Install Honeywell RTH111
I am replacing a Colman Mach Tstat with a Honeywell RTH111. Before I do this, I have checked the voltage on all wires. I am surprised to see the unit Green wire that I would think is ground has 12.6 v...
Forum Discussion
Old-Biscuit wrote:
Coleman Mach to Honeywell
Coleman
Red = +12vdc
Blue = -12vdc
Green = Fan High
Gray = Fan Low
White = Furnace
Yellow= Compressor
Honeywell
Red = +12vdc -----'RC/RH'
Blue = -12vdc NOT USED/Tape off
*Green = Fan High ----'G'
*Gray = Fan Low ------'G'
White = Furnace .....'W'
Yellow= Compressor ,,,,'Y'
*Green and Gray are used for the A/C Unit fan speed
If you do not install/modify your thermostat with a mini switch to have/use both Hi-Lo fan speeds just connect GREEN (Fan High) to 'G' terminal
Thank you so much for this post. I just installed the new thermostat and all systems are working great. I am just curious why the blue wires are used in the Colman but not the Honeywell. Once again thank you!!!!!
