Did you clean the little screen on the sensor?

Sometimes those sensors get a little dirty and won't read properly.

Also, just so you know (and I was schooled on this very website).....net oil pressure is oil pump outlet pressure minus crankcase pressure - NOT - suction pressure.

 

Market techs right there.. use crackcase pressure if possible to get a true reading.. Oil problems r hard to fine in real life, never mind over the computer.. But i always pull the sensor and see if its clean and change the o ring and reinstall.. make sure system pumps down and check for proper defost.. r there traps installed??

 

that pressure is very low. You could try a new oil pump, but i think you are on the way to a compressor.

 

are you saying that you had 50 to 60 net oil psi before changing the oil and now you only have 20?

What did you do to it, tell the truth.

 

Hi everyboby!! On new compressors, I remember watching the pump discharge pressure go up to 50 - 60 psi (low temp systems), with suction pressures 20´s and below.

As the oil was getting kinda dirty in the sight glass, I changed oil and cleaned up the screen mesh and pump in this low temp compressor. Now, as I put the pump back in service, I read pump discharge pressures in the 30´s with suction pressures in the 10´s. That means about 20 psi of net oil pressure (well above the 9 psi recommended value). Even so, the PENN 545 electronic oil pressure controls keeps shutting down the system. This didn´t happen before I serviced the pump. What´s wrong here?

Great info from market and yoto but I'm corn-fused about something.

You mention "on new compressors" you remember seeing so and so pressures. Is the dirty oil compressor the same as the "new compressor" you reference or another one? If not, did you record the oil pressure before you cleaned the oil or was there another problem. Also, is this a rack system or a single compressor system?

Just asking to clarify what you have.

 

According to the Copeland manuals available to me, the net oil pressure ( pump discharge pressure minus suction pressure)

No No No, Copeland never said above.

net oil pressure is crankcase pressure subtract from oil out
(Crankcase not suction, got it?)
9 psi is when it trips
net oil around 40 is good

bad, thin oil causes lower oil pressure

 

Even so, the PENN 545 electronic oil pressure controls keeps shutting down the system. This didn´t happen before I serviced the pump. What´s wrong here?

you probably broke the wire harness or sumting !!!!
p545 sensor harness are fragile......

carlyle use them

 

Let me clarify a little bit my previous post:

I recall one ocassion in which a brand new 22 HP replacement compressor upon start up on a low temp R-22 rack, fresh oil in crankcase, had pump outlet pressures above 50 psi.

But this isn´t the compressor I am dealing with right now. This is a 15 HP low temp Discus compressor. I just changed the darkened oil, inspected and cleaned up the pump, just to have the electronic oil pressure control shutting down the system continuously. I think I remember some check procedure for the sensor outlined in the JC instruction sheet. I just cannot recall what it is.

 

Why did you pull the pump to clean and inspect, if this was just an oil change you were doing. Guess I have never pulled a pump without having a reason to beleive there was a internal problem. I do believe you have a problem with the oil pressure safety if it wasn't tripping before you did the change.

 

Most oil pump replacements are a waste of time and money. Now to properly check oil presure BE SURE THERE IS OIL IN COMPRESSOR. If it has an oil pot with sight glass and compressor is not level it can give you a false indication of oil level . If oil pressure is below 25 psig net on 2D or 3Ds or 30 psig on 4Ds change oil clean screen and clean sensor and replace O ring. Watch oil pressure for at least 1/2 hour if you see a drop in oil pressure you may have worn rings,pistons pumping oil out of compressor faster than oil pot can return . worn bearings will also cause drop in pressure as compressor warms up. I have also seen loose connections in motor wiring and bad contactors causing internal overload to trip and oil control to trip. Always ckeck voltage and amp draw ,all wiring connections as part of any oil failure check. I have been working on rack systems in supermarkets for over twenty years and curently am responsible for service and emergency calls on 51 stores with over 450 copeland compressors. I have two stores with hussman racks and 9R compressors that have been running since 1984. Hope this helps. I enjoy telling people I have a cool job.



