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  1. #1
    Join Date
    Apr 2010
    Location
    Northern Illinois
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    22

    Single phase condenser motor running backwards

    Forgive my lack of detail as I'm not the one working on the system (and am a new apprentice)...

    The basic situation is that we have a single phase condenser fan rotating backwards. The fan blade has not been changed or flipped. The wiring was moved to the other fans for troubleshooting and the problem transfers to the other fans each time. The capacitors have been replaced as well. The problem remains.

    It's a Carrier package unit with two stages and three condenser fans.

    I understand how this could happen in 3 phase, but what might cause this to happen in single phase?

  2. #2
    Join Date
    Aug 2007
    Location
    Winter Haven, FL
    Posts
    4,379
    Your fan motor has 3 wires just like the compressor (single phase). If the run and start wires are reversed on the capacitor then the rotation will be reversed.

  3. #3
    Join Date
    Mar 2006
    Posts
    31

    Question

    As per the AOP Rules only Professional Members * can reply with advice to the OP. Anyone may post and ask questions. They may even question the * member answer but not give advice or expand on the advice given. Please read these rules for a complete understanding. AOP Rules

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    Last edited by Chris_Worthington; 07-23-2011 at 07:55 AM.

  4. #4
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,563
    As per the AOP Rules only Professional Members * can reply with advice to the OP. Anyone may post and ask questions. They may even question the * member answer but not give advice or expand on the advice given. Please read these rules for a complete understanding. AOP Rules

    For those in our industry who wish to become a Professional Member, please click here and follow the instructions. Apply for Professional Membership
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  5. #5
    Join Date
    Apr 2010
    Location
    Northern Illinois
    Posts
    22
    Further info:

    motor is 460, single phase.

    The tech today tried reversing the start and run wires on the capacitor with no change in rotation. He once again moved the wires to another fan and this time, the problem did NOT move with the wires.

    I am beginning to think there is a gremlin in the machine.

  6. #6
    Join Date
    Jul 2003
    Location
    Massachusetts
    Posts
    288
    the fan may not have the right power at all, and may only be giving the illusion of running backwards. think about this, and see how you could prove that this statement does not apply.

  7. #7
    I have had this problem 2 times so far. Not saying that your answer will match mine cause it may not. So you should check into it more. I found that the motor was bad and the winding was so burned out that it made the motor spin the opposite direction. Everything was wired up right I went over it 3 times. I replaced the condenser motor and wired it the same way and it spun the right way after install. Again not giving you the answer this was just my situation only.

  8. #8
    Join Date
    Apr 2010
    Location
    Northern Illinois
    Posts
    22
    Quote Originally Posted by hvacjamie View Post
    the fan may not have the right power at all, and may only be giving the illusion of running backwards. think about this, and see how you could prove that this statement does not apply.
    Well, as I said, I'm a new apprentice...you lost me at "giving the illusion of running backwards." It's definitely running backwards...sucking air instead of blowing.

    Are you trying to say that if the motor is under-voltage, it'll run backwards?

  9. #9
    Join Date
    Jul 2003
    Location
    Massachusetts
    Posts
    288
    Quote Originally Posted by killer v View Post
    Well, as I said, I'm a new apprentice...you lost me at "giving the illusion of running backwards." It's definitely running backwards...sucking air instead of blowing.

    Are you trying to say that if the motor is under-voltage, it'll run backwards?
    sometimes, if both fans are running, and only one has power, it will pull the other and make it appear as though it is going backwards. other than that, your problem will be in the wiring. study the schematic carefully.

  10. #10
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    Quote Originally Posted by killer v View Post
    Well, as I said, I'm a new apprentice...you lost me at "giving the illusion of running backwards." It's definitely running backwards...sucking air instead of blowing.

    Are you trying to say that if the motor is under-voltage, it'll run backwards?
    Carry on lad. There's a wealth of discussion on this very topic on the pro side. Get your posts up and then apply for pro status. You'll be amazed at the help and discussions and the huge talent pool of those on that side. The motor should not run backwards. If it does, well.....

  11. #11
    Join Date
    Apr 2010
    Location
    Northern Illinois
    Posts
    22
    Quote Originally Posted by hvacjamie View Post
    sometimes, if both fans are running, and only one has power, it will pull the other and make it appear as though it is going backwards. other than that, your problem will be in the wiring. study the schematic carefully.
    Now I see what you were saying. The motor is definitely running backwards though. The one time I was there, we isolated it and I gave it a spin in the correct direction. My partner pushed in the contact and it spun back the other way.

    Granted, my electrical knowledge isn't quite there yet (more classes coming) but I just can't wrap my head around this one.

  12. #12
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,124
    If you're double certain its wired correctly and has a good run cap, throw a new motor in and be done with it.

  13. #13
    I agree with chuck. New one.!

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