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  1. #1
    Join Date
    Sep 2009
    Location
    Arlington Texas via Pennyslytucky
    Posts
    10

    Need Help solving a Mystery Comp. Fail.

    I need help solving a Mystery about a Compressor failure. A friend who owns another small AC Co. asked me to Change out a Comp. on a 5 Ton, Trane Rooftop Unit. I replaced it and it ran for about a week when he called and said it wasn't working. I went back out and checked it out. I couldn't get into the building so I went on the roof and saw it running. First I felt the Heat coming off the cond. fan and it was Hot. Then I felt the Suction pipe and it was cold and sweating. I looked over at the drain and could see water draining onto the roof. By eye everything looked good. I put my gages on and the pressures seemed high. I couldn't get into the space because it was locked.... I adjusted the pressures (-1.5lb.) without checking superheat and left. The next day my friend sent me a pic of the Frozen E-Coil. He said he had to add 5lb R-22 and left it running at a 10deg superheat. About 2 days later (total aprox. 2 weeks) the Comp. fails. He calls me and says that the Comp. was wired wrong and now he has no pressures. I went out to confirm and ohmed the Comp. windings. They had perfect ratio and no windings burnt. Comp. tried to start by dropped out quickly. I got a start kit hoping that Thermal wasn't still open. It wasn't and needed 120amps to start...then dropped to about 23 amps and continued. Still no pressures. Is it possible that I wired the Comp. wrong? Note: My friend is one of the best AC Techs I know... he doesn't miss much. I think I'm getting a bad rap. LOL Is it possible for a 220, 1ph, R-22, Trane Comp. to run with CSR wires wrong? Is it possible that 2 Techs with 20+ years of experience to both miss it?

  2. #2
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    Anything is possible right? I would have said "hey you sent a pic of the frozen coil where is the proof I miswired it "

    Because I know after you replaced the compressor you checked the amp draw on c r s and compared to data plate and also check c + r together and compare that amp draw to S right?

    Trust me I know after a long job like that some stuff can get overlooked but always try and cycle the new compressor and try and see if you can find what killed it.

    Also don't buy into the myth that hard starts are for dying compressors. A high quality 5-2-1 is a good upgrade for any compressor.

  3. #3
    Join Date
    Jul 2009
    Location
    Kansas
    Posts
    393
    Kinda hard to give any good advice without all the information... You said pressures were kinda high, exactly how high? Superheat before and after you removed refrigerant, Subcooling, Fixed orifice or TXV, Drier good? Did you weigh in Nameplate after compressor change out? Comp Name Plate Amps would be good too. Current Ambient Conditions. But it sounds like a mechanical failure to me just from the information you gave. Was the old compressor electrical or mechanical failure?

  4. #4
    Join Date
    Jul 2013
    Posts
    63
    It sounds like you've had trouble with the charge. High pressures then freezing and what not. But for him to say you wired it wrong and now it won't compress after he reworked sounds like he wired it wrong. Maybe switched run and common? Usually when it mechanically fails it won't compress but with draw little amps. It's possible it's failed mechanically but that's fast for a new compressor. I'd double check my wiring. Check charge for sure. 10 degrees of superheat is over charged. 15-18. Is it a txv? Piston?

