Out of the fireplace I have Red and White millivolt wires leading to the tstat. Red is connected to RH and White to W. I have a 24VAC transformer I was planning to use to power the wireless module. From the transformer, was planning on running the "C" wire, but I am unsure whether I need a common or neutral wire between the tstat and transformer. I need to hook both wires to transformer to get a full 24 volts. Thanks for your help!