New stove - scary situation

[netmouse]

I am now considering a new Jotul stove, the Oslo style. I did a Google search on overfiring as my current VC Definant seems to be a victim of that - I'm not sure why. I found a website describing explosions in wood stoves (using Jotul, but I am sure not limited to this brand) that shatter the glass front. Part of the problem seems to be keeping the ash pan open to get new logs going - something I have seen people on this forum mention they do - which seems per this website to be a very bad idea.


http://chimneysweeponline.com/howhuff.htm

With the Defiant I did the following to get new logs going. I left the side loading door open a crack and let the temp get up to about 500 - 600 in the red zone (magnetic temp gague on pipe about 12 inches above stove top). When the temp got to that, the fire was roaring. I'd then shut the side loading door and turned the handle down to close the damper (it is either open or closed). The temp would slowly reduced to about 200 - 300 and cruise nicely. The front is whiteish and the damper is now warped, signs I'm told of over firing. Not sure what I could have done differently to prevent that.

Before I buy a Jotel or any new stove, I'd like your thoughts. This is the link.

 

[fraxinus]

Keeping an ash drawer open and partially opening the side door on a Defiant would have the same effect. Each would tend to produce a very concentrated flame like that of a blow torch. My guess would be that the "explosions" are not really explosions but the glass breaking because of an excessively high temperature in a small area which would produce enormous thermal stress. The case with the Defiant is similar. Your thermometer reads only 600 degrees because of the mass of the stove. The concentrated flame, though, can be much, much higher - high enough to cause buckling, cracking, and other symptoms of overfiring. Routine use of the side door to quickly get a roaring fire is not a good practice.

 

[begreen]

Puffbacks are often caused when the draft is marginal (like fall/spring burning) and the user opens something (like the ash pan door) to provide a lot of air to get a balky fire going. Then once satisfied that it is going, the air (ash door) is closed off. This causes the flames to die and the wood to smolder badly. When the fire finally rekindles, that first flame ignites the large mass of unburnt wood gas trapped in the stove and it is explosive.

Normally this puffback just makes a mighty whoomph! and smoke oozes out of every gasket and crevice. But I suppose it could under the right circumstances blow the glass out, especially if the glass had a flaw or tiny crack to begin with. This is why one makes sure that the stove is in good working order and installed with 3 screws per joint. I've had a few puffbacks in my day and none has done anything but startle the hell out of me. The solution is to use good dry kindling and leave the primary door ajar slightly, but still on the latch, until the fire is burning well. If closing the door snuffs the fire or if the fire is balky, then be patient and solve the problem. Don't let the fire smolder.

Often the problem is just a matter of trying to start too large pieces of wood or the kindling is not really dry. Sometimes it is bad cold-starting draft. In the case of our F400, it was that the horiz stub before the elbow going up was installed heading downhill. This made for lousy draft, especially in September. Fixing that made a world of difference.

Re: using the ashpan door. Regardless of what people may say, you'll notice many manuals including the Jotul's explicitly say - Don't do this!

From the F500 manual:
• The ash pan door on the stove must always be securely closed
when the stove is in operation.
• Burning the stove with the ash pan door open will overfire
the stove and cause interior damage.

and -

Warning. Do not, at any time, operate this stove with the ash
pan door open. This condition will lead to overfiring and will
damage the stove. This damage is not covered under warranty.
Only empty the ash drawer before refueling, when the fire is low
or out. The ash door should be open only long enough to empty
the ash drawer and then securely closed. Inspect the gasket on
the ash pan door regularly and replace as necessary.

 

[woodconvert]

I am now considering a new Jotul stove, the Oslo style. I did a Google search on overfiring as my current VC Definant seems to be a victim of that - I'm not sure why. I found a website describing explosions in wood stoves (using Jotul, but I am sure not limited to this brand) that shatter the glass front. Part of the problem seems to be keeping the ash pan open to get new logs going - something I have seen people on this forum mention they do - which seems per this website to be a very bad idea.


http://chimneysweeponline.com/howhuff.htm

With the Defiant I did the following to get new logs going. I left the side loading door open a crack and let the temp get up to about 500 - 600 in the red zone (magnetic temp gague on pipe about 12 inches above stove top). When the temp got to that, the fire was roaring. I'd then shut the side loading door and turned the handle down to close the damper (it is either open or closed). The temp would slowly reduced to about 200 - 300 and cruise nicely. The front is whiteish and the damper is now warped, signs I'm told of over firing. Not sure what I could have done differently to prevent that.

