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First Rocket Mass Heater Going In My Basement  RSS feed

 
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hello all, i am desperately looking to make my first build a good and effective one. i want to heat my home in the long super cold winters i have to gloriously be subjected to(below 0 degrees regularly and from November to May easily accumulating 300+ inches of snow). i have purchased, in .pdf form, designs from the Bonny Convection Bench Heater on ernie and erica's web site. great people from what i can tell, and seem to know their stuff. i plan to use the under vent plans to not only keep my basement floor from keeping all my heat, but to also keep my RMH off the wetness that happens mainly in the spring and sometimes during heavy rains. i think it will be perfect!! i have it in mind to understand what i need to do from the readings and tutorials i have found. and i hope to keep all the useful info tidbits in the forefront of my mind whilst i build. so that being said i will have success! lol.

anyway one main concern i have is that i plan to use my existing chimney that is in pretty good shape for this old house as my exhaust. my basement ceiling is only about 6' max in height. my vertical exhaust plan is to go up behind the 55gal. drum about roughly 5' and right angled directly into the chimney. i worry is as i read of peoples issues getting the flew to operate correctly that i will possibly encounter the same bellow of smoke back into my face. i am wondering if people have tried this and would like to anticipate if inevitably it will be an issue or not. i have two kids(8mo. & 3.5yrs) and im not looking to poison them. i love them deeply. so id rather avoid having this issue to the max.

i know one common issue is making sure the unit is completely dry before starting because the moisture traps coldness around the flew(heater core and bench). and we all should know that a cold flew makes a back draft when starting a fire. my hopes is that my chimney that runs through the 2 floors of my home will be warmer than anything in my basement anyway for initial fire starting, and that the 90 degree angle wont hinder the flew currents. am i in the right school of thought?


other thoughts and questions:
what is fireclayed perlite exactly?(how do i make it?)
can i use perlite for all my insulation needs?(it is cheap and easy to get for me)
do i have to insulate the fire bricks in the heat riser if i use full sized bricks from the core all the way up?(or should i just plan on insulating the whole core from base to top with "fireclayed perlite"?)

i notice that in the design i mentioned its states a "3" or more" gap in the down draft area below the barrel is marked... do i need to leave the whole area all the the way around the core open then exited along the floor ducting wherever?(just to clear it up for me)

also mentioned in those designs was not to use aluminum, galvanized steel, or corrugated duct in any way in the first 5' of exhaust from the barrel down draft exit. what kind of duct exactly?

a random question.. are dragon heater designs worth while to reference?(they seem to have no insulation around the heat riser? but the lower insulation method seems nice and easy especially with removable drum clamps and what not)

i cant seem to find a fire brick that will withstand 3000 degree temps and up. i could use a good source if anyone has one?
and while im talking about it.. how about using high alumina castable refractory(http://www.hightemptools.com/castablerefractory.html)? i will say i have zero experience with masonry, but this looks to be quite affordable compared to buying bricks outright, and cant be too hard to do right(as in making the specific molds and what not)? how thick would/should i make all the walls if i should choose to do this? would a 20lb bag or 50lb bag be enough/too much? any others thoughts on building my entire heater core out of one of these castable products? also i have read you are supposed to fire the casts in an oven in a particular way on up to the "working" temperatures that are goin to be used. so i have to find a kiln that gets up to 3000 degrees? any thoughts on that?

last but not least as i seem to have many questions... its this RMH still in use and are there any updates or corrections to the original design i should be aware of?


many thanks in advance!

-matt
 
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One common piece of advice for siting a rocket mass heater is that it should be in your common living area. If you have to make a trip downstairs every time you want to check it or feed it, it will quickly become a chore and either difficult or neglected. As it burns small wood, it needs to be fed frequently while burning. If you spend a lot of time in the basement (shop or something) it could be a good location. I am assuming that if you have done much reading on the subject, you chose this location because the main floor is too weak or too crowded to contain the RMH. In that case, you might want to consider an alternate to the cob bench, which is known as a bell: a vertical tower of masonry where the hot gases collect and give up their heat before exiting at the bottom to the chimney or a second bell. You could even have bells in two different rooms. These would also need support, but smaller columns from the basement floor would work instead of needing long walls of masonry.

Some details about your house and its layout would help the experts advise.

You will never have to worry about 3000 degree tempeatures; if the core of your heater ever approaches 2500 you will have an unusually efficient setup. 3000 degrees is for steel smelting equipment or extreme industrial applications. You might want some 2500 degree refractory cement for the inner layer of your core, but most if not all of it will be fine with 2000 degree material. Castable refractory generally wants to be at least 2" thick, and one product I was looking at recently said 10 pounds makes one square foot at 1" or 2" (I forget which) thick. A 50 pound bag will not do all of any likely core. If you are just using it to reinforce a cob/perlite mix, you need to do calculations based on the recipe you are following.

Refractories do not need to be fired to the temperature they are to resist. Nobody will be able to fire something to 3000 degrees for you, and 2300 would be about the maximum a stoneware pottery kiln could do (and I doubt you could find any potter with a suitable kiln willing to fire your core). Moot point since it is not needed. Most materials you will use only need to be slowly heated by fire inside to cure them before use.

Lots of others have more experience and can flesh out these comments.
 
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Matt B. : Welcome to Permies.com, our sister site Richsoil.com and a big welcome to the Rocket and Wood stoves Forums !

Like Glenn I worry about you trying to install an RMH in a Remote location ! please take the time to research and understand "Stack Effect"
and " Whole House Stack Effect " This is a very important point to have clearly in your mind as Cloths driers vented out doors, even the
small fan located in your Bathroom vents or over the cooking range in your bathroom can cause Your RMJ to vent backwards !

