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rocket mass heaters

rocket stove and butt warmer

pollinator

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Location: Englehart, Ontario, Canada

posted 12 years ago

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Just reread the book and have another question. Most of the examples have been implemented in cob dwellings where the walls were inherently non-combustible. We have just purchased almost 11 acres out in the country of NE Ontario, Kirkland Lake. The house is electrically heated (URK!) but I believe an RMH can help with that! The question I found no hint of in the book is building in a regular stick frame house. It's slab on grade so weight isn't a problem, I'm concerned about overheating surrounding surfaces such as the exterior wall the unit would be placed against. For the bench part I'm thinking a layer of Roxul (rock wool) insulation between the cob and the stick frame wall. Some of the diagrams seem to show a partial cob sleeve on the drum, How efficient is this at mitigating temperatures towards the wall? For insurance purposes would an additional reflector such as those used in reducing woodstove clearance distances be needed? If someone has this kind of setup could you measure the temperature at known distances behind the cob heat shield and compare with the same distances in front of the unshielded drum and post that info please.

It can be done!

john smith

Posts: 70

Location: western u.s.

posted 12 years ago

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mekennedy1313 wrote:
We have just purchased almost 11 acres out in the country of NE Ontario, Kirkland Lake.

Congratulations!

I'm concerned about overheating surrounding surfaces such as the exterior wall the unit would be placed against.

If possible, I'd put the furnace in the middle of the house, not adjacent to an outside wall.

how to convert a chest freezer to a fridge

Where liberty dwells, there is my country. -- Benjamin Franklin

Jim Argeropoulos

Posts: 96

posted 12 years ago

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Ernie and Erica built one in their home. You can see in the pictures how they dealt with insulating the walls. http://picasaweb.google.com/eawisner/DanaAnnexRocketStove#

Max Kennedy

pollinator

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Location: Englehart, Ontario, Canada

posted 12 years ago

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Silver wrote:
Ernie and Erica built one in their home. You can see in the pictures how they dealt with insulating the walls. http://picasaweb.google.com/eawisner/DanaAnnexRocketStove#

The "heat shield" on the wall looks like a single unit as in one of the photo's it is off to the side of the drum. Although it has the appearance of brick I am doubtful that is the case, perhaps a fibrous insulator with a brick appearance? As for putting it in the middle of the house, not practical with the design and remodelling the house isn't in the cards right now so an external wall to make venting easy is the current plan.

It can be done!

Posts: 278

Location: Iowa, border of regions 5 and 6

posted 12 years ago

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All the pictures I've seen of RMHs so far have had the butt-holders along an outside wall. Is there any reason why the bench can't extend out into the middle of the room? Can you build up one side of the bench to form a backrest?

Ernie Wisner

gardener

Posts: 791

Location: Tonasket washington

posted 12 years ago

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the heat shield is a sliced brick facing in cement with a steel rim it is set 1" from the wall on spacers to allow air flow. the thermal mass of the bench is isolated from the wall with 1" of perlite. remember we are trying to get the stoves permitted so we built in excess of the standard. this means we built the entire thing to current wood stove code. I would suggest the same for anyone putting a rocket in a stick frame. I think we are being overly cautious but it sends the message to the building officials that we really mean to see good work done.

Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info

Max Kennedy

pollinator

Posts: 490

Location: Englehart, Ontario, Canada

posted 12 years ago

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Thanks for the info on the heat shield. Was it premade or home made and if the latter please indicate what was the process. Was it attached directly to the wall with the frame providing the space or were there insulating spacers to hold it out from the wall, ie is the metal frame a heat conduction issue to the potentially flammable wall? Ahh, the perlite would be the small white beads I see in some of the photo's. That should simplify things. Would your installation have met the guidelines in

http://www.woodheat.org/woodbook/woodbook.pdf ?

If not what are the changes as these are what I have to meet. Thanks.

It can be done!

