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Jimmy Smith
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I'm looking to build a contraflow in my house with a white oven. I have an old Lopi woodstove that I heat with now and would like something that burns a little less fuel more efficiently. I have considered a rocket mass heater but with the high winds I have where I live (northern NY on the Canadian border) along with the idea of feeding it constantly make it unattractive for my needs. On the other hand building a fire in the morning along with maybe in the evening when it gets cold without tending it after lighting it off I believe a masonry heater is better suited for my needs. My home is a single story ranch with R-38 insulation in the ceiling, R-21 in the walls and floors that I built 8 years ago. I have a monolithic slab on a crawl space that is reinforced with 1/2" rebar and 4x4 mesh strapped to it. The heater would be centered over top of a 12" haunch, the rest of the slab is a 6" slab. Under the slab is a 12" layer of compacted sand and gravel and under that is hard pan clay. I would be building up a core filled block footing about 40" high to support the heater. I have an image in my head of what I want for a design but want to make sure I am doing it properly. I have layed plenty of block and brick over the years so that part of it doesn't bother me. Any advice and ideas would be helpful.
 
allen lumley
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Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Jimmy Smith : The rocket mass heater RMH has been given a bad rap by the vary people most in love with it, not done in spite of our high regard, but Because
of it !

Yes it is true of the RMH, exactly like all wood stoves that they should be carefully located centrally within the home and should not be left unattended! It is also
true that the rocket mass heater like all wood stoves needs a operator who has taken the time to learn how to start the morning fire, but name any other Wood
stove that will have an operating temperature consistently above the ignition temp of creosote ~ 500ºF~ by 1500ºF within 5 minutes of its start! Further the core
of the RMH will maintain that temperature until after the fire is out !

The RHM will need several seconds attention perhaps as many as 2-3 times within the first hour, thereafter the skillful operator, alerted by the current depth of
the Rockets roar will again spend several seconds to tend the needs of his rocket per hour, this amount of attention done Automatically with no more thought
given than you expend adjusting your glasses. Depending on weather/climate, this service to Your RMH Spread out over a 3-6 hour period, will provide up to 24
hours of hands off Radiant heating !

A fair comparison is like having a Amply Savings account into which you deposit small regular deposits of Small very dry fine split wood and receive Automatic
withdrawals of Heat, Soul hugging, bone warming heat !

Ah, but you tell me that a masonry heater can do the same job only better. Well kinda, not at the freaky high Temps that ensure the clean burn and higher
efficiencies, A simple price comparison shows that unless you posses the necessary skill sets yourself the cost of a 'Russian ' Masonry stove is easily several
thousand dollars ! This compares to the cost of a D.I.Y. built RMH which is do-able by most 'handy' persons, who find that building one to code requires a final
vertical chimney of no greater cost than the ones required for ether a conventional wood stove Or a 'Russian',Masonry stove ! Indeed this is often over 1/2 the
cost of a well built RMH.

There are many areas with high winds located in 'upstate' New York, but careful siting and due diligence in installation should allow the RMH to work anywhere
the conventional wood stove or Masonry stove will work !

I am offering a link to a E & E Wisner Build located outside of Canton New York, this is now in its 3rd heating season and working well, and I can even show you
a crapy built RMH ( the owner tried to many modifications to sort all its problems) with a poorly sited chimney that works flawlessly after its initial lighting
problems are overcome !

See Link below :

http://www.permies.com/t/25435/rocket-stoves/video-great-rocket-mass-heaters

The first installation shows a typical installation and whole house heating load !

Four the good of the craft ! Big AL
 
Keith Coldrain
Posts: 20
Location: British Columbia, Canada
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Jimmy Smith ^ ©

I'm wondering just how different your "older" lopi stove is from that newer very efficient lopi endeavor that has the secondary burn chamber? Maybe you could upgrade it with a little modification?
Just a thought.

And just a suggestion here, you might want to visit the woodheat.org website for advise on getting more out of your current wood stove.

As for your quedtion. There may be other mass heaters, but the only other one's I've looked at are at
www.mha-net.org

They have some really nice units. Some with ovens too.


Keith.
 
