i have a 5 zone radiant floor, oil fired heating system. Each thermostat only has 2 wires running to it. i have a TACO SR506 switching relay that receives the wires from each thermostat and controls the circulators and burner. The TACO relay has a 24v transformer inside. Can i attach a single wire to the COM terminal and run a wire to each thermostat that i want to upgrade?
UPDATE: due to finished ceilings in the basement, i have no access to the thermostat wires and cannot snake a wire to the COM terminal on the transformer. But a ground is ground, right, so i am wondering if i could simply run a wire to a nearby ground wire inside an outlet?!?!? I tested this idea with a multimeter and i get 26V. it seems like it will work... what do you think???