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  1. #1

    Trane twr contactors close 24V but open with full power

    With circuit breaker box power on (24V) but outside disconnect removed on Trane TWR split system heat pump, the relay contactors pull in. But, when I reinstall the outside disconnect (120/240V), the single-pole relay contactor points release and stay out. The condensor fan tries to start for that millisecond before contacts pop back out. Once contactors pops out, fan stops.
    Points stay out until I remove the disconnect. Then they pop back in due to 24V. When I turn power off at inside breaker box, then the points release due to no power.
    I find no obvious visible problems. I recently replaced the start capacitor. Using ACV 500 meter setting, the fan motor draws about 50 volts (out of 230 rated) for that milisecond it stays on before going back to zero V. Anybody actually seen this exact problem before.
    I had the relay out and cleaned it of bugs etc and reinstalled it following my own drawn wiring diagram. Is this a short somewhere. where to check first or next???

  2. #2
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    Unless this is a packaged unit, the power for the contactor originates at the air handler. I'd go looking for a bad ground/neutral in the low voltage circuit.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  3. #3
    Thank you Skippedover. It's not a PTAC. It's a Trane residential split system unit.
    One other note, when the contactor points are released, the points are not just released, they are pushed out further than they go when at rest with no power. It is like the coil is repelling instead of pulling. How could a short cause that? What would happen if when I reinstalled the relay, I wired it so the contactor side was on the right instead of on the left side? Being alternating current, should that matter?
    Lastly, grasping at straws, a dumb question. I filed off some carbon from the points. I didn't remove that much silver to matter. But, could the steel filing have magnetized the steel plate the contacts are welded onto, so much so as to cause them to repel when the full 120/230 Volts hits it?

  4. #4
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    you are boardering on DIY info request, might want to read those rules you agreed to when you signed onto this board.

    if you have to ask what to check.......................the phone book is the correct response
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  5. #5
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,418
    electrictim

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