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rocket mass heaters

Taking the Plunge!

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Howdy y'all,

I came on a few months back, and got recommendations for resources to educate myself on Rocket Mass Heaters. Since then, I have read through Ianto and Leslie's book "Rocket Mass Heaters III," watched the Wisners' four part series on Rocket Mass Heaters, consulted with my brother in law (who introduced me to the topic), and with my wife's cousin's husband, who works with cob, masonry, brick, etc.

So, I have a plan, an idea of where and what I want to do, and a lot of questions. I tried to answer as many of the questions through the materials I listed previously, but still have some. Probably because I didn't permit the materials sink in sufficiently well, so please forgive me if the materials I previously studied answered my questions.

Here's my list:

I took out some walls and two flues recently, and have old red brick, some mortar, some cinder block that was used in lieu of brick, and some square terracotta flue liners (some still entact). Are any of these items undesirable to put within the thermal battery?

I plan to put the combustion unit on one side of a wall, and the thermal battery on the other side of the wall. Is that an issue at all? I plan to build the bench through the wall itself (the wall consists of plaster and lathe on one side and gypsum drywall on the other, with 70 year old pine 2x4s).

I plan to exhaust through an existing flue with the terracotta flue liners (7"x7" I believe; I need to get up on the roof and measure). Does that sound fine for an 8" Ianto RMH?

My wife's cousin's husband recommended opening up the wall where the bench will be to allow heat to flow more easily to the other side of the house. This is a non-load bearing wall. Are there any particular considerations I should bear in mind in doing this?

I built my prototype "in my back yard," and it drew very well, after I built it properly. I'm using 4"x9"x2.125" firebrick. Any tips or videos on properly putting the brick together to get a good 7"x7" dimension for the feed tube and the heat riser? My prototype is a little off 7"x7" on the feed tube.

Those are my questions for now.

I may have more in the course of time.

Thanks!

"Let him who possesses a field, so partake of its yearly fruits, that he may not suffer the ground to be injured by his negligence; but let him endeavor to hand it down to posterity as he received it, or even better cultivated. Let him so feed on its fruits that he neither dissipates it by luxury, nor permits to be marred or ruined by neglect."

John Calvin

allen lumley

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Posts: 4154

Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''

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posted 10 years ago

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Adam Jonathan : Recently I was trying to explain to a new Fellow member exactly how to use heavy dense materials in the Thermal
mass of the Rocket Mass Heater RMH, explaining that while it was very important to properly encase the Rocks in Cob, with no voids
to change the heat transferring capacity of those materials, and that the more heavy Dense material he put in his Mass the less
Cob he was going to have to make.

That was when another Member shared that a good thermal bench was like a Rock and Cob Lasagna, Rocks being the primary
ingredient. You can put any thing you like in the Cob as long as it is heavy and contains no voids !

A sketch of the layout will help, with old construction (ruff cut 2 X 4s) heat trapped in walls can lead to out-gasing of the flammable
wood gases, opening up your walls is a good idea.

Now would be a good time for you to share your plans for dealing with the weight of your bench, how you are going to protect the
floors from the heat energy radiating from the RMHs Combustion core, and using thermal barriers to protect exposures !

7 X 7 gives you a Cross-sectional area of 49sq. in. the Cross-sectional area of an 8'' circle is Radius squared Xs Pi ~50~sq. in. So
your only problem is to fit the perimeter of an 8 inch circle 24'' inside the perimeter of an 7 '' square 7''+7"+7"+7"=28'' Q.E.D.

If necessary your burn tunnel can be 8'' high by 6'' wide, better more tall than wide.

The feed tube should end up with a level plumb flat top that two fire bricks can span and direct the flow of air through Your
Small, very dry, Fine split wood pieces. If necessary you can cut a brick with a diamond blade and a very small stream of water

Your ear will tell you when you have it right, you need NO musical training to

"Play it by ear!"

Did you hear the old one ''A Camel is a horse designed by a committee, Generally on major construction projects the guy who buys
the Beer makes the rules! We can only suggest your family can really make things interesting ! Good luck! Hope this was helpful
and timely For the Good of the Craft Big AL

Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Thanks for the response!

In the attached sketch, it should be noted that where the pipe leaves the dining room is the point where the two rock wall foundations converge (the part of the house with the dining room is a secondary addition to the house built in the mid 1900s some time. As the bench extends toward the flue, I planned to add cinder block support to th floor joists.

For insulation, I was going to use perlite and clay under the combustion unit, as well as around the stovepipe where it passes through the wall to the living room.