Simply opening a window on the 2nd floor of a two story house can cause your RMH to " smoke backwards'' !

Since you have grasped the idea of Alumina refractory Cements, pointing out that all fire clays contain a high percentage of Alumina in their
composition should help you put your mind at rest, while their are high alumina Fire Clay and Fire bricks, there is little need to use a fire clay
, or fire brick rated above 2500dF! I have found 2000dF sufficient for my needs !

A quick look at traditionaloven.com should be helpful to grasp the basics of your materials of construction !

You design as planed does not mention the Extensive use of a thermal mass to extract the maximum amount of heat from the hot Exhaust
gases prior to them being vented into your existing chimney, one of the largest side brnifites of a large thermal mass is its ability to extract
so much Heat energy out of your hot exhaust gases that they are cooled don to the 150dF range, maximum heat to you, minimal waste heat
safely exiting the chimney !

I can only stingily recommend that you get your existing chimney checked by a professional 'chimney sweep ' before using it for the final
chimney for your RMH, also the internal size of your chimney often is the deciding factor in determining the size allowable for your Wood
Stove, regardless of type !

Generally speaking, Your closest exposure to a combustible surface can be reduced by the following, at least 6'' from the heater cores high
temps to a reflective barrier , with a further 4-6'' of Air Gap, as you have selected the Bonny Convection Heater, this standard should seem a
natural follow-through !

Due to outside issues I will have to address your other issues in a thread that continues my thoughts ! Please be assured that you have come
to the right place, and if there is a rocket mass heater in your future, we will help you build it ! For the good of the crafts !

Think like Fire, flow like a Gas, Don't be a Marshmallow, As Always, your questions and comments are Solicited and Welcome ! Big AL

 
allen lumley
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Matt B. : i am jumping around in an effort to follow your Thread ! Fire Clay is any clay that you can fire and it has a low % of Expanding with firing,
and again a small % of contraction while cooling, this tends to guarantee little or no cracking of the monolithic structure of the rocket mass heater
RMH and it's component sections !

COB, is a low expansion clay mixed with lots of sand, the clay slurry replacing the otherwise inevitable air gaps between the grains of sand! This can
easily lead to mixtures where sand is 2 : 1 to clay, The sand prevents your 'Local' Clay from over expanding, and the clay slip (just about like pancake
batter) filling the gaps between the individual grains of sand. Google 'Soil testing' where you allow time for the various types of materials within your
soil to settle out and form layers, Perhaps as far down as 3 - 6 feet below your feet you will find local clay nearly every where in THE WORLD !

A good grade of Fireclayed Perlite will be close to a 50 : 50 Mix of a good grade of fire clay ( Lincoln 60- or local clay ) and Perlite - no sand !

Allowing for the use of fire brick to make bridges and maintain structural integrity, as visually represented by the ''Bonny Convection Plans'' and
always referring back to "The Book " rocket mass heaters'' in the new 3rd Edition, available for download at Rocketstoves.com, the
skillful use of clay slip and perlite or perlite alone will give you a monolithic structure that will be long lasting !

The use of full-sized bricks is generally recommended for ALL 6" and 8" systems, with split bricks often being used for 4'' systems1 A 4'' system is
a difficult 1st time build, and is probably a poor match to your existing chimney ! The out side of the Heat Riser should be insulated to isolate the two
continuous hot exhaust gas streams -the 1st one rising inside the heat riser, and the second which has cooled From it contact with the inside of the
surrounding Barrel ! If you use a built up tower of Fire Bricks, and wrap the outside of the bricks with rock wool an often used cheep insulator, you
can expect long life from both components ! As an over wrap a sheathing of fire clay slip and Perlite Probably will not last as long but it should with
minimal maintenance last for a couple of years or longer !

Your remarks about a 3'' gap are a little vague, but i am petty sure if you re-read that section of your instructions - it refers to to air gap between
the underside of your barrel and the topmost section of your Heat Riser, If this is not clear to you please come back here with a detailed quote
from your plans.

THE gap at the bottom of the barrel where the vertically falling gases enter the horizontal mouth of the start of the Thermal Mass should be as
large as you can make it ! Making this area smooth walled and with a gradual and sweeping transition from the descending vertical to the
horizontal as posible is preferred as this is usually a major area where problems occur !

With the expectations that the whole system will easily last for 20 + years with minimal seasonal maintenance, the horizontal ductwork leading
off of the RMHs Core should be considered to be a throw-away form! The smooth-walled ductwork acts as the form or mold around which you
pack a layer of clay slip and cob, allowing for the quite possible future failure of the original ductwork ! Because of the monolithic construction
AND its thickness, we can expect no hot exhaust leakage even if the original duct work fails, With this expectation I generally plan to purchase
the cheapest grade of ductwork available in my location - Cold Air or Return Duct work ! after the 1st 4 feet or so the rapid cooling of the hot
exhaust gases, means that i can then use Galvanized or Aluminized or even Aluminum Duct work for the rest of my Thermal Mass !

My personal Highly Favorable opinion of the Dragon Heater has been shared here at Permies.com ! Proper use of insulation is made in this
construction, they do have an understandable proprietary interest in how much they share!

Again Buy the best brick you can afford, though there is little reason to go above 2000dF !

I personally have little experience creating entire combustion chambers/ Heat Exchangers, out of this material, Generally I would consider
the use of this material as something to try as an experiment, perhaps in the area below the Barrel in the area where the vertically falling
exhaust gases turn 90 degrees and flow horizontally through the Thermal mass !

You may have noted a generalized mention of the Hot exhaust gases flowing 30 feet through a 6'' system, and near 50 feet through an 8''
system, as a general practice we subtract 5 feet from that figure for every ELBOW that the gases flow through ! As stated you should not
have a problem !

