Huge Puffback!

Modern and vintage hand fired coal stove are similar to a wood stove and in some cases can burn either. They need to be regulated and fed by hand usually every 12 to 24 hours depending on your usage. They require no power to operate making them ideal for rural settings with long power outages.
DoubleD
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Stove/Furnace Make: Chubby

Post Sat. Dec. 17, 2011 12:28 am

Had the scare of a lifetime today. Only experienced one puff back prior. I had a low coal fire going for most of the day, stove temp. approximately 250 degrees, (ash door vent closed and MPD closed). I knew I was going out tonight and instead of letting the Chubby stove maintain the temp, I decided to shake and add coal although I barely needed any. I opened the ash door vent and MPD all the way and shook the grates. After adding coal the fire stayed around 250 degrees. I was in a rush and opened the ash door all the way with the mpd open. After 15 minutes the temp never got hotter. Because I was in a rush I closed the ash door and vent all the way. I also closed the MPD. I was standing near the stove as I was told my family I was leaving. A few seconds later, I heard a "shotgun blast" and looked at the stove. The top circular plate on the Chubby as well as the soapstone fire pot filled with water almost fell through the top of the Chubby. Coal dust was everywhere and the face of the barometric damper blew off the stove pipe landed approximately 15 feet on the floor. The explosion was so loud my ears where ringing. I managed to put everything back together, opened the ash door as well as the MPD and the blue ladies eventually appeared. I shut the ash door as well as the vent and left the house with the MPD open. I have a new respect for coal as fuel!

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Freddy
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Stoker Coal Boiler: Axeman Anderson 130 (pea)
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Coal Size/Type: Pea size, Superior, deep mined
Location: Orrington, Maine

Post Sat. Dec. 17, 2011 2:53 am

Wow... that's scary, as well as a bit messy. I've heard tales that the Chubby can do that. I think it's why they added holes above the fire. I'd go back to square one and start a new process for loading. If an open flame is always left visible, booms should not (can not?) occur. That is, when you fill it, never cover the top with new coal, leave it banked in such a way that the dancing flames are always on top in one small area.
Orrington, Maine
Fred

"If you can't say something nice, don't say anything at all".

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grizzly2
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Hand Fed Coal Stove: Hitzer 30 - 95
Coal Size/Type: pea and nut/ anthracite
Other Heating: Jotul #3 wood stove in garage. Oil backup in house. Electric backup in house.
Location: Whippleville, NY

Post Sat. Dec. 17, 2011 7:08 am

Well, that sure sounds exciting :!: :blowup:
The only redeeming value of winter is that I can have a fire in my stove.

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freetown fred
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Hand Fed Coal Stove: HITZER 50-93
Coal Size/Type: BLASCHAK Nut
Location: Freetown,NY 13803

Post Sat. Dec. 17, 2011 7:19 am

Glad nothing more serious happened DD. All these stoves definetly deserve that respect, and if you DON't have it, you better find it. Anyone reading these posts has got to have a basic knowledge on the do's & don't do"s. Being in a hurry ain't one of the do's. Good post DD, hopefully you've opened quite a few sets of eyes. Thank you. ;)
"A people that values it's privileges above it's principals, soon loses both"--Dwight D Eisenhower

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Rex
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Stove/Furnace Make: D.S. Machine
Stove/Furnace Model: Circulator 1500
Location: Indiana

Post Sat. Dec. 17, 2011 7:31 am

I just had a large puffback this morning with our DS 1500. After about an hour after the shakedown and reloading the coal hopper, the unit huffed a deep low roar. Scared the dog enough to have him jump up and sprint away from the stove. The blue dancing flames appeared right after and slowly burned down.

Not sure what I could have done differently. Believe the rear air damper eventually opened up after the shakedown, igniting the gases then woof.. Maybe the shakedown allowed the coal to cover over the coal bed not allowing any exposed red coal. Sure got my attention!!

Suggestions?

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freetown fred
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Post Sat. Dec. 17, 2011 7:48 am

Don't misconstrue my last post, sometimes them puffs just happen because they can--just the nature of the beast.The couple, three I've had over the yrs, seem to have been alleviated by my back thermo. flap---BOOM--tink, tink, tink. You sure are right, it does get one's attention. ;)
"A people that values it's privileges above it's principals, soon loses both"--Dwight D Eisenhower

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I'm On Fire
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Hand Fed Coal Stove: DS Machines DS-1600 Hot Air Circulator
Location: Vernon, New Jersey

Post Sat. Dec. 17, 2011 8:17 am

I had several like that when I had a Chubby stove. I've also had several with my DS-1600. I'm not sure which stove is worse though. Probably the Chubby, mainly because it had the potential to break stuff when that little top goes flying.

Vinmaker
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Location: Central MA

Post Sat. Dec. 17, 2011 8:24 am

Can someone explain to me what went wrong with the posters situation?

I have been burning coal for over 20 years and have never had this happen. I routinely fill the stove up and cover all of the red coals. The stove prior was just too small to leave a corner open. The slope of the piled up coal would just fill it in. So I always just filled it up as much as I could.

