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Author Topic: New tank in tank build. Suggestions please.  (Read 5385 times)

bradinwnc

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New tank in tank build. Suggestions please.
« on: January 12, 2015, 10:55:15 AM »

Hey Guys, I'm new to the site and looking for any input I can get. I've been wanting to start this project for years and have finaly taken the plunge after getting the tanks donated by a family member. The master plan here is to use the 250 for the firebox and the 500 for the jacket. Basically I'm planning on welding the exhaust on the back of the 250 and running out the back of the 500.

What I'm looking for is ideas to make this thing more efficient, possibly a gasifier. I have loads of ideas but you guys have the experience so please, any input is welcome. So far I have cut the 250 off on one end and cut a hole in the 500 for the 250 to fit into. See the pics in the link below. I'm planning on using the pipe in the pics for the exhaust and putting the fan on the front, under the door. Any thoughts on straight out the back or through the top? For some reason having a turn down from the box through the jacket seems like a good idea with a fan to keep from using a damper and holding heat in. Any thoughts? I've also been debating using some 1" pipe I have for a grate and running the fan into them with holes drilled in to route the air. Not sure if this is worth the time but seems like it would be better than just blowing under the grate. Also thinking I could add propane injection to get fires going pretty easy with this setup. Planning at this point to use the end of 250 I cut off for a door, maybe insulated with something to keep the heat in.
Here are my main concerns/ questions.

1. The 250 is 30" in diameter and the 500 is 37". Do you guys think 3.5" is enough water between the box and jacket to keep  from boiling or having any other issues. I'm thinking the pump running continuous will prevent this.
2. As it stands now after cutting the end off plus a few inches, the 250 firebox is about 5'10" deep and the 500 jacket is about 9"6" long. I love the idea of such of deep box for being able to load allot, but do you guys see any issues? efficiency ? keeping fire going between burns? etc.

Again, any comments, suggestion, concerns are much appreciated. I want to make this thing as efficient as possible and have access to just about any kind of scrap I need. I'd especially like to hear suggestions on making this thing a gasifier. All the ones I've seen have the secondary burn chamber above or below the primary but obviously, I don't have the option here. I've contemplated maybe making my box shorter and having another smaller tank behind it for secondary burn but have no clue if this is feasible or how to make it work.

Here is the link to photos of the progress so far, which is't much.

https://drive.google.com/folderview?id=0By8dBr58fkJUczQ1dHg2Um80ck0&usp=sharing

Thanks in advance guys and sorry for the rambling post.
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bradinwnc

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Re: New tank in tank build. Suggestions please.
« Reply #1 on: January 12, 2015, 06:19:21 PM »

.....Also, I know I'm a "new" user guys, but I have been lurking for over a year and have read allot of posts. I'm not one of those" here I am, I'm to lazy to read the other posts, tell me what to do" guys. If there are any good posts I missed pertaining to what I am trying to do, please reply with them.


  Thanks again
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MerrellRoofing

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Re: New tank in tank build. Suggestions please.
« Reply #2 on: January 12, 2015, 08:31:01 PM »

Not much help but I will try.

1. I think the tank should be low off center. 2" below-5" above.
2. A long firebox is good but it can waste wood. 24" 28" wood is best IMO.

I don't like exhaust thru the top, seems like easy escape for heat.
I think a gasser will be tough to accomplish with what you have and what you are doing.
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Re: New tank in tank build. Suggestions please.
« Reply #3 on: January 13, 2015, 03:14:38 AM »

Be sure that either a supply or return comes from the very bottom of the tank, no circulation there will promote corrosion like you won't believe!
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woodman

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Re: New tank in tank build. Suggestions please.
« Reply #4 on: January 13, 2015, 06:02:28 AM »

Are you going to have a ash pan. If not a firebox more than 4' would be difficult to pull the coals/ashes from the back. Keep it simple and remember the more surface area the fire box has the better the heat transfer, and the more water surrounded area the flue passes through the better.
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bradinwnc

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Re: New tank in tank build. Suggestions please.
« Reply #5 on: January 13, 2015, 06:50:28 AM »

Merrell, I agree with your thinking on the exhaust. Seems like several of the commercial units that do  exit through the top extend the flue down into the box to keep the heat in. My thoughts, since the pipe I have already has the elbows on it, is to come out the back of the box,  turn down, then back horizontal. My thought is when the unit is idling and the fan is off, the heat won't be able to flow out. I would think that this would be as good as a damper on the fan. As far as the placement of the box inside the tank, I've pretty well commited with the hole I cut. I suppose if boiling does become an issue, i can always cut off the top of the water jacket tank above the firebox and weld on half of a water heater tank I have.

What is your thinking behind such a short box? Seems like it would need to be loaded often.

Slimjim, that's in the plan . Haven't decided exactly where I'm going to put them  but I'm planning to have several 1" ports on the bottom and top, both back and front so I've got options and can expiriment. The 500 already has several ports on the top as you can see in the pics, one of which actually runs through a pipe to the bottom of the tank. Not sure if it will clear the box though.

Anybody have any thought/experience with paint on these things. I was planning on cleaning and pressure washing the inside of the water tank and sandblasting or water sand blasting the outside of the firebox tank, then painting them with something. I guess the outside of the firebox would have to have a heat paint? but would this hold up to the water? Or is it even needed?

Thanks guys
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dukethebeagle

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Re: New tank in tank build. Suggestions please.
« Reply #6 on: January 13, 2015, 08:11:42 AM »

true top exhaust does loose heat,but back exhaust need insulated chimney to the bottom of exit or creosote forms
i learned this on my first build
the last two i've built are top exhaust and the draw much better andwith a baffle it works real good
can use draft with this way
if u use a back exhaust you'll need a blower to help with draft
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MerrellRoofing

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Re: New tank in tank build. Suggestions please.
« Reply #7 on: January 13, 2015, 08:36:12 AM »

Big firebox is ok. I had a 60" firebox. I was cutting 6"-8" limbs at 4'-5' long. I stack them to a point and make it thru the night. Had a bunch that were a little too long. I cut them in half, 2'-3' and made the same stack, but half deep, and was getting the same burn time. That firebox had a ripple top with a baffle in the back to hold heat. So anything behind the baffle would go straight out the stack.

As far as ashes go. It wasn't bad raking and shoveling the big firebox.
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BoilerHouse

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Re: New tank in tank build. Suggestions please.
« Reply #8 on: January 13, 2015, 07:21:26 PM »

Cleaning and blasting the water/fire side is good.  Painting is not necessary and may help prevent heat transfer on the waterside and will definitely burn off on the fire side.  A link to a home built  "Garn" style gassifier with a tank in a tank design.

http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=1513.0
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bradinwnc

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Re: New tank in tank build. Suggestions please.
« Reply #9 on: January 14, 2015, 08:05:31 AM »

Thanks guys for the great input do far. I had a thought on the exhaust flue.. Even thought it would mean two more watertight welds, I've debated cutting the pipe I have in half between the elbows and running two.. My thought on this is twofold. One, the pipe is only 4 or six inch which seems on the small side. The other is that this would be twice as much flue surface area in the water.. Any thoughts?
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bradinwnc

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Re: New tank in tank build. Suggestions please.
« Reply #10 on: January 16, 2015, 09:40:00 PM »

No comments?

Bill, Thanks for the emails the other night. Great info. As I said, you really eased my mind on the direction I'm going.
« Last Edit: January 16, 2015, 09:43:31 PM by bradinwnc »
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