I am trying to replace my old thermostat with a Honeywell RTH7500. My old wiring is as follows.
C-blue wire
G-green wire
R-red wire
W2-white wire
O-orange wire
B-black wire
Y-yellow wire
E-brown wire
Everything matches up to the new Honeywell just fine except for the O and B. On the new thermostat, I still have an O/B terminal and an L terminal available (as well as the RC which is currently connected to R with a jumper).
The manual says "If your old thermostat has seperate O and B wires, attach the B wire to the C terminal. If another wire is attached to the C terminal, stop now and contact a qualified contractor." An account that I read online said to connect O to O/B and tape off B. Any other suggestions?