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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our stove in the house exceeds the requirements for stoves in the document we have a double walled vertical stack and the heat shield on the wall done with one inch clearances.
the heat shield on the wall is 1" sliced brick 1" thermal cement with a 1/4" steel plate behind the bricks and cement. it was made at home in about 30 min. its on 1" PVC spacers. your rocket probably wont get hot enough to ever bother the heal shield but a bit of extra thermal mass is always good.

we could have made the clearances much less but we decided to keep the standard stove clearances to make the inspectors more comfortable with this new type of system.

Brice Moss

Posts: 700

Location: rainier OR

posted 12 years ago

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<hijack>
so Ernie once you get the permit done how much do you think you would charge to install one for me out in Columbia county?
</hijack>

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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Well Brice i would say quit allot since i teach folks to install them

Erica and I teach workshops we are not contractors cause while i like folks I also like my sleep and dont want to get a call at 2:00 am cause someone's stove that i built doesn't work. (not that this stops folks from calling anyhow but at least it's other folks installs) However we are happy to help set up a work shop for the stove build and i can say that generally the stove is completed up to the plaster in three days.

Erica and I never want to be contractors we just want to teach folks how to do it them selves.

Brice Moss

Posts: 700

Location: rainier OR

posted 12 years ago

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thats it

I'm ordering the book and then in three weeks I'm gonna email ya so many questions it'll make both our heads hurt

and at 3am if the bleedin stove wasn't workin I'd just kick the electric blanket on and deal with it later, but I hear ya.

biggest concern I have is permittin the beastie so I'm watching your page with great interest, I figure if you can get it past Portland city regs and I can manage an exact copy of your design I should be able to get it past the half wits out here in Columbia county, of course no guarantee that I could cause they are pretty short on imagination if they don't have a code book for it.

I geuss the next question is how I would go about talking you into running a workshop at my place next summer while the weather's nice.

Brice Moss

Posts: 700

Location: rainier OR

posted 12 years ago

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brice Moss wrote:

I geuss the next question is how I would go about talking you into running a workshop at my place next summer while the weather's nice.

nevermind I found it on your site here http://www.ernieanderica.info/arrange-a-workshop

Max Kennedy

pollinator

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Location: Englehart, Ontario, Canada

posted 12 years ago

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Ernie, how will you deal with the exhaust. I'm a little doubtful the window exit will be approved

. Are you planning to use a standard chimney thimble for walls?

It can be done!

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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Oh we left off the sticking it out the window that was to Classy for us. All that Bling dontchrknow

we took a double wall telo-scopic up to the thimble then triple wall through the roof and a chunk of SS single wall to the ridge. I know its boring but hey we are quiet folks who would never cause the slightest stir.

Max Kennedy

pollinator

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Location: Englehart, Ontario, Canada

posted 12 years ago

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Thanks Ernie, the question was asked due to the statement in the book that due to the lower temperatures the standard clearances from combustible materials might not apply. Funny how of all the seven it was GRUMPY that got Snow White

It can be done!

Ernie Wisner

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Location: Tonasket washington

posted 12 years ago

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he he he That would be Erica

The clearances would not apply if the stove is to be uninspected, However; in order to satisfy the worst case scenario in the inspectors minds we had to go with the standard plumbing. We will be working with the city to get the clearances and chimney requirements modified. currently the language is in to allow horizontal exhaust and that in itself is a huge thing to get allowed by the Code and inspectors.

Max Kennedy

pollinator

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Location: Englehart, Ontario, Canada

posted 12 years ago

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Has the question of insurance been addressed? I can't seem to find it if it has.

It can be done!

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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well thats the thing. insurance wont look till the building code approves it. so we sit in limbo waiting for that time. I assume that the insurance industry will take to it due to its inherent safety features but frankly you can never tell.

Max Kennedy

pollinator

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Location: Englehart, Ontario, Canada

posted 12 years ago

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I've been talking to a friend who just happens to be the fire-chief here. He indicated approval for masonry heaters and other thermal mass heaters falls under the jurisdiction of the local fire department for insurance approval. Now that is here in Ontario but it could be the case for you also. These guys seem to be willing to consider practicalities and tentatively he has indicated he would prefer to see something like the RMH "if it works as advertised" as compared to regular wood stoves.

