Scary Progress Backpuff

[fire_man]

WOW that was the worst Backpuff I ever had. It's 42 degrees outside and I just wanted to take the chill out of the house, so I loaded the stove about 1/3 way. The stovetop got up to 250F so I engaged the cat as usual. I noticed the firebox was awful dark - no flames, so figuring I'd get a backpuff, I disengaged the cat and opened the draft a little.

About 4 minutes later WHAM! major backpuff/explosion but this was more like a BACKFIRE. The stove lid jumped up and a shower of sparks flew out from under the lid and sprayed the room - smoke detectors now in full swing. Holy crow I've been burning for 15 years 24X7 and never had anything like that.

I've noticed when the box is loaded less than 1/2 full the backpuffs are worse, but this was just plain nuts.
I'm just glad I know there are 3 screws at every pipe joint holding things together!

I also had the iconel screen in place and think that limited the sparks from escaping.

I don't think I ever read a post where sparks flew out from a stove and it wasn't from an open loading door.

 

[rdust]

Yikes! Glad the house is still standing.

 

[fire_man]

I'm guessing the sparks might have come from bits of the iconel screen. There was already a hole in the screen and now it's bigger. Woodstock got rid of the screen on newer stoves. I'm not sure if the screen helped or hurt in this case.

 

[Woody Stover]

Was there a lot of creosote coating the box? I've seen that stuff burn off early in the burn after re-loading and create a lot of volatiles in the box, just waiting for enough oxygen to ignite. In that case, a bit hotter/longer burn when ramping up to temp might burn more of that creo out. If it's just a chill-buster fire, you could do that partial load but burn it a little hotter. I think some of the problem is less draft when it's not real cold out, which allows volatiles to build up in the box. If I'm not mistaken, your wood is plenty dry. My BIL said that would happen with his old Resolute on the 13' stack in warm conditions, but I'm not sure if he's had any problem with the Fireview I sold him. Have other Progress owners mentioned this happening?

 

[fire_man]

I am pretty sure there was not much creosote in the box - at least visibly it looked clean before loading. In fact, the fire had gotten hotter than usual this specific time before I engaged the cat - I stepped away from the stove while it was firing up (bad Fire_man) but my wife was in the room and saw it was burning too hard and lowered it.

Yes, my wood is extremely dry - at least 3 years C/S/S. I remember someone else on this site (Texas Boy I think was his name) had ancient dried wood and had constant severe lid popping backpuffs with the Fireview, so I agree very dry wood is definitely a factor. My flue is about 16' tall, so it's not pulling that hard. I think he switched to the Progress, but I have not seen new posts since then.

I think Woody Stover is correct, extremely dry wood and a poor draft were the cause. To prevent it, the only thing you can do is make sure not to lose a flame in the box - so keep the draft open right from the start.

 

[webby3650]

Wow! It's scary to think sparks were able to escape the stove. Now you have to second guess starting a fire and running out the door. That wouldn't work in my house!

 

[fire_man]

I have had backpuffs (as many have had) but the unusual thing was the sparks. Now that I think of it, the other unusual thing that happened is that I had disengaged the Cat IN ANTICIPATION of the back puff, so the cat was not in the backpuff path. If it was (like it usually is), the Cat would have acted like a filter/deflector to the sparks. The open Cat bypass door made it a straight shot directly from the firebox to the bottom of the lid.

I would never leave the house with the Cat disengaged so based on past experience and this logic, I still feel safe leaving the house with the stove running.

 

[webby3650]

I have had backpuffs (as many have had) but the unusual thing was the sparks. Now that I think of it, the other unusual thing that happened is that I had disengaged the Cat IN ANTICIPATION of the back puff, so the cat was not in the backpuff path. If it was (like it usually is), the Cat would have acted like a filter/deflector to the sparks.

I would never leave the house with the Cat disengaged so based on past experience and this logic, I still feel safe leaving the house with the stove running.

