EWC Controls Forum

Hi - It was recommended from my last post that I upgrade my existing EWC-ST-2D board to an NCM-300 if I want to use a Nest Learning Thermostat. Looking at my existing board, on the System Terminal Block, I have a red wire and a yellow wire going into the same yellow terminal (See photo). The upgrade ...

I am trying to install a Nest Learning Thermostat (3rd Gen) to my 22 year old EWC-ST-2D. The Nest has a single O/B wire and the Ultra-Zone has both a Blue and Orange wire. 1) Is the Nest Learning Thermostat compatible with the Ultra-Zone Controller(EWC-ST-2D) Zone 1? 2) If so, how should the ...

I have a EWC-ST-2D Ultra Zone Controller that originally had mercury thermostats. I replaced both Thermostats with RTH2300 series (Home Depot). In the thermostat instructions, they state if you have an orange and blue wire, then connect the O-wire and leave the B-wire open. Since the installation, I ...