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Thread: Rack Oil Change

  1. #1
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    Rack Oil Change

    Would love to here from all the techs out there that do oil changes on Refrigeration Racks. Is there a set way on how to do it? Does any of the old timers have a recommeded A to Z method? Lets just pick an old Hill Phoenix Low Temp. Rack with a AC&R oil seperaotor, reservior, and say 5 compressors with oil regulators. A oil changable core filter. R22 Mineral oil. Maybe we can have some fun with this and see if we can have the educational committee pick the best method. Lets pick October 1, 2012 the deadline. I'll go first on how I have always done mine!!!

    First thing I do is pump the rack down in an attempt to pull as much of the old oil out of all the evaporator coils and all the traps. When all the compressors have shut off I'll force one on and run the suction down to about 3psig being sure not to go into a vacuum! At this point I will front seat the suction and discharge valves on all the compressors and shut off the oil feed to each oil regulator and the liquid on the demand cooling line Start at compressor # 1 and pull the pick-up screen and oil safety sensor. Do this to each compreesor. Clean all and replace. Install new oil filter. Pull the oil float from the seperator and install new one. Drain all oil from reservoir. Pump in the new oil --approx. 1-gal. per. compressor and or 1st ball up on reservoir. Since the rack is already pumped down I alway install new filter/dryers. Pull good vacuum. Open all the lines that were closed off exept for the suction lines. Open up suction line on #1 compressor Slowly start each compressor ensurring no liquid is comming back!!

    How do you do yours?

  2. #2
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    Sep 2008
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    Pumping the rack down isn't going to bring too much oil back.

    If you want oil return, a few defrosts on your big circuits might help, but pumping it down will reduce mass flow through the lines and reduce oil flow.

    I typically valve off one pump at a time, making sure to crack a fitting so that I don't take an oil bath.

    Pull the float and rinse it out with carb cleaner, brake cleaner or some other degreasing solvent. If the glass is dirty, I'll clean it. Clean the pickup screen, the sentronic sending unit and anything else that looks dirty.

    Pump it full, pull a vacuum while I do the next one.

    This way, no more than 2 pumps are offline. I can take a little extra time with the parts because the rack isn't DOWN.

    Blow the reservoir down (sometimes you need to pressurize it to get it empty faster.

    Replace the float in the separator (make sure to clean/inspect the screens in it and add oil precharge)

    I'll also replace any oil filters and rack driers while I'm working on it.

  3. #3
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    Quote Originally Posted by jpsmith1cm View Post
    Pumping the rack down isn't going to bring too much oil back.

    If you want oil return, a few defrosts on your big circuits might help, but pumping it down will reduce mass flow through the lines and reduce oil flow.

    I typically valve off one pump at a time, making sure to crack a fitting so that I don't take an oil bath.

    Pull the float and rinse it out with carb cleaner, brake cleaner or some other degreasing solvent. If the glass is dirty, I'll clean it. Clean the pickup screen, the sentronic sending unit and anything else that looks dirty.

    Pump it full, pull a vacuum while I do the next one.

    This way, no more than 2 pumps are offline. I can take a little extra time with the parts because the rack isn't DOWN.

    Blow the reservoir down (sometimes you need to pressurize it to get it empty faster.

    Replace the float in the separator (make sure to clean/inspect the screens in it and add oil precharge)

    I'll also replace any oil filters and rack driers while I'm working on it.
    Those screens are almost imposable to clean just replace them.
    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


    Educational forums are open.

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  4. #4
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    Some of the ones that I've seen have a screen around the float.

    That is the one I was talking about.

  5. #5
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    Quote Originally Posted by jpsmith1cm View Post
    Some of the ones that I've seen have a screen around the float.

    That is the one I was talking about.

    This is the one I was talking about. Fig 4.
    Attached Images Attached Images  
    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


    Educational forums are open.

    If you would like to submit a link or an article or other related info to the EF. click here

  6. #6
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    Quote Originally Posted by jpsmith1cm View Post
    Pumping the rack down isn't going to bring too much oil back.

    If you want oil return, a few defrosts on your big circuits might help, but pumping it down will reduce mass flow through the lines and reduce oil flow.

    I typically valve off one pump at a time, making sure to crack a fitting so that I don't take an oil bath.

    Pull the float and rinse it out with carb cleaner, brake cleaner or some other degreasing solvent. If the glass is dirty, I'll clean it. Clean the pickup screen, the sentronic sending unit and anything else that looks dirty.

    Pump it full, pull a vacuum while I do the next one.

    This way, no more than 2 pumps are offline. I can take a little extra time with the parts because the rack isn't DOWN.

    Blow the reservoir down (sometimes you need to pressurize it to get it empty faster.

    Replace the float in the separator (make sure to clean/inspect the screens in it and add oil precharge)

    I'll also replace any oil filters and rack driers while I'm working on it.

    That's pretty much how I do oil changes. If the oil is super nasty, I'll do 2 changes about 2 weeks apart so anything left out in the circuits has time to get flushed out.

    I can't fix it if it won't stay broke..

  7. #7
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    I know this is an old thread but do you guys usually try to achieve 500 microns when evacuating each compressor out after the oil change?

  8. #8
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    I would want to see a 500 micron level vacuum and holding for at least 30 minutes without rising over 50 of your initial level when you turned the vacuum off. If you can't achieve this it means you have a service valve leaking by or a leak within the closed portion of the system you have isolated to change the oil . Good time to determine why you can't get the micron level low enough. Critical on POE and makes leak testing easier since your confined to the part of the system you've isolated and shut down assuming you used the second method(post) of changing oil. I would use the same the refrigerant to leak test if I'm convinced the service valves are not the issue after a holding test.
    If your convinced the service valves do hold than its safe to use dry nitrogen to raise your pressure greater for leak testing

  9. #9
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    Just to warn you, the o-ring in copeland oil sight glasses isnt rated for deep vacuum and may not hold vacuum level.

  10. #10
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    Quote Originally Posted by mjm88 View Post
    Just to warn you, the o-ring in copeland oil sight glasses isnt rated for deep vacuum and may not hold vacuum level.
    Do you have any literature on this ?

  11. #11
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    I cant find any. We were told by our supplier. I just emailed Emerson and will let you know what they say.

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  13. #12
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    Ummm. Yeah, a Copeland o-ring will handle deep vacuum.

    I've seen it on multiple occasions.

    Your "supplier" is full of mud.

  14. #13
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    Quote Originally Posted by jpsmith1cm View Post
    Ummm. Yeah, a Copeland o-ring will handle deep vacuum.

    I've seen it on multiple occasions.

    Your "supplier" is full of mud.
    I've started many new stores, some needed to hold 500 mic for 24 hours, and have seen them leak. Not always, but often enough.

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