Flue question.....

[Robbie]

I have an Avalon Mission stove (love it !) 1 year old. It performed amazingly perfect all last winter for us. I heated our whole house with ease. Our house is 1850 square feet 2 story and it kept temps at an average 78 degrees all winter. (rather warm)

Here is my stove, (please feel free to remove link if not allowed)

(broken link removed)

I had filled the stove with oak and left damper open one night and I was just getting ready to go down and damper it down because I knew it would be roaring soon. I got downstairs and sure enough it was getting rather hot but not dangerous hot, so I dampered it all the way closed.

When you damper all the way closed it will "dance" blue flames all over inside for a pretty long while, it did this as usual and then I decided to open damper a "tiny bit" to keep the heat coming.

I then heard a low WHOOSH......not real loud.....kind of like a wadded up news paper you might lay on coals.

Then I heard a slight steady rumble...........it started just above my stove and the sound went up my stainless double wall insulated pipe and then stopped almost as quickly as it started, 3 seconds at most.

I hurried outsdide and looked at the top of my pipe expecting to see flames but saw nothing, quiet as a mouse.

After this, I inspected stove and pipe and could not see or find anything abnormal at all. The pipe never felt any hotter than normal as I checked inside and out.

It all happened when I opened damper within a couple seconds after closing when I had a really great fire going.........does anyone know what this could have been ?

Thanks for any help.

Robbie.

 

[BrotherBart]

When you dampered down the wood wasn't smart enough to know that it was supposed to stop releasing combustible gases. Those gases coming off the wood are what burns in your stove. When you dampered down the secondary burn consumed most of the oxygen available while at the high temp gases kept being released from the wood. When you opened the air intake oxygen rushed in and combined with the stove and chimney full of oxygen starved gases and they ignited.

Like forum member Eric Johnson said one time "That is why you have those screws holding your stovepipe together.". So the pipe doesn't blow apart when this happens.

 

[Robbie]

BrotherBart, that makes perfect sense. I am sure that is what happened. Thank goodness it was very minor, at least it seemed that way.

Is there something I need to do, or not do when this happens ?

Should I just not damper ALL the way closed ?

I just want to make sure and not have this happen again.

The screw deal is probably right, but mine was never that severe I don't think. It sure scared the heck out of me for a couple minutes.

Thanks.

Robbie.

 

[BrotherBart]

There are a lot smarter woodburners than me here who might disagree but I say never close one all the way down. Just too much creosote production in a deal like that. And under a heavy creosote buildup situation if you got one of those instant ignitions like you had that could be all it needs to light off the whole pipe and then you would see those flames out of the chimney.

Also, be sure that you crack the door just a bit for a few seconds before pulling it all of the way open when a fire is burning. If you have those gases trapped and suddenly swing the door open, what happened in that stove and chimney is going to happen right in your face. And the house takes on the distinct smell of burning eyebrows.

 

[Robbie]

Thank you for your reply. I will certainly follow your advice.

I just wanted to get complete control of that hot fire........but made a mistake when I opened it up so soon, even though I had done this many other times with no problems at all. In other words I would damper closed and then wait a couple minutes and then open just a bit.........no problems before, just a slight increase in flames.

Robbie

 

[elkimmeg]

Dampering down I would leave open the air inlets a bit before dampering then once things stablize reduce the air inlet.
Naturally I will be watching the stove top / flue thermometer. To try to obtain the balance of producing a good vollume of heat and longer burns. BB descrived back pressure rush you are experiencing.

BTW when adding more wood make sure you open the damper wait a minute or two then crack the door and slowely open it
You should be fine. What you experienced many here have , a little more practice with air inlet and you will learn a proceedure, that is a smoother transition while dampering down

 

[precaud]

Something to keep in mind - on most pre-EPA "airtight" stoves, there was only one air inlet, so closing down the air feed was an effective way to snuff a potential runaway fire. But on most modern stoves, the secondary air feed is separate from the primary air control and is 'always on'. So there's always a supply of air, and that's what gives it enough air to create the Dance of the Blue Flames for quite a while, as you saw. Honestly, I'm surprised that the EPA rules allow for such a thing - I consider it a safety hazard. I think the best solution is to find the secondary air inlet on your stove and install a simple slider so you can truly shut the thing off.