It can be done!

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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I would love to talk to him and build a stove for the fire dept to play with. It seems that any group that can get this approved in anyplace would be a giant step in the right direction. Erica and I would like to be the folks who build stoves for the approvals so we could be sure of the build. We will be heading east in the spring to fleshertin/ durham area and if we know a date we may be able to do a stove on the way.

Brice Moss

Posts: 700

Location: rainier OR

posted 12 years ago

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So
I bought the book about 12 hours ago
And geuss what I did instead of my homework today?

My head is spinning with questions and ideas just a crying shame I'm not gonna have free time to play with fire the next couple weeks

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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thats what we wrote the book for Brice

Brice Moss

Posts: 700

Location: rainier OR

posted 12 years ago

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so if my understanding of thermodynamics grabbed the stuff outa the book right
basically what is going on inside a rocket stove is the same effect as powers a thermosiphon cooling or circulating system except using gas, the gas gets a lot lighter as it gets hot inside the burn tube and then is suddenly cooled in the barrel making it a lot heavier.
the siphon effect will self regulate to the available feul because as that temperature differential changes so does the airflow in something close to a direct proportion. BRILLIANT!

were the critical dimensions discovered by trial and error or calculated?
If someone did the math and has everything jotted down somewhere I'd love to sit down with my dad and play with numbers for a week or so sometime, he's an electrical engineer but he does thermodynamic equations for fun when he gets interested in something

has anyone tried a liquid fueled version? (I'm thinking drip fed waste grease here)

what about using a large airtight firebox and feeding its exhaust along with a fresh air tube into the rocket so that the rocket unit can burn the pyrolysis gases?

the bloody what if's? are endless here ain't they?

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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The dimensions where worked out both best guess and with math the figures are in africa some place as far as i know. most of the work has been best practice to get the results needed for the effect desired. yes it will burn liquid fuels however it was developed to meet a need for heating with solid fuels and creating no or very little wasted combustibles. last-ly it already does the re-burn and the exhaust gasses are steam and CO2.

Work is continuing to refine the stove dimensions to make it optimal using waste stream or cheap materials. the guiding principals of the stove is for it to belong to the public, be cheaply built, use passive systems, be as fuel efficient as possible, burn as clean as possible for a hand built heater and maintain its primary function (heating your hind quarters). everything else is candy floss. pretty much those of us who develop the stove are working to become obsolete by teaching and developing the stove till its as simple as it can be. (kinda like a good knife its a simple thing that does its job brilliantly despite any "improvements")

Brice Moss

Posts: 700

Location: rainier OR

posted 12 years ago

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Ernie wrote:
(kinda like a good knife its a simple thing that does its job brilliantly despite any "improvements")

love that analogy, and much like I could name the purpose of a dozen shapes of blade each simple and brilliantly elegant the rocket burn chamber will likely yield an endless number of variations suited to different tasks environments and hands over the next several generations of builders

I'm hooked the greenhouse rocket heater/testbed just hit the top of my major projects list, I just hope I'll be able to make the next workshop

Ernie Wisner

gardener

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Location: Tonasket washington

posted 12 years ago

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We will see you when we see you. Till then keep asking good questions and we will keep answering them. Erica and I have probably answered most of the basics here already so do a bit of reading. then ask. Keeps us sane and out of esoteric land.

tel jetson

steward

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Location: woodland, washington

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posted 12 years ago

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getting ready to install a rocket stove to heat a sauna in the next week or so. there won't be a lot of thermal mass involved, so I'm expecting the exhaust to be rather warmer than a typical mass heater. I'm wondering if I can preheat air to the feed tube using some of the heat in the exhaust. I would run a six inch stove pipe from outside through a ten inch exhaust pipe then to the feed tube. it's an eight inch system, so the area inside the ten inch pipe should be just right with a six inch pipe inside it.

is this a terrible idea? just trying to salvage some of that energy that will be headed out the exhaust.

