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Thread: Left her dead in the water. However, tomorrow...

  1. #1
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    Left her dead in the water. However, tomorrow...

    Working with 2 different Rheem heatpump RTUs.

    Trades are remodeling interior of a local buisness. Poor guys would really like some cool air. I am tasked with resolving the situation.

    Anyway, ran out of time on this one, was looking for some kind of collective brain storming magic for tomorrow.

    Power on unit, Thermostat calls for cooling, indoor blower engages, 5 minute compressor delay, then the sound of a contactor pulling in (sounded strange, almost as if it immediately released), no start on compressor or condensing fan (Of course), 10 seconds later smell something cooking, 10 more seconds go by my transformer goes critical and blew up in a fit of smoke & dissatisfaction. Never popped my 3amp fuse on the transformer, which I have never seen in person.

    Hoping to pull a direction to go out of the ether, besides I am sure you all like to play this game

    If I was just guessing, I would guess the contactor but, my guess has been off before.

    Strange it did not pop the fuse though.

    Thanks for reading!

  2. #2
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    Did you check the compressor windings?

  3. #3
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    Thread Starter
    The stepdown 208v to 24v transformer went critical, literally popped & smoked out.

    I will add that I did have this RTU in operation for about 2 hours in cooling mode.

    Yes, I will say the compressor windings are intact & not shorted/grounded.

    My next guess might be the thermostat wiring to the thermostat. I would imagine my issue is on the control side of this circuit.

    Basically, I had this unit running in cooling mode, I had removed my thermostat wires from the RTU's PCB & connected my R,Y,G to throw in some cool air. The unit operated fine. Some time later I make the move to wire the thermostat back up, do the deed, turn my disconnect on &

    Thermostat calls for cooling, indoor blower engages, 5 minute compressor delay, then the sound of a contactor pulling in (sounded strange, almost as if it immediately released), no start on compressor or condensing fan (Of course), 10 seconds later smell something cooking, 10 more seconds go by my transformer goes critical and blew up in a fit of smoke & dissatisfaction. Never popped my 3amp fuse protecting the transformer.

  4. Likes trippintl0 liked this post.
  5. #4
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    Where did you connect R,Y,G? Sounds like someone mis-wired the t'stat or could be one of the workers damaged the t'stat wire, ohm it out. The cooling was fine for two hrs, then you rewired t'stat and then the problems happened. The RTU's are heatpump? Whats up w/ B & O ? What is line voltage? Single or 3 phase? Where were you when you heard the contactors energize & de-energize?

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  7. #5
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    Time to start troubleshooting instead of guessing. One thing at a time.
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  8. #6
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    logic would dictate a stat wiring issue....

    which side of the transformer smoked...primary, or secondary?

  9. #7
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    Maybe thermostat wires rubbed through in the wall?

    Sent from my SM-G892A using Tapatalk

  10. #8
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    Quote Originally Posted by MrReedz View Post
    Working with 2 different Rheem heatpump RTUs.

    Trades are remodeling interior of a local buisness. Poor guys would really like some cool air. I am tasked with resolving the situation.

    Anyway, ran out of time on this one, was looking for some kind of collective brain storming magic for tomorrow.

    Power on unit, Thermostat calls for cooling, indoor blower engages, 5 minute compressor delay, then the sound of a contactor pulling in (sounded strange, almost as if it immediately released), no start on compressor or condensing fan (Of course), 10 seconds later smell something cooking, 10 more seconds go by my transformer goes critical and blew up in a fit of smoke & dissatisfaction. Never popped my 3amp fuse on the transformer, which I have never seen in person.

    Hoping to pull a direction to go out of the ether, besides I am sure you all like to play this game

    If I was just guessing, I would guess the contactor but, my guess has been off before.

    Strange it did not pop the fuse though.

    Thanks for reading!
    Any follow up?

  11. Likes R600a liked this post.
  12. #9
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    contactor not pulling completely in and if so it will take out a transformer if not fused,,,
    “A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot.”
    ― Robert A. Heinlein

  13. #10
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    pull the cover off of the contactor and look at the burned contacts.
    " The more I learn the more I realize how much I don't know"

  14. Likes R600a liked this post.

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