Flashover in my wood stove

[rwachtell]

I seem to have a problem in my wood stove that occurs when I reload it with wood. When I put a new load of wood in the stove on some hot coals and open the vents for a good level of air intake ... After a few minutes ... I sometimes get a small or low pressure explosion in the stove ... its more of a sudden poof ... then an explosion ... but it seems like the gasses in the stove all of a sudden ignite ... forcing smoke and a little ash out the vents into the room. Seems to me this could be caused by a improper venting with the stack but any thoughts on the matter and preventing it are appreciated.

Sometimes the "poof" is louder and more aggressive ( with regards to smoke be shot out the vents ) then other times.

Stove is a Jotul 3CB ... rear venting with about 18 inches of horizontal pipe ... and then 14 feet of vertical pipe up the chimney.

Rob

 

[DiscoInferno]

Perhaps leave the door open until you have some flame? If the door is closed with no flame the smoke will fill the box, and then when it finally ignites you get the little explosion. If you have flame before you close the door, it shouldn't happen. I imagine the problem is worse in stoves with poor draft.

 

[begreen]

Robert, after putting in the fresh wood, do you open the ashpan door for a little bit to get the wood going? If not, how quickly do you damper down after adding the new wood? What type of wood are you burning?

 

[webbie]

It may be that you cannot 100% stop this, but you can probably cut down on it a lot by following some of the advice above. Two mechanical ideas that might help are a turn damper in the pipe and a barometric damper in the same.

Also, make certain your stove top is fitting on tightly, as well as the pipe connection to rear of stove. It may be sucking air into these points.

As far as reloading, when you have the time it might be best to thrown a couple pieces of kindling and smaller wood on those coals, get that going and then fully reload. Bottom line is that you are building up unburnt gases because of a stove inside temp that is too low. Those gases should be burned as flame in the stove, not go up the chimney as gases and then ignite.

 

[rwachtell]

I've seen this happen under all circumstances ... more often with a reload of wet wood ... doors closed ... and dampered down ... thats a mistake obviously ... but it has also happened when reloading with DRY wood and both vents and the ash door open wide for quick recharge.

I guess its also a function of how much hot fire was left for the wood to go on top of.

But I also guess that what I am really asking here is if the 18" horizontal run out the back of the stove helps contribute to this lovely little wood stove firework display?

Also ... does anybody know how difficult it is to replace ( I know what the part costs ) the bottom plate on a 3CB. I've cracked the hell out of mine from overcharging on reloads and probably should get around to replacing it. Do you have to take the stove completly apart to do it ?

Thanks

Rob

 

[BrotherBart]

I've seen this happen under all circumstances ... more often with a reload of wet wood ... doors closed ... and dampered down ... thats a mistake obviously ... but it has also happened when reloading with DRY wood and both vents and the ash door open wide for quick recharge.

I guess its also a function of how much hot fire was left for the wood to go on top of.

But I also guess that what I am really asking here is if the 18" horizontal run out the back of the stove helps contribute to this lovely little wood stove firework display?

Also ... does anybody know how difficult it is to replace ( I know what the part costs ) the bottom plate on a 3CB. I've cracked the hell out of mine from overcharging on reloads and probably should get around to replacing it. Do you have to take the stove completly apart to do it ?

Thanks

Rob

I can tell you that it means a complete dis-assembly of the stove. I did a re-seal on mine in September. Let me guess on the part: Around $200 plus shipping?

 

[begreen]

This will almost certainly happen at some point if you are opening the ashpan door for a quick recharge. The reason is that with the ashpan door open you are suddenly putting a blowtorch under the raw logs. This causes them to ignite fast and start outgassing very quickly. Then by closing the ashpan door the source of mass oxygen is cut off, but the outgassing continues and once the fire ignites, it is explosive.

Not trying to sound like a smarty-pants. The reason I know is that I've been there and done that with the 3CB and learned my lesson. Don't repeat this procedure, it's dangerous and has to be hard on the stove.