Fire in Coal Hopper - Keystoker KA6

I have just purchased a Keystoker KA6 Coal Boiler and had it installed by professional plumber based off the Keystoker instructions. Everything was working fine until I went down to put in some coal ( buckwheat size ) and I saw smoke coming out of the hopper and yes it was on FIRE ! . I quickly pulled the loose coal back and poked the rest down into the heat box. Contacted Keystoker who said my coal was to dusty ( not ) or the feed rate might be wrong adjusted feed rate to less coal and thought that had it , too only wake this morning and look down into hopper and could see the fire had once again moved into the hopper this one almost got away from me but once again moved coal got the rest in the fire box and right now waiting for the fire to go out, Has anyone had this problem ( I live in Southern Ohio ) Looking for service or information , I am afraid to relight it , Some one please Help !!

Love in Jesus Christ
Jay Williams

I'll have to ask just to make sure, you are using anthracite? and, do you have a barometric damper on the flue pipe?

There's a lengthy thread here regarding hopper fires, Hopper Fire - Alaska Channing 3 with direct vent

There are few reasons but the first thing I would look at is why the air is being forced into the hopper instead of up the flue.

As far as dirty coal, not sure why that would have any effect and I would think it would have the opposite effect because dirt generally blocks air flow.

Hello Jay, welcome to the forum.
I don't know who at Keystoker you spoke with but it sounds like you had someone who was not very helpful. First of all is the boiler set up with a direct vent or going into a chimney. If it is a direct vent I do not think you can use buckwheat size coal. You can only use rice in the direct vent stoves and I think this is also true for the boilers. If your boiler is hooked up to a chimney and you have a natural draft do you have a barometric damper? You must have a barometric damper and must have it set to limit over fire draft to .02 updraft. It is critical that this draft be checked with a draft gauge. Your plumber should have done this. It should have been checked with a hot fire and the stoker OFF

Assuming the draft is controlled to .02 as per Keystoker's specifications the next area that could be a problem is the grate seal. The grates are set in place with a generous amount of furnace cement between them and their top edge at the top 3 inches of the grates. This is the part of the grate with no holes in them. Once again assuming the boiler is new, this should have been done properly at the factory but then again... If the boiler is used and especially if someone else had it apart this could be the source of your hopper fires. I had this problem myself last year. I had sealed the grates on my stoker improperly with bad or wrong furnace cement, not sure which, but it cracked and broke up and eventually some fell out and next thing you know the hopper is smoking! If this is the source of your hopper fire it will start burning back to the hopper within hours of re lighting it.

Now that the hopper had fire in it twice the "pusher bar drive yoke" is held in place on the "pusher bar drive shaft" with two set screws. The screws can loosen up from the heat and make your pusher bar go out of adjustment. This will result in improper coal feed. The push bar is to be 3/4" from the "throat strap" at it's closest point. In other words when the "feed crank" is at its furtherest forward motion adjusted to full feed there is to be a 3/4" gap between the "pusher bar" and the "throat strap".

Keystoker usually gives good information but I can't see how dusty coal or improper feed can cause a hopper fire. Improper feed may cause over fire or no fire but should not cause a hopper fire. A hopper fire is the result of air being pulled in through the coal in the hopper due to too much draft or air being forced up into the hopper from the stoker fan due to an air leak somewhere around the grates. Coal needs a steady flow of air (oxygen) moving through it to burn. You need to find the source of this air to solve your hopper fire problem.

I hope this is a good place to start, good luck.

Wow, that's scary. I'm not familiar with that boiler but I've got to agree, it's not the coal or the feed rate. I would assume there is a combustion blower fan on this boiler. The fan has an intake area which likley has an adjustable plate that can slide to close off some of the intake area and reduce the amount of air going into the combustion chamber. When I first started up my Harman, I had flue gas and CO coming out of my hopper because too much air was being blown into the combustion chamber and was over coming the draft. The air took the only other way out which was back through the hopper. The wonderful Harman manual, which appears to have been written as a third grade school project, never mentions this part and does not even have a picture of it in the parts schematic. If the boiler had been kept running, it would have resulted in a hopper fire. No problem though, I would have been long dead from the CO. Which brings me to my main point. Do you have a CO detector? If so, it should have been going crazy long before you actually had a hopper fire.

