Smoke explosion

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Smitty090

New Member
Dec 31, 2010
21
Eastern Canada
I'm a little bothered by this but maybe someone has more of an explanation.
I cleaned my pellet stove tonight as I always have for 2 years now. I started it back up with a normal small handful of pellets in the burn tray and they started burning normally while I waited for the auger to start pushing more (I cleaned the dust out of the auger too) so fresh clean everywhere.
After about 45 seconds of burning the flame just disappeared. I looked in and could see a small little flame in the ash pit below the burn pit. A couple seconds of that and BOOM, almost like an explosion there was a big puff of smoke that came out of lots of places and mostly put of the ash tray door (even though it was closed). Seemed like a backdraft of some sort but first time ever that has happened.

It's been running fine for the last 30 minutes since as I am sitting in front of it monitoring it.
Anyone else see similar?

Thanks!
Smitty
 

Bioburner

Moderator
Aug 4, 2012
7,317
West central Mn
Sounds like extra load of fuel in the system you had a flashover. What did you start your pellets with? Google "flashover" and you find alot of examples and a good explanation of this. A firefighters nightmare.
 
T

The Village Idiot

Guest
Happened to me once earlier this season as well. (First season pellet stove operator.)
Operator's manual hinted at the fact that putting a handful of pellets in the burnpot before a light-off would be a great thing in order to get things moving along in the "fire-in-the-hole" department. I figured, hey, if ONE handful of pellets helps, why not put TWO handfuls of pellets and get this party started in the right way. The party started all right. I hadn't considered the fact (Again, first-season noob) that the stove itself was going to send a good amount of pellets according to it's own thinking for the light-off (The HearthStone Heritage is fully automatic) so the burn pot ended up with a heavy load of fresh pellets (pretty near close to 3/4 full) and because of that, they ended up starving for air during the ignition stage. They just sat there smoldering and smoldering and smoldering until all I could do was just stand there and watch the firebox fill with rolling smoke. Told the wife to stand back as I knew that eventually the pellets would "find" their air that they needed and would eventually reach their critical mass breaking point. Sure enough...there it was....BOOOUUUFF! Had a couple of wisps of smoke creep out the door seal real quick, but no damage done to anyone or anything. The stove did it's job at keeping everything safely contained during this "Puffback".
Great thing about all of this is that there was a lesson learned when it came to lighting-off after a stove cleaning, and that was this: Go easy on trying to help the stove out with handfuls of pellets and let the stove do the feeding. Even if that means that it takes an extra 5 minutes for light-off due to having a small amount of pellets in the pot. An ounce of prevention most definitely equates to a pound of cure.
 

SmokeyTheBear

Minister of Fire
Nov 10, 2008
13,363
Standish, ME
Anything that causes an air flow restriction will prevent the smoke that is generated when the igniter heats up the pellets from leaving the system via the vent can lead to a delayed ignition (the boom).

Make certain that your entire combustion air path is clean this starts at your air intake and ends outside your vent systems termination cap.

Do not add additional fuel to "help" start the stove.
 

Defiant

Vermont Castings Geek
Dec 5, 2007
2,128
Old Lyme CT
Anything that causes an air flow restriction will prevent the smoke that is generated when the igniter heats up the pellets from leaving the system via the vent can lead to a delayed ignition (the boom).

Make certain that your entire combustion air path is clean this starts at your air intake and end outside your venti systems termination cap.

Do not add additional fuel to "help" start the stove.
STB X 2
 

Harvey Schneider

Minister of Fire
Oct 9, 2012
1,321
Southbury, CT
delayed ignition (the boom).
Sorry Smokey, the "delayed ignition" leads to a "rapid expansion". I believe those are the correct technical terms;)
 

stoveguy2esw

Minister of Fire
fuel air explosion on a small scale, heat gassifies the combustible elements of the fuel, add a little air after it builds up and boom, im with the members above , check everything in the exhaust and intake passages make sure you have clean airflow so combustion happens smoothly not suddenly, oh, and check any gaskets where you may have blown smoke out through, they should have contained this type of incident, we test for that stuff during the design stages
 
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Northwoodneil

Feeling the Heat
Feb 10, 2012
341
Land of Cheese

chrisasst

Minister of Fire
Aug 13, 2008
1,289
cortland ny
Also if smoke is coming out of the stove in places, isn't that a gasket problem or not in this situation because there was a heavy amount of pressure?
 

Cross Cut Saw

Feeling the Heat
Mar 25, 2012
404
Boulder, CO
Surface Transportation Board (US DOT)
Singapore tourism Board (Google)
Set Top Box (cable guy)
???????;em

I think he means he agrees with Smokey The Bear...

Kind of like +1.

That or Share The Biscuit.
 

Northwoodneil

Feeling the Heat
Feb 10, 2012
341
Land of Cheese
LOL.
 

SmokeyTheBear

Minister of Fire
Nov 10, 2008
13,363
Standish, ME
In this case Bioburner has a more correct description of this situation since the ignition had already occurred and there was a flame present before, during, and after the boom the root cause however is the same the smoke (actually the flammable gases created by the heating of the pellets) built up because it couldn't exit the system before reaching a level high enough that when it got enough air it went boomy or in Harvey's words rapidly expanded (some folks call that energetic expansion, some an explosion).

There are several examples on youtube and in a number of them you can see massive amounts of smoke trying to make it out the vent as well as swirling around behind the door and then boom it all disappears, except for some of the stuff that came out along the sides of the door that didn't get a chance to light up.

ETA: Even good old fashioned dino juice burners can and do do this as well.
 

DBCOOPER

Minister of Fire
Jan 23, 2010
509
Stowe, Pa
I've had that happen in my Quad CB1200i when I was using a non swing setting thermostat. It would start while it was still warm enough for the board to think there was a fire already established and feed to many pellets. Lots of smoke and then it would light off. The smoke would actually come out of the gaps where the airwash sucks in air. It will also do it if there is any ash/clinkers in the burn pot keeping the pellets away from the igniter area. The smoldering pellets create a combustable cloud that will make a "rapid expansion" once the flame appears.
 

glenc0322

Minister of Fire
Dec 30, 2011
604
long Island NY
sounds scary having that happen. i am not worried about it my Harman starts itself just turn a dial and in 5 minutes FIRE love it i have a pellet stove in my hunting cabin that is a manual start and light it with starter jell and a hand full of pellets guess i wont go for two hand fulls just incase thanks for the insight
 

Bioburner

Moderator
Aug 4, 2012
7,317
West central Mn
Cold air dam could start this event. Not enough air moving out the exaust and colder heaverier air fighting to come down flue,wind can effect the problem as well. Remember fireplaces usually have to have some newspaper lit in the flue to warm them up to start proper draft before starting the main fire. One would have to look at how long of vent pipe and wind direction to rule this out.
 

Harvey Schneider

Minister of Fire
Oct 9, 2012
1,321
Southbury, CT
Cold air dam could start this event. Not enough air moving out the exaust and colder heaverier air fighting to come down flue,wind can effect the problem as well. Remember fireplaces usually have to have some newspaper lit in the flue to warm them up to start proper draft before starting the main fire. One would have to look at how long of vent pipe and wind direction to rule this out.
Most pellet stoves that have igniters run the blower and the igniter for a few minutes before fuel is added. That gives time for the fire box and vent to get cleared whether it is of volites or cold air. It's when we tinker with the way it's supposed to work (because we think we know better) that problems happen.
 

Bioburner

Moderator
Aug 4, 2012
7,317
West central Mn
Unfortunately smitty gave us no stove model or other details of his setup. To broad of possibilities to refine a good answer or solution.
 
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