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Thread: C wire attachment for a Filtrete 3M-30

  1. #1
    Junior Member

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    C wire attachment for a Filtrete 3M-30

    I installed a Filtrete programmable 3M-30 on a 1993 American Standard (Trane XL1200) heat pump without auxillary heat. The 4 existing wires Y, R, G & O wires are hooked up and the system works as it should with batteries installed in the thermostat. I have an extra wire that can be used for the C wire but need to know where to attach it in the heat pump so I don't have to rely on battery power only.
    Inside the heat pump there is only one transformer with a 24 volt output. One side of the 24 volts goes to the heat pump wiring and the other side runs to a grounding screw with numerous other grounds. My question is where do I attach the extra wire so I can power the new thermostat? Do I attach it to the other grounded wires or is there some other place it ties in? I don't want to short out something and ruin the new thermostat!




    Thanks

  2. #2
    HVAC Thermostat Specialist

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    Quote Originally Posted by Desert Heat View Post
    Do I attach it to the other grounded wires or is there some other place it ties in?
    Yes. Connect a wire from the C terminal of the Filtrete 3M-30 to the grounded wires.

  3. #3
    HVAC Thermostat Specialist

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    You would attach it to the grounded connection or a terminal in the HP labeled B.

  4. #4
    Junior Member

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    Thanks for the info guys, works perfect.

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