.

Some types of pumps on the copelands have little relief valves fitted
that stop excessive oil pressure and they may be set at differant pressures.

So if the pack is at the same temp / pressure then all the comps should run
at similar pressures but if they are at differant pressures then they will have differant
oil pressures.

Hope this helps



27-02-2012, 04:22 PM
They are fitted with oil pressure cut out switches and the 2 compressor that has the lower psi on them were tripped out and not running. I also found that only 1 condenser fan motor was running and it was calling for 3 fans to be running . So I fixed the problem with the fans not running and reset the oil pressure switch on the compressor that were not running and noticed the 2 compressor with lower oil pressure ......... Would the condenser fans not running like their supposed to be cause the compressor to cut out on low oil pressure ? I know that the 2 compressor not running out of the 4 caused some of the store meat cases to loose temperature . So would the condenser fans not running as should be have possibly caused the the compressor to cut out on oil pressure ?

27-02-2012, 05:17 PM
I would guess that your crank case oil filters are clogged if two comps have 58 psi oil pressure and the other two have 80 psi oil pressure. If the filters are clean it could be your compressor oil level control e.g float assembly/Trax system not allowing enough oil return. Unlless your head pressure was extremely high I doubt this would have caused the oil problems as your HP safetys would have probably shut the plant down.

27-02-2012, 10:27 PM
as RONB said id say it is your crankcase filter or oil float or oil separater.. you might have liquid coming back and lifting your oil aswell

28-02-2012, 11:40 AM
Warm crank-case due to high temp can lower the oil pressure since viscosity changes