Oil Change

[Collie]

Hey lads, have a variety of different hermetic compressors that have either little or no oil in them. Some are copeland ZR 90 and some are maneurop SZ series of varying capacities.
Originally the customer requested these be topped up but having investigated the issue ive been advised that "topping up" of oil levels is poor practice as even if the poe oil is of the same grade as stated on the compressor label, it is most likely from a different manufacturer and therefore, slightly different oil so they shouldnt be mixed with old oil.
A full oil change with liquid line drier replacements has been whats recommended to me.
Having checked on the forum here I found a few posts saying that you shouldnt touch the oil in an hermetic compressor?? hence the sealed nature of them ...........so what are you supposed to do when the oil needs to be changed or added to? any thoughts lads? thanks

[Collie]

sorry forgot to ad the details for anyone interested.
Airwell condensing units running r407c serving DX coils in AHU's cooling high tension electrical rooms.
Compressor types Copeland zr90k3e-twd-522
Danfoss preformer sz300a4aba
danfoss preformer sz185s4cc
danfoss performer sz160t4cc

[monkey spanners]

I'd probably just top them up if low, emkarate sw32maf in the copeland and whatever spec maneurop say in theirs.

Where has the oil gone to make them low?

I changed the oil in a ZR90 on monday so it is possible (and i have done a few in the past too)

What i do is run them up so they are nice and hot, pump the system down or isolate the compressor, put a few pounds ofn in the comp, use your schreader remover tool, (the type you can change them under pressure, not the other ones or you will get covered in oil!)
Make a note of the oil level on the sight glass.
Fit a gauge line on the remover tool, open the tap on the tool and fill a jug with the oil to the level of the plug.
Once the oil level is at the level of the filler you can unscrew it and use a thin tube and a syringe to suck the rest of the oil out. I have a specially adapted bottle to vac the oil out.
Refit the plug with some thread sealant, comp holds around 4L. You can either pump the new oil back in with a hand pump or suck it back in with vacuum.

Pressure leak test etc etc.

Jon

[Gingerair]

Think you need to find where the original oil's gone first, you could just end up logging the evap if you add more oil..

'Topping up' is fine as long as the oil is compatible, oil type should be on the compressor label.

Some of the Danfoss Scroll comps have a socket part way up the side which come fitted with a plug.
This is a dip tube down to the sump, if you relieve the pressure, remove plug then fit an access valve, the oil can then be removed with a bit of help from some OFN & new oil added whilst under vac.

For any smaller Danfoss's or Copelands Monkey's ya man..
Or there is another way using an old oil can, vac pump & hoses...

Ginge

[Collie]

Thanks gents, where the oil is gone is a good question? There have been a few refrigerant leaks on each system and oil samples been taken during services may account for some of the ones that are a little low, but im barely able to convince myself of that least of all the customer!! hah!
Lets say for arguments sake that the oil has gone off the evap and is sitting there insulating the pipes, is there any method for flushing oil from the system and starting from scratch and maybe fitting an oil seperator?

[Fri3Oil System]

Hi,

If you want to make a proper oil change and ensure you eliminate the old one, you can do it this way. (Enclosed pic).

Of course this process is carried out with our system, but does anybody know another method to ensure the total elimination of the old oil?

regards,

Nando

[chemi-cool]

The first thing to do is find out why there is no oil returning to the compressor.

Adding more oil will not solve the problem as it will not return as well.

When you change oil, weight the oil and add exactly the same amount. Too much oil can blow your discharge valves or destroy the scroll mechanism.

[Tayters]

Lets say for arguments sake that the oil has gone off the evap and is sitting there insulating the pipes, is there any method for flushing oil from the system and starting from scratch and maybe fitting an oil seperator?

In my dark days of supermarkets this was the technique taught to me that worked well on packs.

Assuming oil is low because it's stuck around the system, pump it down and leave it off for about 5 minutes. Open up the liquid line and the surge of refrigerant coupled with all the compressors on to cope with the load (might need some manually turned on) should get the oil back round. Make sure there are no cases on defrost or they'll get missed out. Repeat if required.

Now thats all hunky-dory as those systems I worked on had oil separators and you could see it coming back in the oil sep sight glass followed soon after by oil management warning lights going out. What happens in your case as I assume the system is smaller. If people have been pumping oil into it I wonder if it could come back and damage your compressor? I know of instances where pipes have been cut and a few buckets of oil drained out before addresing the oil return issues so maybe don't try it on a Friday afternoon.

[Collie]

Hahah, oh yes those friday afternoon jobs have a habit of seeking me out!
Thanks lads, will keep all the advice in mind.