Question about Honeywell Programmable Thermostat Heater

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Heat will not shut off

I replaced a honeywell CT70 thermostat with a honeywell rth3100c. My wiring from the old stat was: X= blue, W2= white, R=red, G= green, O=orange, Y1=yellow, and E=brown. My new stat has E, Aux, Y, G, O, L, R, B, and C. I hooked up the new one E=brown,Aux=white,Y=yellow, G=green, O=orange, R=red, and B=blue. The AC worked fine but when the heat is turned on the fan comes on right away and the heat doesn't shut off automatically. Any ideas on what I did wrong?

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I would not connect the X (blue wire) to the B terminal. I would connect the X (blue wire) to C. Attaching X to C is actually "Optional" if your thermostat has batteries, and I know the RTH3100C does have batteries. You could just tape it off. The other wires are on correctly.I hope this works for you.

Posted on Jan 03, 2013

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Take white off of Aux, and attach it to L

Posted on Feb 16, 2009

  • Jeremy Reddick
    Jeremy Reddick Feb 16, 2009

    Sorry whit eneeds to go to common you need a common wire

  • Jeremy Reddick
    Jeremy Reddick Feb 16, 2009

    • {Terminal
      name}, {color}, {function}

    • (R),
      Red, hot side of transformer.

    • (C)
      Common side of transformer (See B)

    • (Y),
      Yellow, Compressor activity (cooling or cooling and heating on a heat pump).

    • (W),
      (W1), (W2) White, "Heat" (gas
      , oil burner
      , electric heat,
      (auxiliary heat on a
      including defrost output from the outdoor unit to activate electric
      heat and turn on the AUX. heat lamp). Note: some thermostats require a
      jumper from "W" to "Y" for heat pump operation.

    • (G),
      Green, furnace blower fan. (needed for air conditioning, heat pumps and
      some electric furnaces). NOTE: on most thermostats the "G" and "Y" are
      connected together at all times when the fan switch is in the "Auto" mode!

    • (O),
      Orange , Energize to cool (used for reversing valve on heat pumps)

    • (B),
      Blue or Orange, Energize to heat (used on some systems, Rheem/Ruud is notorious
      for this).

    • (B)
      or (X), Blue, brown or Black, common side of transformer. Needed on some
      electronic thermostats or if you have indicator lamps. Do not confuse with
      (B) Reversing valve (energize to heat) above. York and Trane like to use
      (B) as common.

    • (E),
      blue, pink, gray or tan, emergency heat relay on a heat pump. Active all
      the time when selected, usually not used.

    • (T),
      Tan or Gray, outdoor anticipator


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