Another adding the C wire thread (to WiFi thermostat)

Discussion in 'HVAC Heating & Cooling' started by Shai, Jul 6, 2016.

  1. Shai

    Shai New Member

    Jul 6, 2016
    I hate to do this, but the other posts don't give me a clear answer, so here I am putting up this post.

    So I have two wires connected to my thermostat. The voltmeter says I have 28V when I test the two wires and when the heater turns on, it doesnt show anything. I suppose that means I have a a Common and Hot wire? If so, can I jump the Common wire into the common slot on the Ecobee3 thermostat?
    If so, how do I determine which wire is the Common and which one is the Hot?

    Any help would be appreciated!

  2. Stuff

    Stuff Well-Known Member

    Mar 7, 2013
    Two wires means there is no common. One is hot (Rh) and one is for heat call (W) .

    Sometimes there are additional wires hidden in the wall. Easiest to check on the furnace end.

    If you really only have two wires you can use this:
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