Please see rough draft sketch attached.

image.jpg

Byron Campbell

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Posts: 293

Location: US, East Tennessee

posted 10 years ago

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Man oh man, that's a lot of elbows. Counting the last one facing up at the flue, it looks like a total of 6 elbows. This configuration may well end up being a pain to get it drafting from a cold start. May I suggest trial fitting all the pipe together, connect it into the masonry flue, duct tape or what ever to seal it to the flue and see if it has a natural (and hopefully strong) draft at the RMH burner end/pipe-input?

By blowing a hole in the side of the fireplace? and going straight in with your pipe at the end of the straight 6+ foot run, that would eliminate several problematic elbows.

best regards, Byron

allen lumley

pollinator

Posts: 4154

Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''

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posted 10 years ago

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Adam J. : O. K., maybe this sketch is worth a 1000 questions, and we will get there, 1st, we are practically already in agreement that wind
direction permitting we will be using the chimney you have marked as the final vertical chimney. We will need much more information on its
make-up and condition, Byron C.s question is a good one,and we should look for other co-located flues, their condition and shape.

Because we are trying to place Your future Rocket Mass Heater RMH into your already existing structure compromises must be ~~made~~ Found
Putting the entire thermal mass along an existing outside wall may be one of them.

I am assuming a two story house, unless you have a very favorable open lay out very close to Your RMH I would not expect to get much heat
upstairs !

So- more sketches, more detail, pictures if possible, and we have to work on supporting the Thermal Mass And Protecting the original floor.

Heres where I rage against all the crap videos on U-Tube, Steaming Mounds of stinking-to -high-heaven CRAP! Please regard everything
you see on youtube.com with suspicion unless sent there by a trusted friend or fellow member !

Having said that, Please goto :::-->

http:www.youtube.com/user/villagevideoorg/playlists hint highlight the Bold part and right click. It should open in a new
address window or as a Google Search !

When the You-tube Channel opens into a playlist page, click on the ''Rocket Mass Heater Scenes'' Playlist, Have your family gathered
and drinks and popcorn !

This will take you to a set of short video clips of a for-sale professionally made DVD of an upscale build, you are getting a free peak at the
1st ~3/8ths~ of that DVD. Virtually every second Video-logged is eye candy ! Enjoy!

It is probably just coincidence that it was only after I selected this exceptional video for you that I noted that your 1st design includes a
Thermal Mass Bench that curves inward towards the outside wall before it wraps around the fireplace surround and final vertical chimney.
If you have a large~ish window at that point the coincidence will be striking !

I am sure that you will enjoy the Video, Ernie and Erica Wisner the builders chronicled in this build are the Rocket and Wood stove Forum
Moderators here at Permies.com and they have plans for this build at ernieanderica.info/shop Their RMH book is coming-out soon
as a kickstarter and based on past efforts will be worth the price to have in your library !

Final note: why can't your RMHs location in the Dining room be ether rotated 180 degrees to eliminate a set of elbows or even just moved
further into the bottom left of your sketch to accomplish the same straightening of your pipe ?! For the Good of the Crafts ! Big AL

Late Note : Top right of this page, below the Permies Banner, and above the Permies Video of the Week, is the Permies Toolbox, Find
and Click on the [search] tab, here you can connect with the 10s of thousands of Forum/Threads posted by your fellow members, as an
example type in the search window RMHs in remote locations and do a search within permies. While there are quickly learned steps
in your use of the Permies search tool this will get you started! A.L.

Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !

Glenn Herbert

Rocket Scientist

Posts: 4645

Location: Upstate NY, zone 5

635

posted 10 years ago

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In the spirit of reducing the number of elbows while increasing the length of flue for heat transfer (a 3000 sq. ft. house will need the maximum possible), I would suggest not putting just a single run of flue following the wall angles, but a straight bench with back, and a triple run of flue, straight from the heater barrel through the wall, 180 back under the seat closer to the wall, then 180 straight up and back toward the chimney in the bench back. If you can then go straight into the side of the flue chase, that would give you four elbows plus one to the chimney, and about 25 feet of 8" flue for heat excange.

Opening up the 4' wall the flue passes through would benefit heating effectiveness as well as safety. The barrel needs standard woodstove clearances to combustible walls as well as heat protection.

Trying a text sketch...
I
I____
I O . I <-chimney
I-H--I
I HH
I HH <-H= horizontal flue
I HH
I HH
I HH
I HH
I__H___ <-wall with doorway
. .. H
.F--O <-barrel (feed tube at left)

(Dots . just for spacing of graphic)

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Thanks again! I like the idea of a straight bench with two 180s, and the videos were very helpful!

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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A few more questions. I was intending to use my old 7" duct work from my forced air furnace. What are the disadvantages of the 7" vs 8" stove pipe?

Has anyone used fire ready stove pipe? Apparently, it's painted with a 1200 degree rated paint. Does the stove pipe get that hot?

