I have a vermont castings DVBR36 fireplace that I had installed by a certified HVAC contractor in our new house. However, I have yet to see it burn for more than 5 minutes. The pilot light will stay lit for as long as I want, but as soon as I turn on the wall stat the flames will go for about 3-5 minutes. I have had the contractor raise the roof cap as I am in a high wind area, and he has also replace the thermal pile as it was apparently not generating enough of its own electricity to keep it burning. Still this did not fix the problem, and now I cant seem to get ahold of the original contractor. Does anybody have any suggestions on what is wrong or how to fix the problem?