Rocket Mass Heater Workshop, with emphasis on heating water!

Hello everyone!
This here is an invitation to all of you, join us for an RMH workshop. This workshop will focus on heating water in a safe, zero boom-squish manner(safely).
Heating water with wood is usually a smoky, inefficient and dangerous activity. In this workshop, you will learn how to do this in a safe and clean way with
recognized Rocket Stove authorities, Kirk Mobert (known in the Natural building/Rocket Stove realms as Donkey) and Leslie Jackson! (co-author of the RMH book)
October 3-5

See (and read about) the conceptual design at: https://donkey32.proboards.com/thread/1096/hot-water
You can get more information about the workshop at: https://www.sundogbuilders.net
Sign up by e-mailing [email protected]

We hope to see you there!

 

HI Have you made one of these with this configuration before?

I have made one with a very similar configuration and it is not very efficient.

It works much better with the drum laid on its side.

 

Where the heater goes (inside) has limited space. Vertical method has smaller footprint and solves for other issues as well. The current system partners with a hand-made solar panel as pre-heat in the winter and primary in summer. I'm going to attempt to keep the solar loop in the system and tolerances are tight as is (for good thermpsyphon), the taller aspect helps solve for that.
As usual, there is a compromise going on between competing needs, It will be a little less efficient down the wood heated portion of the design but all things taken together, it should be a better, more useful device on the whole.
Another thing is that I plan to make the buffer water tank MUCH smaller, in the range of 15 gallons (my drawings used a 30 gallon tank). Coupled with an 8 inch, J-feed firebox and an insulated bell, I expect a very fast response time.

 

my experience small tank is no good. the heat response time is only a little better but there is not much hot water for long.

on its end with the thermosyphon is better for that but no good for the rocket stove heating.

I have done one with the tank on its end and it just did not work.

as for incorporating a solar panel i would not recommend it as i have had the pipes burst in them.
Not unless you make it yourself with the design in mind that it can handle super heated steam. You will eventually end up with a broken pipe.

Depending on what it is for but on its side a 44 gallon drum on a 8 inch j-feed tube will produce enough hot water for a family of 4 for a day with 1 20 min burn.

I would experiment with a mok up before fully making it to see how it works.

I wish to do more work myself.

I am just sharing my experiences.

 

I've been using a 15 gallon tank on it's end for the last 2 years running.. Granted, what we have been using is a little different than this newer design, it's a single tank inside of a bell chamber, pressurized by gravity from our tnakls on the hill. My experience has been that it works a little TOO well and since it is a pressurized tank of water, I act like a Nervous Nelly around the thing. Constantly testing the temp, testing the TP valve, fiddling with the wood, etc. It's a bomb, waiting to go off, about 3 loads of wood and its just this side of boiling.

Did you encorporate a bell into your design? Placing the tank inside of an insulated bell chamber changes the dynamic somewhat. On it's side IS a better arrangement for heat transfer, agreed. Fortunately, bells repair enough to make upthe difference.

I see your point but I've been using this for some time now without difficulty. Of course, I NEVER allow the system to get hot enough to produce steam. Training of the users is KEY.
The new design will have it's own issues. The tank being heated will be open and not under pressure; this is the tank that I plan to connect to the solar loop. IT will NEVER be under threat of bursting, though it will steam off and the level will fall so I plan a float valve to keep it topped off. I expect that the efficiency of the solar loop connection-to-shower will drop somewhat, We will see.

It's just going to be used for showers/bath. We're using a different system for inside the house.
In my experience with the current 15 gallon system, the advantage is it's quick turn around. Once it's hot (about 20 minuets), we can CONTINUE showering people with a 3-5 minuet break and a handfull of wood in between, till the cows come home. We once showered 18 people, back to back, and accidentally popped the TP valve on the last shower.
With my family of 4 using it, it's usually sufficient to heat it up that first go. Sometimes, on a cold night, gotta put in another load between the second and third shower.

Well said, sir! I am CONSTANTLY telling people this and it's very good advice.
Fortunately, none of the parts of this stove are new to me. The only bit that's new (for me) is that it's a double-boiler instead of a stand alone.

I appreciate that. It's ALWAYS helpful to have a bit of back-and-forth with ones ideas. It's why I started the Rocket Stove Forum over at: https://donkey32.proboards.com Working with folks over there has changed everything or me over the years. Made me a better stover as well as provided a place to talk this stuff through.

I'm not sure I was entirely clear as to the design.. It's essentially a re-make of Tim Barker's design here. His is a VERY good design. One look at it made me slap my forehead and go "why didn't I think of that??" The only real improvement to it that I can bring to the table is to make the heat chamber a proper bell. Even though Tim has placed the chimney at the bottom, it LOOKS to me like the gap 'round is too tight for "Free Gas Movement" to occur. When the gap is tight, heat is pumped through at the speed of the fire; when the gap is AT LEAST 4 times system size (CSA of firebox, in an 8 inch system is 50.24 square inches) hotter gasses will float to the top of the chamber and remain until cool enough to sink to the chimney exit.
This is how I can make up for the less efficient arrangement of the tank, by holding heat against it for a longer period. It may be enough to eliminate the difference between tank orientations entirely, though I doubt it.

 

Well my experience is working with Tim Barker on the designs with came before this one.
We did use a bell housing on an upright tank and it just did not have the flow of heat.
There was little heat escaping out the chimney but less flow rate resulting in less transfer of heat to the tank.
The current design which is there is more efficient but it does take longer to warm up and it takes a lot more tendering.
The design before it used more wood and more heat was lots through the chimney but the heat transfer was quicker and it needed less tending and the heat lasted longer.
It was set and forget.
Not keep tending.
But as long as you have tested stuff that is the important thing.
I would love to see any test results.
Keep publishing stuff.
Good to talk to you.

 

Thanks Danial,
We plan to do the build Oct. 3-5.
I'll get back after with results.

In the mean time, I'd like to extend the offer to you (and anyone else who is listening to come on over to donkey32 forum. I think you're likely to have a good time there, lots to learn and share. A lot of smart people working things through, helping to move this technology to a new level.