Ernie and Erica Wisner are the moderators for this Forum, I consider them to be personal friends ! I do know that Ernie insists that any
design they share has been used in multiple locations for at least 1 year before they share them on their web site, as long as you were
thorough in your research you should be able to follow their plans with confidence that you are getting a well thought-out perfectly
feasible construction Plan ! Hope this helps and is Timely !

Think like fire, flow like gas, Don't be a marshmallow ! As always, your questions and comments are Solicited and Welcome ! Big AL !




 
matthew boersma
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first off, thanks for the generous replies to my post! and sorry if you where awaiting my reply back again. i have been extremely busy lately and broke my nose the other day which made it hard for me to sit in front of a computer screen for too long. i am doing much better now and am still as eager to make this wood heat my thing, and an efficient one. from reading the replies to my original post im realizing i need to rethink a few things... it seems that my main concern at this point lies in the category of my heater location before i make any definitive decisions. i will say that the size of this convection bench heater is a bit unwieldy in my house. so yes, you are right in assuming i chose this location as mentioned(my basement) due to space issues in the upstairs. there simply isn't a great location for it without making numerous modifications to the main floor of my home.

that being said i am thinking a lot about these "bell" setups that are giving me trouble in my research escapades. i need some good examples of how i can do this. i mean how can i incorporate a bell design while keeping my combustion chamber in my basement? is this really a feasible option? how exactly do i build these bells, and how do i link them up with my heater. and since i am not using directly a traditional flue concept with the flue pipe going strait up in these bells... can i run the exhaust into my chimney at basically any angle and/or length? for instance can i shoot over somewhat horizontally at a bit of a distance(5'-10'max) to my chimney? i do read that the natural draw of these systems are usually a bit better than using a traditional bench design. which leads me to believe i have more play in how i exhaust eventually out of my house. any thoughts on that specifically?

the best example i have found was a dragon rocket masonry heater that had a reasonable over all footprint which may even be imprinted into my upstairs without too much fuss. although it did have the rocket stove core built into the bell system direct so this confuses my thinking process when i think of the burning of flue gases. i am curious if i still need or can use a 55gal. drum for the "re-burn" chamber or not. these metal drums i can get for like $10 a piece so i could get many of them if i needed. the only other examples i can find with some sort of schematics are full-on masonry heaters with surprising efficiency of an upwards of 85% and higher. i just was under the impression of the re-burn effect was a large component to the efficiency of rocket mass heater solutions. i know the "mass" or "thermal mass" is really the key for not losing(rather storing it) the heat created. this is why im thinking the "bells" are just as good(or better) as well because they trap a rising heat in the dome of the bell as well as storing it in brick or whatever.. which reminds me to ask.. can i use materials other than brick to build these bells if i want or need due to what i can scrounge up? i need a good concept of how to design these bell innards(especially if i can use more that one bell and how?) and how to link them to a rocket stove in the most efficient manner. i need some clarity before i start to get materials together.

thanks again!

-matt

 
Glenn Herbert
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There is no "re-burn" feature with a rocket heater of whatever style; complete combustion happens in the burn tunnel and heat riser. The rest is all heat storage and radiator elements. The standard rocket stove depends on the barrel to radiate heat immediately and assist the temperature differential which drives its ability to push gas through the horizontal bench. The bell version needs less push as it doesn't have the long run, so presumably the reduced radiation and increased mass of the first bell is not a handicap. I don't know as much about the bells as about the standard design. My impression is that if you could put an ordinary woodstove in any room in your house, you could fit a complete bell-style rocket there (with, in your case, extra foundation piers or columns down through the floor to the basement). As far as the technical matters of the bell, you need to consult the experts - masonry heaters which this starts to resemble can only safely be done by experienced professionals for tens of thousands of dollars. Unless you are confident about the details and your capacity to execute them, it may be worth your while to pay for the relatively proven Dragon stove.
 
matthew boersma
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i guess using "re-burn" as a term to describe the combustion of the flue gasses is a bit misleading and may sound like i am a moron. which i may be and sound, so correct me if i am wrong. i am talking about the collection of flue gasses in the heat riser. with the built up heat from the main combustion chamber the gasses burn instead of being forced out through the flue before they get hot enough to get the chance. the insulation used for the riser as i understand it is there to ensure that all of the wood gasses get hot enough and subsequently burn and not lost out the typical chimney setup. i was thinking the 55gal. drum made some sort of bellow effect in the heat riser to a point that would keep those gases from being wasted, and instead burn. that is why there is a limit to the gap at the top of the heat riser and the top of the barrel from what i understand. otherwise the flue works too well and the flue gasses are wasted because the combustion chamber doesn't reach a hot enough temperature. that waste i speak of along with the direct lost heat in a conventional wood stove is what makes these RMH's so amazing, popular, and better in most all ways. so not really "re-burn", but i have seen the effect as described as somewhat of a "controlled chimney fire". as a chimney fire is created when creosote is built up causing a choke point where flue gasses then collect, get hot, and then proceed to ignite in a place where combustion is not meant. i want proper and complete combustion along with a thermal mass component in my heater design. which is why of-course i am choosing some sort of rocket mass heater as a direction to go. please anyone correct me if i am wrong about my fire science.

