The old Robertshaw thermostat has a black wire to the G/F screw, a white wire to the W/H/4 screw, a red wire to the B screw, and a jumper between R/RH/5 to Rc. A green wire is not connected. The new Honeywell thermostat needs an R or RH or 4 or V wire. It has screws for G, W O/B, Not used, Y, R, and Rc. Where does the Red wire that goes to the B on the Robertshaw go to on the Honeywell?

What is the model number of the new Honeywell thermostat?

Rth6300b

Go here page 13

http://customer.honeywell.com/techli...0s/69-1717.pdf

Looks like it does not get connected.

Many times wiring color code is not followed by the original installer. Any time you suspect that it is better to see exactly where each wire connects to you unit so as not to cause a problem.