Turns out, draft is pretty important.

[BrianH]

Let me preface this post by saying, I'm no longer having any trouble with my USSC King Model 8500 pellet furnace. I've been burning sawdust and wax through this thing for 5 years and had a forced air log burner for 10 years before that. I'm no noobie to the wood fire world. Just thought I'd pass along some findings that I've found with my furnace. I don't burn in my house because of the mess, the smoke, yadda yadda. I have a small shed I built just off the house that I house my pellet furnace in. I then pipe my warm air to the house via a 10" hard pipe and built a return air box for the furnace and pipe the return air back to the shed where it goes back into the furnace. This year, I decided to change up my chimney system from a 3" horizontal running 2' out the wall to a 7' through the wall system, but completely spaced off that I also replaced the control panel last summer too. The chimney runs from the furnace horizontally 1' through the wall with a clean out T and a 7' rise to a 90 elbow and then a 45 turn down cap. After running it for a few nights, I noticed it was going through a lot more pellets than it used to. Flame looked good and solid, but only with the air slide door completely closed. Turns out I was over running the draft fan with the new chimney because of the factory settings in the control panel. By a lot, as it turns out. Got into my settings and turned the draft fan down to where it only kicks on for a second every few seconds on low and only slightly more often on high. Instantly, my door temps shot up 100 degrees. I actually had to back my feed rate down out of fear of overtemping the furnace. It pulls a good, steady draft now with the air door open 1.5" instead of pulsing when the draft fan kicks on. It's actually quite a bit more efficient than previous years when I was relying on the fan to keep the draft going. I should have done this 5 years ago.