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  1. #1
    Join Date
    Feb 2012
    Posts
    11

    help with trane comm

    hey i'm working on trane commercial heat pump 2 stage .i was changing out the txv on the outside .i had started it up while it was running the indoor fan stopped . i looked into the problem and found the 3 pole contactor not pulled in i then pushed in contactor it started to run but chattering it has a aux contactor . voltage 208 pulling 210 high voltage 24 volt coil pulling 21v. i have never seen this before could you please help with twa180

  2. #2
    Join Date
    Feb 2011
    Location
    Sacramento, CA
    Posts
    147
    Does it have a muli tap transformer? If so make sure it's wired to the 208v terminal. Is this the only contractor that as 21v at the coil?
    I have done so much with so little for so long, that now I can do almost anything with nothing at all.

  3. #3
    Join Date
    Feb 2012
    Posts
    11
    i don't think so but it worked for years with no change.what are you thinking voltage drop or maybe weak coill? i'm all ears

  4. #4
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,855

  5. #5
    Join Date
    Feb 2011
    Location
    Sacramento, CA
    Posts
    147
    When doing start-up, one of the things you are supposed to do is set the line voltage on the transformer. With that said I have seen many units started up with 208v incoming power and the tap left at 230v. The unit will run fine for a while, eventually the coils weaken on your contacts and thats when the service calls start. Low coil volotage with make your contacts chatter, if this goes on for to long you will start to damage componets ie compressors or motors. Check the transformer and check your line voltage and your low voltage. It could be set correctly, and your transformer is going bad or you have a bad IDF contactor.
    I have done so much with so little for so long, that now I can do almost anything with nothing at all.

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