I purchased a Regency F2450 high-efficiency stove. We had all kinds of issues with getting a fire started. Over time we learned that if it is under 250 it needs a lot of TLC. However at the end of the season the chimney was almost 100 percent occluded. I checked with the dealer and they NEVER called me back.(no help). I finally was able to clean it out and started using it this season, within 6 weeks, it is again plugged enough that it will not draft enough to support a fire. I am looking for any help I can get. Firebox runs at 400-500 and stack is about 250. 10ft single wall inside, 15ft Triple wall outside stack. Thanks.