[cobalt63]

I am trying to replace an old Lenox 2-wire thermostat with a Honeywell TH8000 (similar to the Honeywell RTH8500) programmable thermostat. The old thermostat has only a red and a white wire, connected to opposite sides of a coil device with no mercury bulb. I can find no markings for the wires.
The directions for the new thermostat indicate that I can connect it to a 2-wire system by connecting the power wire to the "R"/"RC" terminals (connected by a jumper) and the common side of the transformer to the "C" terminal. I connected the red wire to the "R"/"RC" terminals and the white wire to the "C" terminal. Although I've turned the thermostat to 75 degrees, nothing happens. (Yes, I turned the breaker back on :-))

I read the previous posting on this site regarding a 2-wire thermostat replacement, but it didn't seem to get to a successful conclusion. It looked as though the person inquiring just gave up.

Any thoughts? What happens if I got the wires backward?

Thanks!

[hvac1000]

Connec one wire to RH-RC and the other to W. make sure you have fresh batterys in the unit then follow the directions to set up the thermostat.

[cobalt63]

Thanks! It works now.

[hvac1000]

Glad you got it running it is cold outside.