I bought an earth stove natural fire stove by lennox used. It is about 10 years old. Having a problem with pellets not burning on higher feed settings. On this stove, manual, the draft fan can be set to off, low and high. The feed rate can be set on low, medium and high. When feed is on low and draft is on low or high, pellets burn up to completely to ash. When feed rate goes up to medium or high, lots of flame, lots of heat, but also lots of black, unburned, wasted pellets. Have to clean ash pan everyday. Can't keep house warm enough on low feed sometimes. Wasting lots of money on pellets. Draft fan doesn't seem like there is much difference between high and low. Please help soon. Any suggestions would be appreciated. By the way, I am female, new to this, and do all the work myself.