-matt
 
matthew boersma
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allen lumley wrote:Again Buy the best brick you can afford, though there is little reason to go above 2000dF !



by the way.. according to my bonny convection heater plan i bought from Ernie and Erica the flame path in that RMH reaches a recorded 2800 degrees Fahrenheit!! so since that is the basis of my plans i need to consider a very high heat brick or cast my own as it seems the cheapest option and may be fairly easy to do. a bit more work yes, but that doesn't bother me any. i am one of those weird people that like to work extremely hard for a well deserved future benefit. unless out there are some good sources to get deluxe fire brick for a reasonable price? i kind of have it in me to try to basically build the same heater Ernie, Erica, and others did in Bonny Doon, CA. with a bell system instead of a bench presumably. i really could use some advice on construction methodology. how to construct these bells. how tall, how wide, and what kind of materials? anyone out there try this particular build style? please and thanks permaculture fanatics!!

-matt

-
 
matthew boersma
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So this is a rough paint brush drawing of my current thought on how to make this rocket bell heater. i chose to not stack the bells, but to rather lay them out in series horizontally along the floor. i feel this will be better for my floors weight handling ability as i stack the bricks up. although i will probably still reinforce my floor with support jacks anyway just to be on the safe side. my basic plans in mind are having the total dimensions be around 30"x 60" giver or take a few. im thinking ill make the first bell a bit taller than the second, and both the bells taller than the barrel that i have pointed out in the drawing. im hoping to encourage more heat capture with that kind of idea. hopefully this will help the efficiency since i have been reading that the height of these bells are seemingly a non issue and might be better the taller they are. one question i have to the bell construction is regarding the walls in each bell that presumably direct the incoming heat upward into the bell cavity. are these necessary to have at all or can i have strait horizontal path under the bells and just allow the flow to do its thing? let me know if this design makes sense to anyone with experience.

-matt
Rocket-Bell-Heater-Concept-Design.png
[Thumbnail for Rocket-Bell-Heater-Concept-Design.png]
 
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matthew boersma wrote:i chose to not stack the bells, but to rather lay them out in series horizontally along the floor. i feel this will be better for my floors weight handling ability as i stack the bricks up. although i will probably still reinforce my floor with support jacks anyway just to be on the safe side. my basic plans in mind are having the total dimensions be around 30"x 60" giver or take a few. let me know if this design makes sense to anyone with experience.


Matt,
Like you draw the things, those won't act like bells, rather like a forced gas movement system. First, skip the separation walls inside the bells. The dimensioning of the in and outlets should be the same as the final exhaust to the chimney, that one is situated right.

For a given space to act like a bell, the inlet and outlet should be at floor level. Directly behind the inlet there should be enough room to slow the gases down nearly to a standstill in order to allow the forces of gravity do their thing. In effect, the hot gases will rise almost immediatly behind the inlet, thereby pushing other gases out. Since the exit opening is also at floor level, the cooler gases would be pushed out. Don't make it complicated, just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.
 
matthew boersma
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here is an updated concept drawing without the walls now ensuring "free gas movement". i read this(http://www.stove.ru/index.php?lng=1&rs=16) and decided you are right about the walls. ensuring free gas movement will keep the flow of gasses operating properly, and will hopefully keep me from getting back drafts and what not.

Peter Berg wrote:For a given space to act like a bell, the inlet and outlet should be at floor level. Directly behind the inlet there should be enough room to slow the gases down nearly to a standstill in order to allow the forces of gravity do their thing. In effect, the hot gases will rise almost immediatly behind the inlet, thereby pushing other gases out. Since the exit opening is also at floor level, the cooler gases would be pushed out. Don't make it complicated, just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.



i think/hope this is what are saying i should do?

-matt
Rocket-Bell-Heater-Concept-Design.png
[Thumbnail for Rocket-Bell-Heater-Concept-Design.png]
 
matthew boersma
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allen lumley wrote:Think like Fire, flow like a Gas, Don't be a Marshmallow, As Always, your questions and comments are Solicited and Welcome ! Big AL



i love this quote by the way. also id love to hear more of you thoughts and concerns on my new concept drawing. you seem to know your stuff as well. if possible i'd also love to somehow hear from your friends the Wisner family about these bells used as thermal mass instead of the cob bench. the thing is where i come from this heater could save me about $1500 a winter if it works correctly. especially versus the oil furnace i have currently. it would be better once i am able to afford the natural gas installation i now have the opportunity to even get it if i so choose. the gas company is asking $4000-$5500 for the install so it would likely take me 5 years to get my moneys worth(not including $1000+ what it would cost for the furnace and what not). so i could spend quit a bit on a rocket bell masonry heater and start to save instantly if my build works properly. this i why i describe my eagerness as a desperate one.

-matt
 
Peter van den Berg
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matthew boersma wrote:i think/hope this is what are saying i should do?


Yes, you've got the picture.
Don't know what size the bells ought to be, when too large you are loosing too much draft and the "thing" will backfire.

As an afterthought: when quick heat isn't required there's the possibility to build the rocket inside the first bell and skip the barrel.
 
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I don't have experience building with bells (except earthen ovens, which do have a similar effect in trapping heat in the dome). So I will leave the tips on proportions and heights to those who know better.

As to the 3" or 4" marked on the manifold part of the diagram:
If you are connecting a barrel to exhaust ducting, and you have less than 3" gap between the barrel and the heat riser where the exhaust duct joins in, then there will be a flow constriction at that point. In general I want a gap that is about 1/2 the diameter of the exhaust ducting at that point, on the assumption that the main flow of gas has to pass through the top of this gap into the duct, and there will be some turbulence there. This minimum gap can be tricky to achieve when making the manifold out of the same standard 55-gallon drum, so I point out the possible constriction in our diagrams. The reason we allow 3" instead of 4" is that it has worked for certain projects - for an 8" diameter system, 4" would be the theoretical minimum, but 3" has sometimes worked out OK in practice (especially if the gases can flow down around more than half of the opening and enter from the lower sides).

