Hey gang. I have a Brunco 190 as well in my workshop. This year is my first attempt at burning coal and I am amazed with how challenging this is proving to be. The Brunco burns wood great, and puts out lots of heat with minimal smoke and no draft problems EVER using this fuel.
My Brunco is a forced air system, with a switch on the induction fan so I can run it forced or natural draw. No spinner on the ash door.
A local supplier who burns in his shop and is a Brunco fan recommended Kentucky bit coal. Nice big chunks (some as big as a volley ball). I broke this up into smaller pieces, no bigger than the size of a lemon, to start experimenting.
Here's my experience:
I started a wood fire, and got the chimney and unit up to good operating temperature (around 400 degrees). Let the fire burn down to a nice bed of coals, and added a small shovel full of coal, evenly distributed on the bed. Started burning right away, and drafting well. So far so good. Let that burn about 15-20 minutes, then added another shovel full. Going great. Temp is climbed up to 500-550, but didn't get hotter than that so I left the blower wide open to help make sure the coal was completely ignited.
Let that go for another 20 minutes or so until it seemed the coal was burning good. The next step is where it goes bad. I added more coal to fill in the bed, to the top of the fire brick. This was about 4" depth worth of new coal.
It smokes like crazy, which I expected, but apparently the draft can't keep up and a ton of smoke is getting out. Through the spinner, and through the chimney seams, neither of which I've had a problem with to this point. I opened the ash door a crack to help the draft, and while this did help reduce the smoke, it's still coming in. I'm talking billows of smoke. Right now, I'm thankful this is my workshop and not my house! I opened up the bay doors to the shop to let things air out while I continue to fiddle with it, thinking that I just need to keep it burning until the coal gets going and the smoke reduces. Wrong.... Plus, through this whole part of the process, the furnace temperature plummets until the chimney temp is below 100 and the blower fan stops. It was over 500 before adding the 3rd round of coal.
I made every adjustment I could think of with no improvement. Forced air multiplied the problem, so I turned it off. The best scenario I could create was to leave the ash door open, turn off the forced air and leave the induction flap full open, and close the door spinner. This all but stopped the smoke from coming in, but the temp stayed very low... Below 100 on the flue, and practically no heat coming off the furnace. I left it that way overnight.
This morning, the coal was still red hot, and had burned down considerably with minimal ash. The smoking had stopped. This would be fine, but there was practically no heat. I raked it a bit and tried adding a little coal. Smoke like crazy again, and since the flue was so relatively cold I'm assuming the draft was even worse. I abandoned ship earlier this time, scooping out the coal and closing everything down.
Totally frustrated. If i can get this to work, the advantage is I can keep the shop warm consistently. Right now, burning wood, it needs filled every 4 hours or so which is impractical for me as I'm not in the shop every day and I have no interest in filling it in the middle of the night. The shop is insulated, but large, so it takes a long time to warm up from dead cold. Often, by the time it warms up, I'm done doing what I was in there for anyway. Coal should allow me to keep the edge off in the shop so its nice and warm when I'm ready to use it with only a couple tendings a day, which is why I'm even going to the trouble.
Any advice would be appreciated!