smoke snorting hot!

[johnstone]

I'm burning a freestandin Osburn Victorianaire MKII..a fairly large woodstove and the only source of heat for my 1500 sq. ft. home here in Eastern Pennsylvania.I've been burning this stove for about 18 years with only a few repairs to it, it's in decent shape for an oldtimer.The stove is top vented,and the flue is 20 ft. tall, made up of rigid 7" SS flue liner going straight up and out the roof. I've always had a real good draft.
The other night at bedtime[10:00pm]I put in three pieces of ash and damped the fire down about 85% for the night [the wood I'm burning is mostly ash, oak and maple and is well seasoned and stored in a dry wood shed]. Through the glass, I could see the firebox quickly fill up with smoke, and I noticed the thermometer on the stovetop read 350-400 degrees. I woke up at 1:30 am to the sound of water hissing from the kettle on the stove. I got up and went into the kitchen and the thermometer read 600-700 degrees and orange flames could be seen rolling violently through the glass.
I damped the stove down all the way and the rolling flames disappeared but in a few minutes the flames reappeared as a small explosion of smoke came out where the flue fits into the stove collar...sort of like a bull snorting on a cold winter day. After the small smoke-snorting explosion, the flames disappeared again, only to reappear again in a few minutes with another snort of smoke. I undamped the stove a little bit to about 85% and the flames reappeared and the smoke-norting stopped.
Has anyone ever run into this problem? I don't like to see the stove running that hot[600-700 degrees]I feel that's too hot for at night or when no one is home. What causes that smoke to shoot out of the joint at the flue collar?

 

[Martin Strand III]

Hey Johnstone:

Your old stove has seen better days. Moreover, its damaged, dangerous and polluting.

Do yourself, and everyone else, a favor and get a new stove.

Aye,
Marty

Grandma used to say, "When something is new and shiney, you'll take better care of it."

 

[Eric Johnson]

Sounds like a gasket problem to me.

Other than the age of the stove, what's your reasoning, Marty?

 

[Martin Strand III]

It's a PM10, PM2.5 and other crud dumper.

That's all.

Aye,
Marty

 

[Eric Johnson]

Guess I don't know what that means.

 

[Martin Strand III]

Eric:

You know early pre-Phase II stoves are inefficient, expensive, unhealthy and unecological to operate.

INEFFICIENT:
1. They (old pre-Phase II stoves) dump about 50 Grams of pollutants per hour into our atmosphere vs 6 Grams per hour for Phase II stoves. Pollutants include
2. PM10 - Particulate Matter 10 microns or less in size from the unburned organic vapors of wood tars and gasesthat aggrevate respiratory problems in humans.
3. PM2.5 - Particulate Matter 2.5 microns or less in size (a human hair is about 50 - 100 microns in diameter) which are know to increase health risks as they can lodge deep in the lungs and even enter blood vessels being particularly harmful to humans being known to cause early death in people who breathing this and have existing heart or lung disease.
4. VOC's - Volatile Organic Compounds which react with sunlight and cause smog. They also are toxic to humans and can cause CA: benzene, formaldehyde, etc.

EXPENSIVE:
Because the above crud goes up the chimney, this wastes wood since most of the wood's BTU's are in the unburned smoke.

Hope this helps.

Aye,
Marty

 

[thechimneysweep]

It sounds like you might have been experiencing the phenomenon we call whuffing. You can read about it here -> http://www.chimneysweeponline.com/howhuff.htm

 

[johnstone]

Tom,
Thanks for your insight on "whuffing"......that's exactly what my stove is doing! Is there a way to prevent this from happening altogether? What about installing a barometric draft damper on the flue?

Johnstone

My Grandpa used to say, "People who do not know the answer hide their ignorance by spouting useless facts"

 

[thechimneysweep]

I'm not a big fan of barometric dampers on woodstove flues. The introduction of room-temperature air into the connector pipe above the firebox tends to simultaneously cool the exhaust and slow its passage up the flue, which can cause excessive creosote formation that can in turn lead to chimney fires. If you have a chimney fire with a barometric damper in the system, the increased updraft caused by the chimney fire will pull the damper WIDE open, allowing the chimney fire to rage out of control.

