oil pressure problem

[jpsmith1cm]

JP

are you insinuating that the cc pressure or suction pressure effects the pressure you would read off the top of the oil pump?

are you insinuating that if the compressor was running on a bench with no refrigerant that his oil pressure would be less than 85 psi?

[supertek65]

JP

are you insinuating that the cc pressure or suction pressure effects the pressure you would read off the top of the oil pump?

are you insinuating that if the compressor was running on a bench with no refrigerant that his oil pressure would be less than 85 psi?

[jpsmith1cm]

JP

are you insinuating that the cc pressure or suction pressure effects the pressure you would read off the top of the oil pump?

are you insinuating that if the compressor was running on a bench with no refrigerant that his oil pressure would be less than 85 psi?

Whassamatter, stinky?

You think that was so important that you posted it twice?

[ryan1088]

He's one of "them" who has to make his point twice!

[valdelocc]

JP

are you insinuating that the cc pressure or suction pressure effects the pressure you would read off the top of the oil pump?

are you insinuating that if the compressor was running on a bench with no refrigerant that his oil pressure would be less than 85 psi?

The discharge pressure varies in direct proportion to the crankcase pressure.

I wonder if the discharge pressure builds up to the point where the relief valve opens? maybe thats why it runs fine for a little while.

[welling service]

It starts up at about 85PSI and then drops to around 50 PSI. My CC pressure is about 25 PSI. I never see much variation in the suction pressure. It will run like this for various times and sooner or later trips on low oil pressure. It has run for two weeks one time before tripping. I have not had my gauges on it when it trips so I don't know if the pump output is going down or the CC pressure is coming up. I have done a piston blow by test and found no problem. The comp. pumps down just fine and holds. I thought maybe the OPC was bad so I installed a new one with the same results. The oil pump is newly installed because at first I thought the pump was worn and not maintaining pressure. I have never run up on this problem before and I don't mind saying I AM STUMPED!!

[jpsmith1cm]

New oil pump. Did you use the right gasket?

Have you checked for a pressurized crankcase?

What does your contactor look like?

[valdelocc]

It starts up at about 85PSI and then drops to around 50 PSI. My CC pressure is about 25 PSI. I never see much variation in the suction pressure. It will run like this for various times and sooner or later trips on low oil pressure. It has run for two weeks one time before tripping. I have not had my gauges on it when it trips so I don't know if the pump output is going down or the CC pressure is coming up. I have done a piston blow by test and found no problem. The comp. pumps down just fine and holds. I thought maybe the OPC was bad so I installed a new one with the same results. The oil pump is newly installed because at first I thought the pump was worn and not maintaining pressure. I have never run up on this problem before and I don't mind saying I AM STUMPED!!

it may not even be an oil related issue, maybe the compressor is tripping on overload, have you thought about that?

[ryan1088]

Is this a part start motor?!

[jayguy]

It starts up at about 85PSI and then drops to around 50 PSI. My CC pressure is about 25 PSI. I never see much variation in the suction pressure. It will run like this for various times and sooner or later trips on low oil pressure. It has run for two weeks one time before tripping...

if it runs long enough that you can not catch it with your gages on it, then it is not a failed compressor. 25 psid is a fine pressure for the compressor...hell, 10 psid is fine as far as copeland is concerned. the question that i have is this: what was it 1, 2, 4 or more months ago and what is it now? it sounds to me like several issues may be happening here.

how long does it take to drop from 60 psid to 25 psid? what is the application? are you watching the oil temperature while it runs? as the oil gets hotter, it thins out. that causes the net oil pressure to drop. you show up and the oil is 'cold' and all seems fine. perhaps your oil is also hanging up in the system some what.

[supertek65]

[jpsmith1cm]

You can't whistle cryptically.

I'm already whistling cryptically, so quit copying me.

[supertek65]

QUIT SAYING EVERYTHING 5 SECONDS BEFORE I SAY IT!!!!!!!!!!!!!!!!!!!!!!!!

[welling service]

No it is not a part winding start .

[welling service]

Yes I used the right gasket. I also did a piston blow by test and the CC pressure and suction pressure dropped at the same rate down to 0 psi. The oil temp is normal. The contactor is just fine. I reset the OPC last Friday and the unit has been running just fine. Checked NPOP today it was 15 PSI. Pump pressure 55PSI, CC pressure 40 PSI. Like I said the unit just takes a notion to run just fine for a while and then starts tripping the OPC. WE have had 29 degree nights and 50 degree nights for the past 3 days so I can't see ambient temp having anything to do with the tripping problem.

[jayguy]

...WE have had 29 degree nights and 50 degree nights for the past 3 days so I can't see ambient temp having anything to do with the tripping problem.

low head pressure usually = low suction pressure. low suction pressure = low refrigerant flow rates. low refrigerant flow rates = poor oil return. poor oil return = no oil. no oil = 0 oil psid. < 10 psid = trip oil pressure switch. trip oil pressure switch = unhappy customer. unhappy customer = unhappy service tech.

math is fun!

[GT Jets]

low head pressure usually = low suction pressure. low suction pressure = low refrigerant flow rates. low refrigerant flow rates = poor oil return. poor oil return = no oil. no oil = 0 oil psid. < 10 psid = trip oil pressure switch. trip oil pressure switch = unhappy customer. unhappy customer = unhappy service tech.

math is fun!

That's not math....That's Arithmaslick....

[jpsmith1cm]

Are the suction and crankcase pressures the same?


Could you be seeing an intermittent floodback?

[ryan1088]

low head pressure usually = low suction pressure. low suction pressure = low refrigerant flow rates. low refrigerant flow rates = poor oil return. poor oil return = no oil. no oil = 0 oil psid. &lt; 10 psid = trip oil pressure switch. trip oil pressure switch = unhappy customer. unhappy customer = unhappy service tech.

math is fun!

This is the only kind of math I actually understand!!!!!

[welling service]

jpsmith1cm yes they are. I did the piston blow by test by putting a gauge on the CC and one on the suction port. I slowly closed the suction service valve and watch my gauges. They both fall at the same rate down to 0 PSI at which point I know I do not have an over pressurized CC. I guess it's possible to have an intermittent flood but haven't seen one. My rooftop condenser has 3 fans with one controlled by a fan cycle switch. The unit also has a 3-way head pressure control valve.