Steam out of chimney,,,,,why?

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guest5234

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I know my wood is 100% dry 3 year old oak 10% moisture, but today I am getting white smoke that dissipates as soon as it comes out of the cap, I am sure it is moisture but what is causing it? my chimney has a single wall liner.
 
Yes - it's steam. hot flue gases meets cold outside air = condensation = at least that's how I understand it! Others will correct me I'm sure! Cheers!
 
pgmr said:
CH4 + 2 O2 → CO2 + 2 H2O + energy

H20 is a product of combustion.

Okay - not a chemist. Where does the methane come into the equation? Cheers!
 
NH_Wood said:
pgmr said:
CH4 + 2 O2 → CO2 + 2 H2O + energy

H20 is a product of combustion.

Okay - not a chemist. Where does the methane come into the equation? Cheers!

He's just being generic. A combustion reaction is a combustion reaction.

pen
 
pen said:
NH_Wood said:
pgmr said:
CH4 + 2 O2 → CO2 + 2 H2O + energy

H20 is a product of combustion.

Okay - not a chemist. Where does the methane come into the equation? Cheers!

He's just being generic. A combustion reaction is a combustion reaction.

pen

Pen - okay, but is the steam from the exhaust itself, or from hot air meeting cold? Cheers!
 
As a gas, you can't see steam. It is technically steam as it is traveling up the inside of your chimney and it would be invisible. Once it gets outside of the chimney it cools rapidly, the steam begins to condense back into tiny little water droplets that can be suspended in the air making a colloid, also known as fog.

pen
 
Take an automobile tail pipe. Upon start up you'll see the exhaust on a cold morning. As things warm up (ie. tail pipe), the exhaust will disappear. Now on real cold days, sometimes you'll see exhaust from tailpipes and this is hot gagses meeting cold air. It disappears and dosn't linger because the air is so dry when it this cold. Your fine as long as it disappears within a few feet of the stack.
 
The steam you are seeing is caused by the rapid condensing of the water vapor in the flue gases as it hits the cold dry air. Same reason you see it coming out of a car's cold exhaust pipe. FWIW, wood is never 100% dry. Typically, very dry firewood contains about 15% moisture.
 
NH_Wood said:
pgmr said:
CH4 + 2 O2 → CO2 + 2 H2O + energy

H20 is a product of combustion.

Okay - not a chemist. Where does the methane come into the equation? Cheers!
The way wood burns is basically to get hot enough to produce methanol (CH3COOH),
which is why methanol (aka. methyl alcohol) is traditionally called "wood alcohol".
 
pen said:
As a gas, you can't see steam. It is technically steam as it is traveling up the inside of your chimney and it would be invisible.
I've been waiting for someone to make that correction.

As for hot meeting cold , that cannot "make" water out of nothing. All it can do is condense the steam.
 
Yeah don't worry. On a really cold day just watch all ht flues from homes with gas boilers/furnaces. White steam pouring out. totally normal from any fuel burning flue on a cold day.
 
Why not? We live in a damp climate and our seasoned wood is just fine.
 
I think what is trying to be said is that as long as you are burning wood, there will always be some water vapor exiting your flue. Even if it were possible to have 0% moisture, the water is actually made by the oxidization of the carbon-hydrogen molecules of the wood. Thus the chemical equation someone provided.

When water is truly vaporized you don't see it. It condenses as visible "steam" when the hot water vapor exits the flue and cools off. If you look very closely you'll see that just a few inches from the flue opening you see no "steam", then as the hot gases migrate away you'll see the steam "appears". I put steam and appears in quotes because to the chemist steam is actually invisible - but this is hearth forums not a chemistry lab so I'll try to pacify both.

Don't forget that you did say your wood has 10% moisture. While that is very dry wood, it still is water. So if you load your stove with 40 lbs of wood you just put 4 lbs of water in the firebox. That's about 1/2 gallon. It has to go somewhere - most likely out the flue.
 
BeGreen said:
Why not? We live in a damp climate and our seasoned wood is just fine.
I guess it depends what you mean by damp climate. Anyway my point was that in a place that has a mean temperature of 47 degrees (averaged over a year) and a mean humidity of 75-80% it is not possible for wood to dry to 10% moisture content. When wood reaches a water content that is in equilibrium with its environment it does not lose further moisture however long it is left to season.
 
bokehman said:
BeGreen said:
Why not? We live in a damp climate and our seasoned wood is just fine.
I guess it depends what you mean by damp climate. Anyway my point was that in a place that has a mean temperature of 47 degrees (averaged over a year) and a mean humidity of 75-80% it is not possible for wood to dry to 10% moisture content. When wood reaches a water content that is in equilibrium with its environment it does not lose further moisture however long it is left to season.

I believe you're confusing the relative humidity of air (a rather complex number to determine - see http://en.wikipedia.org/wiki/Relative_humidity) with the simple percentage calculation of "weight of water in wood to total weight of wood". The two numbers aren't really related other than that a high RH of air might slow down the drying of the wood a bit.

10% water by weight does seem a bit low for non-kiln dried wood, but the OP was probably only trying to stress that his wood had been fully seasoned.
 
bokehman said:
pgmr said:
I believe you're confusing the relative humidity of air (a rather complex number to determine - see http://en.wikipedia.org/wiki/Relative_humidity) with the simple percentage calculation of "weight of water in wood to total weight of wood". The two numbers aren't really related other than that a high RH of air might slow down the drying of the wood a bit.
I'm not confusing anything. Equilibrium Moisture Content

You're right...I was the one confused. Thought you were saying that % of water in wood could not go below RH % of air. A more careful reading of your statement cleared that right up! Please accept my apology.
 
bokehman said:
Neil said:
I know my wood is 100% dry 3 year old oak 10% moisture
If you live in Stratford Upon Avon there is no way your wood is that dry (unless you store it in a kiln).

Well my moisture meter is wrong then, it is 3 year old oak that was dead for perhaps 50 years when cut down, has been in the sun and covered for 3 years, in the the house for about a month before burning and showing 10% ...is that not possible then
 
Neil said:
Well my moisture meter is wrong then, it is 3 year old oak that was dead for perhaps 50 years when cut down, has been in the sun and covered for 3 years, in the the house for about a month before burning and showing 10% ...is that not possible then
If you've had it in the house a month in RH of 50% or below maybe the skin would be down to 10% but unlikely the core would be.
 
You guys say this steam should dissipate within a few feet, but I find the opposite sometimes. And it has me bugged, because now I'm thinking there could be some smoke in there also.
This morning temp. was about 18*. My breath fogged and trailed several feet behind me, the car exhaust filled the driveway with a noxious fog, and my flue had about 20 foot of steam (?) trailing over the yard. Is that possible?
Pipe probe temps. were around 700* at the time. Combuster was doing its job, or so I am thinking.

Is this steam business relative to flue temps and wood moisture? I've seen furnace exhausts on homes really pouring out the steam in certain weather conditions.
 
Troutchaser said:
My breath fogged and trailed several feet behind me, the car exhaust filled the driveway with a noxious fog, and my flue had about 20 foot of steam (?) trailing over the yard..
It is not a hard and fast rule. Why would you expect the condensate trail from your flue to be any different than your car exhaust? If the outside humidity is near 100% there will be fog.
 
Neil said:
Well my moisture meter is wrong then, it is 3 year old oak that was dead for perhaps 50 years when cut down, has been in the sun and covered for 3 years, in the the house for about a month before burning and showing 10% ...is that not possible then

If you are just measuring the outside of your split, it is probably correct. To get an accurate reading, you need to resplit a piece and take a reading from the freshly exposed face.
 
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