Oil Dissapearing act

[patchdf1354]

I work on a 10 hp r-22 cycling off on low oil safety. At first look I added oil. Found out after starting oil went from full to empty in sight glass within 1 minute of start and periodiocally shutting off again on low oil safety. When compressor starts oil goes low (1-2 minutes) and then immidiately way full after shutting off. Whats up???? Check valve?? 2 year old compressor. There is flood back if it runs for more than 3 minutes. Would an accumilator help? Pressure control cycles temp. No solenoids, 3-4 deli display cases tied on one line.

[Dowadudda]

Low superheat? Is that due to TXV's, lack of air flow, oil logged evaporator?

You have to try and get the superheat up first if you can. The low superheat is impeding good oil return, due to low velocity of the refrigerant vapor.

The flooding is causing the oil and refrigerant to be entrained and being pumped out of the compressor. You always will discharge some oil, but if it is refrigerant laden, you'll pump more oil.

How are you looking for piping for good oil return. Has this line up been remodeled, loads taken away, anything like that?

[lolson]

do you see the oil in the sightglass foaming at start up? if so is the crank case heater working? i have seen a crank case heater that has been replaced, and it was wired on the load side of the contactor and it requires to be energized at all times to prevent liquid refrigerant from migrating to the crank case, mixing with the oil, then washes it away. :mad:

[rocket]

CHECK 3 PRESSURES
1. SUCTION PRESSURE
2. CRANKCASE PRESSURE
3. OIL PUMP OUTLET PRESSURE

1 and 2 should be within 3 lbs, if more than that it is too late - BlowBy
3 - 2 = net oil pressure (should be 40 psi)

check condition of oil as well

[mark itziro]

In your post you said there is floodback after three minutes. If thats the case you need to find out why.

Are the cases iced up/fans out/plugged mooray grill? You can front seat the suction to see if the valves have been lynched. If they have you could be pumping oil out of the comp. What is your net oil pressure?

If your still are not sure you might have to pull the heads off and have a look. Make sure you have spare gaskets if you do.

[NedFlanders]

Had the same thing on a construction job. Single 10 HP , on a lineup of Hussmann Impacts. 1 powerhead was wrong and literally would sweep all the oil out in 1-2 minutes. The guy who put the cases in , swore they were all correct.
I drained the oil out to check the screen , and the oil was boiling refrigerant out like hot soup.

Cracked heat exchanger, bad mechanicals in the comp would do that too.
Just another idea