Hi,
I have a furnace with a heat pump. My original thermostat is a Honeywell T8411R1002 manual. The new one is a Honeywell T841A1217. The old one has places to hook up 7 wires. The new one has places for 9 wires. The Gray wire is marked as X on the old one. On the new one there is no X for the gray wire. L, B, and C is not being used. Where does the gray wire go?

Thanks,
big larry

here is a diagram for the old thermostat.

http://customer.honeywell.com/techlit/pdf/69-0000s/69-1037.pdf


here is a diagram for the new thermostat.


http://customer.honeywell.com/techlit/pdf/69-0000s/69-1217ef.pdf


According to Honeywell the new thermostat is older than the new thermostat? Could it be you got them switched in your post? I would reconsider your selection of heat pump com=ntrols if this is the case. Why would you replace a newer with a older control?

X is used as a common by some manufactures.

What brand is your heat pump?