copeland oil level issue

[danod]

I have a problem with oil dissapearing out of the sight glass at start and run, but when the compressor shuts off the level comes back to the top of the sight glass within minutes. Compressor is 3 months old, freezer temp setpoint -32deg celsius, 5 other units all run ok, oil levels stay in sight glass, compressor pumps down and holds ok, no broken valves, compressor pulls temperature well, no change after hot gas defrost level still the same, unit does not have an oil seperator, I believe if oil was being pumped out the level would not appear in sight glass right after shut down, I suspect something internal but don't know what. all Ideas greatly appreciated.

[lana]

Hi there,


Are the compressors connected in parallel? OR is there standby compressor in the circuit (which is connected in parallel)?

[D.D.KORANNE]

probable reasons
1) low load on evaporator whereby oil return velocity is low .
2) pressure difference between suction line & crankcase ( this suggests suction filter in compressor partiallly blocked).
4) if accumulator is provided , the hole in U tube bigger in size or blocked .When the compressor is off, the suction pressure build up in accumulator pushes oil throgh it .
5) If the compressors are in parallel , oil level regulator or oil& gas balancing line valves needed ; if not provided .
6) Check oil viscosity usually 46 to 55 is suggested .

IN APPLICATIONS LIKE THIS , OIL SEPARATOR IS REQUIRED , SO IS ACCUMULATOR .

[chemi-cool]

Superheat might be too low.

[Sandro Baptista]

The problem is why only happens on that on if all the compressors are working on the same manifold?

[Sandro Baptista]

Maybe the piston rings or the oil scrapper rings are worn.

[Sandro Baptista]

Does the crankcase of that compressor is hotter than the ones of other compressors?

[NoNickName]

If the compressor is stand-alone, I suspect frost on the suction strainer. When frost thaws, oil drips into the crankcase.

[taz24]

I have a problem with oil dissapearing out of the sight glass at start and run, but when the compressor shuts off the level comes back to the top of the sight glass within minutes. Compressor is 3 months old, freezer temp setpoint -32deg celsius, 5 other units all run ok, oil levels stay in sight glass, compressor pumps down and holds ok, no broken valves, compressor pulls temperature well, no change after hot gas defrost level still the same, unit does not have an oil seperator, I believe if oil was being pumped out the level would not appear in sight glass right after shut down, I suspect something internal but don't know what. all Ideas greatly appreciated.


I don't think you mentioned the refrigerant type??
But at -35 the back pressure will be low..
I would initialy look to the oil float on the side of the comp (assuming it has one) and then failing that
if the condition persists look at the comp itself.

You do not state what type of comp it is??
But we are assuming that it is a semihermetic. If it is a scroll
the fault could be very differant to a semi.

If it is a semi and if the oil float is ok (swap it for one off another comp),
then I would look to the comp itself. You may need to strip it down and check the valves and pistons.

If it is only 3 months old, is it a rebuild? or brand new? does it have a warentee?

taz

.

[danod]

I should have been more specific. there are 3 separate freezers, each with 2 compressors
and there own condensing units and evaporators. refrigerant is 404a. this compressor will pull the room temp down with no problem even with the 2nd compressor in defrost. It will pull down to 10hg vacumm no problem and hold for a pump down test. The compressor is a copeland 3db, was new from Copeland in 2008, sat on the shelf for a spare until July this year when it replaced one with broken connecting rod, probably a slug of oil. The last contractor installed a 2nd suction accumulator in series on both compressors for this particular freezer because of smashed comp's.

[jpsmith1cm]

I should have been more specific. there are 3 separate freezers, each with 2 compressors
and there own condensing units and evaporators. refrigerant is 404a. this compressor will pull the room temp down with no problem even with the 2nd compressor in defrost. It will pull down to 10hg vacumm no problem and hold for a pump down test. The compressor is a copeland 3db, was new from Copeland in 2008, sat on the shelf for a spare until July this year when it replaced one with broken connecting rod, probably a slug of oil. The last contractor installed a 2nd suction accumulator in series on both compressors for this particular freezer because of smashed comp's.



Hmmm.

The word 'Probably' is rarely a good one when dealing with diagnosing the cause of failure for a compressor.

Was is a slug of oil or a slug of liquid refrigerant?

I'll bet that, if you are able to answer this question, you will find the thread that unravels your larger problem.

2 Suction accumulators in series is crazy as far as I'm concerned. Either install a properly sized accumulator or resolve the problem that is creating the liquid floodback condition that necessitates the accumulator to begin with.


If presented with a problem like this, I would start with a logging device and log temperatures, pressures and other data I felt pertinent to the problem based on the exact equipment on-site. After a period of time, you will be able to establish baseline performance and see when things deviate from the baseline. Once you know WHEN things are deviating from the baseline, then you will be able to investigate WHY they are.

[danod]

jpsmith 1cm, I know 'probably' isn't the correct way of diagnosing a problem. I only used that word based on my observations of a rising ice level on the first suction accumulator over a couple of days. If you saw what I observed you would Probably agree that an oil slug took out the last comp. Based on my observations on the first game the Giants will Probably win the series.

[danod]

found the problem to the dissapearing oil level. turned out the factory remanufactured compressor was missing the bearing on the motor end on the crank, all the oil would get pumped into that end

[NoNickName]

found the problem to the dissapearing oil level. turned out the factory remanufactured compressor was missing the bearing on the motor end on the crank, all the oil would get pumped into that end

Impressive carelessness from Copeland.

[phil2424]

Copeland do not remanufacture compressors - I think Danod is saying an independent compressor rebuilder Messed up

[mbc]

how it could be .
carter is lower than motor side and between there is a bearing (it is check valve ) from motor side to carter side

[DTLarca]

Why were there broken rods before? Has the cause been remedied?

Broken rods on refrigerant cooled Copeland's from "slugging" can only happen if the compressor suffers flooded-starts - not flood-backs.

http://fridgetech.com/articles/recipfailmodes/#GlossB

Rods can also break from flood-backs on refrigerant cooled compressors but you would see heatless white metal smearing along the journals (big end) and especially the main motor-end bearing.

http://fridgetech.com/articles/recipfailmodes/#GlossA