Thermostat wire codes don not match

Discussion in 'HVAC' started by ufatbasted, Oct 12, 2008.

  1. Oct 12, 2008 #1

    ufatbasted

    ufatbasted

    ufatbasted

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    Hello

    I'm attempting to install a Honeywell programable thrmostat to replace my old mercury white rogers t stat.


    When I pull the old T stat it has 4 wires coded as follows
    TC
    T
    RH
    W.


    The new thermostat mentions RH and W wires but I'm nit sure what the T1 and T wires are for. My guess is a timer as the old TStat had a timer and did not use batteries. I'm tempted to just cap them and go on with the install.

    Anyone have any ideas?


    Thanks
     
  2. Nov 3, 2008 #2

    Katonah Medic

    Katonah Medic

    Katonah Medic

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    I just replaced my old mercury stats with the same Honeywell P'gramable stat.

    My 24v system only has two wires.

    The Rh and W are the only ones you need to have it run, assuming its heat only and hot Heat/Cool.

    Check the transformer on your zone circulator and you should see only 2 wires attached..

    This may be a late post. Let us know how it worked out for you.
     

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