I purchase the Honeyell rth6300b thermostat. I have eight wires coming from my old mercurury switched labelled as follows...
o
Y
X2
B
W
R
T
G

The honeywell has G, W ,Y, R, Rc inputs on the back. R and Rc are connected by a jumper. I am able to attach G, W, Y, R to the new thermostat. That leaves O, X2, B,T left. Can someone tell me if these are dead, or if I have to connect these? If so, I may not be able to use this honeywell in my home. My current set up is a heating unit, and ac unit that are connected to the old mercury system.

Regards,

David

If you have a heat pump with two stage heat this stat will not work. IE heat pump with electric heat is a two stage heat system.

Read this. It also came with the thermostat. READ page 6

http://customer.honeywell.com/techlit/pdf/69-0000s/69-1717.pdf