My Lopi Leyden back puffed and blew the lid open once. It had to go! I can't have a stove that's unlredictable in my home. They cost way too much to take the risk. Back puffing is somewhat normal for some folks, but showering Sparks and blaring smoke alarms takes it to a whole different level.

 

[rdust]

Wow! It's scary to think sparks were able to escape the stove.

This is the main reason I dislike stoves with removable lids or too many pieces. Not only do you have more place for gaskets to wear out but you also open yourself up to scary stuff like this when things don't go as planned. It seems stoves with lids that open should have a latch to hold them down. No different than a stove pipe requiring screws so it stays together when things like this happen.

 

[OhioBurner©]

I don't have one (yet), but the lid looks massive on the progress, cast iron with soapstone on top. That must have been one heck of a backfire to lift the lid! Wowza!

 

[begreen]

Wow, that is scary. I had a backpuff or two with the Castine, but nothing so dramatic. None so far with the T6. So glad that you were at home and able to watch over things and eventually recover composure. Hope the laundry doesn't mind the soiled pants. I'm with webby, I want boring peace of mind with each fire. 42F is frequently normal winter burning temp here.

 

[fire_man]

I don't have one (yet), but the lid looks massive on the progress, cast iron with soapstone on top. That must have been one heck of a backfire to lift the lid! Wowza!

There was a soapstone griddle accessory on top of the stove's soapstone lid, which was on top of the cast iron griddle! Quite a lot of weight I would say.

 

[Calentarse]

There was a soapstone griddle accessory on top of the stove's soapstone lid, which was on top of the cast iron griddle! Quite a lot of weight I would say.

All that pressure and force had to go somewhere, just hard to believe it was less to lift that lid that simply go up the chimney (no matter how warm it is outside)...

 

[Calentarse]

WOW that was the worst Backpuff I ever had. It's 42 degrees outside and I just wanted to take the chill out of the house, so I loaded the stove about 1/3 way. The stovetop got up to 250F so I engaged the cat as usual. I noticed the firebox was awful dark - no flames, so figuring I'd get a backpuff, I disengaged the cat and opened the draft a little.

About 4 minutes later WHAM! major backpuff/explosion but this was more like a BACKFIRE. The stove lid jumped up and a shower of sparks flew out from under the lid and sprayed the room - smoke detectors now in full swing. Holy crow I've been burning for 15 years 24X7 and never had anything like that.

I've noticed when the box is loaded less than 1/2 full the backpuffs are worse, but this was just plain nuts.
I'm just glad I know there are 3 screws at every pipe joint holding things together!

I also had the iconel screen in place and think that limited the sparks from escaping.

I don't think I ever read a post where sparks flew out from a stove and it wasn't from an open loading door.

So I'm unfamiliar with this feature of the PH...the top comes off? There's no lock or anything? The weight of all that keeps it sealed tight?

 

[fire_man]

I wondered the exact same thing - why the heavy lid lifts before the shock exits the flue. I guess it's like a shock wave smacking into things, finding the path of least resistance along the way. The lid sees the force of the shock wave before it gets redirected up the flue (what's left of it after the lid lifts).

The Progress and Fireview both have large lids that lift for easy access to the combustor. There is no lock, only weight and a gasket keep it tight. The gasket is not really much of a wear item - the lid only gets raised a few times a year.


My old Resolute had a top loading door which also lifted during a backpuff.

 

[Nick Mystic]

This is a good example of just how heavy air is. We think of air as being light since we can hold our hand out and lift it into the air and don't feel like we are lifting anything but our hand. However, air at sea level actually weighs around 15 lbs. per square inch. That means a one inch square column of air stretching from ground level to the top of the atmosphere weighs around 15 lbs. A six inch diameter flue pipe has roughly 28 square inches of space inside the pipe. That means you have about 425 lbs. of air stretching from the top of the wood stove to the top of the atmosphere.

When you set off an explosion inside your stove (which is basically what a back puff is when it ignites) the gases expand extremely rapidly and the weight of the air column inside the stove pipe simply cannot be displaced fast enough to exit out the top of the pipe. Having a chimney cap probably slows down the exit of the gasses even further. Apparently, such an explosion produces enough force to raise the rather heavy lid of Woodstock Progress, or other stoves with similar lids.

