[AT] OT - Old Chimney Question

[charlie hill]

Larry,

Boilers and industrial stacks sometimes have ID blowers.  I wonder if that 
would work to correct a problem on a chimney.   I guess it wouldn't be a 
good solution.  I'm just wondering if it would work.

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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