Almost got her tamed... almost.

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epidioxte
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Hot Air Coal Stoker Furnace: Stokermatic Mountainman 85

Post by epidioxte » Sat. Dec. 26, 2020 11:22 pm

Good morning everyone!

Thanks to the immense amount of help I've received from this forum, I finally have a working stoker! My Mountain Man 85 is finally keeping my family warm, but there are still a few problems I'd like iron out.

I've attached photos to display what I'm trying to describe.

Every otherday I am forced to completely clean out the stoker. HUGE clinkers build up and smother the fire - it just plain goes out about every 48 hours no matter the temperature I seem to run it at.

I feel like the chamber fills up so quickly! In just a 4-5 hours after cleaning and shopvacing the stoker completely empty, the chamber will be nearly 75% full of coal, so much so that when I open the door a mixture of red hot and warm black coal spill out of the door.

My thoughts have been lack of airflow, or some other issue not allowing the coal to burn correctly.

I've completely cleaned out every area involved with the blower, including the blower itself.

I'm totally stumped. I'm hoping I'm just doing some little thing wrong and this could be easily fixed if I just knew better.

Here's what I am doing:
1. Get home to a cold house, turn off stoker, clean out chamber, shopvac everything out, try to clean out airvents.
2. Unscrew compartment below (IDK what it's called) and shopvac debris in there. Not much usually.
3. Unbolt blower and shopvac any debris in there (also not very much usually).
4. Turn on motor till I see coal approaching the surface of chamber.
5. Start wood fire to get things going.
6. Close chamber and try a new experiment with auto-motor timings. (Currently set to turn on for 1 min. every 30 min.)
7. Set thermostat to about 65*
8. Check on stoker about 2 hours later, pull out some of those giant clinkers, raise thermostat to 75*
9. Check on stoker occasionally, pull out clinkers, etc.
10. 48 hours later, fire has smothered itself and I start over.

Attachments

PXL_20201224_205243947.jpg

This happens after 4-5 hours of running the stoker.

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PXL_20201215_020145640.jpg

This is about 12 hours after complete cleaning.

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PXL_20201208_220948974.jpg

48 Hours worth of clinkers. I pull out about this much every 48 hours. Pulling them out along the way doesn't seem to help. The coal eventually fills up the chamber and smothers itself anyway.

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PXL_20201208_220957222.jpg

Average size of clinkers.

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franco b
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Post by franco b » Sun. Dec. 27, 2020 9:32 am

I have no stoker experience, but clinkers are formed from excess heat.
I would cut down on the air to run cooler. Also are you using the recommended size coal for that stoker? Smaller sizes should run a bit cooler at the same setting.

Other stokers form clinkers too, but the ashing system seems to handle them. How does yours ash? And is it working?

 
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carlherrnstein
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Post by carlherrnstein » Sun. Dec. 27, 2020 9:46 am

How much coal do you burn to get that much clinker?

It's possible your coal just has a high ash content and you need dig out the clinkers a couple times a day.

The bituminous stokers I'm familiar with are supposed to clinker the ash. So I don't think that's a problem.

Edit: after rereading and thinking a little bit. I wonder if it is feeding too much coal. The fire should burn the coal at the same rate it is fed in. If the feed is too fast or there isn't enough air it could build up and smother the fire.

 
epidioxte
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Hot Air Coal Stoker Furnace: Stokermatic Mountainman 85

Post by epidioxte » Sun. Dec. 27, 2020 1:51 pm

Seems like there's quite a few variables to consider thanks for the thoughts both of you.

Concerning the ashing system... I'm honestly not sure what that system is supposed to be. There's some sort of chamber beneath the burning chamber that the blower pushes air through. Although I clean it out regularly, I've only had to REALLY clean it out once (when I moved in). Other than that there's only about a handful of debris in there that I vacuum up.

In this stoker, the motor and the blower are wired together so one doesn't run without the other. Is that normal? I'll bet I could rewire things if necessary.

I burn about 1.5 wheelbarrows full each of those 48 hours. So that's about 4.5 cubic feet of stoker coal.