Before I buy a Jotel or any new stove, I'd like your thoughts. This is the link.

No,nonononono...no. DON'T OPEN THE ASH PAN TO GET A FIRE GOING.

As far as your overfiring, I don't see anything wrong with your procedure. Opening the side door is fair game and 500-600 is in the ballpark. Were you burning some over dry pine or something that burns hot and fast???. Just wondering if you heated it up too quickly.

 

[cmonSTART]

Growing up, our old VC Defiant used to backpuff often in the spring and fall, especially when smoldering. A big poof, the sound of the metal flapper door flapping, and a puff of smoke into the room...

 

[webbie]

Interesting that the chimney sweep (a board member) used three Questions concerning Jotul (a brand it appears he does not sell on the site) as an example......

In any case, one stove is as liable as another (in general) to be able to back puff if operated incorrectly.
https://www.hearth.com/econtent/index.php/wiki/flashback/

 

[BrotherBart]

All ya gotta do with any of them is wonder "Why isn't it burning more" and forget to open the primary air before you open the door. With the exhaust exit being at the front of a typical non-cat, a burst rolling up out the door over the front of the stove is very possible.

I hear tell it can singe eyelashes. :red:

Those bursts are also the reason that you put those three screws in every pipe joint. Flex liners make a neat expansion sound when it happens. Pipe joints could decide they wanna open up and breathe a little. So could a liner adapter that doesn't have screws. :ahhh:

 

[thechimneysweep]

Interesting that the chimney sweep (a board member) used three Questions concerning Jotul (a brand it appears he does not sell on the site) as an example......

The letters that appear in our online Sweep's Library are from real people with questions about whatever stove they might have. The two letters that prompted our whuffing page happened to be from owners of a VC and a Jotul, and two subsequent contributors had Jotuls, but, as I state in my response to one of the letters on that page, whuffing can happen with any stove.

So, why the disproportionate number of inquiries about back-puffing Jotuls? I think what happens is, someone with a Jotul who's experiencing back-puffing Googles "Jotul back-puffing" to try to find a solution. I just tried it, and our whuffing article comes up on the first page of Google's responses. This phenomenon tends to create visits to our whuffing page (and follow-up letters) from folks with back-puffing Jotuls. I just tried a Google search for "Fisher back-puffing" and in seven pages of responses, our whuffing page doesn't come up at all.

Another example: the letter that prompted our "Cat vs Non-Cat" page happened to be from the owner of a VC Defiant cat. As a result, we received follow-up inquiries on that topic from owners of VC Defiants far out of proportion to the actual relative presence of Defiant catalytics on the planet. It may seem to the casual site visitor that we're singling out the Defiant, but the fact is, we publish 'em when we get 'em.

 

[WOODBUTCHER]

This will be my 4th winter with the Oslo, the stove is always going 24/7....never been over fired....no explosions. We have 4 Jotul's between family now, 2 Oslos's, a Firelight and a F3 CB....no issues. I'm not going to say I don't use the ashpan door......but I will say Jotul makes a high quality stove.


WoodButcher

 

[Dexter]

We've had a Jotul Firelight CB for 8 years. The first couple of years, it would back-puff disconcertingly. We re-installed the stove with a shorter horizontal stovepipe section (it is vert/horizontal/vert) and stopped shutting the air down so soon (or quite so completely). No backpuffing in six years. None.

We run the stove full time in the winter, 2 to 4 cords. If we let a hot fire mature 'til there's almost no flame remaining, then shut it down (80-90%?), it still holds coals all night, and the glass doesn't even get dirty (well seasoned pine.) We run the stove between 450-575 degrees when air is open (thermometer on stove top, right rear).

Top baffle (plate?) tended to warp every couple of years, letting flame to the thermal blanket. I finally replaced iron baffle with split fire bricks, and held them off the fire tubes with 3/16 in. cold rolled steel dowling. Works great. 3rd season. About the same weight as original equipment. When cleaning, the chimney shows no difference, and the fire-tubes flare nicely.

Best Regards, and good luck with the backpuffing.

Dexter