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ronie dean

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Location: NW MO

posted 12 years ago

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I've tried twice to quote and reply and it hasn't worked. So Tel, it falls short of a terrible idea, but it wouldn't be worth while.

You might come up with a peculiar set of circumstances that would make it worth doing.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

tel jetson

steward

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posted 12 years ago

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darn. ronie, do you think it's not worthwhile because the incoming air won't pick up enough heat, or because it won't allow enough air into the stove? or something else?

I'm going to be ducting air from outside the sauna anyway, because I believe the humidity inside it will be high enough to negatively effect combustion. I also want to avoid drawing heated air from the sauna through the stove.

it may be clear that I'm fairly attached to this idea. I really want it to work, but I'll listen to reason.

I've also thought about increasing the surface area of the exhaust flue to strip more heat out of it. either splitting an eight inch pipe into several smaller pipes, or using some rectangular duct with equivalent cross section.

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ronie dean

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posted 12 years ago

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First of all the extra expense of construction "might" only pay for itself if you have a high cost for fuel. If you have a free or nearly free source of sticks to run the stove, it would not pay for the added construction cost.

It seems that the load chamber would need to be air tight in order to draw air through your intended intake... (More construction cost and harder to load fuel.)

It seems to me, if you can breathe in the room, then the moisture in there will not harm the stove burn. If the moisture is so high that the stove can't burn, then there won't be anyone conscious in the room to notice.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

ronie dean

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posted 12 years ago

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Something is screwy here on 'permies' ,.. It is hard to post anything over a few lines.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

tel jetson

steward

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posted 12 years ago

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Something is screwy here on 'permies' ,.. It is hard to post anything over a few lines.

some sort of server switch causing the problems I think.

anyhow...

First of all the extra expense of construction "might" only pay for itself if you have a high cost for fuel. If you have a free or nearly free source of sticks to run the stove, it would not pay for the added construction cost.

we grow our own firewood, but I still try to conserve it. it would also be nice to not wait as long for the sauna to heat up. obviously buying stovepipe involves consuming resources as well, so whether or not it balances out is certainly a consideration.

It seems that the load chamber would need to be air tight in order to draw air through your intended intake... (More construction cost and harder to load fuel.)

I was planning to build a lid on hinges on top of the load chamber and duct the outside air into the side of the chamber. it will add some expense and a bit of complication, but I don't think it will be too bad. alternately, I could just put the outlet of the fresh air pipe near the intake of the stove. I've tried to seal the sauna fairly well in its current configuration (old failing electric heater), so most of the air drawn in should come through the duct.

It seems to me, if you can breathe in the room, then the moisture in there will not harm the stove burn. If the moisture is so high that the stove can't burn, then there won't be anyone conscious in the room to notice.

I didn't think that the humidity would stop combustion, just that it would negatively effect the efficiency and clean-burning character of the stove, which is my primary motivation for building the thing. this may not be an issue at all, just something I was thinking about.

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ronie dean

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posted 12 years ago

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Quote Tel; "
I was planning to build a lid on hinges on top of the load chamber and duct the outside air into the side of the chamber. it will add some expense and a bit of complication, but I don't think it will be too bad. alternately, I could just put the outlet of the fresh air pipe near the intake of the stove. I've tried to seal the sauna fairly well in its current configuration (old failing electric heater), so most of the air drawn in should come through the duct."
------------------------------------------------------------------------------------------------------

If you put the outside air source outlet near the stove intake, it won't draw air from the outlet into the stove, after the outside air source pipe heats up. The hotter the outside air source gets, the harder it will be to draw hot air down. The stove will draw its air from cracks around the room and your fresh hot outside air pipe could draw in reverse. (Hot expanding gases want to go up not down.)

If the room was airtight it wouldn't be comfortable for people.

To keep the outside air source pulling fresh air down, you need a totally air tight system with your outside air source going straight into the burn chamber. During certain wind conditions a downdraft could make the whole system reverse.

If you are wanting to use an outside air source piped in, I think it would be better to run the outside air straight in and not down through the exhaust.

