[mausland]

I've been struggling trying to figure out the wiring of a new thermostat. Oil, forced hot air and AC.

The existing system has 6 wires. It is running off of a EWC-ST-2E control system. - Pic of manual attached. Wiring of existing system in the attached files.

I tried to install a new Honeywell Wifi unit (RTH6580WF). Talked to Honeywell and they said I only needed the W, R, G, and Y wire. Said to take the existing B or O wire and connect it to a common (C) for power. This configuration worked for Zone 1.

The issue I have is that with this configuration, Zone 2 (which is only 3 wires) stopped working.

I can't seem to figure out how Zone 1 is impacting Zone 2.

Any thoughts? Can I even use the new thermostat with this control unit?

Thanks,

Mike

 

[beenthere]

That panel requires the O to be energized as long as the zone 1 thermostat is in cool mode, and the B terminal to be energized in heat mode as long as th zone 1 thermostat is in heat mode. So you can't use either of the wires on O or B for teh common to your new thermostat.

 

[mausland]

Thank you beenthere.