Newbie looking for advice and suggestions !

[MagicManAmps]

Hi all, Looking for some design advice here. My wife and I were looking at originally buying, then building an OWB. I am a handy guy that's very good with tools and building things. My main concern is my ability to weld a water tight firebox inside a storage tank. After many hours of research I have heard mention of instead using lines around the firebox embedded in sand to tranfer heat to an external storage tank. This seems the easier route to go for me but I have a few questions as I can't seem to find much info on a setup like this. First is what kind of line would I use ? I assume soft copper ? Since it could be wrapped directly around the firebox ? Or could I get away with something like PEX as long as it wasn't directly touching the firebox and supported in the sand ? Second would be I assume you would have to run a constant circulation pump between firebox and storage tank with the aqua-stat mounted on the tank for a auto draft system ? Any help I can get here would be greatly appreciated , and if this is a bad or inefficient design then just say so, no hard feelings.

Thanks Again for a great site and the wealth of information I have already learned by searching and reading.

 

[hobbyheater]

The original design was known as a Hassa. A cement block building filled with sand as heat storage surrounding a brick firebox, the stored heat transferred to the water which was contained in stainless steel piping with welded joints. This sand could attain temperatures of 1,000 F, so standard copper with soldered joints would not stand up.
It is doubtful soft copper encased in sand around your firebox would stand up much better.
Also I believe water accepts heat transfer better than sand and stores heat better per pound than sand.

 

[BoiledOver]

Hey MagicMan:

Been there and done that. Hobbyheater is right-on about the sand reaching high temperatures and that water is a better medium. My outfit was done on the cheap with what was laying around; copper pipe, sand, scrap sheet metal, an old wood stove and a few firebrick. It did a fair job of heating the home with the circulator on 24/7, but never did the output reach anything above 145 F. My fear was a flash to steam in the sand encased copper piping, so never allowed the cirulator to be off. After 6 months the interior of the firebox was severely caving in and the experiment was scrapped. The weight of the sand against softened steel will eventually fail. With the sand acting as refractory cement does, that bugger ran hot like ghost peppers, glowing door and all. It was an interesting education but I truly wish I had spoken with someone who had done such a thing. Happy and warm with a wood fired boiler now !

 

[maple1]

I'd be hard pressed to recommend an owb to anyone I considered a friend - be even more hard pressed recommending they build one.

 

[MagicManAmps]

Thanks for the advice guys, they always say if seems easy then there is a reason.Next step is to find a local welder that can be hired for a decent price to do the welding for me. Maple1 , may I ask why ? We looked at buying a unit but just couldn't justify the price ( $6,000 - $8,000+). The more I looked at them the more I realized they are really a simple design and that I have most all the material needed to build one already as well as 40 acres worth of good hardwood surrounding me.

 

[JP11]

By the time you pay a welder…

never mind.. you seem determined that this will be easy and cheap.

JP

 

[Coal Reaper]

Add up costs of doors, blower, controls, materials, $20-40 per inch of weld for a good welder, refractory brick, insulation, and im sure a few other things. Now take that cost and weigh it against potential failure and lack of warranty and less efficiency than a boiler with years of r&d and see if its worth it to you. Plenty of guys do it. They weld themselves and have material laying around. Donts forget stays and a good pressure test. And you might want to see what your insurance company has to say about coverig you in the event of a loss. You know what happens, just sayin...

 

[MagicManAmps]

Jp11, I never said it would be cheap or easy, I know better, the rest of you, I thank you for your knowledge, concern, and advice.

 

[BoiledOver]

MagicMan:

The members here are keen on gasification boilers.

There are plenty of good reasons to support gasification boilers over OWB and also plenty of good reasons to use a conventional OWB. Different strokes for different folks ya know. There is another forum at the following link where you may find the information you are seeking.

http://outdoorwoodfurnaceinfo.com/forum/

For a handy guy with tools and material, building an OWB is easily accomplished. To build an efficient gasification boiler is a totally different fruit, but it can be done with some serious research.

There are so many OWB on the market that you could probably find one to fit your budget and meet your needs. Where I live, OWB (smoking dragons) are the norm and a good percentage of the folks have heated with wood in some manor since they can remember. When your choices are LP, wood or electric, it's an easy choice.

 

[JP11]

You're looking for advice. My advice is this. If YOU cannot weld it with the skill and equipment that you already possess, you will not win in this battle.

You're gonna waste any money you throw at this. Save up and buy a boiler. Ask in a new thread about what boiler is cheapest and best for your scenario.