 

[Robbie]

The blue flame on mine only last a few minutes at best, then it will die pretty well out. I thought it was doing great because it virtually kills a fire dead within a couple or three minutes.

I'm learning, and what I've learned so far is I need to learn a lot more.........


Robbie

 

[BrotherBart]

Something to keep in mind - on most pre-EPA "airtight" stoves, there was only one air inlet, so closing down the air feed was an effective way to snuff a potential runaway fire. But on most modern stoves, the secondary air feed is separate from the primary air control and is 'always on'. So there's always a supply of air, and that's what gives it enough air to create the Dance of the Blue Flames for quite a while, as you saw. Honestly, I'm surprised that the EPA rules allow for such a thing - I consider it a safety hazard. I think the best solution is to find the secondary air inlet on your stove and install a simple slider so you can truly shut the thing off.

I have pondered that too. Of course one of the things the pre-EPA "air-tights" have been known to do is to go to the nearest source of air when in a damped down, high burn or chimney fire situtation. Said nearest source being sucking air back down the chimney.

Had it happen twice and when it back-puffs into the room you get a little demonstration of which places on your stove are not truly "air-tight". Mine was vented into a clay tile chimney but it made me wonder what would have happened had it been single-wall, press-seam pipe and the stove had been truly air-tight. My bet is the pipe would have split open. I now put a screw or two in the seams to lock them in on my single wall pipe on my free-standing stoves. May not be needed but it is cheap piece of mind.

 

[precaud]

Hmmm... interesting, BB. I've never had a situation that sucked air back down the chimney.
Last season I had one event of this type. I had carelessly put in a piece of resin-soaked pine along with with others in a load. The fire roared, and amidst the flames you could see long, stringey chains of unburnt gasses form as they left the firebox. Closing the air inlet didn't stop it, so I put on my stiff, insulated fireplace gloves, grabbed the pine split and tossed it out onto the front porch. Those gloves come in very useful every now and then...

 

[elkimmeg]

Little history here concerning the EPA stoves. Back in the mis 80's, pre EPA, many stoves were built just about air tight
One could close down the damper and starve out your fire. The first designs was to create a secondary air passage threw another exhaust chamber, where earlier clean burning was achieved by secondary burn using a cat combustor. A couple of things had to happen, one to meet EPA passage stoves could not be completely shut down. When air scource was starved off, stoves produced the dirtiest burns and most cresote buildup. A secondary air out allowed enough air to ensure cleaner burns which passed EPA grams per hour emmission test and over all effeciencies. These secondary air inlets were not user controlled. However VC figured aout a way to automatically control them. The secondary air inlet cover is attached to a theromatically spring similar to your stove top Thermometer. The hotter the fire the spring expands and closes off some of the secondary air opening. The cooler the fire, the spring contracts and opens up the shutter. One of VC claims to longer controled burning. They initially were found coupled with cat combustor stoves and still are today. There Everburn technology and and top mounted air tubs technology are used by modern stove manufactures to achieve secondary smoke burns. It only works with a secondary air outlet. It is by design, that secondary air inlets are not user opperational

 

[precaud]

However VC figured aout a way to automatically control them. The secondary air inlet cover is attached to a theromatically spring similar to your stove top Thermometer. The hotter the fire the spring expands and closes off some of the secondary air opening. The cooler the fire, the spring contracts and opens up the shutter.

Methinks VC has it bass-ackwards. The greatest need for secondary air is during the peak flaming phase. And as the peak flaming period passes, less is needed. More secondary air at this point only becomes dilution air in the exhaust. You can prove this for yourself by adding an adjustable slider over your stove's secondary air inlet and adjust it at verious stages of the burn cycle.

 

[elkimmeg]

VC has it right my description is probably wrong

 

[precaud]

I hope that's true, Elk. The VC Aspen uses a thermostatically controlled air supply that closes down as the stove heats up. It's a very annoying feature, according to users.

 

[elkimmeg]

The Aspen is like a dollhouse stove, not big enough to be considered a real heater in nothern climates. What I'm talking about are Defiant or Encore stoves,USA made quality, serious heaters.