Building an outside wood boiler from old propane tanks.

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scottm1

New Member
Jan 30, 2012
5
S E Missouri
Hi everyone. I'm new here....just signed up. I am a welder and I ran across this site searching for info on building a wood boiler using salvage propane tanks to heat my shop building. I have seen them in the past, and heard of people doing this, but at the time I didn't pay much attention because I didn't think I would be doing it. I have a 250 gallon I was going to use for the fire box, and a 500 gallon to put the 250 gallon tank into to use for the water jacket. I have already cut them open so the threat of explosion is no longer an issue and am ready to get started. I know the specifics of how a wood boiler works and their parts in them because I have been around factory built units, and homeade units that were copies of factory units. I was wondering if there was anybody on here that has built one from propane tanks, and also if there are things I can do to make the boiler more efficient, burn hotter, and use less wood, like many of the factory ones claim due the routing of the exhaust to hold the heat in longer, as opposed to just cutting a hole in the top for a flue pipe? Any opinion from the experienced would be appreciated.
 

Singed Eyebrows

Minister of Fire
Jan 22, 2009
1,439
Midwest
Welcome to Hearth, I have not built a boiler of any type. That said, hopefully you are welding up a non pressurized boiler? If you put a blower in the unit it will burn hotter & with less smoke. It will be trial & error as to placement. You can put firetubes between the 2 jackets, you need to be sure you can clean them though. Good luck, Randy
 

scottm1

New Member
Jan 30, 2012
5
S E Missouri
yes it will be an open loop system, and I will be putting in a blower. I have a friend that has built several that are copies of the Hardy. I just felt there might be things I could do to improve its efficiency.
 

Singed Eyebrows

Minister of Fire
Jan 22, 2009
1,439
Midwest
scottm1 said:
yes it will be an open loop system, and I will be putting in a blower. I have a friend that has built several that are copies of the Hardy. I just felt there might be things I could do to improve its efficiency.
Fire tubes will do that, Randy
 

Singed Eyebrows

Minister of Fire
Jan 22, 2009
1,439
Midwest
OK, I'll bite, First of all check the you tube videos on the Portage & Main Optimizer 250, while this is a gasification boiler you will at least be able to see the firetubes & ease of cleaning them. I would put tube bundles on either side of your boiler with cleanout doors at least on the front. I would make a grate about 6" wide running most of the length of your boiler & feed air from the blower under the grate, this will force a very hot fire. Run the gas through the exchangers & out the discharge. Do not make the opening for the fan large, when it shuts off you want the fire to die down. When this would be running wide open it should be a very clean boiler, when it idles you will have creosote, no way around that with a non gasser. Much of this is borrowed from a boiler that I know works. I wouldn't want to build a boiler either where the smoke would just pour right out the top of a box, Randy
 

Blevesque

Member
Oct 17, 2008
155
Maine

benjamin

Minister of Fire
Nov 7, 2009
693
SW WI
The problem with most OWBs is the steel is all cold because it is in contact with water. It's difficult to get a fire to burn completely inside of a cold barrel. You need the fire to burn hot and clean to be able to get the most heat from it, then you can afford to send some of the heat up the chimney and still be ahead of most OWBs, even without any heat exchange tubes.

Time, temperature, and turbulence, and of course oxygen are what create a hot, clean fire. I'd try to copy a design that maximises all three, probably by using blowers and fire brick/refractory.
 

ozzie88

Member
May 13, 2011
199
maine
WELCOME!! Glad to see another welder building there own boiler. Sounds like you have good idea and start. If there is any way you could make it with couple chambers with fire brick and panels would be worth it. I seen someone els [Bob] I think, took his boiler added panels and brick works alot better. I built a indoor Gassser that works very good, I may be able to help sone? Uses propane tanks for storage water.
 

PolarLoon

Member
Mar 1, 2013
2
Sunrise MN
I have built 5 boilers and the last two have been using propane tanks just like what you have in mind. These last two have been in service for 3 years now and I think it is a simple yet very effective design. Cut off the end of the 250 to make a clean end about 32" deep in the middle, cut the 500 with about 40" deep in the middle. Then I welded the small tank cut end on a piece of 1/2 plate 40" square centered and about 4" off the bottom edge, I welded a support on the bottom back end of the 250 so that it would rest on the inside of the 500. Then I cut out a 16" round door about 4" off the bottom of the 250, climbed inside and welded the inside of the 250 to the 1/2 plate. Dropped the 500 over the 250 and welded that onto the plate. I then cut a exhaust hole on the front of the plate on the top part of the 250 that connects to a 6" pipe, that way the exhaust stack never goes through the water jacket. On all my stoves I have always used a disc from a farmers disc for discing a field. The stoves I build 30 years ago still have the same disc for the doors so I know they last and work quite well. Let me know if you want more detail, I can probably get some pics together too. I heat my house and 2 barns with mine, it is all about how much wood you want to burn. I use glycol, you can get it usually for free from auto salvage yards if you bring your own 55 gal drum that way you don't have to worry about freezing anything or rusting out the boiler.
 

ComnRailPwr

New Member
Oct 30, 2012
4
Like this one I built this year, works excellent. Not finished yet. Got some small change to make and build the exterior. Holds 173 gallons, boiler temperature can be seen and controled from inside the house. Heats domestic with sidearm I built. 300 & 500 gallon lp tank. Hardy h4 combustion fan.eBay other details just ask. Got under 2k in the entire project. All work was done by me.
 

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PolarLoon

Member
Mar 1, 2013
2
Sunrise MN
Nice job too, I opted on my last two to have the flue come out the front above the door, I built a top baffle to draw from the back middle that is removable. That way less welding of stuff that goes through the water jacket. I will be starting 3 more shortly and after having issues with the oil used to add the smell to propane soaking in the metal I am going to try heating up areas where I am welding with a acetylene torch to cook the oil out. The oil kept bubbling out when I was welding the front plate on. Did you put some kind of foot on the bottom of the inside tank before welding over the big one?
 

ComnRailPwr

New Member
Oct 30, 2012
4
No foot, the flue holds it in the back and the front plate holds the front. The flue pipe is 6" sch80 so no support worries. Flue travels through 2' of water jacket to savage as much heat from it as possible. Their is the same amount of welds inside the water jacket regardless where the flue is put, unless your water jacket doesn't cover the entire top of the boiler.
 
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