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triciaburford
Jan 12, 2007, 08:15 PM
I have a lennox airconditioner and I am trying to wire a new honeywell thermastat to it.
There are 8 wires showing but the thermastat only calls for 5.
I need to find out what colors go to what.
Colors we have are
Yellow
Blue
Red
Orange
White
Black
Brown
Green

The thermastat is a Honeywell rth230b, can someone help?

labman
Jan 13, 2007, 11:05 PM
Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. Many have RH and RC to allow separate transformers for heating and cooling. With just one red wire, jumper them. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.