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View Full Version : Replacing T874C1018 (Honeywell multi-stage ) with RTH221 (programmable thermostat)


tsimaryland
Dec 2, 2008, 08:00 PM
I am replacing a honeywell mutlistage thermostat with a programmable one. All of the wire designations seem pretty clear, except that the programmable unit does not have a designation for location w2 (this is a blue wire that's being used with the current thermostat.. do I put w1 and w2together and terminated them at the "w" location that's provided on the programmable thermostat?

greghvacguy
Dec 2, 2008, 08:18 PM
No if you do that 2nd stage on your furnace will run all the time when your thermstate calls for heat. Sounds like your new stat is for 1 stage of heat not 2. is your furnace 2 stage or one. On your new stat what is all of the hook ups (r,y,w,c,g,w1,w2,y1,y2)

tsimaryland
Dec 2, 2008, 08:23 PM
Thanks for responding... the hookups on the programmable thermostat are: y, g, rh, rc, w.

greghvacguy
Dec 2, 2008, 08:29 PM
What about the old on. Sounds like you have the wrong t stat

tsimaryland
Dec 2, 2008, 08:36 PM
On the old thermostat the hookup is: y, g, rh, w1, w2


(rh and rc locations are bridged on new thermostat)

greghvacguy
Dec 2, 2008, 08:42 PM
Rh 24 volts for heat and rc 24 volts for ac.keep them jumped. The old t state is a 2 stage heat the new one is not if your furnace is 2 stage then you need new t stat that does 2 stage.check your furnace and find out what is hooked up to what.

tsimaryland
Dec 2, 2008, 08:58 PM
... just read paperwork with new thermostat--- "not conpatible with multi-stage systems" which is what I seem to have. I'll have to get the right one. Thanks for your help!