LsFarm wrote:I don't believe the temperature of the door to the ashpan area will be very hot.
I think your idea of of allowing a steady air supply, controlled by the placement of magnets over holes is a good one.. then let the moving flapper control the rest. But I would try your system with very few holes first.. depending on the size of your fire bed, and heat required for your house, you may not need or want too much uncontroled air..
Have you ever burnt coal in this unit with just the flapper controling heat output??
I tried coal 1 time about 30 yrs ago but didn't know what I was doing. I just burned wood after that. If there is nothing calling for heat the boiler will hit the upper limit and the flapper door closes all the way. The wood could smolder there for quite a while but when the flapper reopened the wood could bounce back pretty quick. It worked great with wood once I got all the temp settings on the aquastats syncrhonized with the oil burner temp settings and circulator settings. I just don't know if the coal would have a harder time to get going if basically all the air were shut off (other than whatever leakage might be drawn in? I could simply adjust the flapper to not close entirely in its off position. I can also adjust the max open position as well to some extent. I just thought if I added some holes to the ash door and adjusted them with magnets it would be designed more like the way the hitzer stove works. The main difference is that on the Hitzer the rear flapper is thermostatically controlled w/o electricity and it is progressive in the way it opens-not just open or shut. The Honeywell aquastat on the boiler is just on or off. There are 3 of them. One controls the flapper and a small circulator pump to circulate water over to the oil burner to keep it warm One controls the low temp that opens the flapper and circulates the water. The other shuts the flapper at the high temp and the circulator keeps running until the temp drops below the low limit. Another opens a dump zone if the temp rises too high. It dumps heat into the baseboard of the largest zone in the house. I think it dumps it at around 210 degrees. Worked great with wood. Just never experimented long enough with coal. I'm still thinking a few small holes in the lower door might work best and let the flapper close all the way.
You might find something of use in my thread .. How do you feel about a thermostat controlled hand fired?
. I installed a thermostatically controlled damper, which is wide open or nearly closed, nothing in the middle. It works fine. I think, with the other system you need a modulated system, which means you have to have power to make it move, either one way or the other.
I'm going to check that out right now.