Scroll problems

[Jai]

Hi guys, I'm new to this forum but I think it's a very informative site. I would like to get some feedback on the reliability and problems of scroll compressors.Recently we have lost 4 scroll compressors due to what seems to be a lack of lubrication.These compressors were from different systems with no apparent "system" problems.

[acman]

Check rotation.Read amps.If 3 phase,reverse phases.

[Jai]

These systems were commissioned about 9 months ago and 2 out of 4 compressors failed after 5 months.The system is a York package Liquid chiller with 2 independant refrigerant circuits of 2 compressors each.When the system was started-up,the voltage,rotation,superheat,oil level,pressures etc. were verified.Also a voltage monitor with phase reversal protection was installed.What I found odd is that I had to add 2 gallons of oil to the system and the oil level remained low.Seems as the compressors were pumping the oil out. I am presently working on 2 York Scroll systems and it seems as the compressors are pumping the oil out.I have already added 3 gallons of oil to these systems and the oil level is still low. I have never had this problem with recips. unless its a system problem. I'm trying to find out if other techs. out there are having the same problem.

[Prof Sporlan]

Keep in mind that the oil you are adding to the system isn't disappearing..... the oil is likely residing in the chiller. An appropriate question to ask at this point is why the oil isn't returning back to the compressor.

[Gary]

I agree, Prof. It isn't that the oil is pumping out of the compressor. The problem is that it isn't returning. Adding oil to a system is almost always a mistake.

[Jai]

Gary I agree with you and Prof. Sporlan where the oil can be leaving and not returning.What does not seem to make sense is the fact that this is a package chiller so there is no "external" piping to cause oil return problems. Also the load in the evaporator is not lower than normal.(the g.p.m. is running slightly higher than design). Is there a tendency for Scroll compressors to circulate more oil through the system than Recips.

[Gary]

I know of no particular tendency for scroll compressors to circulate more oil, and the fact that you keep adding more and it doesn't come back should tell you something.

Designed by the manufacturer doesn't necessarily translate to perfect design, although they tend to learn from their mistakes. Perhaps you are witnessing some of their mistakes.

I would want to look very closely at the suction line sizing/sloping/trapping, as well as the chiller barrel flow pattern. Ask yourself, "Where is the low spot that is trapping the oil, while the refrigerant flows above it".

As the Prof points out, it hasn't disappeared, it is hiding somewhere.

[Brian_UK]

Originally posted by Jai
this is a package chiller so there is no "external" piping to cause oil return problems

We had to change out a compressor on a Daikin packaged chiller during last summer. One team started and I had to finish the final connection and get it running again.

Found a lack of gas flow due to the discharge line up to the TEV being full of oil.

Problem appeared to be bad location causing high pressure trips during hot weather....probably pumped out the oil and killed the compressor that way.

[Preston Roy Powell]

Scroll losses!!

First ckeck you line size.. Then ckeck your super heat back to the compressor.

1. DId the compessor ground out!!
2. Are slugging the compressor
3. Are you starving the compressor.

[Dan]

[quote]Found a lack of gas flow due to the discharge line up to the TEV
being full of oil. [\quote]

[stevec]

One might expect some of the oils to come back to the compressor when it starts warm. Unless it is on 24 hr operation.You couls also check water flows etc.
One of the intersting points here being raised also is putting in oils when you can't see it on the ground!!! or ceiling or anywhere.
I have problems sometimes with some of our guys who believe if oil level is low it needs oil. As you all suggest step back and re focus.

[install monkey]

have you done acid test on each circuit ,were drier cores,contactors changed with new compressors,are the compressors short cycling,condenser coils clean,tev functioning correctly.mains problems on site???????????????

[El Padre]

You could try isolating one circuit to ensure compressors are running at 100% capacity which will ensure maximmum oil return, is there an oil return line from the evaporator?

Cheers

[El Padre]

Just a thought, is there a water flow problem on that site, did they leave flow rate measurements on the commissioning sheets? If you post the model number one of the Yorkies might be able to give you more information.

Cheers