Thanks!

allen lumley

pollinator

Posts: 4154

Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''

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Adam J. : To compare an 8'' Rocket Mass Heater RMH, to a 7''RMH we just find the Cross-Sectional Areas, or C.S.A.s

The C.S.A. of an 8'' system is 50.24 sq. inches, The C.S.A. of a 7'' system is 38.46 sq. inches slightly more than 20% smaller, Because both will burn
the wood at the same High level of efficiencies. The only difference that counts is, if while you are away and there is a power failure and the house is
cold your 8'' system will deliver at maximum 20% more radiant Heat at the barrel to more quickly warm the core of your home !

All of the stovepipe everywhere in the Rocket Mass Heaters footprint And the Thermal mass MUST be considered to be a Sacrificial Form
around which the RMH/Thermal Mass is cast, For that reason this is the place to use the cheapest and lightest air handling pipe you can find. Usually
this is a grade of cold air return ducting salvaged from the demolition of a Commercial Building, You may be able to get elbows from this location but
at least 3 of the elbows you were planning on using in your build will actually be '' Clean out 'T's with caps'' these pieces are not usually available in
lighter weight materials, and are $pendy!

For the Good of the Crafts Big AL

Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Thanks Big Al!

I have my sand (I have a local quarry that does limestone sand), barrel, fire brick and plan.

The pearlite and 8" stove pipe, Ts and elbows are due in early next week. I'm going today to look at clay piles from construct sites. I'm hoping to get a couple major scoops early next week, God willing.

I need to get footer pads and dig out 6 8" deep holes, and stack up to 6"x6" beams across the three parallel floor joists to the thermal battery.

Cheers,

Adam

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Allen,

In the YouTube video 13 about builder's felt, the brick was stacked on the felt and then some form of large square stones were stacked on top of the brick.

What were those square stones? Are they insulative to protect the wood floor, or simply part of the thermal mass?

Cheers,

Adam

allen lumley

pollinator

Posts: 4154

Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''

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Adam : These are actually Concrete 'Pavers' and at this point with the combustion core wrapped in insulation AND the air channels under them we
Do Not need to worry about excessive heat damaging the Concretes structural integrity.

These can be found at Lowes, Home Depot, and/or Menards in their garden/ landscping areas, or at many 'Nurseries/Garden Centers, glad to see
someone paying that close attention ! Big AL

Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Thanks AL!

One final pesky question and some good news.

Good news first: a local excavator is going to dump a ton of subsoil clay into my pickup tomorrow morning, DV.

Pesky question second: I'm paranoid, and don't want to use heated aluminum foil, except to cover my left ear in case of alien invasion.

Any thoughts on a putatively safer reflective substitute for aluminum foil?

Cheers,

Adam

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Also, is rockwool insulation rated at 1200° still sufficient for the heat riser?

allen lumley

pollinator

Posts: 4154

Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''

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A. J. : Alminum foil shin-y side-up. nothing is better, you will most breathy pin where there danger lies, while still scary, eating Aluminium Oxide will act as an
anti inflammatory agent reducing Ph in the stomach, and reducing heart burn and immediately passing completely through your system !

About the 5th grade 'Mrs Pat Heart' announced to the class that "Joe Randall'' and I were actually pepper, she expected us to reman constant irritations
to the system, arriving at the far end of the system basically unchanged !

It is the breathing in of Fine Aluminum Particles that like Asbestos is dangerous, simply swallowing it is nowhere merely as dangerous ! A nearby town has
asbestos water supply piping, totally legal as installed at that time ~

Yes Rockwool is fine at that location !BIG AL

Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Thanks AL!

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

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Here's my first ever batch of clay slip. Any comments?

image.jpg

allen lumley

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Posts: 4154

Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''

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Adam : If you can use a paint brush to apply it, its good enough, Start will painting the Stovepipe to ensure good contact with the cob. When working with the Cob you
should plan on always leaving a roughened coat behind when you get to the end of a days work, then ether Use a spray bottle to remoisten the top of an old layer or
add a thin coat of Clay slip, A fellow member refers to a well made Thermal mass cob as making a Rock and Cob Lasagna, the resulting mass should contain lots of
heavy dense rock, the more rock the less work in whipping up more cob ! Always do a trial fit, then paint or dip your Rocks in clay slip to ensure there are no voids to
slow the heat transition through the cob ! For the Good of the Crafts ! Big AL

Success has a Thousand Fathers , Failure is an Orphan

LOOK AT THE " SIMILAR THREADS " BELOW !

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

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Thanks for the great tips!

Adam

I don't get it. A whale wearing overalls? How does that even work? It's like a tiny ad wearing overalls.

Rocket mass heaters in greenhouses can be tricky - these plans make them easy: Wet Tolerant Rocket Mass Heater in a Greenhouse Plans