I contacted Harman several times with this problem and made them aware of the danger their lousy manual was causing. Their response was less than enthuiastic. To this day, the manual has not been updated or improved.

Good points by everyone so far. I'll add that I had a hopper fire with my Keystoker stove using buckwheat. It's a direct vent, and I don't believe I had the draft adjusted properly for the buck (it was too high) and the larger size of the buck allowed too much air down through the throat of the stoker and into the firebox. The fire just followed the air right up the grate. You're lucky on the KA-6 as you have no nylon cam or screws on the stoker pusher to melt. I was shut down for a week waiting for parts, plus the fun of cleaning up melted plastic from the stoker.

I'd almost be tempted to try it again and verify I have no more than .02 draft overfire at any time during the burn cycle. But, my stove woke me up at 1am with the stench of melting nylon throughout the house. That's not something I want to repeat.

You should be able to burn buck just fine, but verify you have a well sealed grate (rear edge and sides up to the draft holes). Also verify you have no more than .02 draft.

coalkirk wrote: When I first started up my Harman, I had flue gas and CO coming out of my hopper because too much air was being blown into the combustion chamber and was over coming the draft. The wonderful Harman manual, which appears to have been written as a third grade school project, never mentions this part and does not even have a picture of it in the parts schematic. If the boiler had been kept running, it would have resulted in a hopper fire. No problem though, I would have been long dead from the CO.
I contacted Harman several times with this problem and made them aware of the danger their lousy manual was causing. To this day, the manual has not been updated or improved.

My manual specifically states in the installation section To be sure to have a draft measurement done at two points the flue and stove and to calibrate as needed to obtain a minium .04 before putting the stove into final operation I went back and double checked your manual should have contained the same but I see it doesn't

I'm glad this subject came up again, as yesterday I installed the gaskets on the grate in the Alaska. I have ceramic fiber rope in the channel under the cast iron grate and along the back surface. I think I'll go back and run a bead of furnace cement along the edges. I think that if there is a poor seal in these areas, especially along the back edge, the combustion fan can force air out along the edge when the grate is covered with coal and ash. This air being forced out in the wrong place will contribute to a fire burning where it shouldn't. I ran the combustion fan and covered the grate holes with a piece of cardboard and checked along the gasketed surfaces for air leaks.
Yes, the Harman manuals are very poorly written, a lot is left out. They seem to assume that all purchasers should have their stoves installed by the dealer and the dealer will explain everything about the product to the owner, which is not the case, at least in my situation.
The correct draft is very important. Measuring with a manometer is a must.

Thanks so much everyone for the kind words and welcome. I have restarted the boiler and here are some things I have noticed , Keystoker says there should be 4 inches of unburnt coal from hopper , then 3 inches of fire , then 3 inches of ash, it looks like I do not have 4 inches from the hopper how do I increase that distant, Also both time I have had this fire issue I have almost been out of coal ( meaning I could see the fire in the hopper from looking down thru the hopper ) I also made the mistake of opening the little side door which let flame ( well mostly smoke come up thru hopper ) When I shut side door the draft pulled it back into the heat chamber. I am not sure of draft being measured and yes I have one of those Baro dampers on my flue pipe. Also If I want the fire to go out how do you do that ?? just turn it off ?? but then wont the fire just follow the trail of coal up into hopper. Waiting your response

Love in Christ Jesus

Jay Williams

Oh also where can you get this draft guage ?? and yes my boiler does hook up to my chimney. Also does it matter what kind of coal you burn ?? anthracite or bitmous ?? thanks


Love in Jesus Christ

Jay Williams

Four inches of unburned coal at the top of the grate sounds about right. This is the area of the grate that is solid, without holes. You cannot increase this distance. If the fire is traveling up the grate toward the hopper this is an indication of a problem. A properly set and adjusted Keystoker like you have should just go out when the hopper runs out of coal. This being said it i a good practice to keep the hopper half full or better.
Is your damper always open a bit. With cold weather and a good chimney your barometric damper will be open a bit almost always. At times you may see it almost fully open.
Draft must be measured with a gauge. This is critical. .02 over fire, hot, stoker off. .01 over fire hot, stoker running. The latter is adjusted by opening the air shutter. Open the air to the point where enough air is introduced to lower the draft from .02 to about .01. This is not quite a critical as keeping the idle draft at .02 and no more.
If everything is correctly set up when you turn the switch off your fire will just die out. It should be out within an hour depending on how big it was when you turned it off. Most Keystokers will go out within 20 minutes.

