hvactechfw's Avatar

Join Date: Jan 2011
Posts: 6,245

01-26-12, 04:07 AM   #23 (permalink)  
If you really do have a millivolt system you are going to let the smoke out of your gas valve by wiring it without the relay. A millivolt system runs on 750mVDC. When the thermostat calls for heat it connects RH and W. Using your transformer you connect RC and C and from your millivolt system you would connect RH and W. This will only work as long as RH and RC are not internally or externally connected otherwise you need to use a relay. Not all 2 wire systems are millivolt systems. Goodluck with your endeavors.