EWC Controls Forum

Thank you for the explanation and info; Appreciate it! Not sure what is meant by the O and B terminal, but I assume I need to bring in a common wire since the Nest doesn't have a battery. Does that need to come off the same 24v transformer as is serving the R wire? I see 2 transformers on my air ...

have a 3 wire EWC thermostat,part of 2 zone system with damper control board from EWC. Installation 1990. There is a remote switch for heat/ac/off along with fan auto/on I'd like to change to a smart thermostat, and note 3 wires in my thermostat: Y6; R5; W4 are there equivalents of these wires to ...