Harmon Mark III Out of Control!!!

Hello all, I have been lurking for a while now and decided to ask for some help. I just put a new Harman Mark III in my home. I am new to burning coal. I am having trouble controling the heat output. I get the stove burning, fill with coal set the draft to 1 and 1/2 turns open (like dealer said to do) and most of the time it just gets to hot in the house. If I use less coal (don't fill all the way) and close the draft it wants to go out.

What am I doing wrong? I have a Baro Dampner on the pipe (dealer said I need one) but I don't think it does anything. It is always wide open, not leaving any air in from the room. How is it to be adjusted? My dealer said to turn the adjusting screw half way and leave it there.

I really like the stove but just can't figure out how to use it. My dealer is no help, he says keep fooling with it, you will figure it out sooner or later!!! Sooner or later has come, my wife is ready to throw me and the stove out the back door. Any ideas?

Thanks Pap

Get range coal next time or even pea. Smaller sizes are easier to control because of the restricted air flow. Range is pea and nut mixed.

Get a couple of bags of pea coal, you can try the range by mixing with the nut you have (under the assumption you have nut) and try just the pea and see which works better for you.

Many of my customers have a manual damper on the exhaust pipe. That can work well too, make sure if you get one you get the heavy duty one... they make ones that are cast iron. My brother bought a cheap one once and it didn't last very long.

Pap--

I used a Mark III for 3 years. It took me till the 2nd year to get a good feel and by the 3rd year I was a pro. ( I am a sloooow learner! ) It is very hard to control the heat output on a handfired unit. If you do not fill the box, air will flow right on past the coal and it won't burn. If you don't have a really hot layer of coals, the fresh stuff on top will not burn. If you loose draft, it'll quit. I could go on.

Try this: Set the barometric damper so that it stays closed. ( for now anyway. I'm not a believer in the baro but I guess it has a purpose ). Get a good fire going and adjust the ash door damper down if the fire gets too aggressive. I like to see a blue flame dancing on top of fresh coal. Try using a thermometer. 400-500F on the stove top is great. 180F on the flue pipe is a good number.

It is very difficult to try and adjust heat with a handfired unit as if it was a typical furnace or even the stokers. If you back it down too much, it will die. Too much air and it will glow. The flue size in diameter, height & material type effect the operation of a coal stove a great deal. The only way to be able to get any heat control out of a Harman hand fired, in my experiences, is by controlling the draft with the use of a SS liner. A standard clay flue will cool off and reduce the draft causing you to wake up cold.

Keep trying and let us know. Describe your flue to us.

My baro dampner is adjusted so it is closed. My flue is one 90 out the back. Four and one half feet of single wall pipe into the roof support. Six feet of stainless steel insulated pipe. The stove sits on an eight inch high platform. I have what I think is a very good draft. I am using what is supposed to be nut coal but the size of coal varies alot.

It goes from pieces about the size of a quarter to pieces up to about three or four inches long. I bought it in bulk and hauled it myself. I asked for nut coal when I got it. I need more coal real soon so I will try another coal yard near by. I will try pea coal like the Coal Man said to do.

Thanks for the replies, I will get some more coal this weekend and let you know how it works. Thanks for letting me be part of your board. Seems like a good place to hang out and get the answers I need.

Pap

I had the same troubles you describe with the first batch of coal I bought. I got some from a different yard and I can burn it slow enough to keep my house 68 when it is 55 out side. I have a barometric damper but it doesn't open unless it is below 30 outside. I have a 35' tall chimney with insulated ss liner so to little draft is never an issue for me. With a chimney as short as yours you may have troubles with poor draft when you burn it slower. If you still have troubles with the new coal, try a double walled pipe to the ceiling. It will give more consistent draft, if it pulls to hard when burning hot set the damper so it opens a little to slow it down. My damper never opens more than a half of an inch, unless the wind is blowing then it swings all over the place. I am attaching a picture of my furnace, sorry for the poor quality.

I went to the coal yard yesterday and bought half a ton of pea coal to try. I asked but they didn't have of even know what range coal was. I told the guy it was nut and pea coal mixed, he said we have rice, pea and nut.

So anyway I put the last of my nut coal in last night. This morning I shook it down and loaded it up with pea coal. I will let you know how it works out.

Pap

Pap wrote: I asked but they didn't have of even know what range coal was.

Well it's not a specific size like nut or pea. Whwn my cutomers order it I just load the truck up half with nut and half with pea, it mixes as it's coming off the truck. They should know what it is though as many of my cutomers use it. Perhaps it's not as common where you are at.

Well, it looks like burning pea coal is the answer for me. Today the temp went up to almost 60 here in Middletown Pa. This morning before leaving for work I shook my stove down and filled it up with pea coal.

I only opened the draft knob 1/2 turn. After leaving for work I thought maybe I made a mistake...... I should have opened the draft more. I thought sure the fire would go out so at lunch time I drove home to check the fire. It was pretty low but still burning pretty good down deep in the coals.

I opened the draft knob a little more to 3/4 of a turn total and went back to work. When I got home tonight to my suprise the stove was burning nicley!!!!! It was a little warm in the house but remember it is almost 60 outside. Using nut coal the stove would have been out at that draft setting, and to open the draft enough to keep it burning would have been out of the question.

With a little more fine tuning I think my wife and I will be very happy with our new stove. Looks like it is best to fill the stove all the way up to the top of the fire brick. Is this what should be done? Seems more even burning the fuller it is or maybe it is just me.

Thanks to all who replied you were a big help.

Pap

Pap,
I too an new to the Harman III this year. I have used the nut size coal and thankfully had no problems. After the wood had burnt down to hot coals I added two small shovels of coal, waited about 5 minutes until that was glowing then added two more shovel fulls. After repeating this for 15 minutes loaded it up to the top of the fire brick. Left the bottom door open
for about 5 mins until blue flame was dancing on the top layer then closed the door and damped it down to 1 full turn of the damper dial. The stove went for a full 24 hours and my house was 70-75* throughout. Outside temps were in the mid 20's.
Can't wait until the temps get back to normal ,,,, cold !

Pap wrote:Looks like it is best to fill the stove all the way up to the top of the fire brick. Is this what should be done?

Pap

Yes, just make sure you don't have too much air on it and it will be fine. 24 hopurs as mentioned above is ideal but hard to achieve in most stoves unless you have it really low. Most get on a 12 hour schedule, shke it down and add coal in the morning and at night. If you're there to tend to it you can always turn it up a few notches if you want some more heat.

Keep in mind what you do now takes a while to take affect. It's not like wood where you can just cut the air off and it will slow the fire. If you do that with coal the fire will continue to accelerate for up to an hour if you have a good fire going.

I have been tending my stove every twelve hours. I shake it and fill with coal in the morning and again in the evening when I get home from work. This works out good for me, I am sure the stove will go for longer times because there is still unburnt coal on top.

The nut coal I was burning worked fine when it was cold outside. But when it warmed up outside I couldn't slow it down enough without the fire going out. Yesterday when I got home from work the temp on top of my stove was 200!!!! With nut coal it would have been out with the same draft setting as I am using for the pea coal.

Pap

When it gets warm out(above 40) I only fill half of the fire box. When you do this leave some coal and ash at the other end to block air flow thru the grates. Then fill the other end ful as you would normally. I have been able to control the temp when up to 55 outside using this method. When it is 55 out I use about 20# a day.