My coal supplier says that he's never heard of anyone getting this much, especially of this size. He runs a similar stoker and said he pulls his once a week or so and they're never larger than his palm.

I'll also point out that there is often a mixture of red hot burning coal, with mounds of coal that isn't yet burning. Usually it's more the not burning stuff that comes pouring out so I assume coal is being pushed to the sides and not burning correctly.

Maybe changing the pulley sizes would alter the speed of the coal feed?

Would draft issues be a possibility? I'm not confident in the chimney itself. There's been so much poorly done work on this home from the previous owners that I wouldn't doubt a poor chimney installation. They modded the stoker itself and moved the chimney directly above the chamber, when the original manufacturer had it slightly offset. I talked to someone who repairs coal stoker when I first moved in and he said that was a big no no but we were too focused on solving earlier problems to go over that at the time.

Would videos of the coal burning with the blower going help the community to determine if I'm getting enough air flow?

I'm happy to offer whatever info might help.


 
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freetown fred
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Post by freetown fred » Sun. Dec. 27, 2020 2:29 pm

Each heating set up varies so much from the other--I believe it's more about paying attention to the individual stove & knowing what to do with climate changing. I know with my HITZER, if it's POWERFUL windy, I just make sure my bi-metallic thermo is set appropriately & let the stove do the rest. I basically don't have to touch her the whole season. Ya do need the basics--proper chimney height, proper under air, proper tending & ya should be off & running.

 
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carlherrnstein
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Post by carlherrnstein » Sun. Dec. 27, 2020 3:58 pm

I have tried to dig up some information on your specific stove but couldn't find a manual for it. You might contact this place to see if they can help with a manual. http://www.peasefeedandcoal.com/Mountain-Man-85.html

I can pm you a manual for a combustioneer 77b that's what I have. It won't do you much good for ordering parts but it has a good deal of general guidance for operating a stoker of this type.

The chamber under the firebox is called a windbox it's just a area under the hearth. You can probably see the back side of the tuyere if you look in there. Air is pushed into this space and through the tuyere (pronounced twee-uer) and into the fire. This space should only need to be cleaned out once a season. Unburned coal fines should be the only stuff to get in there.

It is my opinion that the combustion fan should only run if the auger is feeding coal. The 3 stokers I have worked on have 1 motor that runs the auger gearbox and the combustion fan. If you separate them you will have to figure out how to independently control them.

It's very odd that you would have unburned coal pushing up into the firebox the way you are decribing it. The air holes/slots in the tuyere could be plugged up and not letting air into the fire correctly.

I will ask some general questions to try to narrow things down.

Is this hooked up to a thermostat on the wall? Or does the stoker mechanism run continuously?

Is there a plate or disk on the combustion fan to regulate the air that's pushed into the windbox?

The next time you clean out the firebox, take off the clean out cover off the windbox and shine a light in there and see if you can see light through the air holes and poke a nail or screw through all the little air holes in the cast iron "bowl" where the coal feeds from. I'm betting they are plugged up and not letting air into the fire.

These are pretty easy machines to operate, and once they are going right work with very little attention.

 
epidioxte
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Hot Air Coal Stoker Furnace: Stokermatic Mountainman 85

Post by epidioxte » Sun. Dec. 27, 2020 5:31 pm

The general information from your manual would be so helpful! I'll contact the place linked for a manual of my model as well. Thank you so much!
In answer to your questions:

It is controlled by a thermostat on the wall.

Is there a plate or disk on the combustion fan to regulate the air that's pushed into the windbox?

I've looked all over the fan and I don't see anything that might control that.. Although your question prompted me to fiddle with a plate that was in the tunnel between the fan and the windbox and I found that it moves!

I've attached an image of the part I'm talking about. It seems to reduce air by physically blocking the path to the windbox.

It was set to be nearly completely closed before I fiddled with it and took the photo.

I'll begin to experiment with the airflow then. Are there any signs I should look for that might predict an improvement? Am I trying to increase airflow in my predicament, or reduce?

Thank you!