Look for the "Manometer Loaner Program" thread if you want to borrow one, instead of buying one.
Once the combustion blower is shut off, the fire should go out since there is little oxygen feeding it. You can also dump the burning coal into the ashpan with a small hoe to speed up the process, maybe others have better suggestions.

Hello jcw265, welcome to the forum.

You mentioned that you have had this problem only when the hopper is very low. Does your hopper lid have vents or screens in it or is it solid metal? Are you keeping the lid in place on the hopper??

The only way coal will burn is with a supply of air. So if it is burning further up the grate toward the hopper than it should, there has to be air supplying the fire up there. So if you have very little coal and the lid removed or a lid with screens in it, then the chimney will pull air through the hopper and fresh coal the the fire will burn 'uphill' into the hopper.

I would suggest keeping the hopper full. and the lid on.

Borrow the Manometer in the Manometer loaner program, just PM member Matthaus with your address. I'll find the link to the program thread. Here it is: Manometer Loaner Program

As mentioned if the grate is not properly sealed at the top there will be air at the gap to support a fire, but since this only happens with a low hopper, it indicates that the air is getting through the remaining coal in the hopper, so keep it full and keep the lid on the hopper.

You don't want to burn bituminous coal in your boiler. Use anthracite coal only too many problems with trying to get Ohio, West Virginia, Maryland and Kentucky coal to burn in a stoker. The stoker was designed to burn anthracite only. I've tried bituminous in a bed type stoker like yours, didn't work.

Hope this helps. Greg L

First let me say again thank you all so much for your very very quick replies to my issue. What a very great and well run forum , I am so glad the Lord led me here. Now I have called the mine where the coal came from because I am not sure what coal I have and let me make sure that I understand that I can ONLY burn anthracite or is that what is recomended because my fear is that if I have bitmous coal I have got alot of coal I cant use !! ( great ) !! Now I see this talk of lid on the hopper , mine has no lid ? does this mean I am missing something ? I am going to check out the thread on the meter and will post back shortly , I have shut the boiler down and waiting for some calls might be a lil cold but beats burning my house down ! thanks again to all of you

Love in Christ Jesus

Jay Williams

jcw265 wrote:.. it looks like I do not have 4 inches from the hopper how do I increase that distant,

The pic that Europachris posted of sealed grates is for a different style grate but the concept is the same. As others have already posted, make sure your grate is sealed to prevent any air from the plenum from coming up through the coal and allowing it to burn. It is a simple concept, no air no burn so leaks are dangerous.

jcw265 wrote:..I also made the mistake of opening the little side door which let flame ( well mostly smoke come up thru hopper ) When I shut side door the draft pulled it back into the heat chamber.

This problem relates to the posts which indicated you must check the draft inside the boiler. There should be a little hole in the side door you mentioned for that purpose. I would shut the boiler down and get your plumber to come back with a draft gauge immediately and properly set up the draft inside the boiler. if it comes up through the hopper when the door is opened you could have too much combustion air being introduced. There should be a metal flap over the combustion air fan to adjust this.

As also suggested you can take advantage of our manometer loaner program to verify draft during different operational situations, which you should do also.

The main thing you need to remember, no bituminous, make sure you have CO detectors, and don't operate the boiler with a known problem. It isn't worth the risk IMO.

Keep us posted.

jcw265 wrote:Now I have called the mine where the coal came from because I am not sure what coal I have and let me make sure that I understand that I can ONLY burn anthracite or is that what is recomended because my fear is that if I have bitmous coal I have got alot of coal I cant use !! ( great ) !! Now I see this talk of lid on the hopper , mine has no lid ? does this mean I am missing something ?

Only burn anthracite coal. Anthracite is ONLY mined in eastern parts of Pennsylvania. If you bought from an Ohio, Kentucky, or West Verginia mine it is not anthracite unless they trucked it in for resale.
You are not missing a lid. Keystoker boilers do not have lids on the hopper. You could fashion a lid if you like but this would be a bandage over an underlying problem.

I think you have a pretty good check list of things to look at. Keep us posted.