A Whuffing/ Back Puffing Wood Stove??

[jotulburner]

I Just moved to a new home and am getting use to a new stove. Have been burning a Jotul old # 3 for years, never had a real problem with it. We have a Vermont Castings Encore in our new house have been burning for last 3-4 weeks off and on no problems. Tonight, however out of the blue the top door of stove started pushing out puffs of smoke. Stove is only a few years old and I had the entire system inspected before we moved in. I had the fire box about 1/2 full stack temp was at around 475 and I was in catalytic mode. After we noticed the smoke in our living room I opened draft and it seemed to stop smoking. I have never heard of Wuffing or Back Puffing before but am wondering if that could be the problem. If this is Wuffing how can I keep it from happening again or be sure it isn't going to happen in the middle of the night while we are asleep. Any insight from the members of this forum would be appreciated thanks.

 

[bsj425]

If it is at the door not really a bi deal you just need a new gasket. Even if it is pretty new that is a every other year type deal they get compressed after a while after having the door latched all the time. Not a big deal takes about 10 minutes to change.

 

[jotulburner]

Sorry when I said top door I think it is called the griddle on the vermont castings no latch held down by gravity

 

[Backwoods Savage]

When back puffing occurs, that smoke will seek out the easiest way to get out of the stove. It can even come out of the draft!

Back puffing will occur more frequently in fall and again in spring when the outdoor temperature is not that cold. Also, filling the stove and then turning the draft down too much will definitely cause it. Naturally another cause, and this is one you need to check on quickly is the chimney. Is it beginning to plug? Creosote and soot buildup can quickly close off the draft in the chimney and cleaning it is the only cure. So make sure nothing is shutting off the draft and don't fill the stove at this time of the year. If it backpuffs, give it more draft and that should stop it if all else is in order.


As for replacing door gaskets, I've replaced one door gasket in the last 28 years. Test the door. Ever heard of the dollar bill test? With a cold stove, insert a dollar bill and close the firebox door. Now pull on the dollar bill. If it comes out easy, either tighten the door or replace the gasket. You can also simply look at the gasket. One that is leaking will turn color quite fast.

 

[raygard]

I had the same problem in the last two weeks and posted here. do a search on the phrase "Backpuffing with a CAT". It's an interesting read. In short, you probably need to turn the air a little higher. That's the Right Hand Side knob, pull it further forward.

Ray

 

[Chettt]

At 475 nothing should be coming out of the box.

 

[BrowningBAR]

If it is at the door not really a bi deal you just need a new gasket. Even if it is pretty new that is a every other year type deal they get compressed after a while after having the door latched all the time. Not a big deal takes about 10 minutes to change.

No, it is not the gasket on the griddle. As BackwoodSavage said "smoke will seek out the easiest way to get out of the stove." No matter how new that gasket is, the Griddle only relies on it's own weight to create a good seal against the gasket.

The back puffing created enough pressure to make it's way out from the griddle.

 

[BradSmithSC]

...filling the stove and then turning the draft down too much will definitely cause [puffing]

Is this video an example of puffing (or back puffing) for a wood stove? Trying to understand the terminology.

More images and descriptions http://www.diybackyardworkshop.com/2011/12/wood-stove-puffs-fire-and-smoke/

 

[LLigetfa]

The usual cause if not enough air for the amount of off-gassing that is happening at the moment. It results in a series of mini-explosions, like deiseling.

The lean air condition could be from a transient pressure deficit. Was it windy at the time or had you just recently adjusted the air?

 

[Lynch]

wow do you heat with just cardboard thats awsome lmao

 

[Gark]

The backpuffing was all but eliminated with our Encore when we improved the flue draft (insulated the liner). Burning in cool weather (vs. cold weather) reduces draft. If you very gradually close the primary air (lever on right side of stove) in increments after closing the damper (left side lever pulled toward front of stove) backpuffing won't happen. If you take several minutes to slowly close the primary, it gives the burning splits time to gradually reduce their smoke output, instead of having the firebox fill with smoke faster than the cat can draw it out. On ours, we end up with the primary air lever about 5: O'clock position for the long burn. Just turn down your air handle very slowly.

 

[BradSmithSC]

Was it windy at the time or had you just recently adjusted the air?

This stove will do this anytime windy or not. It was not windy on this day.

The air valves can be almost any level. I had not adjusted them in this video though from one scene to the next.

I wish the camera could better capture the whoomp-whoomp sound the stove makes. Quite guttural. The camera is quite a few feet away from the stove due to the heat projection when the door is opened.

I can get my stove to puff fire using only wood but it does not do it as frequently or intensely. I used cardboard in the video as it makes for a more intense dramatic show and easier to capture on video.

The fire is quite hot so that is why I am using a tool, in this video it is a golf club which works great to manipulate the latch and open/close the door.

 

[Jags]

Please pay close attention to Backwoods Savage and LL's post. They are both spot on. Your back puffing is caused by not enough oxygen present to combust the fuel. It is drawing air from somewhere, and when it hits the fuel you (as LL stated) are getting mini-explosions. MORE PRIMARY AIR will stop this in its tracks.

Now you have the task of finding out WHY you are having this problem. My first blush guess is that you are used to running the old stove cranked way down, and when you do the same to this stove you are creating a oxygen deprived environment. I think you will find this happens during the outgassing stage of the burn for the most part.

 

[Pagey]

I've had this happen twice in the three years we've operated our Endeavor. And both times giving the fuel a little more primary air has solved the problem. In both cases, I simply ended up shutting down the primary too soon, which resulted in the problem in the first place. Basically, both times were operator error on my part. It does make for a weird scene inside the firebox, though: random, rolling, minature "explosions" as the combustible gases finally get enough oxygen to ignite, then back to a calm, dark box. The slight hint of a smokey smell in the room lets me know what I've done.

 

[fire_man]

The backpuffing was all but eliminated with our Encore when we improved the flue draft (insulated the liner). Burning in cool weather (vs. cold weather) reduces draft. If you very gradually close the primary air (lever on right side of stove) in increments after closing the damper (left side lever pulled toward front of stove) backpuffing won't happen. If you take several minutes to slowly close the primary, it gives the burning splits time to gradually reduce their smoke output, instead of having the firebox fill with smoke faster than the cat can draw it out. On ours, we end up with the primary air lever about 5: O'clock position for the long burn. Just turn down your air handle very slowly.

Good to know insulating the liner helped - it makes sense. My local chimney guy told me its a national code that the liner has to be insulated - can anyone confirm this? My plan is to pull my rigid liner in the spring and insulate that sucker.