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

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.