I have a older Whitfield Advantage and the fire surges. I mean when the pellets tray get some in it flames up and burn that pile down and then almost goes out then the pellets build back up again and burns till it almost goes out. The cycle is about 5 minutes.This goes on all nite till I shut down in the morning. Every thing has been cleaned and the flu pipe is brand new. I adjusted the dampener for every position and nothing seems to help. Is this normal or what should I do? bjr23