Outside Rocket mass water heater????

Hi there, I'm the new guy on the forum so be kind to my lack of know how. We just bought a small farm and are getting it off the grid. Two of our neighbors have homemade outside water heaters. They are used for radiant heat and for an endless supply of potable hot water. Theirs use a standard fire box built/welded inside a 250gal drum. The water for the radiators surrounds the firebox and the potable water runs in coils inside the tank. So my question is can we build/weld some form of rocket heater inside a large tank to make it more fuel efficient???

Have you looked through any of these threads on the topic?

https://permies.com/t/22260/wood-burning-stoves/RMH-principle-heat-water

https://permies.com/t/22895/wood-burning-stoves/ideas-Central-Rocket-Heater-provide

https://permies.com/t/22471/rocket-stoves/Large-Rocket-Mass-Heater-Boil

https://permies.com/t/22229/rocket-stoves/Instant-Hot-Water-systems-Rocket

https://permies.com/t/21721/rocket-stoves/rocket-bath-water-heater-filter

https://permies.com/t/22031/rocket-stoves/Quick-Easy-Rocket-Stove-Hot

https://permies.com/t/20844/rocket-stoves/Water-Mass-RMH

https://permies.com/t/12378/rocket-stoves/rocket-stove-oven-hot-water

https://permies.com/t/19487/rocket-stoves/outdoor-water-heater-RMH-project

Bryan D. : Welcome to Permies and a big Welcome to the Rocket Stove Forums! Please go to rocket stoves.com and download a PDF copy $15.oo U.S.,
of Ianto Evans' great book 'Rocket Mass Heaters' there is no other book with as much information in any language. (and I don't make a dime !)

As you work thru the rocket stove forum threads posted for you by Tom O'hern you will absorb a lot of information on practical ways to use the rocket stove
to heat water.

As you have access to a working water heater that has been duplicated at least once, and never seen before on these pages send us some pictures or even a
video of loading and running these wood fired beasts !

For the good of the Craft! Be safe, keep warm, PYRO Logically Big AL

OK, so this is what I've come up with.......The sole purpose of this heater will be for making water hot. I've seen the videos on youtube and I have read alot of the material posted on this site about standard rmh's. So lets talk through this. Instead of using a 55 gal drum weld together something heavier. Remember this is outside the home. the"mass" will be the water inside the tank. This "mass" water will be the flow to the radiators in the home. Also inside the "Mass" water tank we will have copper coils that are gravity fed with fresh water from our spring. This water line will be the potable hot water for the home. You can put an additive in the mass tank that will prevent corrosion. Now this system will have the appropriate bells and pop of whistles. And it will be housed in a shed and insulated. I was thinking that someone on this forum might have tried this idea before.

Bryan D.: While the design you have crafted will heat water, Waters ability to steal the heat away from the heat exchanger is so potent
that in order to use the rocket stove for its maximum efficiencies, upwards from 1200 F, you have to have your heat exchanger at a
remote location from the rocket stove itself. Delivering the heat to the remote heat exchanger is not the problem, The problem is the
high temperatures involved. Guaranteeing that your heat exchanger can handle this heat load is a miner problem, The major problem
is to create a system that Guarantees that the water does not flash to steam ! If you have not seen the ''Myth-Busters Video of the
exploding Hot Water Heater, look it up ! This is very serious business!! Think of something on exactly the same scale as what
happened at the Boston Marathon, only with many more scalding water 2nd and 3rd degree burns.

We were not ignoring you, we were asking you to do your home work !

For the good of the Craft, Be safe, Keep warm, PYRO LOGICAL Big Al

Allen, I know you did not mean to be insulting by telling me to do my homework because I know that you are smart enough to realize that by posting on here I am doing my homework. And you also did not mean to be insulting because I know that you abide by the one and only rule of the forum. Be Nice. The "mass water tank" is not pressurized there for no explosion. There are many commercially made examples of what I talking about(if your willing to spend 6k+) that use wood gasification to heat water. I am in the process of building one from scratch modeled off of 2 that are in operation by my neighbors. I was simple trying to make mine more fuel efficient.

Check out this link if you don't know what I'm referring to.
http://www.centralboiler.com

Why survive if you can't thrive. In a few more weeks we will have endless free hot water and our radiant home heating will also be free. I've done enough homework to know that this is the right way for our family.

Bryan, I didn't take Allen's post to be condescending, but it sounds like you did. If you listen to the podcasts from Paul, Ernie and Erica about these topics, they are much more harsh in their warnings so please don't take what anyone here says as insulting.

With that said, I was not able to infer from what you previously said that your system will not be pressurized in anyway. You have been fairly vague in what you are thinking about for your design. Can you please make some sketches so we can better see what you are thinking about? That will go along way in helping us to see what you are thinking about and possible prevent any further misunderstandings.

Bryan Davis : Mea Culpa ! Please accept my sincere apology, when it comes to safety issues I often seek to be clear even to the point of Bluntness.
It is clear however that you feel that i have stepped over a line! It was not my intention to do so and I regret that I am responsible for the injury
felt by a new member !

For The Good of the Craft ! be safe, keep warm! PYRO Logically Big Al !

