Combustion Air Duct/Draft Curtain generator

[Techstuf]

For those that are relatively new to the Woodstove scene....I just wanted to share an idea I had several years ago. It was borne of necessity and has proven quite effective:

Let me start off by riskily re-stating the obvious: The volume of air coming out your chimney must be replaced from somewhere. (One might be amazed at the number of woodstove users, new & old, I've known that never truly consider that fact!)

Study closely for a moment, the sheer volume of gases emanating from one's chimney. Such is a good visual indicator that one's woodstove is, in effect, a voracious vacuum looking to suck any and all frigid air it can get from any crack or crevice in your home's exterior. I know of more than a handful of families who become dismayed at the lower temperatures in several rooms in the home after installing a wood stove. I have installed a Combustion Air Duct to feed my stove fresh oxygen from outside the home, no more virtual vacuum cleaner sucking all the cold air it can get right on through the rooms that need heat the most! Of course, it helps immensely to have proper home insulation and seal up any leaks in the home's exterior. Also, I have a wide 'Draft Curtain Generator' at the end of the Combustion Air Duct, directly above my woodstove's door such that when I open it to put wood in, a "draft curtain", generated by the influx of fresh oxygen to feed combustion, prevents the smoke from coming into the room as it passes down and into the stove. The smoke just comes to the door and then rolls down and back into the stove along with fresh air!

Works great! Of course, one would need to tweak the width and gap size in order to get the flow rate and shape desired for one's particular setup.




Here's to a warm winter for you and yours!


TS

 

[snowtime]

My thought is you have one serious setup. The problem is most would be better served sealing and insulation their home than having a system that will overcome all air leaks etc. I say that because you first want to seal the house to minimize the wood burned. It would be real easy to just install an outside air source and not deal with insulation etc and have to cut more wood. An outside air source will replace stove air if done properly but any other leaks you have will still exchange cold for warm air just at a slower rate.
I only think an outside air source is warranted if you have draft troubles due to to tight of a home. I know many do not agree but my thinking is our home is just tight enough that I like some fresh air replacement. For those in there first year of burning when the temp is cold out and you have the stove putting out is the time to go around and find those leaks. IMHO

 

[fossil]

There are many modern, efficient, EPA-approved woodburning appliances to which a factory Outside Air Kit can be attached, if so desired. In some applications, they are required. As for the "draft curtain", if a stove is properly installed and operated, and draws well, there will be no appreciable amount of smoke coming out the loading door when it's opened. Rick

 

[Techstuf]

Good points, Fossil. Obviously, my set up is the 'poor man's' solution. Also, I should have mentioned that I burn hot for greater secondary combustion, which, combined with a well sealed home with good insulation, allows me to let my fires burn out completely with several hours of thermal lag time between burns. This emulates somewhat, the burn cycles of a central heating system only one can go much longer between 'on' cycles. Having studied the seasonal wood requirements of the most efficient wood furnaces, for similar Sq. Footage heating requirements, I feel blessed to be able to match their efficiency with my $200.00 setup.


Here's to a warm winter for your and yours,


TS

 

[LLigetfa]

Lots of modern stoves have an air wash system for the door glass which does a similar job to your curtain. Your curtain is a good idea and I suspect you let enough air into the room at all times to keep the house pressure balanced. Adding the makeup air needed at the stove, allows it to be warmed, eliminating the cold drafts. That is one benefit that the internal air wash will not do for you. While OAKs provide combustion air to the stove, they don't provide makeup air the the house to counter other losses and the deficit can cause smoking when the stove is opened.

People have a tendency to seal up where they feel cold air infiltrate and don't seal where warm air is escaping, leaving the house pressure in a deficit.

 

[karri0n]

I'm slightly confused. Air comes IN the pipe we can see at the front of the stove, and when the door is open, flows from the U shaped thing downward into the stove? Or is that the flue pipe we are looking at? It appears to go up and through the roof. I would imagine that this creates positive(upward) draft, if this is the case.

 

[Techstuf]

Great observations LL....maintaining balance is key in my setup. It is located in the basement along with an old coal room w/coal chute which serves as our wood room. The only time I usually notice the draft curtain getting a workout is when I'm starting fires with a small scoop of wood pellets and a long 'cane torch', or if I run through a patch of lower quality wood.


Regards,


TS

 

[Techstuf]

LOL, I guess I should have shown that it pulls a sharp right angle at the ceiling and goes right out the side of the basement!


TS

 

[karri0n]

LOL, I guess I should have shown that it pulls a sharp right angle at the ceiling and goes right out the side of the basement!


TS

gotcha. crisis averted. The Curtain doesn't pull unwanted cold air into the room when the door is closed?


edit: nvm, the stove would be drafting said air into the firebox. Seems like a nifty setup.

 

[Techstuf]

Thanks, the stove paid for itself the first month we put it in. That gas bill was an outrageous affront to human decency.


TS

 

[karri0n]

Burning less wood? Is that due to the house now not having a pressure deficit, or are you saying it somehow increased your burning efficiency?

 

[Techstuf]

@ Karri0n,

Efficiency is maximized several ways. By feeding combustion direct, much less cold air is drawn in through the home's exterior. LL's mention of 'pressure balance' covers this. Also, I burn hot, which increases secondary combustion. The large amount of 'blackbody' radiation emitted, increases heat capture. Thermal lag cycles are longer allowing for greater stove 'off' time.

Just the other night, for example, we got down to single digits, went 4 hours with the coals burnt out, for a temperature swing of less than 10 degrees. Go to bed at 80 degrees and wake up at 71/72.

I'm becoming a big fan of wood gassification, I'll tell you that!


TS

 

[Techstuf]

@CzarCar, thanks, interesting idea.


TS