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LeroyFrick 11-02-2007 09:57 PM

Changing from one Honeywell to another...
I recently purchased a Honeywell 7 day programmable thermostat replacing an older Honeywell (it was round).

Here is my question:
The older Honeywell had 4 wires to it which were marked
G, R, Y, W
and there was one wire that was not hooked up to anything coming out of the wall.

The new Honeywell (instructions) says 5 wires are needed.

The RC is the unknown wire. Do you think the 5th wire coming out of my wall is the RC wire? If not, any ideas?

cjett 11-03-2007 11:33 AM

No, the unused wire is a spare. But you can use it to get the fifth wire needed. What they probably want is the common hooked up to your transformer to power the t-stat. If that's the case, use the extra wire and hook it up to the "C" of the furnace low voltage strip, and the "C" on the t-stat.

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