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corudstr
10-06-2016, 09:13 AM
I have a Carrier 5H60 using R507 to operate a Northstar ice maker. I have a problem with low oil pressure. I suspect there is some kind of problem with the hydraulic unloader system.

Compressor had a leaky shaft seal, while replacing the shaft seal some metallic debris was noticed behind the seal. Inspected inside of compressor and found wore out connecting rod bearings. I do not have any records of its operating condition before this. Replaced crank, rods, bearings, oil pump.

Upon start up there is no apparent oil pressure, after the compressor runs for a few maybe 10 seconds you can here a sudden clatter that I believe is one or more of the cylinders loading up, immediately after the cylinders load the oil pressure rises. The pressure comes up to about 20 to 25 psi, the book says it should be 45 to 50. While testing the machine it has been started and run numerous times, occasionally I have seen 50 psi, but only intermittently.

If the compressor is running and you close the liquid line solenoid the system will continue to run for a minute or two, about the time that you would expect all of the liquid to be boiled out of the ice maker drum when you would normally see the suction pressure drop instead the oil pressure drops to 0. I think the suction pressure may drop a little bit and the compressor unloads and then loses oil pressure.

Why does the oil pressure only seem to come up when the compressor loads?
Why is the oil pressure so low?

Thank you for any help you may provide.
C.O.

Grizzly
10-06-2016, 04:13 PM
Hi Corudstr.
I am not very familiar with these old school comps.
But have you tried adjusting the capacity controlled modulating Valve?
This controls the loading gear oil bleed back to the sump and regulates oil pressure relative to the Suction Pressure.
What condition is the Oil Strainer in?
Good Luck Grizzly.

corudstr
10-06-2016, 08:35 PM
I have not tried adjusting the capacity control valve yet. There is a plugged port that allows you to measure the capacity control pressure, when I was working on it last time I did not have a fitting to put in that port. I think that is the next step. Get a pressure gauge on the control oil circuit and see what is going on with the unloaders.

The oil strainer is clean. I pulled the side cover off and checked that first.

Grizzly
10-06-2016, 11:20 PM
Somewhere positive to start.
good luck.
Grizzly

RANGER1
10-06-2016, 11:54 PM
Corudstr,
There could be a non adjustable oil pressure regulator adjacent to shaft seal housing, maybe it's cactus, see page 25 in link.
Also sometimes you can remove sump side cover, hook up manual hand pump to main oil gallery & pump with clean oil.
See where oil comes out, if it's coming out for example oil pressure regulator return line in sump that most likely is problem.
Other areas like leaking or fractured unloader lines or seals etc might narrow things down a bit.
Trouble shooting page 38,39 on oil pressure.


https://img.sigmaequipment.com/equipment-docs/27434/Carrier.pdf

Tol
11-06-2016, 01:25 AM
Hi Corudstr
It could be the unloader power element gasket is leaking or a leak in the power element itself.
One thing I always found was a good idea was to blow out all oil ports when I had the compressor open.
Bits of bearings and iron filings do get stuck in the oil ports and under the unloader power elements.
You do have the compressor assembled so this would be a last resort.

corudstr
28-07-2016, 10:37 PM
Thank you for all the responses. I just wanted to give you a follow up now that the problem is solved.

I had obvious oil pressure problems with this compressor, but since it was just rebuilt with a new oil pump I thought that the problem must be something other than the pump. After looking at everything else I finally went back to the pump and discovered that the pump rotor clearance was not shimmed correctly. Readjusted the clearance and the problem went away.

It is interesting how a person can get off track when diagnosing something. I knew I had an oil problem but just could not believe that the new oil pump was it.

C.O.