Hey everybody, I hope you can help me with the problem I am having converting my old Trane Mercury thermostat model #3AAT80A1A1 to a Honeywell Digital thermostat model #RTH7600B. I currently have a multi-stage heat pump system.

The Trane has wires that are connected to O, R, T, G, Y, B, W and the W wire is also connected to X2.

The Honeywell has locations for C, G, Y, O/B, RC, R, AUX, E, L (for heat pump installation)
The Honeywell also has locations for RC, R, W, Y, G, C, Y2, W2 (for conventional installation)

I have accounted for all the wires from the old system to the new system, except for the T wire. This is according to the instruction manual that accompanied the new thermostat.

Thanks in advance for helping me solve my problem.

v/r
reespy

T will probably go to l, what color is it?

t will probally go to l, what color is it?

It is green, we did eventually hook it to L, the system seems to be running properly, except it is not cooling.

Do you have a jumper between rh and rc?

do you have a jumper between rh and rc?

There is a jumper between RC and R on the Honeywell, but there is no RH

OK by not cooling do you mean it will not run in cooling mode or it is running but blowing hot air?

ok by not cooling do you mean it will not run in cooling mode or it is running but blowing hot air?

We figured out why it was running, but blowing hot air... we didn't program the thermostat to reflect that we had it hooked to a heat pump. It is cooling now, if I have anymore problems I will post another question. Thanks for your help in resolving this matter.

T is for a cooling anticipator in the thermostat. It is hooked to a thermistor in the outdoor unit. This functin is not needed and should be deleeted when replacing with a modern programmable thermostat.