I want to hook up my Honeywell rth9580wf to a natural gas garage heater that only has R, W, and G (not in use). It's currently hooked up to a standard battery powered Honeywell thermostat. I've read up on other posts for installing furnaces without C terminals, and gave it a try without luck. Here's what I did: -Using a voltmeter I tested across the R terminal, and the red wire from the control board to the transformer. Each measures ~27V. -No matter the heater's running state, I measure a constant ~27V at the R terminal and on the post of the transformer. -Hooked up the G wire (which wasn't in use) to the R, and put this in the C on the thermostat. This did not power up. -Was about to run a wire off the post on the transformer to the C, but held up before asking for advice.
I'd like some guidance I'd anyone can assist? Thank you.