Combustion Air Intake Systems?

[rfactor]

How do any of you handle combustion air? If my house is relatively tight I don't have an adequate way of feeding combustion air to my wood boiler. Or do you use a air to air heat exchanger to balance the combustion instake?

Rurik

 

[rfactor]

How do any of you handle combustion air? If my house is relatively tight I don't have an adequate way of feeding combustion air to my wood boiler. Or do you use a air to air heat exchanger to balance the combustion instake?

Rurik

I should add that my furnace in my basement not an exterior version.

R

 

[tom in maine]

I think you might try the system out without a fresh air intake. There is usually enough infiltration to accomodate a system.
My experience is that a fresh air inlet is usually woefully oversized for most installations.

If you are skeptical, I would suggest a blower door test to determine how tight the building is.

 

[pybyr]

I'd originally been intrigued at the idea of perhaps ducting external combustion air straight to the blower on my gasification boiler-- but there seemed to be a consensus by informed/ experienced people that feeding the unit directly with cold outside air might in fact be a dis-advantage, as the cold air would lower the net temperatures in the unit.

 

[rfactor]

I like that -- wait and see how it all works out. Less to do for now!

Thanks!

Rurik

 

[Nofossil]

My brother, who is certifiably obsessed, runs an aluminum gutter downspout down the inside of his chimney flue for combustion air. That way, the combustion air is preheated by the few BTUs that manage to make it to the flue. His flue temps are around 120 degrees.

I wouldn't suggest that anyone go quite that far, but I've thought about fabricating an outer shell around the stovepipe that I have between the boiler and the chimney and preheating outside air that way.

 

[Eric Johnson]

My understanding is that preheating combustion air will give you an appreciable gain in efficiency. That said, all I have is a dryer vent with a flap going through the wall at approximately the same height as the fans. I suspect I could get by without it.

 

[RobC]

May be have something similar to a barometric damper to keep the cold air out when there is no demand ? Cold air finding it's way to a boiler for prolonged periods could spell " freeze up ".

 

[pybyr]

My brother, who is certifiably obsessed, runs an aluminum gutter downspout down the inside of his chimney flue for combustion air. That way, the combustion air is preheated by the few BTUs that manage to make it to the flue. His flue temps are around 120 degrees.

I wouldn't suggest that anyone go quite that far, but I've thought about fabricating an outer shell around the stovepipe that I have between the boiler and the chimney and preheating outside air that way.

Wow- I take it that this is the same BroOfNoFo who built his own wood gasification boiler from scratch out of stainless?

With flue temps that low, I'm amazed that he's getting much draft for the chimney- and that there aren't abundant amounts of condensation going on somewhere in the system. He sounds methodical enough to have certainly addressed such things- but that's got me curious as to how he has addressed those factors.