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Author Topic: Owb chimney question  (Read 554 times)

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Offline Dairyman

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Owb chimney question
« on: January 21, 2021, 06:50:01 PM »
I've been a lurker here on FF for awhile and I have this forum to thank for being able to do my entire owb install myself. Most questions I've had were easily answered by looking back at the archives but here's one I can't seem to find specifics on. I have an older, used, non gasifier boiler. I installed it inside an old shed. The owb is fan draft with a flapper that closes when fan shuts off. The chimney pipe only stuck up about 1' over the top of the owb. Being inside a building I had to add another 12' of pipe to get well above the roof. The pipe I got is 8"steel tubing with 1/8"wall (11ga. I believe). Problem I'm having is condensation dripping down where I have the pipes connected (they are both 8"dia that simply meet each other, not one inside the other). I figured this might be an issue but had to try something other than the $50+/ft stainless double wall insulated stovepipe. Question is would wrapping the pipe in fire rated insulation at least up to the roof line help keep flue gases warm enough to get out without so much condensation? There's about 5' sticking out past the roof I probably couldn't wrap without some kind of protection from weather. Another question regarding my "modified" chimney is I've found in high wind the flapper tends to "flap" with the fan off giving the fire enough air to over heat. Anyone else have this problem? I'm playing around with magnets as weights to keep it closed during idle but not so heavy the fan can't blow it open. 

Offline armechanic

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Re: Owb chimney question
« Reply #1 on: January 21, 2021, 08:43:06 PM »
Your pipe is probably to long.   The forced air draft don't need to "draw"  so your pipe don't need to be more than 1' above the roof.
1989 Lt 40, D6C CAT, Home made wood processer in progress.

Offline thecfarm

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Re: Owb chimney question
« Reply #2 on: January 21, 2021, 09:30:21 PM »
What kind of OWB you got?
I had about 6 feet on the Heatmor that I had. It rusted out and I am just using regular stove pipe now. As with yours, the stack sticks out about a foot. I left it that way when the other one rusted off, Little did I know, the smoke comes in through my eaves vents and smells up the house.  :o   Off I went to buy some stove pipe.
12 feet might be a bit much. 
By the way, do you have a cap on top? 
The insurance guy made me put one on mine. I bought one with the diamond shaped holes. I forgot how long it was, but that cap got all plugged up, only took a month? Now I just have a cheapy cap on top.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Offline Dairyman

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Re: Owb chimney question
« Reply #3 on: January 22, 2021, 04:41:02 PM »
The brand is Heatsource 1. The company no longer exists but none of the parts seem proprietary and can be had from grainger in a day or two. No chimney cap on top as I've learned by reading on here that rarely works out on an owb.

Offline Arctiva

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Re: Owb chimney question
« Reply #4 on: January 23, 2021, 12:55:36 PM »
I'd try shorting the pipe. Hopefully the shed is metal roof and wall? If so I'd put it a foot above and see what happens. If after shortening still does it, I'd spend the money and a proper pipe.

I wonder if your flapper draw issue is from so much pipe? I dont see how wind would open a closed flapper, unless your fan and flapper are exsposed directly to the wind? Maybe create a wind deflector somehow

If your overheating I'd lower the set point temperature. Cause sounds like you have too much idle time to allow overheating. I base my temp on outside temps, fall / spring 130-150 winter 160-170 ish. Below zero 180-190. I also pay attention to how much the furnace runs, long run time and frequent need hotter water, dont run long or  very often lower water temp. I might change temps 2 or 3 times a week based on conditions 

Offline hedgerow

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Re: Owb chimney question
« Reply #5 on: January 23, 2021, 02:41:41 PM »
Welcome to the forum
Years ago a buddy of mine had a Heatsource 1. Made in Beatrice Ne fairly local to him. He had his in a cold storage pole shed and had the same problem. Running single wall pipe just doesn't work. He finally bit the bullet and bought the double wall pipe and then it was ok. He ended up quiet using his as his insurance guy was out one day on another deal and saw that OWB in a storage building with a million dollars worth of equipment and told him those are not designed to be inside. He made him move it outside. That was the end of the OWB.  

Offline E Yoder

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Re: Owb chimney question
« Reply #6 on: January 23, 2021, 08:12:51 PM »
12' will keep a strong vacuum on the unit and cause a lot of boiling issues. Plus the condensation. 
I got called out to replace two furnaces ruined in woodshed fires this year. I'm a big fan of keeping it outdoors. :)
HeatMaster dealer in VA.

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