Have an old Robertshaw Energy Manager thermostat. It has a three wires connected: a G/F, a W/H/4, and one attached to B. There is also a jumper between R/RH/5 to Rc. There is no R wire. I need to wire my new Honeywell RTH6300B and don't know where the B wire goes. It has the G/F, W/O/B, Y, R, and Rc-but no B. How do I wire it up. The heater is a BDP Hvac 349DAW000080. Don't know where to connect the three wires to themostat.

Very simple installation once you know what's what.

Turn off power to furnace at breaker or service switch on furnace.

Go to the furnace, and open up the electric compartment (in the bottom in the blower compartment). There will be 3 wires connected, but you will now need 4. This will not be a problem in most cases, as there should be 2 wires or more unused and wrapped around the sheath.

The wires being used are probably red, green, and white. Hook them up in the furnace as follows. Red wire to R. Green wire to G. White wire to W. Now the 4th wire you will need to wire to the C terminal on the furnace. Now go to the thermostat. At the thermostat, hook red to RH, green to G, white to W, and the final-fourth wire-to C.

The jumper between RH and RC is for cooling, and it really doesn't matter if it stays or goes. Leave it, you may wish to add A/C later and this way you won't have to make a jumper... LOL.

If you follow this wiring, you will be golden.

Note: If you DON'T have a 4th wire available, simply abandon the G terminal on the thermostat and wire the G wire to C at stat as well as at furnace. This will not affect heat, but will remove the ability to control the fan from the thermostat. In this case-R-R, W-W, C-C. Good Luck!