Reloading a Coal Stove

Hi All!

So here is my process for reloading my stove. The reason I am posting this is because I never load the stove without some type off "puff back". They are all minor, but still result in a sulfur smelling basement.

1. Open the ash door completely and rake till I see good light through the grates and some red coals start to drop into the pan.

2. Close the ash door. Now I have an automatic primary air damper that opens based on thermostat temperature located in the living room.

3. Add Coal

4. Wait for blue flames to appear, while leaving a small section uncovered.

5. Close the loading door and leave the top air dials at about a 1/4 turn. This is recommended by harman.

Thats it... Now a few minute later I can hear the clean out door rattling just a bit. No "puffs" yet. Then, click ,the thermostat senses the dropping temp and opens the primary air damper. Then woosh there it is, a small warm smelling fart comming from the furnace.

Now there is an Idol air adjustment on the primary damper. Its just two holes (small) that I leave 50% open, again as recommended. That part seems to work fine, and I get a good 10-12 hour burn out of it.

I did try leaving the ash door open for a while then shutting it. It seemed to make things worse.

I have a Harman SF-3500 wood/coal furnace. No Manometer (I know, I know im looking for one)

So what am I doing wrong?

I don't think you are doing anything wrong per se, I think you need to try different combinations of things. All stove are a little different. You can try keeping the ash door open while you load her up and keeping some of the established fire uncovered with new coal, maybe 2 loads instead of 1 large, and keeping the load door cracked to let in more over fire air while the new coal cooks. If you have a mpd keep that open and cover the barometric damper with foil if you have one, this will allow the gases to exit easier. just my 2 cents, good luck pal.

After shaking I close the ash door, open the loading doors fill it up to the top of the bricks, close the doors and walk away. 12 hours later repeat! I don't leave the load doors open at all.

I cannot say that you're doing anything wrong. When I load up I always leave something with a little flame available, so that the volatile gases will burn as the new coal heats up and begins to burn. If I shine a flashlight in my fire box after I put fresh coal on, I can see white-ish smoke above the coals, sort of like a BBQ grill where one has sprayed charcoal fluid on slow burning coals. With a small fame in my fire box those volatile gases will combust with the firebox door closed. With no flame in there, I can see how you'd get a puff back when a rush of fresh air enters from opening the firebox door and a flame then ignites the volatile gases.

It is interesting, and I actually enjoy trying to figure out whats going on. I did cover the Baro with foil and that seemed to cut down the intensity of the puffs. Before that, they were somewhat frighting. One time I opened the door, and near lost my beard!

One problem is, I have no idea what my draft is. Is it good, is it bad, I don't know (yet).

I see these guys, and im sure most of you can do this, load their stoves up to the fire brick in one shot, and let her go. If I did that, I may blow the pipes off the back hahaha. Im lucky to get 3-4 good shovels on (a bit less than a 5 gallon bucket).

I guess well see what tonight brings. Boy id love to get that Baro back in service.!!!

Snotzalot wrote:After shaking I close the ash door, open the loading doors fill it up to the top of the bricks, close the doors and walk away. 12 hours later repeat! I don't leave the load doors open at all.

Your a lucky man. I hope to get to that point. I can get a good 10 hours. Anything over that is pushing it. One good/bad thing with my furnace is, it controls itself. It keeps the whole house at a perfectly steady 74, which im really impressed with. The bad side of that is, the damper is variable. So it opens and closes automatically. Now it does have adjustments, but its still sometimes open and sometimes closed.

Without a manometer you can not set the baro accurately. Leave more secondary air through the loading door. The Harman recommendation was with the draft they called for and you don't know what yours is.

franco b wrote:Without a manometer you can not set the baro accurately. Leave more secondary air through the loading door. The Harman recommendation was with the draft they called for and you don't know what yours is.

I'm actually trying that right now. I assume that should not let any gasses into the house correct?

Volatile gases ignite when specific conditions are met. There is a narrow width of ratio between fuel and oxygen mix, where with an ignition source the mixture will explode.

By keeping the load door closed, the mixture stays too rich to ignite. So when you open the load door or a flap opens adding more oxygen, the mixture meets it's needed ratio and ignites.

Then on the other side of the spectrum, you can keep the mixture too lean to ignite by keeping the load door cracked a quarter inch. The extra air coming in over the fuel bed keeps the volatile gases diluted and carries them out of the firebox. There will become a point as fire creeps up thru the fresh coal, where a flame from under will ignite the thin layer of fuel/air mixture across the top of the fuel bed that is at the proper ratio. That's when the blues spread gracefully across the coal without an explosion.

HarMark3500 wrote:4. Wait for blue flames to appear, while leaving a small section uncovered.
5. Close the loading door and leave the top air dials at about a 1/4 turn. This is recommended by harman.

I did try leaving the ash door open for a while then shutting it. It seemed to make things worse.

I had the same problem with my little Harman Mark 1. Very frustrating. Once I got the blue flames and closed the loading door, I would open the ash door -- or open the air inlet a LOT -- until I got the fire burning a lot more. Make sure the fire is vigorous enough that you won't lose the blue flames and hot exposed coals a few minutes after walking away. Unfortunately, in warmer weather this led to temporarily having a lot more heat than I really wanted. But that was the only solution I could find. Sometimes it took 20 minutes of fussing with it before leaving it to fend for itself.

HarMark3500 wrote:

franco b wrote:Without a manometer you can not set the baro accurately. Leave more secondary air through the loading door. The Harman recommendation was with the draft they called for and you don't know what yours is.

I'm actually trying that right now. I assume that should not let any gasses into the house correct?

As long as the draft is negative in the stove nothing will escape. Hold a match to the opening and the flame should be drawn in.