Smoke "Puff back" from Air Vent in Boiler

[svk]

This only happens every so often and only when the fire is first started or if the stove is very full and the air vent opens. Fire and a little bit of smoke sometimes comes out. Sometimes it's enough to trigger the smoke alarm.

What is the remedy? Maybe put an extension on the air tube?

 

[olympyk_999]

disconnect the smoke alarm...a hammer usually works good

 

[svk]

These are serious questions. Let's keep the banter to general threads.

 

[olympyk_999]

fine...you brought this on yourself though

 

[president]

I,ve noticed that when I shut the stove down in my blaze king cat stove it will sometimes puff back
I have attributed it to creating exess smoke in the fire box and it re igniting in the catalytic combuster
which operates at a hotter temp, and converts the exess smoke to combustable flame suddenly?

 

[svk]

Makes sense. It will puff until the boiler gets up to temp and the vent is automatically closed.

What can I do to fix it though?

 

[mohick]

NOTHING!!! Like the guy said forget the smoke alarm. It is just pressure, temp. draft, wind. You name it . Burnt wood for almost 50 years, from cheapest to the most expensive boiler and it's just going to do it. Get over it !!!!!!!!!

 

[Marshy]

Same thing happens to my Shenandoah except I don't get a light show. It pisses me off pretty good because it blows some stinky smoke into the house, generally a little fluf. It will happen in my stove in two different occasions. 1st, low burning coals or fire and I fill the firebox to the gills. 2nd, really hot bed of coals and I fill the firebox to the gills. In both cases what I found is happening is the firebox gets fill with combustible gases and they deflagrate. The best solution I found was to keep the drafts open to keep that build up of gas minimal. Also, push the hot coals to one end of the firebox (if practical) so only one end of the splits catch fire, this will reduce the amount of smoke generated initially and will gradually increase as the rest catches. Things that exacerbate the issue is poor draft due to weather conditions or stove pipe\chimney buildup. If I decide that I have to stuff it to the gills I keep my door cracked and watch to see if the firebox box gets filled with gas and if it does I light my hnd held tortch and stick it in the door opening. The extra heat fro! The torch promotes draft in the firebox and helps this gasses ignite without deflagrating.

 

[Del_]

Makes sense. It will puff until the boiler gets up to temp and the vent is automatically closed.

What can I do to fix it though?

Slightly larger pieces of fuel may reduces it some.

What is happening is the fuel is releasing pyrolytic gas more quickly than there is oxygen to mix with it and combust. Then the mix hits a ratio at which it combust, then flame front. Smaller splits release gas more quickly than larger.

I might get a 'puff back' once a month or so with our Jotul F600CB. For the most part zero smoke odor which is something visitors often find surprising.

 

[Marshy]

Slightly larger pieces of fuel may reduces it some.

What is happening is the fuel is releasing pyrolytic gas more quickly than there is oxygen to mix with it and combust. Then the mix hits a ration at which it combust, then flame front. Smaller splits release gas more quickly than larger.

I might get a 'puff back' once a month or so with our Jotul F600CB. For the most part zero smoke odor which is something visitors often find surprising.

Bino. Except mine is bad enough to smell.
I've been throwing in some small scraps of dry pine, 2x4 scraps are best, to get the fire hot and burning a wood that doesn't emmit much smoke. Its been a significant help.

 

[NSMaple1]

Air you sure you have enough draft?

What do you have for a boiler?

Can't say I've experienced that, with either of the two boilers I have had.

 

[stevetheboatguy]

Have you looked into a draft induction fan? Do you have a 6" or 8" pipe? How tall is it? Is it a straight shot or does it have any bends?

Steven

 

[svk]

Have you looked into a draft induction fan? Do you have a 6" or 8" pipe? How tall is it? Is it a straight shot or does it have any bends?

Steven

It goes straight into a masonry chimney that I believe has 8" clay liner.

 

[svk]

Air you sure you have enough draft?

What do you have for a boiler?

Can't say I've experienced that, with either of the two boilers I have had.

Do not know the brand. It's a big round steel boiler installed in 1982. My dad only really used it as backup so this is a new problem that Ive discovered

 

[svk]

Slightly larger pieces of fuel may reduces it some.

What is happening is the fuel is releasing pyrolytic gas more quickly than there is oxygen to mix with it and combust. Then the mix hits a ration at which it combust, then flame front. Smaller splits release gas more quickly than larger.

I might get a 'puff back' once a month or so with our Jotul F600CB. For the most part zero smoke odor which is something visitors often find surprising.

My pieces of fuel barely fit through the door.

The most certain time it happens is if I fill the box completely full then as it burns down, the first time the air opens and hour or so later is when the blow back occurs.

 

[Del_]

My pieces of fuel barely fit through the door.

The most certain time it happens is if I fill the box completely full then as it burns down, the first time the air opens and hour or so later is when the blow back occurs.

Is there a 'minimum burn' adjustment?

Years ago, the late 70's/early 80's, I ran a Riteway Model 37. It is a 7.5cu.ft. hot air wood stove/furnace. It has a bi-metal type controller on the input air shutter and when not calling for air it would shut off 100% of the incoming.

Advice I got at the time from people closely associated with the factory suggested rigging the air input so it would not completely shut down, but instead would have an adjustable minimum burn. The unit ran much better this way and it greatly reduced the tendency to back puff. In my case I started with a paper clip on the shutter keeping in open at minimum just a fraction of an inch. I later adapted a wedge shaped piece of sheet metal that gave me an adjustable range. It changed the whole operation of the wood burner.

Just thinking out loud.

 

[svk]

Sure makes sense. With the vent closed you can still see a little light in there. In normal burning temps it will self sustain for a couple of hours before the vent will even open. On warmer days with less heat demand it will get higher than desired and the overflow circuit will kick in and run water through the main heat zone to prevent the stove from overheating. Not sure I want to allow more air in and create a new problem.

 

[cigmaker]

It needs more air... my stove will do the same thing on a reload if I shut the air down real fast. I can actually watch it happen, the smoke will build up enough to fog the whole fire box up. Then be it a coal takes off a little better or the draft picks up some to stoke the coals BAM burst of flame. Something to be mindful of it creates a lot of pressure in a tight firebox. Yours seems open enough it breaches the door and comes inside the house. Mine is to tight but I've heard from others it can lift stove pipe from the appliance connector.

 

[Marshy]

The issue occurs because the fire is generating a lot of smoke and it not drafting enough to take it up the chimney. A slight change in how you operate it might help. Burn a smaller hotter fire and it won't happen. If you have to stoke it to the gills then push the coals to the far back or front of the fire box.

 

[cat10ken]

I would definitely sweep up the floor around the stove and keep my kindling and fire starters well away from the stove. I don't like the looks of that fire shooting out the front of the stove into the area you store your wood.

It sounds like the fire is starving for oxygen and then gets enough to burn explosively. It happens to everyone, just be sure it doesn't ignite something you don't want burning.