We are installing a new honeywell wifi thermostat have an extra blue wire in our bundle. We aren't sure where to connect the blue wire on the furnace board.
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Where to connect c wire at furnace for Honeywell Wi-FI thermostat
thermostat-c-wire
Related Solutions
First of all, don't make any assumptions about wire colors. There is no standard, everyone does it differently.
Secondly, there is a very clear C terminal in your picture, at the bottom right of the control board. It also looks like you have an air conditioner connected.
This "blue" wire you're talking about looks like it's not connected at the board. If my assumptions on the wires are correct, then all you need to do is connect the blue wire to the "C" terminal, and you'll have a C wire at the thermostat.
If I'm wrong about anything, or just for more background, you can refer to our go-to thermostat-c-wire question: How can I add a "C" wire to my thermostat? (or read any of the other questions with the thermostat-c-wire tag).
It does look like it might be a common, but only way to know for sure is to either look at a schematic of the board, or test it with a multi-meter.
Using a multimeter, set to VAC (Volts AC) mode, you should read 24V between the R and C (or in your case, "24V") terminals. You'll probably have to at least partially pull out the connector currently on the R to get the multimeter probe on it.
For reference:
- R = Constant 24V ac
- W = Heating contact (the thermostat connects this to R to turn on heat)
- G = Fan contact (the thermostat connects this to R to turn on fan)
Best Answer
First off, the green wire should connect to the
Gterminal on the thermostat. It's connected to theGterminal in the furnace, and so should also go to theGterminal on the thermostat.At the thermostat, the extra blue wire should connect to the
Cterminal. Depending on the furnace (read the documentation, and analyze the schematic to be sure), you should be able to connect the other end of the blue wire to either of theCterminals in the furnace.