I think the easiest way might be the best way...just let the air come in through the cracks under doors etc...(If you are too air tight you might have to open something a little.)

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

tel jetson

steward

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posted 12 years ago

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well, that all makes sense to me.

If you put the outside air source outlet near the stove intake, it won't draw air from your intake into the stove, after the outside air source pipe heats up. The hotter the outside air source gets, the harder it will be to draw hot air down. The stove will draw its air from cracks around the room and your fresh hot outside air pipe could draw in reverse. (Hot expanding gases want to go up not down.)

right. I was hoping that because I won't have long runs through thermal mass, there would be enough draw from a well insulated riser to overcome that tendency. wishful thinking, maybe. I've toyed with the idea of putting a fan in the intake ducting, but that's probably just me trying to salvage a faulty idea. and I don't want this thing to require electricity.

I could see doing one horizontal run of the exhaust the length of the room (maybe five feet) and doing my intake heat exchange there. that should do away with the stack effect for the intake and provide a little bit more surface area for the exhaust to lose heat.

in the end, I think that I'll probably just build it without anything crazy like this and see how it performs. I'll measure the exhaust temperature, and if it's real high I'll consider some changes.

If the room was airtight it wouldn't be comfortable for people.

yeah. it's far from airtight, but I've gotten ride of all the drafts that used to keep it from heating up very well.

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posted 12 years ago

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This is the Rocket Mass Heater. I"m building this in my basement.

http://www.youtube.com/watch?v=-jzKKIHhTU0

and here is a japanese guy who built a 3 burn chamber RMH that heats a hugh floor mass. Pretty impressive.

http://www.youtube.com/watch?v=NaZtGVhSmNo

travis laduke

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posted 12 years ago

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that's... a lot of pipe. Did they put clean-outs in? I didn't see.

Posts: 278

Location: Iowa, border of regions 5 and 6

posted 12 years ago

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travis laduke wrote:
that's... a lot of pipe. Did they put clean-outs in? I didn't see.

There didn't look to be any clean-outs. My guess is that he's going to stick some kind of brush/vac combo down there every few years. Either that, or some kind of Japanese "clean-bot" that will roll through on its lonesome, complete with a video camera and a joystick control that will let him play Pac-Man with the system.

(or, to quote my favorite "Quote Of The Day":
If Pac-Man had affected us as kids, we'd all be running around in dark rooms, munching pills and listening to repetitive electronic music.
- Marcus Bridgstocke

ronie dean

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Location: NW MO

posted 12 years ago

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tel jetson wrote:
getting ready to install a rocket stove to heat a sauna in the next week or so. there won't be a lot of thermal mass involved, so I'm expecting the exhaust to be rather warmer than a typical mass heater. I'm wondering if I can preheat air to the feed tube using some of the heat in the exhaust. I would run a six inch stove pipe from outside through a ten inch exhaust pipe then to the feed tube. it's an eight inch system, so the area inside the ten inch pipe should be just right with a six inch pipe inside it.

is this a terrible idea? just trying to salvage some of that energy that will be headed out the exhaust.

You could get this to work if you turned the outside air source pipe around. The outside intake would be low and then run through the stoves exhaust IN AN UPWARD direction. (Or run it on the outside of the stove pipe.)

As the outside air source pipe heated up it would heat the air in the pipe and it would go up and out into the room. It would draw fresh air into the room and to the stove and would not have to be anywhere near the stove's intake.
\
Once again I think that it would be more work than it is worth. You would get fresh air drawing in, without the system, by just running the wood stove. But if you really wanted to build this for some reason, I think that it would work much better drawing the fresh air in low and then run upwards.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

tel jetson

steward

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posted 12 years ago

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I think you've talked me out of it.

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ronie dean

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posted 12 years ago

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tel jetson wrote:
I think you've talked me out of it.

Hey, Tel, I hope you post some pics of your stove.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

Hey, sticks and stones baby. And maybe a wee mention of my stuff:

rocket mass heater risers: materials and design eBook

https://permies.com/wiki/188812/rocket-mass-heater-risers-materials