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-   -   Wiring 2 wires (red & white) to Honeywell RTH9580 thermostat -NEED 3rd, C WIRE (https://www.askmehelpdesk.com/showthread.php?t=818994)

  • Dec 3, 2015, 01:53 PM
    PenName
    Wiring 2 wires (red & white) to Honeywell RTH9580 thermostat -NEED 3rd, C WIRE
    Hello. I am trying to replace old Lux thermostat (similar to Lux TX500E) with new Honeywell RTH9580 model. Here's my situation:
    - Old (1950s) gas floor furnace.
    - We have NO air conditioning, and no fan - only the gas furnace.
    - We have only 2 wires: red and white. These were connected to the Lux on the W (white wire) and RH (red wire) terminals.
    - The new thermostat requires a third C wire which we do not have.
    - Honeywell's info. Says that if no C wire, this model will not work.

    I watched a video which showed how to create a C wire by modifying an AC power adapter/transformer with plug: https://www.youtube.com/watch?v=8a_f2_iAW1U

    a. Is this safe to do (modified adapter)?
    b. I would rather hardwire, instead of using adapter; is it safe to connect, instead, to a house wall outlet (through wall to the other side of wall/different room), and would this work correctly?
    c. Optimally, if somehow possible, I would like to use only the two existing wires make this thermostat work, with all features operational, including Wi-Fi.

    Please let me know if you need more information to answer, and thank you SO much for any help.

    Happy Holidays!
  • Dec 4, 2015, 02:38 PM
    ma0641
    That is a low voltage connection. Using house voltage will blow the thermostat. Find another compatible model or run another thermostat wire.

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