I have a 100k btu furnace in my house and a 100k btu boiler in my shop both burning the same corn. The one in my house gives me nice white ash with small hard clinkers and never anything stuck to the side of the pot. The one in my shop tho gives me some small clinkers and white ash but most of my ash is the black popcorn balls. Also i am always getting clinkers stuck on the side of the burn pot which i think may have something to do with the kind of ash im getting. My draft is at .04 and my combustion door about 1/3 or a little more open. The boiler has just been cleaned though the big top cover. What is causing my clinker build up and black ash?

How long of burn time on high fire on both burners? When I had my furnace, I would burn very long on high fire, and the clinker would make like a crown around the inside of the burn pot and start blocking off the air supply. Then the corn would be half burned and look like black Styrofoam. I had gotten a second timer for the furnace to give the burn pot a short while to cool off and the clinker would separate from the burn pot as it cooled. It replaced the relay, just plugged in. Since this is happening in your boiler, I would try a mix of some pellets with the corn. You get a much nicer complete burn, and the ash from the pellets help make the clinker a bit softer and seems to burn much more complete. Good luck. Rob

They will both have long burn times when it is cold, however the boiler probably has longer high fire burn times. How hong does the timer have to be set on and off to allow it to cool enough?

The extra timer is only for the furnace, the boiler doesn't have the same relay. I used to have a 3 to 4 minute break for every 10 minutes of high fire. I would still have to break up the clinker and pull it to the center of the pot, but the pellet mix makes it so much nicer, if you have any near by, try out a bag or two per bin of corn.

I even bought a little corn to mix in with the pellets in the boiler, as expensive as it is.

It seems like the furnace in the house has more air coming out of the top holes in the pot than the boiler in the shop does. It looks like the corn on the outside of the pot is burning fast but there is a cool spot in the middle that its not burning very much. Were there differnt models with more or less holes?

As far as I can tell, the burn pot looks exactly the same.

Did you have a little friend build a nest in there??

No little nests that i know of lol. It just seems no matter what i do i get big black popcorn balls and hard clinkers stuck to the pot while my other stove is spotless in the pot

Make sure the tunes in the exchanger are clean take the top off and look down the tubes with youre own eyes and check them dont asume the brush did it. I fought with mine half a year till I did that I would push the brush though and then I looked with my eyes and only had a 3/4 inch hole though them hard build up over 4 years if it can't breath it will be full of popcorn and pot will cover with had build up and even get red hot

I just had the top off last week and cleaned all the tubes and they are completely open.