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-   -   Replacing Old thermostat, wiring confuses me (https://www.askmehelpdesk.com/showthread.php?t=401462)

  • Sep 30, 2009, 06:05 PM
    hiper97
    Replacing Old thermostat, wiring confuses me
    I am replacing an old emerson electric thermostat with mercury for a programmable Honeywell thermostat. I have only a furnace, no A/C. When I took the cover off the old thermostat I have 4 wires, 2 black and 2 white, which were connected on two connectors, black at the top on the right side and white on the bottom right side, each colour attached to same screw.

    My problem now is what wire(s) go where?? W Y or G, I am assuming the W is for white, but does this mean both white wires get attached to the thermostat... :confused:

    Isn't this supposed to be basic?

    Thanks for your help!:D
  • Sep 30, 2009, 06:18 PM
    NorthernHeat

    Connect white to white and black to red. If there is a Rh and a Rc connect it to Rh.
    And I assume you wad White. White to one termainal and Black. Black to the other terminal in the old stat.
  • Sep 30, 2009, 06:22 PM
    letmetellu

    On your new thermostat do you have some small switches that give you an option
    Of "Heat - Off - AC" and another switch that says Fan "On - Auto). If so you have a thermostat that is for heating and airconditioning but that is not a real problem you can make it work on just a furnace.

    I don't know why you have two black wires and two white wires. But here is what you do. Connect the two black wires to the terminal on the thermostat that is marked Rh. Connect the two white wires to the terminal marked W.

    This will turn you furnace on and off as the thermostat reaches the proper tempature.

    The one switch that says heat or cool should be in the heat position the other switch will not matter at all.

    If you need more help let me know.
  • Sep 30, 2009, 07:05 PM
    hiper97
    Just one final thing, there is a jumper wire between the Rh & Rc, so I believe then that I would take that out?

    Thanks for the help!!
  • Sep 30, 2009, 07:12 PM
    letmetellu

    It does not mater about the jumper, it is there for a.C. System that uses two transformers and you do not have A.C.
  • Sep 30, 2009, 07:44 PM
    hiper97

    I think I have it... thanks for your assistance!

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