Under the barrel where Allen mentioned, above the heat riser, the exhaust is free to flow away from the heat riser in all directions. So the minimum is about 1/4 of the diameter or 2". If your heat riser has a big flat top where fly ash can build up like snow, allowing more space in this area may be wise.

If you don't use a metal drum at the base for the manifold, but instead build the hollow base out of masonry, then it's much easier to build adequate flow space. It's also easy to constrict it too much, however. Bears attention.

My biggest concern with the plan as originally described would be the damp factor in the basement. Basements can be large, poorly-insulated spaces, and putting the heater in the basement commits you to effectively increasing the size of building you are heating. Having the heater in the occupied spaces gives you much better return for the investment, in terms of long-term fuel efficiency and achievable comfort.

I would look at bringing a cinderblock, brick, or concrete footing up from the basement floor, and cutting and re-framing a hole in the floor with a 2" gap on all sides to allow the masonry heater up into the main room. This will make feeding it more convenient, improve your draft situation, and get better effectiveness and efficiency from your fuel.
(You can insulate that 2" gap with non-combustible insulation, such as Roxul or mineral wool. It is important as it allows for the different types of movement in a building without the wood and masonry trying to tear each other apart, as well as reducing heat transmission that might over-heat the wood. At the base I'm not terribly concerned about the heat problem, but around the firebox you definitely want masonry-heater type clearances, at least 8" thickness of masonry plus 4" air gap to combustibles.)

I might think about doing a small bench (sitting or lying on the heated portion is delicious) and a larger bell as the back of the bench; seating is not only extremely efficient for personal comfort heating, but it also allows the masonry heater to replace an existing sofa or chairs and so fit into the room with less disturbance. If it's easier to fit in a simple masonry tower block, you might consider making some steps up to the bell, or a ladder, so you can lie on top of the stove like a Tolstoy character. The stove-top bed in Russia was often used for the elderly, ill, or infirm (like people who throw their back out trying to build a masonry heater in a hurry), as well as for contemplative comfort, and is a lovely feature to enjoy.

Hope this helps!

Yours,
Erica W
 
matthew boersma
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Erica Wisner wrote:As to the 3" or 4" marked on the manifold part of the diagram:
If you are connecting a barrel to exhaust ducting, and you have less than 3" gap between the barrel and the heat riser where the exhaust duct joins in, then there will be a flow constriction at that point. In general I want a gap that is about 1/2 the diameter of the exhaust ducting at that point, on the assumption that the main flow of gas has to pass through the top of this gap into the duct, and there will be some turbulence there. This minimum gap can be tricky to achieve when making the manifold out of the same standard 55-gallon drum, so I point out the possible constriction in our diagrams. The reason we allow 3" instead of 4" is that it has worked for certain projects - for an 8" diameter system, 4" would be the theoretical minimum, but 3" has sometimes worked out OK in practice (especially if the gases can flow down around more than half of the opening and enter from the lower sides).

Under the barrel where Allen mentioned, above the heat riser, the exhaust is free to flow away from the heat riser in all directions. So the minimum is about 1/4 of the diameter or 2". If your heat riser has a big flat top where fly ash can build up like snow, allowing more space in this area may be wise.

If you don't use a metal drum at the base for the manifold, but instead build the hollow base out of masonry, then it's much easier to build adequate flow space. It's also easy to constrict it too much, however. Bears attention.

My biggest concern with the plan as originally described would be the damp factor in the basement. Basements can be large, poorly-insulated spaces, and putting the heater in the basement commits you to effectively increasing the size of building you are heating. Having the heater in the occupied spaces gives you much better return for the investment, in terms of long-term fuel efficiency and achievable comfort.

I would look at bringing a cinderblock, brick, or concrete footing up from the basement floor, and cutting and re-framing a hole in the floor with a 2" gap on all sides to allow the masonry heater up into the main room. This will make feeding it more convenient, improve your draft situation, and get better effectiveness and efficiency from your fuel.
(You can insulate that 2" gap with non-combustible insulation, such as Roxul or mineral wool. It is important as it allows for the different types of movement in a building without the wood and masonry trying to tear each other apart, as well as reducing heat transmission that might over-heat the wood. At the base I'm not terribly concerned about the heat problem, but around the firebox you definitely want masonry-heater type clearances, at least 8" thickness of masonry plus 4" air gap to combustibles.)



well noted on keeping attention on the choke points. thank you so much for your input! i will keep all this in mind as i build to make sure i have adequate flow space. although i think i still will use the barrel in the design for the 8" system the best i can. i want that instant heat if i have a suddenly have a need for it. alos i was planning on using it as a cook top unless building in a masonry drum instead works just as good and still has a good hot "cook top" for my cast iron pans? which brings be to a question.. as i was talking earlier about the drum playing a role in how the re-burn works. is it not crucial in using this design with the drum to ensure all the gases are being combusted properly? can i achieve similar or better results with making it out of masonry. should i emulate the 55gal. drum dimensions(height, width, legnth) also with the 2" or so gap at the top of the heat riser along with the other mentioned gap minimum measurements?

i have also decided to for sure put this thing into my kitchen. i have already found a good location next to my chimney that i can cut the floor out, reframe, and build up a solid footer. probably a good idea not to have this masonry wood epic batter you speak of. it shouldnt be too hard to fit this in i am thinking.

-matt
 
matthew boersma
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by the way this is some brick i had given to me. i have 166 of them and will need more, but i figured its a start. the thing is it looks like it is clay brick. but i am not sure. i think i am still possibly planning to build my heater core out of high alumina refactory cement. im not sure where to put certain types of brick where? or if it really matters if i have this castable core 2-3" thick and with a bit of insulation around the core? any idea by recognition of this brick if it will work for the this rocket masonry bell mass heater? lol

-matt
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matthew boersma
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Peter Berg wrote:

matthew boersma wrote:just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.



your talking about total volume of the bell space not a certain dimension worth mentioning are you? i have already noted that all the inlet/outlets need to be the same size as the last exhaust point.

