Why Isn't A Weak Draft Better Than A Strong One?

Devil505 · Post by **Devil505** » Sun. Oct. 19, 2008 2:40 pm

Bob wrote:While in theory you might save some fuel by making modifications to reduce draft--or continuing to operate with a chimney in poor repair--in practice you might also end up with less draft than necessary for safe operation in some circumstances. A very bad tradeoff in my opinion!

I agree Bob & would never recommend deliberately reducing your draft to save coal. My serious question was is there an actual benefit to having more draft than you need other than the increased safety margin it provides?
I guess the answer is this increased safety margin.....which is an important one!

coalkirk · Post by **coalkirk** » Sun. Oct. 19, 2008 4:22 pm

Devil505 wrote:Agreed Greg & I emphasize that my safety margins could be improved but I always have TWO Nighthawk digital CO meters working & have never had a reading since I bought the TLC. (My old Dutchwest "Federal" stove would occasionally register when the fire was low with warm outdoors temps)
This year a did replace the wall thimble but there may still be air leaks into the flue from it & from the missing cleanout door outside.

If your cleanout door is missing, that's gonna have a major effect on your draft. It's like a big unregulated baro. I'd at least do something temporarily to block it off until you can replace it. Also, and I'm sure you know this, but CO detectors are only reliable for 5 years and should be replaced. It's cheap insurance.

Devil505 · Post by **Devil505** » Sun. Oct. 19, 2008 4:29 pm

coalkirk wrote:If your cleanout door is missing, that's gonna have a major effect on your draft. It's like a big unregulated baro. I'd at least do something temporarily to block it off until you can replace it. Also, and I'm sure you know this, but CO detectors are only reliable for 5 years and should be replaced. It's cheap insurance.

The metal cleanout door rotted our years ago Terry but I do have it blocked pretty well with plastic cooler cover.

(it's at least as air tight as the original metal cleanout door) I really think much of the weak draft problem is the fact that I didn't make a real attempt to tightly seal the new wall thimble from allowing room air to escape into the flue from around it. (The thimble itself is sealed to the stove pipe but it's not air tight around the thimble......thus allowing a small air gap between the thimble & the mortar surrounding it) May be "Overkill" from a safety point but as long as the draw works, I can live with it. I figure it's providing a cool "air wash" to the outside of the metal, double wall thimble as it enters the clay flue.

CO detectors are both less than 3 years old.

rockwood · Post by **rockwood** » Sun. Oct. 19, 2008 8:37 pm

coalkirk wrote:You can always mitigate a strong draft with a baro but you can't increase a weak draft without some mechanical assist such as a draft inducer. Given a choice, I'd take the strong draft any day. There are lots of factors that determine how strong your draft will be. A chimney within your home will almost always have a stronger draft than one on the outside of your home. The inside chimney stays warmer, hence stronger draft. The height of the chimney plays a major role. Taller is better. My chimney is outside and not very tall. The thimble is 5' off of the basement floor and that part of the home is a one story family room above. It's on the gable end but my total chimney height is probably about 18'. Consequently my draft is not real strong. If I had known 12 years ago when I built this family room that I would be burning coal in the second flue, I would have built the chimney taller.
Devil, I think in addition to the ideal layout of your split foyer for facilatating air distribution, you close proximity to the ocean must play a role in your low coal usage.

coalkirk is right on the money.