Why is the dragon back puffing?

[TomatoLover]

Lit the dragon tonight (cold stove) with about eight 24" pallet pieces and 4 bio bricks. It took off like a rocket, as it always does. I was trying to warm things up in a hurry and get some heat and coals established before adding some oak for the overnight. About 15 minutes from start up, the stove top was about 500 and climbing fast and furiously (this stove chugs like a freight train while it's climbing). Air intake controls were shut down about 1/2 way. As I sat there waiting to shut the air down some more as it approached 600, the dragon started belching smoke out of the intake dials on the front, soon filling the house with the smell of burning wood.

I didn't know what to do, so I opened the door to take a look. Nothing unusual going on, so I shut the door. More back puffing. It finally stopped and I was able to load the oak and go to bed.

Why the back puffing? Is that a draft issue? Too many pallets in there? Trying to bring the heat up too fast? Please help correct my operator error. Thanks!

 

[jatoxico]

Any noise or short bursts of smoke or was it steadily coming in house? With air shut too much too early the stove can whoof as unburned gases suddenly burn up like a mini explosion and smoke can escape. If it was more steady then nothing comes to mind as to what that might be if the stove was cranking along.

 

[TomatoLover]

Any noise or short bursts of smoke or was it steadily coming in house? With air shut too much too early the stove can whoof as unburned gases suddenly burn up like a mini explosion and smoke can escape. If it was more steady then nothing comes to mind as to what that might be if the stove was cranking along.

Thanks for the reply. There wasn't any noise that I recall. It was several short puffs of smoke coming out around the intake dials. But now that you mention it, a week or so ago, my husband loaded it and there was a definite BOOM inside the stove followed by puffs of smoke into the room. So perhaps we are shutting the air too soon?

 

[jatoxico]

Short puffs sounds like it could be that and pallet wood w/ bio bricks is a lot of DRY fuel that will gas off quick and need air so makes some sense.

Maybe try a few small splits of cord wood with the pallet wood at startup to get your coal bed going before you load for the night.

 

[Ashful]

Why the back puffing? Is that a draft issue? Too many pallets in there? Trying to bring the heat up too fast? Please help correct my operator error. Thanks!

Yes, it is often a draft issue. Simply put, wood gas is being produced faster than fresh air can be drawn in to combust it. So, the reaction momentarily stalls until more air is drawn in. When the air/gas mixture reaches critical balance, you get a back-puff, which quickly uses up the available oxygen. Lather, rinse, repeat.

This is often a problem on stoves on short stacks, where draft may be minimal, rarely on tall stacks. If you haven't checked the cleanliness of your chimney and cap recently, it's probably time to check now.

 

[TomatoLover]

Yes, it is often a draft issue. Simply put, wood gas is being produced faster than fresh air can be drawn in to combust it. So, the reaction momentarily stalls until more air is drawn in. When the air/gas mixture reaches critical balance, you get a back-puff, which quickly uses up the available oxygen. Lather, rinse, repeat.

This is often a problem on stoves on short stacks, where draft may be minimal, rarely on tall stacks. If you haven't checked the cleanliness of your chimney and cap recently, it's probably time to check now.

Thanks for the reply. Is the stack the same thing as the flue? I know the flue is over 25 feet, according to our sweep, who was here in December. Perhaps I just closed it down too early with all that dry fuel in there?

 

[claydogg84]

Did you check the cap?

 

[Ashful]

Thanks for the reply. Is the stack the same thing as the flue? I know the flue is over 25 feet, according to our sweep, who was here in December. Perhaps I just closed it down too early with all that dry fuel in there?

Both refer to chimney. I guess "stack" is typically the outside support structure, and "flue" is the pipe / liner.

A big load of dry fuel with minimized draft will definitely cause back-puffing. I have two of the same stove, one on a 25 ft. pipe and the other on 15 ft. The one on the tall chimney never back-puffs, but the one on the short chimney sometimes will, when I cut the air back full. The answer is to nudge the air lever open just a hair, and it will stop after a few minutes.

Certain species back-puff worse than others. A full load of Walnut will cause me troubles with back-puffing on the short chimney, whereas oak and ash do not seem to do it.

 

[TomatoLover]

Both refer to chimney. I guess "stack" is typically the outside support structure, and "flue" is the pipe / liner.

A big load of dry fuel with minimized draft will definitely cause back-puffing. I have two of the same stove, one on a 25 ft. pipe and the other on 15 ft. The one on the tall chimney never back-puffs, but the one on the short chimney sometimes will, when I cut the air back full. The answer is to nudge the air lever open just a hair, and it will stop after a few minutes.

Certain species back-puff worse than others. A full load of Walnut will cause me troubles with back-puffing on the short chimney, whereas oak and ash do not seem to do it.

Thanks! Haven't had any back puffing last night or today burning the same blend, but keeping air open longer. Then I close it down gradually and let it burn down some before putting in the overnight oak load. It seems my operator error was related to closing the intake too fast with that type of load (pallet and bio bricks). We're approaching 1 year of wood burning and I still feel like I'm learning something new every day!

 

[begreen]

What stove is the smoke dragon? What size liner is it connected to?

 

[FishKiller]

too much fuel and too little oxygen. your start up says it all.. i'm all for hot starts, small fires, etc. i;ve had my cat stoves go explosive on me before when trying to get that first flameless burn. it basically did the same thing. usually cause i haven't established a good draft yet. things take awhile to get flowing as your pipes are warming. start with half the fuel and one brick, see what happens. yes this means you'll have to do a intermediate reload before the night fill, but it should solve your problem.

 

[TomatoLover]

too much fuel and too little oxygen. your start up says it all.. i'm all for hot starts, small fires, etc. i;ve had my cat stoves go explosive on me before when trying to get that first flameless burn. it basically did the same thing. usually cause i haven't established a good draft yet. things take awhile to get flowing as your pipes are warming. start with half the fuel and one brick, see what happens. yes this means you'll have to do a intermediate reload before the night fill, but it should solve your problem.

That was the ticket. For the past few days, I have cut back on the fuel on the cold starts and there has been no back puffing. I guess you just can't rush a good fire!