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  1. #1
    Join Date
    Nov 2011

    New Thermostat - Furnace won't power

    Hi, I've just purchased a new thermostat and installed, and now I'm not getting power at the furnace. It worked perfectly before installation.

    Steps I took:

    1) Turn the main power off to the furnace (breaker).
    2) Flipped the switch to turn power off at the furnace.
    3) Remove the old thermostat and take note of the connections:
    - Red to R
    - Yellow - Y1
    - White - W
    - Green - G
    - Blue - not connected
    4) Connected the new thermostat exactly the same (Venstar T110REC and T1100RF).
    5) Flipped the breaker back.
    6) Flipped the switch at the furnace back on.

    The red LED isn't turning on at the furnace. It's as if there's no power to the furnace or something. Nothing happens when I flip the switch. The power light at the thermostat is also not turning on.

    My upstairs furnace has the same thermostat and I installed it a few years ago. The only difference is that the company support told me to connect the blue wire to 'C' both at the thermostat and the furnace. It's worked beautifully for 2 years.

    I tried connecting the blue wire to C on the new thermostat and furnace, but still the same. Nothing happening at the furnace.

    I tried putting the old thermostat back on. Same. Nothing happening at the furnace.

    Now I'm at a loss. Suggestions? Does it sometimes take some time for the furnace to reset? Did I break something?


  2. #2
    Join Date
    Aug 2011
    This is not a DIY site ( read the rules ) If power is on and door closed properly that power switch is engaged and still no go it is time to call a pro. Something shorted out on stat changeover.
    There is no bad beer, some just taste better than others.

  3. #3
    Join Date
    Dec 2002
    Quote Originally Posted by rdblatch View Post
    I tried connecting the blue wire to C on the new thermostat and furnace, but still the same. Nothing happening at the furnace.
    Well that created a direct low voltage short as soon as you turned the stat on if you did that, why did you mess with any wiring at the furnace?
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  4. #4
    Join Date
    Nov 2011
    Sorry. My apologies. Didn't see that this isn't DIY but see it now.

    System finally came back on with the old thermostat. Only reason I connected the blue C to C is because that's exactly how it's setup on my upstairs furnace (same one) and it works fine. Perhaps a poor decision, but panicked with no heat.

    Thanks for your responses. Sorry for the post. Feel free to delete this thread.

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