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Post by esbjornaneer on Sept 12, 2016 1:12:02 GMT -8
Who has installed a bell by-pass vent in their stoves? How have they been made? How have they functioned? Are they needed?
The reason for asking is that I am needing to rebuild my BRMH due to explosion of un-combusted gases after it stalling. Maybe due to damp wood, maybe due to too large ISA though I thought I had calculated it small enough.
The main problem I have is how to make it possible to completely close the by-pass vent once the chimney is well heated and the rocket is well under way. Many thanks for your suggestions.
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Post by peterberg on Sept 12, 2016 4:25:38 GMT -8
How to completely close the bypass I can't comment on that.
But I have seen it done once with a sliding valve, halfway up the bell and well below the riser top. This way, the bypass wasn't situated in the hottest region. It only restricted the size of the bell to half of the ISA, so the chimney would heat up rather quickly. This construction is quite neat when part of the vertical exhaust channel (a plunger tube) is inside the bell.
It could be done at the outside as well, by means of vertical stove pipe at the back or the side of the bell, a 90 degree bend at the bottom and a T-junction halfway up the bell. This way, the bypass could be mounted at the outside of the heater in the T-junction. Not as neat but very easy to replace when necessity would arise.
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Post by esbjornaneer on Sept 12, 2016 13:17:45 GMT -8
I should have given more info regarding my plans: I am planning a mini bell on top of the heat riser as an oven, then an other bell that takes the heat out of the fumes before they exit the chimney.
Thank you Peter, it is the idea of the T-junction that I had in mind. But how do you shut it once the chimney is hot?
I had thought of the T-junction venting from the mini bell/oven space but want a complete seal of that vent once hot. How do I go about that?
Thanks again, Esbjorn
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Post by esbjornaneer on Sept 22, 2016 23:55:08 GMT -8
So this is what I have come up with: But naturally shifted up so it blocks the hole and the brick in the top right will be a top guide for the closing plate. Any comments/suggestions how it would work better?
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Post by esbjornaneer on Oct 18, 2017 2:54:21 GMT -8
The above set-up has worked well for me during the past year though it was very expensive to get the T-junction. In future builds I will attempt to build the lower section of the chimney and the T-section out of masonary materials(bricks/cob). It was a bit tricky to get the seal between the shutting plate and the metal tube as I did it a year ago.
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Post by briank on Oct 18, 2017 4:33:39 GMT -8
Mine is an outdoor stove and bypass draft controllers don’t close 100% but maybe this will help someone.
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Post by pinhead on Oct 18, 2017 4:35:14 GMT -8
I thought about doing a "sliding" valve as well, but making a "turning" valve was much easier. I used a piece of sheet metal and an old electric fence post as a handle. BypassEDIT: I forgot to answer your next question, i.e. are they necessary. I say, unequivocally, yes. If you have a large bell and/or large radiating surface to extract as much heat as you can, a bypass is absolutely invaluable. Even if you have a small bell/single barrel, the bypass will make cold start much easier. I see absolutely NO reason to not include a bypass.
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Post by esbjornaneer on Oct 19, 2017 5:16:30 GMT -8
Thank you for sharing this! Great to see how others have done it.
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Post by Orange on Oct 25, 2017 3:50:38 GMT -8
Brian, how's your stove doing with bypass closed?
I'd rather use a gas torch briefly than to have leaky bypass.
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Post by DCish on Oct 29, 2017 19:07:01 GMT -8
The bypass that I have is a damper designed to allow 20% pass-through. It has about a quarter inch gap all around the edges, as well as some holes on the damper itself. I plugged the holes (ceramic wool and gasket cement) and now have about a 10% pass-through left. It works well for me, because the bell harvests so much heat that I need that much direct heat to just run the chimney at above creosote-accumulating levels.
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Post by briank on Oct 29, 2017 23:44:56 GMT -8
Brian, how's your stove doing with bypass closed? I'd rather use a gas torch briefly than to have leaky bypass. As DCish said above, over the counter dampers only close about 80% but that’s more than adequate for what I’m doing here. If it was an indoor install I’d probably opt for something more airtight, or modify these dampers with a 6” disc of 1/4” carbon felt to help then seal better.
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Post by Orange on Oct 30, 2017 0:14:49 GMT -8
ah, I thought you have a bell bypass instead of chimney damper.
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Post by briank on Nov 4, 2017 12:09:45 GMT -8
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Post by Orange on Nov 4, 2017 13:23:39 GMT -8
hmm I don't tkink those metal thingys are airtight.
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Post by drooster on Nov 5, 2017 9:09:18 GMT -8
The best thing about that guy's bypass is how the handle points in the direction of the airflow ... I wish all stove makers could do that.
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