first out fire

Well on this blusterous freezing late December winter morning(joke), I decided to go out and dig some holes for a sloped coal bin /chute. I kept hearing the birds chirping as I scrounged around looking for metal stakes to hammer some expoloratory holes. i went to check on the boiler that has been running dependable for some time and.........................out fire. I having been pushing the envelope running on two minutes per hour, a very small heating load. The boiler is jacketed with allnew aluminum faced insulation , the piping header, which i let circulate by gravity, is fully insulated and the room it is in is insulated.I am using the two minutes per hours as a "pilot" so i can simply go into the workshop area flick on the stat and get heat. I kept thinking I need to raise the temp of the outfire control as the insulation and no load keeps the boiler really warm for hours without load or refire. . I went down to boiler and of course temp is 110 , and I have a full pot of coal . Luckily last night I emptied the ash pan and now I have a full bushel of coal, Luckily the out fire switch opened . I think it is set a 140 but i likely should move it to 150 for the way Im using it . I am using this heating season as a tutorial as I have to conserve coal as I wont have bin ready till spring and it is all non essential as the house is warmed by hand feds. I was lucky by the skin of my teeth . experimentaion and empirical data. Back to bin design and Ill wait till next cool spell to refire. I did feel a small amount of heat in the pot yet,

What is the high limit setting?

Perhaps 2 minutes per hour isn't enough, but there is also the possibility that your well-insulated boiler reached the high limit and skipped timer cycles.

WE had a very warm day in pa. when the out fire happened. I beleive draft was reduced and the out fire temp sensor was set too low . The warm weather came on suddenly and I should have went to tburn cycles per hour as I dont alway have the stat calling for heat.

If you have marginal draft, you may find that running the timer on a 30 minute cycle rather than 60 will help. 1 to 1.5 minutes every 30 is where I would start. A well insulated boiler with poor draft will always be right on the line between overheating and having outfires.

What are you using for aquastat and feed settings?

200 high limiit 160 and 4 feed 4.5 air

i have the out fire aquastat at 125