[AT] OT - Old Chimney Question

Fri Oct 22 06:44:25 PDT 2004

With a cold chimney one often has to open a windo to get the draft going.  
Todays houses (even the old ones with new insulation and triple glazed 
windows) appear so tight as to not povide adequate updraft.  When I start my 
wood stove and the chimney is cold  I have to open a window briefly to keep 
the smoke from coming into the room, One the cold air is displaced from the 
chimney (a few minutes ) there is no problem.

>From: "charlie hill" <chill8 at cox.net>
>Reply-To: Antique tractor email discussion group 
><at at lists.antique-tractor.com>
>To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
>Subject: Re: [AT] OT - Old Chimney Question
>Date: Fri, 22 Oct 2004 08:11:42 -0400
>
>Thanks Larry I enjoyed reading that.  My reference to chimney design 
>possibly being a black art is because sometimes they just don't work as 
>designed it seems.   A similar situation is boat propellor design.  I have 
>a large book that explains how to properly sellect a boat propellor.  The 
>book is highly technical in nature and sometimes not easy to reason 
>through.  It goes into all aspects of boat hull design, boat speed, 
>waveform design, etc. but in the end the book says  that in spite of all 
>the formulas and charts it still comes down to trial and error to some 
>degree.  I assume that to be true for chimneys to some degree as well.  It 
>seems like the same brick mason can build several good chimneys and then 
>build one that just won't work.
>
>Anyway,  I enjoyed your  discussion of the matter and if you find a link to 
>more information on chimney design please post it.
>
>Charlie
>----- Original Message ----- From: "Larry D. Goss" <rlgoss at evansville.net>
>To: "'Antique tractor email discussion group'" 
><at at lists.antique-tractor.com>
>Sent: Thursday, October 21, 2004 9:21 PM
>Subject: RE: [AT] OT - Old Chimney Question
>
>
>>Super heat and a "rip roaring fire" can make a marginal chimney work,
>>but a well designed chimney doesn't need that.  Ever.
>>
>>Chimneys do indeed have a back draft.  Even the pressurized ones in
>>power plants act like super-sized pop bottles and "whistle".  The
>>frequency is so low that you can't hear it, but a monometer placed
>>almost anywhere inside a flue will show cyclical variations in air
>>pressure as the wind blows by. If you've ever watched the plume off a
>>stack from any distance, you'll notice that it appears to wave up and
>>down as it leaves the chimney.  If you pay attention to any one small
>>section of the plume, you'll notice that it proceeds in a straight line
>>as soon as it leaves the chimney top.  The waviness of the plume is an
>>optical illusion based on the fact that the pressure inside the stack is
>>constantly fluctuating and the smoke leaves at a different vertical
>>speed depending on the internal pressure.  Under some conditions the
>>column of air heading out the stack will not just change its upward
>>speed, but it will actually reverse as the chimney "whistles."  That's
>>when you get smoke inside the house.  A smoke shelf (smoke chamber)
>>helps because it effectively makes the chimney into a "stopped flute"
>>much the same as the organ pipe of the same name.  But making sure the
>>top of the chimney is clear of the pressure fluctuations caused by the
>>wind passing over the surface of your roof is also helpful for exactly
>>the same reason as the fact that the pitot tube on an airplane wing is
>>never mounted close to the wing surface.
>>
>>This is more about chimneys than anyone probably wants to read, but the
>>bottom line is that chimney design is not guesswork.  You can predict
>>ahead of time what certain changes in a flue will make.  And, yes you
>>can successfully have more than one heat source feeding into the same
>>flue and have all of them draw correctly regardless of which ones happen
>>to be working.  There are guidelines to be followed for that.  I don't
>>know exactly where to turn for the complete instructions I remember
>>seeing when I was a kid, but Better Homes and Gardens is one of the
>>sources we used at that time.  Their "Back To Basics" book came out a
>>generation or so later and it gives some of the fundamentals, but there
>>is a more comprehensive source somewhere.
>>
>>Larry
>>
>>
>>-----Original Message-----
>>From: at-bounces at lists.antique-tractor.com
>>[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of
>>DAVIESW739 at aol.com
>>Sent: Thursday, October 21, 2004 6:13 PM
>>To: at at lists.antique-tractor.com
>>Subject: Re: [AT] OT - Old Chimney Question
>>
>>Heat is what causes the chimney to draw if you don't get it hot enough
>>it
>>won't work.  A small stove in a large chimney just won't do the job.
>>Also
>>always start out with a good rip roaring fire to heat the chimney then
>>cut it  back
>>this will get things started and the smoke will go up not down.  A
>>longer
>>chimney won't work if you don't have enough heat to get it  working.
>>
>>When I put my stove in my house in southern Oregon I had a 10 in  1
>>pitch and
>>the expert said that I needed to get the chimney up high enough so  that
>>the
>>wind wouldn't curl around and come back down the chimney, I wonder
>>where he
>>learned that bunch of BS from. We had 80 mph winds up on that hill I
>>don't
>>think they could curl around and blow back on themselves. Now if the
>>wall  was
>>straight up that would be another matter.
>>
>>The main thing is to match the size of the chimney to the amount or size
>>of
>>the stove to get proper heat rise from it. A good stove shop should have
>>the
>>details for what you need.
>>
>>Walt Davies
>>Cooper Hollow Farm
>>Monmouth,  OR 97361
>>503 623-0460
>>
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