My routine at night is very similar to this. I open my MPD, do a quick little shake down, open the load door, load it up with an equal layer of coal all around the firebox, close the load door, close the MPD, then head up to bed. What is wrong with this routine? Never had a problem. Am I just tempting fate? Just lucky so far? I will change if there is a danger. My stove has a glass front and if that blows out, the stove will not work too well until I get it fixed.

Vin.

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lobsterman
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Hand Fed Coal Stove: Chubby, 1980 Fully restored by Larry Trainer
Hand Fed Coal Furnace: Chubby Jr, early model with removable grates
Location: Cape Cod

Post Sat. Dec. 17, 2011 9:01 am

Air is your friend to prevent puffbacks, and it appears DoubleD did not have enough after he closed the top end back down. I always ran my chubby according to the instructions of Larry Trainer which includes "flossing the teeth" to make sure you are not ash bound (probably why the stove did not respond quickly with the ash door open), and making sure you have air on top until the blue ladies dance which happens fast if you are not ash bound. Most important is to have the damper open for 5 minutes or so while the new charge spews forth its initial gasses. I never used an MPD for fear I would not know what the draft was doing. It appeared this happened in this case, the initial gasses came out only very slowly because the stove was ash bound and when the gasses did finally come out they were allowed to build up to an explosive level because the chimney was sucking on the room instead of the top of the coal bed. Anyway, sounds real scary to me!

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echos67
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Post Sat. Dec. 17, 2011 9:44 am

DoubleD, is your mpd a solid style or does it have the holes in it ? I am new to all this but is it possible your mpd sealed more than it was letting vent and caused the back-up of gasses ?

Mine has a few holes but I usually close it at 7/8 shut max because with the 2 dogs I just feel safer that thereis room to allow venting.
Keith V
Glenwood No. 6

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Beeman
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Post Sat. Dec. 17, 2011 10:09 am

DoubleD, those puffbacks are frightening! With my Hitzer insert, I am always watching while filling the hopper how much of the flames I am covering. My desired situation after filling hopper is to still see flames at the front or sides of the firebox such that I know any volatiles are able to be ignited. In this situation, I soon see blue ladies and can relax. Of course, after the blue ladies burn for awhile, they disappear with the volatiles and more normal, steady burn operations ensue.

My scary situation is to notice that I covered all the flames and I know volatiles are accumulating. While keeping ash pan door open, I usually immediately open the main loading door to provide plenty of air input to move the volatiles up the stack--don't wait to open the main door as volatiles accumulate and can explode just when you open the door--an unpleasant surprise! Unfortunately, opening the main door lessens amount of air pressure coming up through the coal bed from the ash pan door, thereby actually extending the dangerous time. I slowly close the main door over time while nursing along the small flames that begin to occur and can be sustained only with the ash pan door open. Nervous time until this happens....

Something I tried recently that worked very well in the situation described in the preceding paragraph is to place a source of flame--crumpled paper or something else that will burn for awhile--on top of the coal bed, then close main door and keep ash pan door open. This flaming fuel provides a source of ignition for the volatile gases given off. With main door closed, air pressure coming up through the coal bed is good and the overall dangerous situation is more time-limited. Once the paper or other temporary fuel burns out, hopefully the coal fire can produce steady flames; if not, repeat the paper routine. Good luck!

Vinmaker
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Post Sat. Dec. 17, 2011 10:21 am

Paper routine? That is just it. I have never done any of that. Thought never even entered my mind until I found this forum. I am not saying what I am doing is right and I may very well have just been lucky. But is all this really necessary?

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Rex
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Post Sat. Dec. 17, 2011 10:32 am

During my puffback this morning, I will admit my shakedown period from the last shakedown lapsed well over my normal 12hrs. Maybe the coal bed was smothered by more than normal extra fresh coal from the hopper during the shakedown, causing no red coals from appearing on top.

More frequent shakedowns might minimize the coal bed from getting smothered completely from fresh coal from the hopper, with the idea of minimizing the puffbacks??

franco b
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Post Sat. Dec. 17, 2011 10:56 am

Beeman wrote:I am always watching while filling the hopper how much of the flames I am covering.
The hopper should have been full from the last shake down. By filling at this point you are loading cold coal to the fire. By keeping the hopper full after each shake some of the coal newly fed will already have turned to coke and the thermostat will have opened the air shutter automatically as the fire cooled down. The hot coal will quickly ignite and the extra air will burn off the gasses. You should never get a puff with that stove.

With a batch fed stove with manual air intake it is always better to load in a few smaller batches if you are available to do that.

DoubleD
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Stove/Furnace Make: Chubby

Post Sat. Dec. 17, 2011 10:58 am

Thanks for the replies everyone. I have a solid MPD in my stove pipe. I after charging the stove, I normally keep the ash door closed (with vent open) and the MPD open until I start to see the blue flames in the stove chamber. I was always filling the stove pot to the top without banking the coal. I was trying to get out of the house last night and closed the MPD and vent on the ash door way to early. I didn't noticed any of the blue flames. This morning I made sure to bank the coal although, I feel it this is going to decrease my burn times. I think I am going to try the paper trick next time I charge the stove. Once I see the blue ladies dancing around the stove do you guys think it is safe to close the MPD and ash vents to the desired temperature settings?

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