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jakb21599
12-04-2013, 11:38 AM
Have a 6 1/2 hp semi-hermatic compressor that has lost 24 oz of oil over the last 2 weeks. It is pulling a 15 glass door freezer case. ( 3 ) 1 1/2 ton evaporators sharing same liquid and suction line. ***** is 404A. Freezer temp is -10 degrees ( F ) Low side 20psi... High side 205psi... SH at compressor 46 degrees....SC 6 degrees... Evaporator SH 6 to 8 degrees on coils... The total line set run is around 70 feet with 5/8 liquid line and 1 /14 suction line with accumulator.
My question is what could be the reason for oil loss in site glass on compressor and having to add 24 oz of oil ? What do i need to look for to find out whats happing and stop it?

Rob White
12-04-2013, 11:56 AM
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You don't mention an oil separator?

Loss of oil for no reason could indicate a few problems.....

Make sure there is no oil leaking out or refrigerant leaks.

If there is no oil separator then you are relying on the oil passing around the system and
back to the comp through the suction pipe. That includes the suction accumulator.

If there is an oil separator, why is it not doing its job?

So is there an oil separator? If so is it working? (they do block up and stop passing).
Is the suction accumulator performing correctly? (they rely on a small orifice hole to return oil).
Are the evaporators logging the oil? (TEV faulty)
Is the compressor faulty and passing oil? (if there is a valve problem or a piston problem
the compressor will pass oil quicker than it can be recovered).


Put the whole system on defrost and warm it through (the evaporators)
then run down to temp and see if the oil returns.

Regards

Rob

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jakb21599
12-04-2013, 12:29 PM
Their is no oil seperator ..and it has a new accumulator on it. I did notice it does not run long before satisfying freezer...on maybe 15 min and off around 10 min....if it was a faulty tev valve wouldn't it show up when checking evaporator superheat ? With the short run times...is it possible that it is not running long enough for enough oil return?

Rob White
12-04-2013, 02:00 PM
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New Suction accumulator?

Did you notice the oil loss after the change or was it changed because of the loss?

Was there much oil inside the accumulator?

It might need a coating of oil inside a new one before it works
and that could account for the loss?

If the system was working OK and it was cycling every 15 mins or so
and the oil was OK in the comp then that should not be an issue.


Rob

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jakb21599
12-04-2013, 03:13 PM
Condensing unit was replaced cause the other one went out. Had new pipes run and accumulator added ...so pretty much a dry system start up....ran for a while with no issues and then checked again and noticed oil level was not where it was at when I left it...so I put 26 oz back in it to get a 3/4 full site glass ...so you think maybe the system had to get coated with oil and that is why I had oil loss ?

RusBuka
12-04-2013, 03:20 PM
Without oil septrator may be some trouble. What difference of height between the evaporator and the compressor, between the condenser and the compressor. The compressor is higher or lower than the evaporator and the condenser, how oil-up loops are made?

jakb21599
12-04-2013, 03:31 PM
Without oil septrator may be some trouble. What difference of height between the evaporator and the compressor, between the condenser and the compressor. The compressor is higher or lower than the evaporator and the condenser, how oil-up loops are made?

Evaporator and condenser at same height.just about 70 ft of line set between them.. condenser and compressor sit on same frame...

RusBuka
12-04-2013, 03:51 PM
Hehe try to close receiver, collect all *****, make defrost, then start up and open receiver. Make open and close operation several times on working compressor. Look what you catch)

Rob White
12-04-2013, 08:30 PM
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If you have replaced components and pipe,
I would expect the oil to go from the comp
because it will need a wet on the inside of
all the surfaces.

If you put oil in and it stays OK then chances are it
was just the system settling down after the replacements.

If the oil disappears again then worry :o

Rob

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