I have a Carrier 58GP furnace w/o AC.

I replaced the old thermostat which was for an older furnace and had only 2 wires, with the LUX TX500.

Currently....
Thermostat "RH" & "RC" are bridged together and "RH" is wired to furnace "R".
Thermostat "W" is wired to furnace "W".

Heat works great as it should.

BUT, I want to run another wire so that I can run the fan (blower) for circulating the air without heating.

Which letter on the furnace (C, Y, Gc, Gh, R, or W) goes to the LUX TX500 (G, Y, W, RH, RC)?

Any help on this is greatly appreciated.

Andrew

G on the tstat to Gh on the furnace. Gc is for the cooling option I believe. Many times the fan is run at a different speed for cooling, and depending on how the furnace controller is wired you could ruin a fan motor with the fan switch ON and then the tstat calls for heat and a different fan speed. If you don't know how to read a schematic to figure it out, or the instructions don't specifically tell you what you need to know, call a technician in. It'll be cheaper than calling them in to replace the fan motor.

EPMiller,

Thanks for the info.

The furnace circuit board has a hardwire bridging the "Gh" & "R".

That would make sense since the original tstat only had the 2 wires.

I'm assuming that I can now break that bridge connection and connect the tstat "G" to the furnace "Gh" for the proper wiring of the tstat with fan control.

Does this make sense?

EPMiller,

I'm assuming that I can now break that bridge connection and connect the tstat "G" to the furnace "Gh" for the proper wiring of the tstat with fan control.

Does this make sense?

Yes.

You should have mentioned that bridge in your original post, it would have made my first post smaller. :^))