Maintaing a Coal Fire

I have a Harman SF360 hand fired coal/wood boiler. While buring wood the boiler works well and heats the home adequately, however I cannot get an overnight burn time. I new to coal burning and understand there is a learning curve. I have no problem getting the coal buring well but it does not seem to last all that long. For example I loaded the boiler last night (75lbs) at 9:00PM and at 6:00AM this morning the house was up to temp but the coal fire was almost out. It took me an hour to get the thing going again. It seems that the fire is still somewhat alive in the center of the firebox but the front and back have a grayish white coal that looks as if it has been burnt. I am burning chestnut coal. I live in upstate New York and it has been rather cold (5 to 10 degrees) the last few nights.

I am following the Harman instruction of having the secondary air dampers opened 1/2 turns from closed. Any help would be appreciated.

Thanks.

Sounds like you may be consuming all of the coal in the period of time you mention. I'd try to throttle down the dampers. Maybe your burning hotter than necessary.

There is lots of talk concerning draft, barometric dampers and using a manometer or other correct device to check proper draft. I am no expert in this area but this could be the area in which needs to be addressed.

I think you need to put some coal in it, 70# is not enough to fill that monster. That thing is good for 170,000 BTUs, and I'll bet it takes 120# or more to fill it. It needs to be filled right to the top of the firebrick. Never run lower even in warmer weather. It takes a lot of coal to get started, but once going will burn less coal per day and you will have no trouble running it. I would shut off any overfire air or at least turn it down to the bare minimum also.
I looked at that unit online, I'm jealous.

Fill it right to the top and start grinning.

Thanks for the quick replies gentlemen. I will try loading the unit full to the firebrick and throttle down the dampers a bit and see if I have better results. I will keep you posted tomorrow.

I would suggest closing the secondary air completely once the coal fire is established.

Coal likes all the air to come up through the coal bed from underneath. Any air above the fire is good only to help burn the initial gasses and fumes from a fresh load of coal. So once the coal is burning and you can see the blue-white flames above the coal close the secondary air vent.

I'd try closing the under-fire air some too. Unless you need a lot of heat, I'd try burning it with less air, and see if you get enough heat.

Do you have a thermometer on the chimney pipe or on the stove body?? These help a lot to determine the best burn rates. If you burn too fast, a lot of your heat goes up the chimney, and a slightly slower burn rate will give almost the same stove temp with a lot lower chimney temp.

Do you have a barometric damper on your chimney? or a hand damper? How tall is the chimney, and what is it constructed of? Masonry with a clay liner, or a Stainless Steel chimney?

Hope this helps.

Greg L

LS Farm,

Thanks for the input. I will try that tonight. I have a thermometer on the stack that reads between 250 and 300 degrees (this temp is before the barometric damper) when the fire is glowing orange. The chimney is a 28' tall interior masonry with a 7 inch round chimney flues up through it. I get any excellent draft from the chimney.

I think you will get just as much heat from the stove body and heat exchanger with the draft closed down to get the stack temps below 250*.

Other members with the same or similar stove will chime in soon I hope. I personally think you just need to cut back on the air, and let the unit run a little cooler.

Greg L

Last night I filled the beast full to the fire brick and turned off the secondary air dampers. I loaded it at 8:00PM and this morning I had a nice bed of coal. I shook it down, took out the ash and added 40 pounds, which broght the bed back to the top of the firebrick. This was the first time since I have owned the boiler that I got up in the morning and didn't have to help the fire along to get it burning well. Thanks much for the advice. Oh and by the way I did close the bottom damper down a bit and the flue temp was running right around 200 degrees. Thanks again.