 

[fire_man]

Interesting summary. Makes you wonder what kind of forces the stove internals would have seen if the lid had not lifted.

 

[tarzan]

I get small back puffs all the time. Guess that's the nature of low and slow in a cat stove. I havn't seen anything that violent since I was running a Made in Taiwan cast iron stove. One morning I woke up, opened the draft, went into the kitchen to make a pot of coffee, walking back to the stove to add wood and WHOOSH! Smoke blew out of every seam! I suppose introducing oxygen to a smoldering fire and a cool chimney that had lost draft did it but that stove was an accident waiting to happen and taught me a lesson.

 

[fire_man]

Backpuffs are nothing new to me, I've seen them with three different stoves and the Resolute was not a cat stove. The thing that scared the bejesus out of me was the sparks that came flying out this last time.

I know it's draft related. I have a Palladian installed with a much taller flue, and that stove never even hints at backpuffing.

 

[tarzan]

Backpuffs are nothing new to me, I've seen them with three different stoves and the Resolute was not a cat stove. The thing that scared the bejesus out of me was the sparks that came flying out this last time.

I know it's draft related. I have a Palladian installed with a much taller flue, and that stove never even hints at backpuffing.

I agree. Back puffs can be expected but the ability for one to seperate the stove enough for sparks to get out into the living space is scary stuff.

 

[BKVP]

This experience is reproducable with nearly any wood stove. When the moistrure level drops much below 7%, the fuel rich environment creates a delayed ignition. In this case, it is the combustor.

Our studies of this suggest that when burning fuel that is below 12%, it's not a bad idea to also load some 18% fuel. This typically fixes the issue. However, also starting the fire with the air control at 100%, allows no room to increase the air to fuel ratio in the "about to go off" scenario.

Start the fire with the air control at 75% and then pay aprticular attention if the load appears to have exceptionally dry fuel. Open the air a bit more to lean out the air fuel mixture.

Just a thought...

 

[BrotherBart]

And have a steel stove. With the top welded to the stove body.

 

[chance04]

Props to BKVP for offering help/advise even if it isn't his product

 

[Calentarse]

Interesting summary. Makes you wonder what kind of forces the stove internals would have seen if the lid had not lifted.

On the old VC encore 2N1, it would backpuff when the stove was 600 degrees and the draft completely shut (didn't know that actually introducing a bit of resh air would actually help keep the temps down) and the lid would pop up over and over. You talk about nasty smelling smoke in the house!

It would backpuff so hard sometimes that the lid would come up and you could see smoke shoot out of every seem because even the lifted lid + chimney didn't allow enough of the force to escape. Scary, scary stuff and definitely not good for the stove. Had to contribute to the wearing of all those gaskets!

 

[fire_man]

This experience is reproducable with nearly any wood stove. When the moistrure level drops much below 7%, the fuel rich environment creates a delayed ignition. In this case, it is the combustor.

Our studies of this suggest that when burning fuel that is below 12%, it's not a bad idea to also load some 18% fuel. This typically fixes the issue. However, also starting the fire with the air control at 100%, allows no room to increase the air to fuel ratio in the "about to go off" scenario.

Start the fire with the air control at 75% and then pay aprticular attention if the load appears to have exceptionally dry fuel. Open the air a bit more to lean out the air fuel mixture.

Just a thought...

Thanks for this advice. I was certain I was going to get a backpuff that time - so I raised the draft (in anticipation) from nearly fully shut to about 25% open, and I disengaged the Cat. A couple minutes later was the violent backpuff. I knew it was going to happen but evidently could not prevent it.

I guess the "mistake" was starting out with the air nearly closed when there was so little fuel in the stove. For some reason, when loaded less than half way, it seems more prone to backpuffing. And yes, I do have pretty dry wood, 3 + years stacked and top covered.