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    Barryoldfart's Avatar
    Barryoldfart Posts: 2, Reputation: 1
    New Member
    		  
    #1

    Dec 14, 2007, 10:10 AM
    thermostat terminal designations not matching
    I bought a new a honeywell thermostat model TH8920 programmable to upgrade my existing lennox model 21J7101 non programmable and the terminal designations DO NOT MATCH \

    Existing terminal and wire on Lennox 21J7101 are as follow:
    O= Reversing Relay, Orange cable wire attached
    G= Fan Relay, Green cable wire attached
    Y1= Compressor contactor, Yellow cable wire attached
    R= Power from 24VAC transformer, Red cable wire attached
    L= NO DESIGNATION, NO wires attached
    T= NO DESIGNATION, Gray cable wire attached
    C= NO DESIGNATION, Black cable wire attached
    W1= Supplemental heat relay, White cable wire & red jumper wire from c to jumper
    E= Emergency heat relay, NO wires attached


    Terminal Designations for Honeywell TH8320 are as follow:
    R= Heating power connect to secondary side of heating system transformer
    Rc= Cooling power Connect to secondary side of cooling system transformer
    C= Common wire from secondary side of cooling system transformer
    Y= 1st stage compressor contactor
    Y2= 2nd stage compressor contactor
    AUX= Auxiliary heat relay
    G= Fan relay
    E= Emergency Heat relay
    L= Heat pump reset (powered continuously when system is set to Em heat, system monitor when set to heat, cool or off)
    O/B= Changeover valve for heat pumps
    S1= Optional outdoor remote sensor
    S2= Optional outdoor or remote sensor

    If anyone can help me match up these Designations or wires it would be very much appreciated. Ty barry
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Dec 14, 2007, 04:11 PM
    Look to the beginning of this board for the sticky notes. There is a wiring crossover ;located there. If that fails you will have to trace the wires to see what they control and wire accordingly.
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