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Author Topic: Sizing my owb...build  (Read 389 times)

tiberiusx

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Sizing my owb...build
« on: October 31, 2017, 09:32:44 PM »

Hi folks, love the site have read a lot of the posts and enjoyed them...
Well here I am I've secured what appears to be the usual for home made units.. a 500 gallon and a 250 gallon propane tanks..have approx 3000-3500 sq ft I want to heat..I am confident in my welding skills..ideas on the amount of water to heat? 150,175..or more or less.. ? With larger capacity I believe more wood,smoke etc.. smaller should be able to reach and maintain temp..my idea is to have the flue not run through water jacket and actually come out towards front by routing smoke from back to front with a baffle.. then vertical.. I will use forced draft and have thought about using the baffle plate with holes in it and mineral wool to help burn some of exhaust gases( my pacific energy wood stove does this quite well)
Anyway just looking for some input from those who have built .. for sizing of firebox and water capacity.
The firebox design I have in my head will actually protrude 10-12" out from water jacket.. to allow for chimney.. and attach door.. sorry no sketch yet..thks for taking a read I look forward to your input..
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BoilerHouse

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Re: Sizing my owb...build
« Reply #1 on: November 03, 2017, 09:22:45 AM »

I built my own but I am not sure how useful I can be, my design is somewhat different than the conventional barrel in barrel.  If you are interested, I posted a bit about the build plus some photos that you can see by following this link.  If you have trouble viewing them let me know and I will PM you.

https://www.garagejournal.com/forum/showthread.php?t=369770

I like larger water capacity boilers as there is more of a "flywheel" effect but I think you are on the right track by not over-sizing it, at least not the firebox.  Smaller intensive fires are better than larger lazy fires.  I doubt you will be able to re-ignite the exhaust gases.  Conventional boilers just don't seem to get hot enough.  I have not been able to do it, and my firebox is completely firebrick lined.  (although admittedly my air system totally sucks and is now very difficult to redesign) I do recommend stainless steal as a baffle plate, I used 3/16 and do not recommend going that thick.  The thing is a pain to move for springtime cleaning.  Go 1/8  or less.  I also have my chimney exit from the front and have to be careful not to bang my head on it when loading wood so that is a "watch out."  Nothing wrong with your build and it should work fine but think of it as training wheels.  Next build start to push the envelope.  The guys at Hearth.com seem to have ideas on some funky designs -LOL.

I am starting to think of build 2.0.  It will likely be a downdraft gassifier, with both vertical and horizontal fire-tube passes, and ideally built modular so that if there is a leak. a HX can be removed, perhaps replaced by a spare, and then repaired.  But that build will not happen any time soon.

Above all - keep us posted.
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WoodMOJoe

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Re: Sizing my owb...build
« Reply #2 on: November 05, 2017, 11:36:28 AM »

I won't be much help answering your specific questions but here is a link to my build thread here:

http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=3693.0

Lots of the pics got purged and I lost most of the others in a hard drive failure.   :(

Used to be a lot of people here that would help out/comment on the homemade builds, not sure what happened to them.

Good luck on yours, I am getting ready to start on the 4th winter with mine...not bad for well less than a $2000 investment, I think it's paid for now.   ;)
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mlappin

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Re: Sizing my owb...build
« Reply #3 on: November 05, 2017, 03:55:32 PM »


The firebox design I have in my head will actually protrude 10-12" out from water jacket.. to allow for chimney.. and attach door.. sorry no sketch yet..thks for taking a read I look forward to your input..

You can run into issues with that from different expansion rates between the water cooled and non water cooled areas.
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WoodMOJoe

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Re: Sizing my owb...build
« Reply #4 on: November 06, 2017, 04:55:34 AM »

You can run into issues with that from different expansion rates between the water cooled and non water cooled areas.

Good point, I had never considered that.

Friend of mine is considering doing something similar (extending fire jacket beyond the water), I will mention this to him.   :thumbup:
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tiberiusx

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Re: Sizing my owb...build
« Reply #5 on: November 06, 2017, 06:16:51 AM »

Thanks, for input.. some food for thought for sure...
I did consider the expansion/ temp differences between the jacketed portion and non..Thant area might benefit from some fire brick... anyway no steel has been cut  yet..
I am looking at all possibilities and designs that are out there and devise one that takes best from those.. thks
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