-matt

 
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So here is my test layout given the space i chose. you'll see the core on the left lower corner. bear in mind i will be insulating the core 8" thick around all sides of the inner dimensions, so thats including the 2"-3" wall of the cast. and the drum will have a slot to fit nicely.. so my walls and divider currently off the core area are going to be slightly different(pushed out a bit) in the final result. all my inlets/outlets in and out of the bells will be matched to the J-tube inner dimensions... which will be approximately 7"x7.5". those dimensions will be carried from the feed, to the burn tunnel, and to the heat riser. out from under the 55gal drum i will inlet those same dimensions from bell 1, to bell 2, and to finally the chimney. all 7"x7.5" . correct me if this is a mistake.

also i plan to make the first bell about 6' tall and second shorter(i havn't decided exactly) around 4' maybe. possibly short enough to hop on and a kind of be a bench to keep my buns warm if i so choose. i also plan to find a cast iron oven to fit into the top of the first bell somehow. i could use maybe a suggestion for this as well. i have no experience in masonry, but i think i can do this if i am patient enough and continue to read and ask questions when and to who i can. which brings me to another question.. i have seen builds where it seems that there is a mortar being used.. first off i would imagine all mortar in this would be some sort of clay/fire mortar only? also it seems as if it is mostly applied to the outside of the stacked bricks unlike a typical masonry face that uses about a 1/4 inch or so to gap each brick. when i see professional masonry heater build online i see they look nice like a typical masonry face like the outside of a brick building. is this because there is a layer of bricks outside the innards that is using a non-fire more standard mortar type? i guess i need a reference guide or a book to read on this matter. im not sure what to think exactly. thanks for those who want to help!

-matt
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Peter Berg wrote:

matthew boersma wrote:just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.


your talking about total volume of the bell space not a certain dimension worth mentioning are you? i have already noted that all the inlet/outlets need to be the same size as the last exhaust point.


This is not about the total volume of the bell, of course. To make matters clear: immediatly behind the inlet opening into the bell there should be a sudden widening in the horizontal plane at the same height as the inlet, not counting the space above (or under) it. This widening will slow down the velocity of the stream, so the hotter and lighter gases are allowed to rise.

The space above the inlet is where those lighter gases can go. Hope this is clear.
 
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Peter Berg wrote:

Peter Berg wrote:

matthew boersma wrote:just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.


your talking about total volume of the bell space not a certain dimension worth mentioning are you? i have already noted that all the inlet/outlets need to be the same size as the last exhaust point.


This is not about the total volume of the bell, of course. To make matters clear: immediatly behind the inlet opening into the bell there should be a sudden widening in the horizontal plane at the same height as the inlet, not counting the space above (or under) it. This widening will slow down the velocity of the stream, so the hotter and lighter gases are allowed to rise.

The space above the inlet is where those lighter gases can go. Hope this is clear.



so is this what you are talking about? either like pictured in the side display, or like pictured in the top down display? if even i am grasping what you are saying correctly.. i want to make sure i am understanding how you mean to explain the horizontal plane you speak of. so to be clear these are not the same thing pictured in both views, but rather showing a taper out either at the top of the inlet or the sides. although, would is make sense to widen the whole opening into a bell? like if each opening tapered out on all sides into each bell? if i am even grasping this concept correctly from you explanation. i am a very visual person so pictures help me a lot. i hope they are clear enough for you to confirm my understanding.

-matt
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My understanding of the English language is too limited, I"m afraid. But I'll try again.

Your side view is more or less correct when applied to coupled bells. However, the inlet of the first bell and the exhaust of the second bell need to be smaller as compared to the cross section srea of the bell floor. Normally, the chimney is the same as system size so both of these holes would be system size as well.

Try to see it like this: picture a 55 gallon barrel with two holes in it of 6" for example. Both these holes are at floor level opposite of each other. This is how a simple bell should look like. When the holes are beside each other there could be a shortcut effect, so in that case one would place the inlet opening a little higher.
 
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Peter Berg wrote:My understanding of the English language is too limited, I"m afraid. But I'll try again.

Your side view is more or less correct when applied to coupled bells. However, the inlet of the first bell and the exhaust of the second bell need to be smaller as compared to the cross section srea of the bell floor. Normally, the chimney is the same as system size so both of these holes would be system size as well.

Try to see it like this: picture a 55 gallon barrel with two holes in it of 6" for example. Both these holes are at floor level opposite of each other. This is how a simple bell should look like. When the holes are beside each other there could be a shortcut effect, so in that case one would place the inlet opening a little higher.



i think i got ya now... let me know what you think. look no shortcuts(or at least a bit more opposite as far as the inlets and outlets! bear in mind this is still kind of rough. i plan to make the 2nd bell a little bigger(wider).

-matt
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Yes, this is the general idea. Best to do the dry layout one brick high first, than the second and third layer and post picture of each. But you are on the right track, it's getting used to an unfamiliar concept which takes time.
 
