[TheForge] coal forge exhaust system

[Bruce .]

I agree with the others that this fan might not be suitable for high
temperatures.

I have seen a kind of impeller, sort of a paddle-wheel inserted into the
flue, that is suitable.  (I don't know where these came from but possibly
somebody I know does know.)   Downside is that it's another hole in the
flue, and that when it's not running, it acts like a damper -- not good.
So it MUST be running constantly, and the noise is a real downer in an
otherwise quiet shop.  (If you have other machines or blowers running, this
may not matter to you.)

But the real question is, how high above the ridge line are you willing to
take the flue?

There's a lot of misinformation about flues on these forums.  I know folks
are going to jump all over me about this, but I know for a fact that a flue
rising maybe 16' overall, including 3' above the ridge line, will draw ALL
the smoke from a coal fire IF (big if!) the bottom end is positioned very
close to the fire (without any sort of "hood").  I know, because I've done
it.  I could not use anything larger than a 6" flue, so I made it work.
Happened the forge table I was using leaked a little smoke beneath -- and
that smoke would wend its way to the side of the forge table, rise, and be
sucked up the flue.  That 6" flue really drew.  (Unfortunately, living in
suburbia, I had to switch to propane.)

That said, you're best off with an 8" to 10" SS flue and SS side-draft
hood.  If you go with common or galvanized steel, it's essential you
protect it from water, lest it rot out very quickly.

The design of the hood does NOT need to be anything special.  It does NOT
need a smoke shelf -- those were designed for fireplaces with flues that
were large enough for a child to enter for cleaning (back in the good ol'
days!).  (A smoke shelf is a deflecting device to allow cold air to run
down the back side of the chimney while hot air runs up the room-side.
It's totally unnecessary in a properly-sized flue.)  You do NOT need a 12"
or larger flue -- those can defeat the purpose by not allowing upward-only
flow.

Bruce
NJ


On Mon, Nov 18, 2013 at 8:43 AM, Paul N <crosspein at sbcglobal.net> wrote:

> Has anyone on the list tried using one of these (or similar) ducted
> exhaust systems for a coal forge?
>
> http://www.pexsupply.com/Fantech-FG8-FG-Series-Round-Inline-Exhaust-Fan-8-Duct-461-CFM
>
> I'm finally setting up a permanent shop, and was hoping not to have to run
> a stack high up above my roof ridge line. If I can run a forced exhaust
> system out my gable wall, I can save some money, as well as avoid having a
> tall stack on the roof.
>
> These things are all for sale all over the place, with some pretty
> significant CFM numbers. I'm concerned about the temperature as well as the
> volume of air moved. I don't think I need a whole lot of static pressure,
> but I do want to be able to exhaust coal fumes without starting the place
> on fire.
>
> Thanks,
> **Paul
> ______________________________________________________________
> TheForge mailing list
> Home: http://mailman.qth.net/mailman/listinfo/theforge
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:TheForge at mailman.qth.net
>
> TheForge mail list group photo site is
> http://www.shutterfly.com
> Login: blacksmithblacksmith at hotmail.com
> Password: anvil
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>