I am trying to replace a heat pump thermostat. It was a Lennox Thermostat and I am replacing with a Honeywell R TH3100C. The letter wiring designations do not match up. On the Lennox I had R, V, F, M, L, A, Y, X the E (did not have any wiring hooked to it). My options on the Honeywell is E, AUX, Y, G, O, L, R, B, and C. I need help as I am very confused. Thanks for your quick response Mom of three kids. :)

I am trying to replace a heat pump thermostat. It was a Lennox Thermostat and I am replacing with a Honeywell R TH3100C. The letter wiring designations do not match up. On the Lennox I had R, V, F, M, L, A, Y, X the E (did not have any wiring hooked to it). My options on the Honeywell is E, AUX, Y, G, O, L, R, B, and C. I need help as I am very confused. Thanks for your quick response Mom of three kids. :)


Lennox and others wiring change over doc.

What about the A (Orange) Wire, where would it go on the Honeywell RTH8500?