Attachments

PXL_20201227_222500551.jpg
.JPG | 478.6KB | PXL_20201227_222500551.jpg

 
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carlherrnstein
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Post by carlherrnstein » Sun. Dec. 27, 2020 11:11 pm

Okay that can only be the combustion air adjustment, that is the only thing that is normal to adjust.

It is best to start off with too little air than too much. Look the plate over well, if your lucky there might be a mark to use as a starting point. If not look at the slots and see if there are marks left by the hold down nuts.

If there is nothing to go by clean out the fire box close it all the way and open it up 1/2". If the flames are yellow and lazy with sooty smoke open it a little and recheck. If the flames are short an white like a torch close it up a little and recheck. When it is adjusted properly the flames should look something like the pictures.

Small adjustments can make a huge difference in the way the fire burns. My stoker has a plate that "chokes" the intake for the combustion fan. The initial setting for my stoker is like 2 turns open from completely closed, and that's very close for most of the coal I have used. However when I get a load of coal I normally have to open or close it by 1/16th of a turn and check the fire over a couple days.

I have sent you a PM with the manual for my stove.

Attachments

20201227_230433.jpg
.JPG | 81.4KB | 20201227_230433.jpg
20201227_230431.jpg
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epidioxte
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Hot Air Coal Stoker Furnace: Stokermatic Mountainman 85

Post by epidioxte » Thu. Dec. 31, 2020 4:14 am

Wanted to post a video to make sure I'm understanding where the sweet spot is. After following your instructions I tried to get a good balance of no lazy flames but not too small and torchlike either... Here's a video:

https://photos.app.goo.gl/FV5nvi5FxMsrqUnx8


Doing this helped me notice two things...
1. The airflow definitely needed to be adjusted. The stoker has gone a couple days now with no giant clinkers! I'm getting a nice gritty ashy/Sandy mixture around the fire that I foresee needing to clean out every once in a while along with clinkers about the size of a finger... So that's an improvement.

2. The speed of the coal input might need to be reduced. Although I haven't had problems yet, I can definitely see that the firebox is slowly filling. While doing the air test as described I physically watched the pile about double in size in the 5 minutes I was messing with the air. After a couple days I'd say it's about 1/5 full. Which is a huge improvement but still not "set-it-and-forget-it".


Thanks so much!

 
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carlherrnstein
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Post by carlherrnstein » Thu. Dec. 31, 2020 2:54 pm

That fire doesn't look bad at all, it's very close. I would just leave it there for a few days and see how it does.

I would save adjusting the coal feed as a last resort unless parts of the heat exchanger routinely glow red. The reason being is if you cut the feed down your potential heat output is reduced and it's not simple to put it back if you have a cold snap and need it. Also these stokers are small and were enginerded around "fixed variables" the heat exchanger, firebox, tuyere an retort were sized around a fixed feed rate with the understanding that coal of various characteristics would be used. If it is slowed down too much the fire will burn down into the tuyeres and cause problems the worst of which is ruining the tuyeres the same is true of the air is way too high.

Unfortunately heating with solid fuel is never zero maintenance you always have to add more fuel and remove Ash or waste. If you have run a hopper of coal through it and the firebox isn't slam full of ash and clinker then you have really good coal.

I normally only remove clinker unless ash builds up above the bottom of the firedoor then I remove it to the bottom of the firedoor. It will turn to clinker, the clinkers are melted and fused ash that take up a lot less space than ash. The ash will insulate the bottom of the firebox and help keep the fire hot, it's sort of weird but, the fire does better with ash surrounding it.

I get more ash when it's not as cold outside and the stoker isn't running much at a time. I get more clinker when it's very cold and the stoker runs continually.

 
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Berlin
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Post by Berlin » Sat. Jan. 09, 2021 6:48 pm

usually a clinker reduces the volume of ash. do not clean all the ash, the ash insulates the fire. you should only pull the clinker. looks like too much feed, I prefer to start lowest feed possible, set air, let it stabilize and see if the home is heated adequately. These things tend to run high stack temps- too much feed and the efficiency plummets.

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