EWC Controls Forum

I went ahead and changed both zone 1 and 2 thermostats (t601-2) as recommended but there is no change. The problem continues as described in my original post above.

Could you please recommend a specific pro1 thermostat, the one pro1 recommended requires a c wire.
Also, in this master slave type thermostat relationship what is the purpose of blue and orange wires as I don’t see a connection for a heat pump?

I have an ST-2D control panel which takes input from 2 thermostats, first and second floor. First floor thermostat is a 6 wire thermostat and second floor thermostat is a 3 wire thermostat. First floor thermostat is connected to zone 1 tstat on the panel and 2nd floor thermostat is connected to zone ...