  5. #5
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    404
    Quote Originally Posted by AirServiceCo View Post
    I need help solving a Mystery about a Compressor failure. A friend who owns another small AC Co. asked me to Change out a Comp. on a 5 Ton, Trane Rooftop Unit. I replaced it and it ran for about a week when he called and said it wasn't working. I went back out and checked it out. I couldn't get into the building so I went on the roof and saw it running. First I felt the Heat coming off the cond. fan and it was Hot. Then I felt the Suction pipe and it was cold and sweating. I looked over at the drain and could see water draining onto the roof. By eye everything looked good. I put my gages on and the pressures seemed high. I couldn't get into the space because it was locked.... I adjusted the pressures (-1.5lb.) without checking superheat and left. The next day my friend sent me a pic of the Frozen E-Coil. He said he had to add 5lb R-22 and left it running at a 10deg superheat. About 2 days later (total aprox. 2 weeks) the Comp. fails. He calls me and says that the Comp. was wired wrong and now he has no pressures. I went out to confirm and ohmed the Comp. windings. They had perfect ratio and no windings burnt. Comp. tried to start by dropped out quickly. I got a start kit hoping that Thermal wasn't still open. It wasn't and needed 120amps to start...then dropped to about 23 amps and continued. Still no pressures. Is it possible that I wired the Comp. wrong? Note: My friend is one of the best AC Techs I know... he doesn't miss much. I think I'm getting a bad rap. LOL Is it possible for a 220, 1ph, R-22, Trane Comp. to run with CSR wires wrong?
    Well, it would not last a week!

    When you visited the rooftop, the hot discharge tells you that it is transferring heat & must be producing near-correct power. The cold suction line says that SH is roughy ball park. That & the condensate discharge means that it is not froze up therefore not terribly low on charge.

    Without further info we're into speculation, eg: your friend grossly overcharged it (add 5lb???) to the point that the returning liquid took out the valves, "no pressure, he cried", and 2 days running with liquid floodback could wash out the bearings (hard start). Just a thought. He's the best tech you know? Maybe he's jerking your chain. Maybe you need a new friend??

  6. #6
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    473
    A five ton package unit only holds bout 5 lbs total

  7. #7
    Join Date
    Jul 2013
    Posts
    63
    Could liquid locked. Remove some refrigerant. Won't compress If grossly over charged.

  8. #8
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    404
    Quote Originally Posted by Tommyz23 View Post
    Could liquid locked. Remove some refrigerant. Won't compress If grossly over charged.
    Good thinking. But after hard start, why NO pressure (& no mention of internal relief howl). FLA is ballpark, that's why I threw in washed out bearings.
    Like Cap says, 5 lbs should be near-listed chge. Did OP leave cap off a leaking access valve?

    Definitely still open to discussion.

  9. #9
    Join Date
    Jul 2013
    Posts
    63
    Quote Originally Posted by IRBH View Post
    Good thinking. But after hard start, why NO pressure (& no mention of internal relief howl). FLA is ballpark, that's why I threw in washed out bearings.
    Like Cap says, 5 lbs should be near-listed chge. Did OP leave cap off a leaking access valve?

    Definitely still open to discussion.
    Hardstart or not it won't compress if its grossly over charge. He got it running. If its running its past starting. It can't overcome the liquid. But if his friend wired and its running backwards, it won't compress either.

  10. #10
    Join Date
    Oct 2002
    Posts
    1,394
    Recip compresses wired backwards will pump. Scroll will not.

  11. #11
    Join Date
    Jun 2008
    Location
    In the Boondocks near Marion, IN
    Posts
    119
    Depending upon the exact model, a 5 ton Trane Rooftop unit holds at least 10 pounds of R-22.

    It appears that the compressor is toast. Now all you can do is replace it with the usual steps, plus I would suggest: document wiring connections, refrigerant charge weight, pressures and superheat values with pictures. Let us know how you resolve this dilemma.
    Rick

    "It is easier to do things right the 1st time rather than to explain why it wasn't when you have to do it the 2nd time."

  12. #12
    Join Date
    Jun 2013
    Location
    N. Canada
    Posts
    404
    Quote Originally Posted by timjimbob View Post
    Recip compresses wired backwards will pump. ......
    Shake the 3ph out of yr head... this is a single ph compressor!

  13. #13
    Join Date
    May 2000
    Location
    Salem, WI US
    Posts
    63
    If the single phase compressor is wired wrong it will not start. Depending how it was wired wrong it could burn the windings and there you go You have a dead compressor.
    You need to verify how the compressor is wired now.

    Jlang
    Betabass



    Success is to be measured not so much by the position that one has reached in life as by the obstacles which he has overcome.

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