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wcb22 01-09-2011 07:57 PM

Honeywell thermostat wiring
I have an old Honeywell Round T87F non-programmable thermostat that I'd like to replace with a new Honeywell RTH7500D programmable thermostat. The thermostat controls an American Standard Freedom 80 single-stage furnace and air conditioner (which heats our bedroom level) and has an additional thermostat in our third floor loft. Connected to my old thermostat, I have the following wires: B, G, Y, W, R, O. How do I connect this to my new thermostat? The "conventional" connections on the new thermostat are labeled: C, G, Y, W, RC, R, W2, Y2. The "heat pump" connections on the new thermostat are labeled: C, G, Y, O/B, RC, R, Aux, E, L. Thanks for your help.

hvactech126 01-09-2011 08:11 PM

do you have a heat pump? is this t-stat you are replacing for the heating only? and the other stat for cooling only?

wcb22 01-09-2011 08:50 PM

Yes, I do believe I have a heat pump. The unit is located in my attic and heats our 2nd floor bedroom level (where the thermostat I'm trying to replace is located) and our 3rd floor loft level (where the other thermostat is located). The other thermostat on the 3rd floor does not control heat/off/cool or fan/auto; it's just controls temperature.

gregzoll 01-09-2011 08:54 PM

Doesn't anyone ever look at the booklets that come with their thermostat, or just toss it in the garbage can with the packaging. WCB22, if you have the book that came with it, it will show you. You need to just land the same wires that are on the existing thermostat on the same screws for the new one. Also, look at the manual for your furnace for the directions it gives on hooking up thermostats.

If you do not have either book, the manufacturer websites have the books available on them for downloading.

hvactech126 01-09-2011 09:16 PM

this thermostat will not work. you need one with separate o and b terminals.

wcb22 01-10-2011 05:54 AM

Thanks, hvactech126.

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