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Author Topic: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition  (Read 51821 times)

WoodMOJoe

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Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« on: March 24, 2013, 01:10:47 PM »

After consultation with my financial advisor (aka wife), a neighbor (master welder and fabricator) and many hours of studying the forums here, I have decided to attempt an OWB build.

It's great to be able to see the great work that so many of you have done here, get ideas, and maybe avoid some pitfalls along the way.

I have attached a preliminary drawing .pdf to this post, please check it out.  I'm sure a lot of the dimensions will change somewhat, but it will give you a pretty good idea of where I am headed.

Outer water jacket tank is a propane tank, 41" O.D. x 79" long, 360 gallon capacity.  One of the half-sphere ends will be cut off, flat plate will be welded to that end to accomodate the 20x20 door opening.

The firebox will be 30" round piece of propane tank (with a section cut out full length on the bottom and flat plate welded in) x approximately 48" deep.

Water capacity should be somewhere around 160 gallons when completed.

Flue will be 6" Sch40 steel pipe, it will extend about 12" into the firebox and exit horizontally into the water jacket, then I will go vertically with more 6" after it exits the water jacket.  The horizontal piece will extend outside beyond the flue and have a cap, to access the horizontal tube for cleaning.

Door will be a pre-manufactured 20" x 20" unit with draft induction fan built in.

No ash pan, no grate.

1" bungs will be provided on the back end of water jacket, from top to bottom:  2 for return, 2 for drywell (aquastat) or thermometer, 2 for supply.  Returns will be extended up high to be near the front of the tank, supply will be drawn from down low and near the back of the tank.  A 1 1/2" or 2" outlet will be provided on the bottom for tank drainage.

A 2" threaded bung already exists in the middle of the top of the water jacket, for fill point, venting, water level float....?

This whole assembly will set up off the slab on a metal framework, and eventually all will be enclosed/insulated in a metal framed and sheathed structure.

All comments/thoughts/suggestions are welcomed!   :)



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skorpyd

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #1 on: March 25, 2013, 05:35:33 AM »

Looks like a very good plan.   Mine is pretty much the same.  The only difference I see in my build is that I welded a 90 degree turn in the horizontal flue inside the fire box so the opening was pointing down, then ran the top of the horizontal flue 3" down from the top of the inside of the firebox.  I haven't got mine going yet so I don't know if it would be better or worse.
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WoodMOJoe

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #2 on: March 25, 2013, 06:35:52 AM »

Thanks skorpyd.  I studied your thread and got a lot of ideas for my build.   :thumbup:

I also am considering going with a 90 turndown on the horizontal tube in the firebox, but wondering about creosote buildup at that point.  I guess, worst case, most of it could be cleared from the opening at the outside end of the tube, and the downward facing section could be accessed from the firebox.

Also planning on copying you on getting the outer structure framed and firing it up without putting the insulation/skin on, to check out operation before it's all sealed in.

How did you get your tanks safe to cut into (explosion hazard)?
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WoodMOJoe

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #3 on: March 25, 2013, 07:58:13 AM »

Here is a revised drawing, firebox is now fully round.  Will post some pics of the tanks next chance I get.

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WoodMOJoe

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #4 on: April 02, 2013, 05:16:52 PM »

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WoodMOJoe

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #5 on: May 09, 2013, 09:27:42 AM »

And just like that, it is done!

Here are some "naked" pics.  Will install and run it for a while like this before it is enclosed.

[attachment deleted by admin for space issues]
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Scott7m

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #6 on: August 18, 2013, 03:35:20 PM »

Looks good!  :thumbup:
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andyhowardcity

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #7 on: August 18, 2013, 05:22:00 PM »

Very cool!  Bring on the cold weather.  I really like the stack design.
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WoodMOJoe

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #8 on: August 19, 2013, 06:03:53 AM »

Looks good!  :thumbup:

Thanks Scott, you gave me some great ideas for this build and I incorporated several of them.

And I bet you may recognize the door also.   ;)
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WoodMOJoe

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #9 on: August 19, 2013, 06:08:29 AM »

Very cool!  Bring on the cold weather.  I really like the stack design.

Thanks AHC, it was a very cool project and I look forward to doing another soon.  We are going to build one for the guy that helped me with mine.  It's gonna have a shaker grate, ash pan and be capable of coal burning.

Can't honestly say I am looking forward to cold weather but I can't wait to install and get the new system up.  We have had the coolest summer in my memory this year, highs in the 70s and low 80s in August...me likey!   :thumbup:
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Scott7m

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #10 on: August 22, 2013, 12:11:47 AM »

Yep, I recognize, you did a good job! It should do great  :thumbup:
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Acetylene420

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #11 on: September 04, 2013, 05:12:12 AM »

Hello everyone. I'm new to the site. I've been doing a lot of research around here and decided to join. I've started my own build of an OWB.

I really like the design of this burner. Especially the horizontal section of exhaust. I may do something similar on mine.

The question I have is why the hot water take off is near the bottom of the water jacket rather than the top? I'm assuming the water will be constantly circulating so its not so much a question of "heat rising" bit wouldn't you still gain a little more efficiency if the hot water take off was near the top and the return was at the bottom so the return water had to circulate up and around the firebox to head back to the house?

The reason I'm asking is because most of the home built units pull from the top and return at the bottom. I'm very interested in the reasoning for your design. I'm second guessing the planned placement of my take off and return now. You seem to have a great grasp of what you want to accomplish and would greatly appreciate any info you could provide.

THANKS!!!
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Scott7m

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #12 on: September 04, 2013, 05:01:37 PM »

You want to have a balanced tank of water for boiler protection, cool temps in the bottom can cause condensation to form in firebox and cause rust out issues fast.  So by top return your encouraging the water to be mixed more than normal therefore creating a more balanced temp throughout the boiler. 

There is no efficiency to gain to speak of, but this simple thing has solved a lot of boiler issues.  Look around, brands like heatmaster and natures comfort all return water to the top for a reason
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Acetylene420

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #13 on: September 05, 2013, 04:53:44 AM »

Thanks for the info. I'm going to pull off the bottom and return at the top.

I appreciate the explanation.
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dukilee76

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Re: Homemade "Tank-in-Tank" OWB-Ozarks Hillbilly Edition
« Reply #14 on: October 18, 2013, 02:02:02 AM »

nice pic jan
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