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ok. well the concepts of design are starting to become much clearer with still much room for visual trials and such till i reach a good fit. i am starting to contemplate the total materials and costs included. i am figuring the full J-tube with castable refractory cement will be about $265 from a source which seems to be the best i can find so far. now on to the flue passages and bells... i am not starting to contemplate how to best do this for both efficiency and far as the heater itself and the cost in materials. i know in a typical chimney there is a clay liner that is sealed at each section joint location with a fire clay mortar of some sort. now my main concern is am in need of stacking these bricks i have with fire clay mortar all the way up the entire bell? i ask because i know that would be quite costly. or can i use a general mortar to make this bell construction? in the examples i have found the outside faces of these masonry heater seem to been like normal brick wall construction... with typical looking 3/8" this mortar in between each layer of brick. they do not usually specify if that is just an outside face or that there is a inside construction that is of different materials. so this i why suddenly i am a bit concerned. because of this i have contemplated using large flue liners like in the dragon masonry heater design to make the bells and then maybe lying brick around those structures in order to get a higher amount of thermal mass. also using a thick thick plaster like stucco(not sure if stucco is cool or not for this?) or cob(i might get more bang for buck with cob) around the whole structure. any ideas or concept i need to know to make a good decision on how to do this?

-matt
 
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You may find the following of value, a ton of photos of a complete masonry rocket style all brick stove constructed from the ground up:

http://www.mha-net.org/docs/v8n2/wildac12g.htm
 
matthew boersma
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Byron Campbell wrote:You may find the following of value, a ton of photos of a complete masonry rocket style all brick stove constructed from the ground up:

http://www.mha-net.org/docs/v8n2/wildac12g.htm



yes helpful indeed... it seems that they use clay mortar around the base of the unit and in the first bell. up top it looks like general mortar in the second bell. although it doesn't specify exactly. it makes sense that further along(i.e. the second bell) the heat will be less of an issue for the mortar. thanks for the link.

-matt
 
matthew boersma
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Erica Wisner wrote:If you don't use a metal drum at the base for the manifold, but instead build the hollow base out of masonry, then it's much easier to build adequate flow space. It's also easy to constrict it too much, however. Bears attention.
Erica W



so i really cant seem to come to an exact decision about the 55gal. drum. i see in the rocket masonry stoves that dragon heater puts out there is no down draft around the heat riser. instead the hollow chamber around the riser is filled with insulation. you suggested in this quote from your post to me to maybe build the "drum" out of masonry i assume to basically emulate the same down draft situation. is this a problem if i choose to skip the drum downdraft method and build the exhaust path directly into the 1st bell(like in the dragon masonry stoves). i know the drum acts very much like a thermal siphon, so i know it is a main element in using the long horizontal thermal bench because we need to not smoke backwards to make it work. from what i understand the draft situation in a "free gas movement" design such as the bell type mass heaters is very good, and generally accepted as better than in traditional RMH. so i guess in theory the drum may not be needed if its main purpose is the thermal siphon? so my main question is will the "re-burn" effect in the burn path and heat riser be effected negatively without the drum system? any others feel free to chime in. for i think this is my main concern about my "final" build concepts. everything thing else seems to be sinking in quite well barring my imperfect brain that is bound to make mistakes. thanks in advance.

-matt
 
matthew boersma
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man i can come up with questions, lol. anyone have a source for oven doors like you see in so many of these masonry heaters? also metal ash cleanout doors?
 
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Barrel wise, there's other options, like square barrels

http://donkey32.proboards.com/thread/1017/pure-genius

The idea is, that you can stack bricks around and leave some bare metal, so you have a mixture of quick heat and accumulation. In the second example there, the plan is to use the home heating oil tank, as a flat bell and cover it with mass. That saves me from thinking about loosy massonry joints.

HTH.

Max.
 
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Satamax Antone wrote:Barrel wise, there's other options, like square barrels

http://donkey32.proboards.com/thread/1017/pure-genius

The idea is, that you can stack bricks around and leave some bare metal, so you have a mixture of quick heat and accumulation. In the second example there, the plan is to use the home heating oil tank, as a flat bell and cover it with mass. That saves me from thinking about loosy massonry joints.

HTH.

Max.



I like the square barrel idea. I thought of using square chimney flues as a barrel as well. With maybe an iron plate at the top for cooking. My main concern is still weather or not the down draft is needed for encouraging a proper burn in the heat riser. Feel free to shout your opinion on that if you have one. Thanks for the link to yet another innovation. When i have this heater up and running i will have an empty oil tank for maybe a similar purpose. We will have to see.

-matt

 
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Matthew, i'd say i'm no expert.

But the downdraft can be skipped. I'm not even that sure it contributes much to the rocket draft.

For example, when you have a free standing J tube in the backyard for testing purposes, with no barrel, it draws real well. Then you plonk a barrel on top, and trouble arises, up to the point that you need, more often than not; to put a chimney on this system to make it work.

To me a barrel is an excelent radiator to shed heat quickly into one room.


Which brings us to he next question, if you don't shed heat quickly, what will happen?


Well, in your case, since you have raised the question about normal mortar. If your exhaust gases are hotter than 200C° out of the first bell, you won't be abble to use a mortar based on cement, or your joints will start spalling.

HTH.

Max.
 
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Here's a very interesting inverted-U masonry riser batch-box RMH design, constructed at a MHA workshop this past year:

Alaska-style rocket mass heater with double burner cooktop and bench:

http://www.mha-net.org/docs/v8n2/wildac14j.htm
 
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For masonry heater hardware, a quick Google of "masonry heater bake oven doors" will bring up lots of links. Be sure you're comfortably seated before viewing prices! Here's one source I was looking over a while back when contemplating a masonry heater construction project:

https://mainewoodheat.com/shop-maine-wood-heat/bake-oven-doors/
 
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Satamax Antone wrote:Matthew, i'd say i'm no expert.

But the downdraft can be skipped. I'm not even that sure it contributes much to the rocket draft.

For example, when you have a free standing J tube in the backyard for testing purposes, with no barrel, it draws real well. Then you plonk a barrel on top, and trouble arises, up to the point that you need, more often than not; to put a chimney on this system to make it work.

