Page 1 of 2 12 LastLast
Results 1 to 13 of 26
  1. #1
    Join Date
    Jun 2005
    Location
    South Jersey
    Posts
    1,461

    Question

    OK, This is a question I was asked by a fellow tech ( one of the best I've ever worked with, 30+ years experience, mostly high tonnage stuff ) about a job he was on recently.

    I don't have all the specifics, but here goes.

    R-12 walk in box, 20 years old. Two cylinder copeland semi hermetic compressor. Oil pump is bi-directional.

    Apparently the box chugged along fine for many years until one day it started tripping out on oil pressure. We send one of our guys out to fix it, he marries it and spends the next three days changeing all kinds of parts. Then my buddy, the senior guy in the shop, gets sent out to find out what the H is going on and it turns out that it's still doing the same thing. He goes through it and the next morning, out on oil.

    At this point he supposedly talks to some (as he put it) old timer who told him to reverse the rotation of the compressor. He did this (three phase) and amazingly, it worked.

    His question to me was, had I ever heard of this and why did it work? My answer was "No and I don't know"

    Does anybody know the answer to this, or is this a case of my chain being jerked?

    Busta
    It Is What It Is

  2. #2
    Join Date
    Mar 2005
    Posts
    664
    it seems sensible enough to me that although it is a reversible oil pump that its possible it would or would not function as well running one way

    stan

  3. #3
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,264
    I've heard the same kind of story over the years and have tried it myself a couple of times. If you have a compressor with a high mileage oil pump, reversing can give you a few extra psi of oil pressure.....often enough to get you up and running. Not a true fix, but it'll buy you some time to get the new oil pump at the supply house in the AM.

    I don't like reversing a compressor though mainly because all the moving parts have settled into a wear pattern that will change if the rotation changes. Leaving it reversed you may well end up worse off than before in a relatively short time.

  4. #4
    Join Date
    May 2000
    Posts
    338
    Ever use an Annie to reverse one and shake it free?

    The compressor may work for a while until you get a new one but... best to get a new one quickly and stop patting yourself on the back for breaking one free..


    That's my story and I stuck with it.


  5. #5
    Yes, due to the way the journals and all that stuff wear. Now you are slowing down the oil to increase "pressure".

  6. #6
    Join Date
    Jun 2005
    Location
    South Jersey
    Posts
    1,461
    Originally posted by icemeister
    I don't like reversing a compressor though mainly because all the moving parts have settled into a wear pattern that will change if the rotation changes. Leaving it reversed you may well end up worse off than before in a relatively short time.
    That's exactly what I was thinking when I heard about this.

    Very interesting. I've reversed compressors to free them up and buy a little time till a new one can be procured, but I never would have thought of the oil pump thing.

    Learn something everyday!

    Thanks, Busta.
    It Is What It Is

  7. #7
    Join Date
    Jan 2006
    Posts
    1,120
    I guess you guys are talken about a 3 phase and just switching a couple of wires around,i have done this to break loose stuck compressors before but never heard of it making the oil pressure come up but sounds like a winner to me for a quick fix until you get a new compressor.BTW can you reverse the polarity on a single phase compressor,ive heard you can and you cant but never seen it done,you know to break one loose if it is stuck.If you can how.
    There are three signs of old age.
    The first is your loss of memory,
    the other two I forget.


  8. #8
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,793
    Originally posted by hillbilly tech
    I guess you guys are talken about a 3 phase and just switching a couple of wires around,i have done this to break loose stuck compressors before but never heard of it making the oil pressure come up but sounds like a winner to me for a quick fix until you get a new compressor.BTW can you reverse the polarity on a single phase compressor,ive heard you can and you cant but never seen it done,you know to break one loose if it is stuck.If you can how.
    modern refrigeration and air conditioning (blue book).I don`t know the edition but on mine page 432.chapter 12 servicing and installing small hermetic systems,starting a stuck compressor.there is a picture.Basicly a capacitor is put to the run winding.I am gonna try this also,when the accasion arises.there are two similar methods in that chapter explained.

  9. #9
    Ice had the best answer, in my opinion.

    #1 .. it does work, many times.

    #2 .. how it works .... it makes the wearing surfaces operate in a different direction. And this new direction, (rotation), simply puts forse on the parts in a way that makes them pump whereas in the old direction they had failed over time.

    Stuff wears in and stuff wears out.

    I would tend to agree with Ice about the compressor itself settling into a given rotation and changing that will bring you trouble.



    The way I learned this trick was the very same way your friend did ... and "ol fart".

  10. #10
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    I've done it. It works.

    But, I change out the oil pump when I run into this.

    Then, I change the oil, clean the pickup screen and replace the oil filter, if so equipped.

    It IS from wear, and reversing the pump DOES cause the other parts to start shedding metal shavings from the "fresh side" (for lack of a better phrase) of the machine.

    Best thing to do is to sell them a new compressor, or, if warranted, a whole new unit, IMO. But, if it's a service contract...

  11. #11
    Join Date
    Apr 2003
    Location
    Somewhere in the Caribbean
    Posts
    221
    I have been told this by my dad. His explanation seems to be sensible. While it is correct that the pumps are bi-directional, they accomplish this by means of a sliding ball to allow for both rotations. In some cases, this ball will become lodged in one end of the slot or not seal at the other end due to wear particles or oil residue or something similar. He has never mentioned that it could be a problem in normal operation. It was always just a comment like "When you replace the contactor / breaker, keep the phases in order"

  12. #12
    Join Date
    Mar 2004
    Location
    Las Vegas, Nevada
    Posts
    1,647
    Short Answer:
    It'll work.

    Most likely you'll find you're on Borrowed Time. Prudent to crunch the numbers now. You'll want to end up with a clean system. Wether that means changing the oil, oil pump, and cleaning system on a very old compressor or just rebuilding the plant are things to consider. One way to pitch it to the customer - the high cost of R-12.
    The views and opinions posted here are my own. They do not reflect the corporate policies of my employer and will most likely get me fired at some point.

  13. #13
    Join Date
    Aug 2004
    Location
    Tucson, Az
    Posts
    337
    What was te net oil pressure before and after the rotation change? Would like to see how much of a difference it actually made.

    Copeland oil fail controls are set for a 9# net cut out. If it only brought the net oil pressure up to , say, 11 lbs, the long term result could be compressor failure.

    Be interested to see the actual increase.
    Last edited by market-tech; 01-02-2007 at 06:40 AM. Reason: spelling error
    Jim
    Tucson, Az
    Keeping the Ice Cream Frozen!

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event