[DenBoy]

I have two thermostats in an old rancher. One is a older model Bard T87F (before Honeywell put their name on it) which only controls the 26vac tank less oil burning heater with just a red and white wires. The second is also a Honeywell T87F wired with green, white, yellow and red wires and controls the attic unit and outside heat pump for cooling only. The latter transferred to a new digital Honeywell RTH6300B programmable thermostat as per instructions. This is working well but I need to incorporate the two wires from the old Bard into the new digital t-stat for heat. How can I do this? Thanks...

[labman]

If you have separate transformers, connect the red wire from the heater to RH or R removing any jumper to RC where the red from the heat pump should be connected. Then connect the white wire from the old thermostat to the W terminal of the new thermostat.

If it is fairly easy to run wires from one unit to the other, I would eliminate one transformer, connecting the other's red wire to both RH and RC. You would then need to connect the common on both units to complete the circuit.

[DenBoy]

Thank you for your help. What you advised makes sense unfortunately the running of the wires is difficult in this house. What I finally did was buy two cheap digital t-stats and just replaced what was there. I still has two t-stats hanging on the wall, but it works. Thank you, talk to you on the next project.