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Powered exhaust on rmh

 
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Hello all,
Been lurking for awhile but now legit. I’m planning to build an rmh (6” j-tube) for my ceramic studio. It’s a pole barn, roughly 40 x 20 feet, divided into two halves, one of which is fully insulated. The electric kiln is exhausted through the exterior wall, just under the eaves, via a high cfm speed-controlled fan. The exhaust temp never exceeds 120F.
My plan for the rmh is to place the feed tube and barrel in the drafty uninsulated space and route the manifold through the interior wall into a vertical red brick chamber (the smaller footprint is essential). I’m using salvaged K26, K23, and hard brick to protect and insulate as necessary.
After all those words, here’s my question: Will I cause problems by using the kiln’s powered exhaust to vent the chamber? Again, cfm is adjustable. I don’t care much for the idea of a passive horizontal chimney, and really don’t want to install a proper one through the roof. I live a bit above 45N and very windy in the winter. I’m afraid the drafty side will pull backwards with a low chimney. Will a powered exhaust help?
Thanks hey,
Dan
 
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Location: Westbridge, BC, Canada
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Hi Dan and a Big Welcome to Permies!
Yes your fan will work but what happens when you leave your studio and the fan dies or the power goes out?
To use a fan temporary to get the exhaust going in the right direction is one thing, but relying on it entirely is another.
Pellet stove‘s operate with the fan but also have safety mechanisms built in to shut down the stove.
Is there any way you can have your exhaust go vertically as high as possible then through the wall to clear the overhang then up past the peak?
 
Dan Jarvis
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Hi Gerry,
Thanks. I was so focused on using what’s already there, power outages didn’t even cross my mind. Sheesh. They’re frequent enough here that the house has a standby jenny, but not the pole barn.
Guess I’m putting in a proper chimney.

Dan
 
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My RMH bell exhaust goes up to ceiling level, out the wall, and up, insulated in the latter part. Once I got the final section on the chimney to go above the roofline (over a three-story drop) it draws excellently in all weather.

For a shop or other place you aren't worried about the letter of code compliance, I have found that it is pretty easy and cheap to make insulated chimneys from lengths of 6" and 8" duct with the space between stuffed with fiberglass. I would take care to orient joints so that rain or internal condensate is shed away from the insulation cavity, and the top likewise protected.
 
Dan Jarvis
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Thanks for the reply, Glenn. Yup, floor to ceilingish is what I’m thinking too. To clarify, does your bell exhaust from the bottom?
 
Glenn Herbert
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Yes it does. From J-tube feed (1' above floor level) to top of chimney is about 15'.
 
I agree. Here's the link: http://richsoil.com/cards
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