Taco Switching Relay
Can I apply 24VAC across the R & W terminals on the t-stat input connections as a demand?
No if you do you
will burn out the transformer in the relay. The connections to R and W have to be dry contacts such as thermostat, aquastat, or end switch on a zone valve.
Dry contacts...
Tim, I think he means to jump out the terminals. No, do not apply 24 vac, yes jump out or dry contacts like in your t-stat. Board provides it own power so do not ad any other t-former.
Peace
Mike T.