JP

 

[BoiledOver]

$20-40 per inch of weld

Gotta call BS on that one. I have a hard time believing there is a welder on this planet getting paid anything close to that to build a residential wood gasification boiler.

 

[MagicManAmps]

Hey Thanks BoiledOver, I appreciate the recommendation, I will head that direction now.
JP, I don't know if i said something to offend you or maybe this is just the kind of guy you are, but Thanks.
I will also say that in my area that welding quote is way high, I have talked to a couple local welders that have said
if I have everything cut,cleaned, prepped, and ready to go the whole job would run $200 - $300.

 

[maple1]

Maple1 , may I ask why ?

Coal Reaper & JP11 pretty well explained my take.

Chances are if you do the real simple design route you might not be happy with the results - simple designs usually equals lost efficiency, more wood burned, and more smoke generated.

Having said that, some have home-built and claim to be happy with the results. If you've got the time, materials, and spare change to roll the dice with on it, by all means go ahead. But you should do ALL your homework first - as pointed out above, I don't think your originally posted ideas would work out very good.

 

[JP11]

Sorry if I offended you. Seems the worse that people think an idea is, the more blunt the reply. I guess I'm guilty of that.

Take a look at some of the threads when someone suggest they are going to re purpose an oil tank for a pressure vessel. I could have been more polite in telling you that I thought it was a bad idea, you won't be happy with the results, and it will likely be a waste of money, time and resources. As the saying goes.. there's always money to do it right the second time.

JP

 

[Coal Reaper]

Hey Thanks BoiledOver, I appreciate the recommendation, I will head that direction now.
JP, I don't know if i said something to offend you or maybe this is just the kind of guy you are, but Thanks.
I will also say that in my area that welding quote is way high, I have talked to a couple local welders that have said
if I have everything cut,cleaned, prepped, and ready to go the whole job would run $200 - $300.

any shop can join two pieces of metal together. heck, grandpappy can do it with a stick and two 12v batteries. just because a weld looks good on the outside doesnt mean it is sound throughout. if you can get it done for that price and you are confident in the welder than go for it. i wouldnt invest TOO much into it for the fact that it potentially could fail after 6 months like BoiledOvers so just be ready for that. we are not trying to discourage you so much as just make you aware of what you are getting into. you are not the first person to look down this road and certainly not the last. the other forum listed is likely a good resource and everybody here loves questions and pictures. good luck to you and let us know how it works out!

 

[SmokeEater]

The original design was known as a Hassa. A cement block building filled with sand as heat storage surrounding a brick firebox, the stored heat transferred to the water which was contained in stainless steel piping with welded joints. This sand could attain temperatures of 1,000 F, so standard copper with soldered joints would not stand up.
It is doubtful soft copper encased in sand around your firebox would stand up much better.
Also I believe water accepts heat transfer better than sand and stores heat better per pound than sand.

Water can store 5 1/4 times as much heat as quartz sand. Other types of sand will be different in capacity, but quartz would be most common.

 

[Frozen Canuck]

Not sure why you would consider building an OWB when they can be had for the scrap price or less $50 - 100 should cover the scrapper. There have to be literally thousands of these ready for scrap. Heck if you really want one bad I have one still in operating condition, pump & manifold included. For the price of freight from here to there that POS is all yours. Glad to see it leave my yard, was considering using it for a bullet stopper. Pm me if you want me to load it up & send it to you, no cost you pay the freight. No way you can build one for what the scrapper wants even if someone gave you the steel, the rods & let you borrow their welder for free.

 

[barkeatr]

I have not read every reply but purchasing a boiler will get you online that much quicker, vs a buildng a boiler. If the time your building the boiler is the winter time then you have to deduct the money savings you would have seen if you had purchased a boiler. I wanted to purchase a indoor boiler and put it in my shack. It was early february one winter, and the fuel savings alone from FEb to may more than paid for the upgrade (30%) from indoor to outdoor boiler. I built the building around it that summer. Now i have an outdoor boiler in a insulated shack that I never have to worry about the heat in the shack. point being it the sooner you can get a boiler (whatever kind indoor or outdoor) on line it starts putting thousands in your pocket.

 

[MagicManAmps]

Hey Thanks Guys, I guess I should have made it clear that after the first two posts my original design idea of pipes and sand was out. I am still studying and doing my research for different designs , I would like to pursue building one as a project and learning experience. Our fuel costs(LP) aren't so high now that its a urgent situation, am just trying to better utilize the acres of woods we have available to us.