[AT] OT - Old Chimney Question

Fri Oct 22 08:50:47 PDT 2004

The fireplace in my current house actually has combustion air piped
directly to the hearth from foundation vents.  In addition, it has
convection heat vents into two rooms and circulates the heated air from
the living area separately.

Larry

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of
Almost-Running Deere
Sent: Friday, October 22, 2004 8:44 AM
To: at at lists.antique-tractor.com
Subject: Re: [AT] OT - Old Chimney Question

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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