Steam coming from chimney

[Rob_Red]

Hey everyone, I have what is obviously steam coming from my chimney on cold low humidity days. I haven’t measured moisture content of my splits recently but I do know they are about a year from perfect (MC had been 19-22%) Is this a sign of wet wood when running a cat stove? Or can this be normal? The wood is burning well and the cat combuster is well with in operating range.

 

[brazilbl]

As I understand it, upon a new or a reload of wood, the chimney may display steam coming out. It is part of the normal burning cycle. Theres a difference between steam and actual smoke. One lingers a bit longer than the other, but the coffee has mot kicked in.

 

[stoveliker]

Any (perfectly dry) organic material burning will produce water - it's the chemistry.

 

[Rob_Red]

This looks like steam, I used to live in Pittsburgh where many big buildings used steam heat they actually have their own steam plants. I would drive past them everyday on my way to work and always notice the large plums of steam rolling into the sky. Steam has a certain distinctive shimmer to it when it’s a bright sunny day also as previously said it dissipated very quickly.

 

[Highbeam]

It is normal and expected to have steam in the exhaust under the right atmospheric conditions. It is also normal and easy for intelligent operators to not be able to tell the difference between steam and smoke.

Cat stoves are more efficient than noncats and usually run lower flue temperatures so the normal moisture in the exhaust is closer to the condensation point.

Even 20% moisture is 20%! Lots of water plus the new water that results from combustion.

 

[brazilbl]

Hadn’t thought of all of the imbedded wood moisture needs to be vented! If I am thinking about practically, a 40 lb “load” of wood @ 15pct mc would possibly 6.0 lbs of water moisture to the equation. Thats like close to 1/2 gal of moisture waiting to be boiled off!

 

[stoveliker]

Hadn’t thought of all of the imbedded wood moisture needs to be vented! If I am thinking about practically, a 40 lb “load” of wood @ 15pct mc would possibly 6.0 lbs of water moisture to the equation. Thats like close to 1/2 gal of moisture waiting to be boiled off!

Yes, but that's not the only water you'll get. Dry wood contains about 6% (by weight) hydrogen - that hydrogen is part of the cellulose etc, not the water in there. When burning that hydrogen combines with oxygen to make water. Oxygen is heavier than hydrogen, and water is H2O, and this results in a pound of dry (!) wood producing about (more than!) half a pound of water!

So you put a 40 lbs load of wood in there, you get (adding pounds of oxygen gas drawn from the air of your home) ~21 lbs of water - going out the stack. Even if the wood is perfectly dry! Add to that your 6 pounds of water that was contained between the wood fibers, and there you have your steam source: 27 lbs of water from a 15% wet 40 lbs load of wood.

 

[thunderhead]

Ya, very normal. The earlier in the burn cycle, the colder it is outside, and the higher the relative humidity outside, the more likely you are to get steam. My propane furnace also creates plenty of steam when its colder and wetter outside.

 

[BigJ273]

Normal in the extreme cold. On really cold mornings, you can see steam coming from my oil boiler flue.

 

[peakbagger]

In europe, district heating plants capture the water vapor with a condensing heat exchanger. There is actually a good amount of energy in the vapor but unless there is an forced draft or induced draft fan on the system there is no good way to capture it.

 

[Rob_Red]

Very interesting responses thanks everyone!

 

[xman23]

Definitely has more to do with the conditions that day than just the wood. I see it more cold morning startup's