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Thread: Thermostat Wiring Help

  1. #1
    Junior Member

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    Thermostat Wiring Help

    I'm trying to change out my old Trane Weathertron Thermostat with a Carrier Thermostat. Below is the information I know about both (which isn't much):

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    Trane Weathertron Baystat239A - Currently there are eight thermostat wires hooked up to this thermostat. Those wires are below with my understanding of what each of them are based on looking through the web.
    X2 - Emergency Heat
    O - Switches the heat pump from cooling to heating
    G - Fan
    Y - Compressor in both heating and cooling
    T - Outdoor temperature compensating thermostat sensor
    R - Hot power
    W - Aux heat
    U - No wires connected
    F - No wires connected
    B - Common




    The thermostat I'm replacing the Trane thermostat with is a Carrier Comfort Series Non-Programmable (33CSCNACHP-01) thermostat.
    Rc - 24V Cooling equipment
    Rh - 24V Heating equipment
    W/W1 - Heating
    C - Common
    G - Fan
    Y - Cooling
    O/B - Reversing Valve
    Y1 - Not used

    Can anyone help me figure out what goes to what? I obviously have very little idea about these but I'm remotely handy so I figured I could replace it myself...Any help is greatly appreciated.

  2. #2
    HVAC Thermostat Specialist

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    Trane X2 - Emergency Heat = You will not have this switching option on the Carrier thermostat.
    Trane O - Switches the heat pump from cooling to heating = Carrier O/B - Reversing Valve terminal.
    Trane G - Fan = Carrier G - Fan terminal.
    Trane Y - Compressor in both heating and cooling = Carrier Y - Cooling terminal.
    Trane T - Outdoor temperature compensating thermostat sensor = Not used on Carrier thermostat
    Trane R - Hot power = Carrier RC & RH terminals. Connect trane R terminal to one of the Carrier RC or RH terminals and then jumper RC and RH together at the carrier thermostat.
    Trane W - Aux heat = Carrier W/W1 - Heating terminal.
    Trane U - No wires connected = Not used on Carrier thermostat.
    Trane F - No wires connected = Not used on Carrier thermostat.
    Trane B - Common = Carrier C -Common terminal

  3. #3
    HVAC Thermostat Specialist

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    X2 and W thermostat wires are commonly both connected to the W terminal of the new thermostat. Most times they are connected together at the air handler anyways. I've not seen an air handler with an active emergency heat terminal that was less than 20 years old.

  4. #4
    HVAC Thermostat Specialist

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    old thread... Servicetech! Please check dates when responding to threads.

    BTW, air handlers effectively do have emergency heat terminals depending upon how they are wired and how many banks of heat strips they have installed. It varies by manufacturer. I have recently worked on bryant air handlers (5-6 years old) that actually had an emergency heat connection on the circuit board that controls the strip heaters.

  5. #5
    HVAC Thermostat Specialist

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    Quote Originally Posted by hvactechfw View Post
    old thread... Servicetech! Please check dates when responding to threads.

    BTW, air handlers effectively do have emergency heat terminals depending upon how they are wired and how many banks of heat strips they have installed. It varies by manufacturer. I have recently worked on bryant air handlers (5-6 years old) that actually had an emergency heat connection on the circuit board that controls the strip heaters.
    Missed the age of the thread, it was on the first page after all

    On the bryant system how did the E terminal respond differently than the W terminal? All the newer stuff typically just has W1 and W2, one for each bank of heat strips. Typically W1 and W2 are simply hooked together at the air handler, rarely is a 2 stage thermostat used to control each bank separately. Digital thermostats rarely have an E terminal, unless they were early models.

    A way to wire the system that would conserve on AUX heat use would be to wire W1 to the thermostat and W2 to the defrost wire coming from the condenser. In most installations 1 set of strips is plenty to keep the house warm if the heat pump were to fail. Defrost would be cooler than usual since only 1/2 of the strips would be used to temper the cold air from the heat pump. If it was really cold the thermostat would bring on 1 bank and the defrost would bring on the 2nd bank of strips during defrost.

    Advanced thermostats can do 2 stages of AUX heat and could activate the 2nd bank of strips if needed.

  6. #6
    HVAC Thermostat Specialist

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    E turned on all heat strips where as w1 only turned on 1 heat strip.

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