If I read your original post correctly, you have experienced whuffing just once in 18 years. I think all you need to do is to be a little more careful about slamming the draft control down too quickly on a freshly stoked fire.

 

[webbie]

I'm not a big fan of barometric dampers on woodstove flues. The introduction of room-temperature air into the connector pipe above the firebox tends to simultaneously cool the exhaust and slow its passage up the flue, which can cause excessive creosote formation that can in turn lead to chimney fires. .

Tom, I think you have some of the effects of baros mixed up....

They greatly SPEED the movement of air up the flue......by letting the chimney have the air it wants. Think about it, when a stove is closed, the only air the chimney can get is through the stove draft control. So, a little bit of air in means the chimeny cannot expel more than this - therefore a slow draft.

A barometric, buy letting the chimney continue to pull well when the stove damper is in varying positions, allows the chimney to exhaust VASTLY more air, which means faster.

Back in the olden days, tests done on woodstoves by Jay Shelton and Corning (catalytic inventors) showed great results from baros - in fact, the top lady at corning told me ideally all stoves would have them!

Now I understand they are rarely used in the real world - but it is my educated guess that they would cause LESS chimney fires - again because of the increased velocity of the flue gases.

As far as the mini-explosions...I think the advice given is good...check the gaskets and that something of this sort on an occasional basis is no big deal. That type of stove temp on the top of a single wall stove is not uncommong.

As far as dirty stoves, well- the jury is out on how much cleaner stoves have gotten since the first EPA units. I say this because many of the stoves are (and were) designed to pass the tests as opposed to working well with the normal wood and methods people use every day. A properly used EPA phase I stove could possibly burn MUCH cleaner than the newest stove operated improperly. If the gentleman has a fairly clean stack, the proof is in the pudding.

Good to know that steel stoves are lasting this long! A 20 year investment easily!

BTW, the Avalons I sold in 1986 were very similar to the ones today....just some tweaks.

 

[thechimneysweep]

Hi Craig,

I didn't say barometric dampers reduce the movement of air up the flue, just the movement of wood exhaust. The classic example is the little slide thingie on the hose extension of a canister vacuum: open it up and the suction at the floor is reduced. When the flapper on a barometric damper opens up, it allows unrestricted flow of room air into the flue, but likewise reduces the suction of exhaust out of the stove. The increased flow of air up the chimney is only temporary, until the influx of room-temperature air cools the flue and reduces the updraft, at which point the barometric damper shuts back down.

Back in the 1980's, we heated our showroom with a size-large Frontier woodstove, connected to a 42' tall chimney. We needed to run that stove fairly hot to heat the place, and once that super-tall flue heated up, the fire would occasionally rage out of control (that's when we learned about whuffing). To even out the chimney draft, we installed a barometric damper. and it seemed to solve the problem: when the chimney got so hot it started to overdraft, the flapper plate on the barometric would hinge open, allowing room-temperature air to be drawn in to cool the flue while at the same time reducing the suction of air through the stove, allowing the fire to settle down a bit. After a few minutes, when the fire calmed down and the flue temperature dropped, slowing the updraft, the flapper would hinge back closed.

We thought we had found an ideal solution to our overdrafting problem, but a couple of months later we had a chimney fire! We were religious about burning dry wood and sweeping the chimney on a regular basis (imagine the headline: Chimney Sweep Has Chimney Fire), and finally figured out that the only thing that had changed was the addition of the barometric damper. Knowing that creosote condenses out of wood exhaust as it cools, it seemed logical to us that cooling the flue with the introduction of room-temperature air in pulses all day had dramatically increased our creosote formation and led to the chimney fire. We replaced the barometric with a mechanical damper, never had another chimney fire, and have been reluctant to recommend barometrics for woodstoves since.