To me a barrel is an excelent radiator to shed heat quickly into one room.


Which brings us to he next question, if you don't shed heat quickly, what will happen?


Well, in your case, since you have raised the question about normal mortar. If your exhaust gases are hotter than 200C° out of the first bell, you won't be abble to use a mortar based on cement, or your joints will start spalling.

HTH.

Max.



yea i just called dragon heaters today to ask about the barrel design to see what they say. they(she) had told me that they have had extensive testing done and there is no other reason mostly for the 55gal. drum except for to shed heat extensively and instantly. their emissions output show to be pretty clean in the masonry bell stoves they have designed. so the combustion of flue gas efficiency is not a noted matter regarding the barrel. its all up to the burn chamber regardless. she(i am sorry i didn't catch her name) had told me the main difference between using the barrel vs not is that with the barrel the heat is shed through that, and not using it means that your thermal mass(bell) keeps all the heat and sheds it slowly and more uniformly through that. i imagine with the long cob bench the "thermal siphon" the barrel creates as it cools due to room air temperature would probably be needed. necessary in order to create a draft to pump all the gasses horizontally while they(the gases) are trying to go up(and cant) due to the effects of gravity on said heated gasses. also why the need for a chimney is prevalent in that style of design because the long horizon of gas movement has a hard time "knowing" where to go. so i guess this is what i suspected. thanks for seconding that opinion and helping me feel more confident about my thoughts regarding.

as for the mortar i had decided to further my designs similar to the dragon masonry heaters made out of flue tiles. this design doubles as a very heat tolerant line and can be put together with way less mortar saving money on fireclay mortar and time laying bricks. i wil l say that the flue liners in the large dimensions that i wanted/needed were kind of pricey, but i figure the time and money i am saving from using brick it will work out in the end very well. i can use willy nilly all the reclaimed bricks i can find for the exterior thickening the thermal mass and use "free" cob to help with the task. i was orriginally planning on buying a bunch of bricks so instead i put the money into the liners. i think this will work out nicely in the end. thanks for the input!

-matt
 
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Byron Campbell wrote:For masonry heater hardware, a quick Google of "masonry heater bake oven doors" will bring up lots of links. Be sure you're comfortably seated before viewing prices! Here's one source I was looking over a while back when contemplating a masonry heater construction project:

https://mainewoodheat.com/shop-maine-wood-heat/bake-oven-doors/



oh boy, luckily i was sitting firmly. those prices are a bit much to say the least. the cheap(around $200+) ones maybe the way to go instead of spending $500 to almost $1000 on anything with a window. good link though, thankyou. gives me a perspective on that prospect. i might wait till next year to install the oven after i save loads on my oil bill, lol. i know it could be tricky to refit a oven after the fact, but if i build a certain way i could maybe set it up so its at least possible. we will see.

-matt
 
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oh btw i just checked out my chimney. it apparently already has a clay liner that is approximately 6.5"x6.5". or at lease slightly bigger that 6" squared. this must sound a bit stupid and i think i already know the answer. but i was wondering if i need to go to a 6" system instead of the 8"(7.5x7 j-tube) i had planned? the only reason why i ask is i know the bell system flows quite well so i wondered if i for sure needed to downgrade the size or not? i guess i was hopeful i could go to a 8" j-tube "style" because my house is 1150 sq ft. living space with 1/3 area upstairs. and id imagine the bigger the j-tube the more heat i get with less attention on feeding(or less often possibly). or would you think that a 6" would heat that amount of space just fine? otherwise i may have to install a double wall chimney through going about 20 feet up. which might cost a ton.

-matt
 
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Matt B. : So - Have you been to rocketstoves.com? - to pickup your copy of the brand new 3rd edition of Rocketmassheaters?
If not, do it now !

Next Make a list of ALL the ?Questions ? we have not answered and re-state them, there is no such thing as an unimportant question !

I am afraid that your current set off bricks will have contraction/expansion problems if used within the combustion core/Rockets heart !
The perforations within your brick show a certain Design age that does not work well with the extreme heating and cooling cycles !

_ While obvious to other posters, they have left their common fears to be covered by another poster! Me !

I want to recommend the triple (or more) set of comments on 'Fire-Brick " To the clearest Explanations rot be found at -

www.traditionaloven.com

The comments on what is fire clay and what is fire brick are worth paying attention to ! I hope this is timely and helps ! Big AL

Think like fire ! Flo like Gas ! Don't be the Marshmallow ! * as always, your comments and Questions are welcome and solicited*! A.L.

* Stolen from Friends ! A.L.

 
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so i have got some liners!! i plan to make this work using them. i have not cut anything yet so keep that in mind. also i have ordered some high temperature refractory cement(kast-o-lite li) for the core i plan to make. also i do plan to add a layer on the outside with cob and clay brick to add thermal mass to the unit. so this is just so i can start to get an idea of how to cut my floor out.

-matt
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matthew boersma
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so this is yet another basic drawing of mine. as far as my brain storming goes i haven't perfected it yet i think, but we will see i just got these today. there are 2 more of the big guys and 2 more of the smaller ones not in the picture. so keep that in mind if you have some much needed criticisms for me. i know the first bells outlet/inlets aren't actually directly across from each other yet. although would it really matter since the inlet into the first bell would be so high(i.e 3- feet). wouldn't it(the gases) possibly not try to short cut anyway and allow the heat still to rise and the cool gas to fall?
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Matthew, your bell combination ISA is way too big for the 6 incher J you plan to use.

You have about 6.38m²

You don't can't use more than 4m² on a 6 inch J

It would be good for a 6 inch batch, and output a more heat.
 
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