I have a Heil Quiet Comfort HVAC system in a mountain log home. The system is about 5 years old. When I turn it on and set the thermostat, the heater will come on and blow warm air for about 2-3 minutes, then shut off. After about 15-20 minutes, it will come on again for about 2-3 and shut off again. I've tried leaving the fan on, but the heating cyle remains the same. The flame looks good when it ignites, and ignites every time it tries. But, I'm anxious to get it about 15 degrees warmer! Lots of snow on the ground! It has taken 6 hours to go from 50 to 58F. Any help would be appreciated!