JUST BECAUSE YOU CAN DOES NOT MEAN YOU SHOULD

 

Most oil pump replacements are a waste of time and money. Now to properly check oil presure BE SURE THERE IS OIL IN COMPRESSOR. If it has an oil pot with sight glass and compressor is not level it can give you a false indication of oil level . If oil pressure is below 25 psig net on 2D or 3Ds or 30 psig on 4Ds change oil clean screen and clean sensor and replace O ring. Watch oil pressure for at least 1/2 hour if you see a drop in oil pressure you may have worn rings,pistons pumping oil out of compressor faster than oil pot can return . worn bearings will also cause drop in pressure as compressor warms up. I have also seen loose connections in motor wiring and bad contactors causing internal overload to trip and oil control to trip. Always ckeck voltage and amp draw ,all wiring connections as part of any oil failure check. I have been working on rack systems in supermarkets for over twenty years and curently am responsible for service and emergency calls on 51 stores with over 450 copeland compressors. I have two stores with hussman racks and 9R compressors that have been running since 1984. Hope this helps. I enjoy telling people I have a cool job.



JUST BECAUSE YOU CAN DOES NOT MEAN YOU SHOULD

Am I the only one that finds this post to be condescending at best?


Almost sounds like the new guy's coming in swinging his d*ck......lettin' every one know just how good he really is.

 

http://www.hvacrinfo.com/cope_ae_bulletins/TAE1275.PDF



and i have a cool job too

 

Was the sensor removed from the oil pump while you were doing your cleaning? If so make sure that the o-ring is still on the tip of the sensor as it will not read a differential without it in place.

 

Thank you all for your great help.

I just figured out another possible reason for the oil control tripping problems: I´m not quite sure if I installed the oil pump gasket in the right way. I just read a Copeland bulletin regarding gasket positioning (gasket tab must be in the 11 o'clock position for the oil passages to be free). I´ll need to go and check it. If this isn´t the problem, now I have more than a few other options. Thanks to your comments.

 

MT

Ya having a bad day??

 

Yeah - maybe I am......

When a guy's first post starts out with BE SURE THERE IS OIL IN THE COMPRESSOR and ends with JUST BECAUSE YOU CAN DOESN'T MEAN YOU SHOULD.....I took it as someone with the expertise in the field and experience from years of service work looking down his nose at an obviously less experienced fellow tradesman.........and it p!ssed me off.

What helpful information can be construed from the last 8 words of his post? I took it to mean just because a guy can tweak a rack or throw a set of gauges on one.......doesn't mean he should.

Now, maybe I read the entire context of the post wrong - and if I did, I owe sodd81927 an apology.

So, in giving you the benefit of the doubt sodd81927...........I apologize.

Heads up though - if you want to help others, it sometimes helps to do so WITHOUT SHOUTING AT THEM

 

When a guy's first post

I got in a habit a while back. I read the post, then look at the post count if their post struck a social nerve then I remember my first month here.


You're a good man MT


=)

 

Copeland oil pump service

I was reading a recent post on proper net oil pressure. After reading all entries, my conclussion is that the correct net oil pressure should be somewhere between 35 to 55 psig, no matter what the crankcase pressure is.
Therefore, if a Copeland Discus low temp is reading net oil pressures below 20 psig, could the pump be somehow serviced or better to completely replace it?
Also, any idea of Copeland´s recommendations on normal oil TEMPERATURES?

 

Also, any idea of Copeland´s recommendations on normal oil TEMPERATURES?

lowtemp,

Oil sump temperatures can vary quite a bit, max maybe up to 200 degrees, but that would be high. It would depend on the application, refrigerant, superheat, compression ratio, refrigerant cooled or air cooled, etc.

Maximum oil temps in the cylinder walls should be about 300 degrees. One way to verify you don't have high oil temperatures is to follow this test.

On conventional refrigeration compressors, recips or scrolls, the discharge line temperature 6" from the compressor should never exceed 225 degrees F. The actual oil temperature in the cylinder walls of the compressor would be about 75degrees higher (300 F).

Oil vaporizes at 310 to 320 F which causes ring and cylinder wear

Oil Breaks down at 350 F which causes contaminates and accelerated wear.

So 225 F is safe. 250 is Danger............275 is certain failure

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