I was working in the garage Monday, after the previous post, turned the slab on in the garage while I wired some outlets and lights, went in the house and put in a load of laundry, coal heated hot water, anyway the boiler just kept running and running, looked in fire box and there sure was alot of unburnt coal, opened the door to look in the fire tubes and saw orange flames and black soot on the tubes. I opened the air regulator a signifigant amount, wow it made some heat, good thing garage slab was cold.
So now 48 hours after the air adjustment, no soot, and the clinkers are round rings, and the ash level in my burn chamber is going dowm, combustion is happening in a much larger area over the grates, all is well.
It was working fine with the other air setting but only because it was running short periods of time. and the natural draft between firings was consuming the extera coal, now it really burns hot, looking forward to seeing the stack in the daylite on turkey day.