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Thread: Rack Oil Change

  1. #1
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
    Posts
    311

    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
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,559
    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
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,504
    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
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,559

  5. #5
    Join Date
    Sep 2005
    Location
    florida
    Posts
    5,504
    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
    Join Date
    Oct 2011
    Location
    East Charlotte Area of NC
    Posts
    421
    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..

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