Evidently from a private message I received, my pointing to the central boiler link shows my lack of knowledge One part of the PM stated "I must tell you that showing a link to the Central Boilers web site, and thereby seeming to hold that assembly of bells and whistles up as a possible standard, shows to the other members how far you have to go to understand thermo-god-damnics and the efficiency possible in wood fired heaters
of all types ! "


I have a decent working knowledge of how the central boilers work, and outside water heaters in general. They work very well and produce radiant heat and hot potable water. My father and my sister both have them installed on their farms. Both of witch are 90% off grid and have been for several years. My sister has a rocket mass heater in her barn that I helped to build. Our new farm is getting up to speed one project at a time. We are building a central boiler modeled after two that are currently in use at neighboring farm in our community. If the question of incorporating a rocked instead of the standard central fire box gets everybodys panties in a wad, I have no problem using the proven and successful design already in use by our neighbors. Rocket mass heaters have their place and if being used in this fashion is not the right place then I'm ok with that. Oh and by the way, I am a Level II NC certified Firefighter, and hold my s-190 and s-220 wildland fire fighting certifications holding an active red card. I've seen a BLEVE first hand I know what fire can do. By the way Big Al with your knowledge of the second law of thermodynamics you must fight a lot of loosing battles. Why the heck do you think I posted this in the first place. I'm looking for better examples of efficient energy transfer in outdoor water heaters. Better transfer = less fuel, less fuel = less firewood less firewood = more time in the garden!!

fyi BLEVE Bottled Liquid Expansion Vapor Explosion what happens to an LP tank in a fire. One HELL of a fireball explosion.

I said it and I standby it ! For the good of the Craft ! Big Al

Bryan Davis : I said it before, and I will say it again ! Welcome to the Permies forums/threads. Your enthusiasm and self assurance is needed here,
we need your kind of directness, someone who can always find the other side of any issue should always be welcomed as a much needed foil to any
discussion .Because you find my terse style to be personally insulting on some level, then I will voluntarily refrain from posting over your Threads.

For the good of the Craft ! Be safe, keep warm! PYRO Logiclly Big AL

Allen I did not join this site to bicker with an obvious know-it-all who cant abide by a simple rule of be nice. Someone who makes a public apology and then messages me more insults. Your arrogance is not good for any craft that I'm interested in. Allen, please do not post again on this thread your wasting peoples time. Tom, I'll send your a sketch of the basic plan so you can give me your thoughts.

Never done this myself, but a similar idea I had was to build a J-rocket burn core, the insulated chimney, and then pipe the hot exhaust through a 90 degree turn and into the top of a standard, gas water heater chimney and force those hot gases down and then out the bottom (gas burner removed) and horizontally out of the house. The water heater should have a similar effect upon the exhaust gases as the standard 55 gallon drum, which is to rapidly draw off that heat, shrink the gas volume, increase density and thus permit the exhaust to be pushed horizontally. For a bonus, build a greenhouse right next to your outdoor water heater, so that the leftover heat not captured by the water heater can be absorbed by the soil in a greenhouse. It's impossible for your water heater to capture all of the heat, since the temp of the exhaust leaving the water heater cannot be lower than the temp of the water itself. There will always be useful heat leftover, particularly in winter.

Make sure there is a condensate drain hole at the lowest point in your flue; done correctly and completely, the steam in your wood fuel will condense and give up most of it's "heat of evaporation", and this is much of why the RMH can heat with a fraction of the fuel that a "75% efficient" EPA woodstove can accomplish.

Hi Bryan,

I've attached the sketch you sent me to this post. This looks to me like a fairly conventional wood fired boiler system and not a rocket stove. I would think that you are not going to have very clean burns with this and you will be loosing a large amount of heat out of your chimney. The idea behind a rocket mass heater is to create an initial updraft in the burn barrel so that no blower fan would be needed. This initial updraft pushes the air through the horizontal piping until the final riser where the last bit of heat lifts the exhaust out of the system.

I did a quick MS Paint style sketch as to what I would think a RM Water heater could look like. This system would probably explode unless there were the appropriate relief valve or flap cap like you had indicated to that it doesn't become a sealed system. And it might not work at all due to the fact that the water jacket might suck too much heat at the point of the burn barrel and that would kill the draw of the system causing the burn to be deprived of oxygen and thus start to burn not so clean or not draft at all. I also moved the gravity fed spring water line to the top of the system as piping it in at the bottom would run it through the coldest of the water and that isn't what you want.

2013?
So how did all this turn out?
I built a wood fired indoor boiler in the early 1990s. It put my natural gas boiler to shame. I used a airtight wood burning stove with a glass door that I had sitting in my back yard. Torched holes through the sides at the upper rear. Welded in 1/2 in black pipe used copper threaded adapters and 90s to connect each of 6 pipes into a serpentine loop. Wasn't hot enough so I added 6 more.still wasn't getting enough heat to all the radiators and to the heated tile floors so I split the loop to the radiators into two loops so it went through the first loop then back to the boiler and then to the second loop. Now it was cooking. It was a 3000 sq ft  2-1/2 story Victorian house that I built. Used it that way for 10 years before we moved. Had one issue with a air bubble that made steam and melted a solder joint at the 90s on the wood stove turpentine loop. No one died or were injured thank God. Lesson learned.
We now live off grid on 40 acres in northern Arizona.
My interest here is to build a rocker mass type boiler however an indoor one. I want more efficiency. The outdoor heaters he was referring to couldn't be more than 50% efficient at best. Too much heat loss.
My concern with the rocket mass idea is loss of flue temperature and therefore loss of efficiency.
Has anyone built anything that works and is efficient?
I've read a lot here but please excuse my ignorance in understanding the design and engineering of the RMH and knowing how to engineer what size flue, what size piping and what size barrel. I would like ours to be able to cook on also. Or maybe several
different RMH for our different needs. My background is in electrical contracting. 40 years. Retired now. I also have experience in automotive  mechanics, welding, plumbing, excavation, equipment operating,  electronics, amateur radio, building residential and commercial,  masonry and probably more.Thanks in advance to all