I inherited a freestanding direct vent fireplace and I'm trying to get it to work with a thermostat. It functions fine using the ON/OFF/PILOT switch but will not work with a thermostat. It is a SIT millivolt system and the previous owner had a thermostat hooked up to it, so it was working at one point.
With that said - the fireplace will turn on with the thermostat but it will not shutoff with the thermostat. Could it be a bad thermopile?
When the fire is lit I get a .330mv reading for the thermostat and .220mv for the thermopile.