Who Needs a Chimney? A Burning Coal Bed Makes Its Own Draft.

Who needs a chimney? A burning coal bed makes its own draft. A report on Bob’s Saturday morning at play.

I was thinking about how people get a charcoal grill burning. Take a large tin can, cut the top and bottom off, fill with charcoal, and light the bottom of the charcoal. The chimney effect within the can draws lots of air through and makes it ignite quickly and burn well. So, how is the can different from a bed of coal enclosed in firebrick, open top and bottom? Does a coal stove really need chimney draft to burn well, or does the coal bed make its own draft, like the can of charcoal?

So I reduced my baro setting from its normal .07 to .02 to see what would happen. That’s way below the recommended draft for this stove. The baro flapper opened up all the way and stayed open for the rest of the experiment. That’s as low a draft as I could get without sawing off the stove pipe and letting it vent into the living room. Stove temperature dropped from 640 to 560 in fifteen minutes. Then I opened up the air inlet. Temp was back up to 640 in another fifteen minutes. I gave it more air. In half an hour, stove temperature was up to 725. I reduced the air until the temp dropped to 600 and it was still holding 600 after another hour.

Conclusion: A hand-fired stove burns fine as long as it is minimally vented above the fire. It makes its own draft through the coal bed. Rate of burn is controlled by how much combustion air is admitted.

What does this prove? Darned if I know. If I were willing to learn all new air-inlet settings, would I be fine with a 3-foot chimney? When I did this there was no wind. What would happen if the wind blew and gusted? The baro was wide open, so it could not open any more in response to the wind. Wind would increase the draft somewhat, but since the baro opening is probably ten times the area of the combustion air inlet, draft on the coal bed might not increase much.

Was I burning less coal and getting more heat out of the stove with the lower draft? Would temperatures fluctuate more over ten or twelve hours, with chimney draft having less relative influence compared to coal-bed draft? Would I lose the fire once most of the bed burned to ash and it could no longer make its own draft? Don’t know. It was time to go to the dump and the post office, so I set everything back to normal. Others will have to carry on this vital research.

rberq wrote: What does this prove?

You have a great chimney.
Even with a gaping hole (wide open baro) the chimney still pulled draft through your stove when you gave it more air. If it didn't the smoke/gases would have vented into the house instead of up the flue.
I lit a stove outside without a chimney and thought the stove wasn't going to work very well because of the way the fire burned and it smoked so much when the loading door was opened. Once this same stove was connected to a good chimney it has never smoked(into the house)and the draft was so powerful I swear it could almost suck the coal right out of the stove.
You proved you have a good chimney system.

rberq wrote:So I reduced my baro setting from its normal .07 to .02 to see what would happen. That’s way below the recommended draft for this stove.

The recommendation is for maximum draft, not operating. It is the high limit, operate it at a level that performs well in your installation.