Question about Honeywell CT87B ROUND HEATING&COOLING MECHANICAL THERMOSTAT - WHITE Heater

1 Answer

Replacing a thermostat

Im replacing my thermostat and the one im replacing the old one with has different colored wires and a little different and newer all together. Just wanted to make sure a had it hooked up correctly before plugging it in and i dont have any instructions to use. i think its a honeywell but not sure. All i have is this info. the product i selected below is not my thermostat but couldnt locate it in your list.
0546 TYPE
LR27935 1F56-486
CLASS 2 153-4242
PART NUMBER 1147165

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  • rwblue Sep 07, 2008


    I am replacing my old thermostat with a Honeywell RTH3100c, but the wires layout is different. Information about the new and old product.




    Old

    H4/Honeywell?

    0546 TYPE
    LR27935 1F56-486
    CLASS 2 153-4242
    PART NUMBER 1147165


    Connection

    White – G Blue – Y

    Yellow – Y Red - RC à RH

    Green – G No wire A and B

    New

    Honeywell

    RTH3100C

  • SHARCNET-USA
    SHARCNET-USA May 11, 2010

    How many wires do you have coming out of the wall and what are their colors? Do you know what the functions are for each color?

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  • 1,420 Answers

Typically if you are replacing a heat only thermostat you will have two or three wires. On the old thermostat these wires will be attached to terminals marked "R", "W" and maybe "G". Document what color wires goes to which terminal and transpose these to the new thermostat. If you have a heat and cool thermostat, you will have two or three more wires and connected to terminals labeled "C", "B" and "Y". Again, transpose these wires to the new thermostat as best you can.

Posted on Feb 12, 2008

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