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    Jonnee's Avatar
    Jonnee Posts: 3, Reputation: 1
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    #1

    Feb 20, 2009, 02:54 PM
    Hooking up 4 wire thermostat heating and cooling.
    I'm replacing an old honeywell thermostat with the clock and peg set up with a new digital. The old one has the standard 4 wire heating and cooling- on the old therm I have an r wire white jumped to C, a blue wire W, a black wire on another C , and a red wire with no letter. Then new one has RH heating supply,RC Cooling supply jumped , W heating signal , Y cooling signal, and G Fan. I tried hooking it up and the heat stays on I need help. The new therm was set lower than room temp.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #2

    Feb 20, 2009, 03:04 PM

    Without a model number of the old stat we are guessing.

    Better yet a link to the manual.
    Jonnee's Avatar
    Jonnee Posts: 3, Reputation: 1
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    #3

    Feb 20, 2009, 04:48 PM
    I believe it is a Honeywell Chronotherm T808A.The new thermostat is a Honeywell Rth230B
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #4

    Feb 20, 2009, 09:12 PM

    I can't find any info but this:

    https://www.askmehelpdesk.com/heatin...ion-14275.html

    Is this by chance a mobile home where heat and cool modes are selected at the furnace?
    Jonnee's Avatar
    Jonnee Posts: 3, Reputation: 1
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    #5

    Feb 21, 2009, 08:27 AM
    No its not a mobile home. The house was built in 1987. I finally found a number on the theromostat. I've had a hard time determining a model number but I think it's 8460 A, this number is stamped on it under the cover by the coil. In some other reserch on the internet the black wire goes to a letter C on the old therm and I read that goes to the clock and I should tape this off and wire as a 3 wire?
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #6

    Feb 21, 2009, 11:34 AM

    What bothers me is that with AC, you usually have a G(Fan) terminal, because in AC mode the thermostat controls the fan.

    R to Y should turn on just the outside unit
    R to G should turn on just the FAN
    R to W should turn on the fan and heat if fossel fuel (oil/gas)

    Common to R will do nasty things like blow fuses or blow transformer. There should be 24 VAC between R &C at all times.

    (C) may well be jumped to R in one case and the other (C) would be considered Common in the old stat.

    It's puzzeling that there is no fan terminal.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #7

    Feb 21, 2009, 12:58 PM
    You may have to look where the thermostat wires connect to the indoor unit, identify the letter designation of each terminal and the color of the wire connected to it, to determine how to wire up the new t-stat.
    Mikie D's Avatar
    Mikie D Posts: 45, Reputation: 1
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    #8

    Mar 13, 2009, 05:13 PM

    Simply go to the furnace and see what wires are on the terminal strip but at the tsat ,jump Rc and Rh W to W G to G Y to one side of contactor at condenser .Mikie D.
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