crisp
New Member
Posts: 3
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Post by crisp on Jul 21, 2012 8:06:14 GMT -8
Given the nature of the exhaust, is it possible to direct vent out of a wall instead of using a vertical chimney?
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Post by satamax on Jul 21, 2012 12:17:56 GMT -8
Been done many times, but subject to smokeback.
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Post by Donkey on Jul 21, 2012 15:20:44 GMT -8
Ben done LOTS! 'Specially in cob huts, seems like a basic pattern... Getting a stove pipe through a piece of EPDM pond liner ( Cob Cottage style dirt roof) and making it NOT leak is pretty tricky.
The biggest problem comes when trying to start the stove. A stove stack outside the building gets quite cold, often there will be a FALLING COLUMN OF COLD AIR inside it. It can be quite difficult to get the draft going in the wrong conditions.
There are fixes.. Primer boxes, when done well, solve nicely. A short vertical run inside the house before popping out the wall gives you room to install a primer box, which is a box with a (air tight) door. You put a handful of burning newspaper in the primer (or a tea candle) to get the draft moving. If you place the chimney next to the barrel, the chimney will sap heat from the barrel, improving draw. (gotta double the pipe back through the bench to the beginning again, but it's worth it)
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Post by Donkey on Jul 21, 2012 15:50:09 GMT -8
Waitaminnit.. You said direct vent.. I misunderstood (a little).. My post above assumes you're running the chimney up the outside of yer building, which is really the way to go..
BUT!
Yes, direct port out the wall has been done too. It is subject to smokeback fer-sure.. The system is lacking the chimney and is totally reliant on the rocket stove heat core for ALL of it's draft.. The main issue is the wind blowing around your house, creating eddies and/or blowing directly down your exhaust. If your exhaust port is facing directly into the wind, forget it. When the wind whips around the house during winter (or spring round here), fluttering and bashing as it goes, the stove will alternately belch smoke (or flame) and run flat out like mad. Fixing this stuff without putting a chimney on is REALLY tricky.. Simplest, most effective fix: stick on a nice tall chimney.
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Post by txango on Sept 25, 2012 10:51:51 GMT -8
I'm toying with an even weirder idea: running the exhaust down through the floor, under a growing bed in a greenhouse, and then to the outside air downhill. My (possibly naive) thinking is that, as the heat is removed, the exhaust gases would get heavier and help with the draft. Would this work?
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Post by satamax on Sept 25, 2012 11:35:20 GMT -8
It's been done too, there's a vid on youtube. May be downhill flue or chimney.
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Post by Donkey on Sept 26, 2012 20:19:31 GMT -8
You HAVE to INSURE that the flue temperature will ALWAYS get cooler than the outside air. If you EVER have a condition where the exhaust temp is higher than the outside air, it'll stop working properly.
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Post by txango on Oct 19, 2012 11:21:58 GMT -8
Thanks, Donkey. I will immediately stop toying with the idea. The logic and clarity of your explanation is really appreciated.
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Post by perilzof on Jan 18, 2015 21:38:38 GMT -8
I have been running a small rocket stove for a couple of years trying to familiarize myself. I have the flue rising inside the room for about 10' where it exits out a window and terminates about 18" in a turbine vent/chimney cap. I am on the 2nd floor of an old warehouse that has 4 floors and so it is about 25' to the roof. So far, i have not added an external chimney. I still have issues with the wind but, the turbine has helped..i hope to add a draft boosting fan to keep the wind from blowing down the flue on very windy days rather than extend the chimney..at least at this point. Do you think this will help?
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Post by satamax on Jan 18, 2015 22:34:38 GMT -8
Yes.
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Post by perilzof on Jan 19, 2015 8:52:56 GMT -8
Thank you :-)
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Post by satamax on Jan 19, 2015 9:17:37 GMT -8
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Post by perilzof on Jan 20, 2015 8:43:33 GMT -8
Thanks again. I am planning to use a fan (like the one that you use) to a WYE duct branch to the vent pipe that exits the room vertically. I was thinking it best to draw cold air from outside into the vent forcing the air upward into and out the flue...in this way, i hope to at least stop any wind blowing down the flue and perhaps if i am lucky, create a draft too. How is your fan system set up? Do you draw in outside air? Is your fan within a duct of some sort?
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Post by satamax on Jan 20, 2015 9:07:04 GMT -8
My fan is at the very end of the chimney (well a weird arangement) sucking the gases out. It's fitted as closely as possible to the elbow exiting the chimney. The chimney has been blocked at roof height by my landlord.
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Post by perilzof on Jan 20, 2015 19:58:06 GMT -8
Wow, pretty clever! Thanks once more.
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