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    nigrafeles's Avatar
    nigrafeles Posts: 1, Reputation: 1
    New Member

    Nov 11, 2006, 09:57 AM
    Thermostat wiring - extra wire
    I'm replacing a Honeywell TH110D non-programmable thermostat with a Honeywell RTH230B Programmable. The old one has 6 wires
    -Rc (jumpered to R)
    -R (red)
    -Y (yellow)
    -C (green)
    -W (white)
    -G (blue)
    And the new one has Rh, Rc, W, Y, and G. I have all those connected as per the directions but there's that extra wire that went into the old thermostat's C terminal. The manual says its "Common wire from secondary side of cooling system transformer" and "Optional when thermostat is used with batteries." , and the wiring diagrams label it as "Optional 24 VAC Common Connection". Since our old thermostat was not used with batteries this was powering the display (new one is batteries only) is it OK to just tape this wire off, or do I need to disconnect or ground or jumper it in the furnice too?
    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
    Ultra Member

    Nov 11, 2006, 12:36 PM
    Yes the new stat doesn't use a common wire since it doesn't use 24 V. to power it just tape it off.
    epro's Avatar
    epro Posts: 2, Reputation: 1
    New Member

    Oct 24, 2013, 04:44 PM
    What if I have an e wire? And know where for it to go?

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