Jimmy Smith
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allen lumley wrote:Jimmy Smith : The Rocket Mass Heater RMH has been given a bad rap by the vary people most in love with it, not done in spite of our high regard, but Because
of it !

Yes it is true of the RMH, exactly like all wood stoves that they should be carefully located centrally within the home and should not be left unattended! It is also
true that the rocket mass heater like all wood stoves needs a operator who has taken the time to learn how to start the morning fire, but name any other Wood
stove that will have an operating temperature consistently above the ignition temp of creosote ~ 500ºF~ by 1500ºF within 5 minutes of its start! Further the core
of the RMH will maintain that temperature until after the fire is out !

The RHM will need several seconds attention perhaps as many as 2-3 times within the first hour, thereafter the skillful operator, alerted by the current depth of
the Rockets roar will again spend several seconds to tend the needs of his rocket per hour, this amount of attention done Automatically with no more thought
given than you expend adjusting your glasses. Depending on weather/climate, this service to Your RMH Spread out over a 3-6 hour period, will provide up to 24
hours of hands off Radiant heating !

A fair comparison is like having a Amply Savings account into which you deposit small regular deposits of Small very dry fine split wood and receive Automatic
withdrawals of Heat, Soul hugging, bone warming heat !

Ah, but you tell me that a masonry heater can do the same job only better. Well kinda, not at the freaky high Temps that ensure the clean burn and higher
efficiencies, A simple price comparison shows that unless you posses the necessary skill sets yourself the cost of a 'Russian ' Masonry stove is easily several
thousand dollars ! This compares to the cost of a D.I.Y. built RMH which is do-able by most 'handy' persons, who find that building one to code requires a final
vertical chimney of no greater cost than the ones required for ether a conventional Wood stove Or a 'Russian',Masonry stove ! Indeed this is often over 1/2 the
cost of a well built RMH.

There are many areas with high winds located in 'upstate' New York, but careful siting and due diligence in installation should allow the RMH to work anywhere
the conventional wood stove or Masonry stove will work !

I am offering a link to a E & E Wisner Build located outside of Canton New York, this is now in its 3rd heating season and working well, and I can even show you
a crapy built RMH ( the owner tried to many modifications to sort all its problems) with a poorly sited chimney that works flawlessly after its initial lighting
problems are overcome !

See Link below :

http://www.permies.com/t/25435/rocket-stoves/video-great-rocket-mass-heaters

The first installation shows a typical installation and whole house heating load !

Four the good of the craft ! Big AL


I'm not knocking the rockets, I was thinking more of what will be a better option for my home floor space as well as what will be a little more user friendly for an extremely busy household. I've been burning wood in the stove I have since the age of nine, the wood stove was always my job where I grew up and when I built my house it was given to me. Great stove no complaints. As far as combustion efficiencies and complete combustion, burners and combustion is my career along with efficiencies. In most modern high efficiency burners, wether they are wood, oil, LP or natural gas the combustion properties are pretty much the same. How you get the most out of what you are burning is where it changes as well as what you are heating and the applications. The name of the game is to keep combustibles in the flame long enough to burn off as much of the hydrocarbons as possible before leaving the flue. In gas appliances this is done mostly by restricting heat exchangers and getting enough of an air mixture into the fuel for complete combustion along with getting the exhaust dew point low enough to condense leaving you with water and carbonic acid. The rocket is the closest I have seen to doing the same thing with wood as a high efficiency gas burner. It's working on the same principles without a power venter to aid in forcing the exhaust through extremely restricted heat exchangers. I believe the combustion numbers I have seen posted on YouTube for a well built rocket is around 88 to 90%. That is amazing for wood burners any way you cut it. The best commercial wood boiler I've worked on is a saw dust boiler at a picture frame factory and the best I can get out of it is around 82% efficiency when all conditions are right. So what I am getting at is the rockets have a lot of merit as far as that goes. When I speak of high winds I live in the middle of a hayfield located off the northern end of Lake Ontario along the St. Lawrence, for a good portion of the heating season it gets pretty damn gusty. I work on enough equipment with drafting issues even when installed properly that I really don't want to chance it. Another drawback for me with the rocket is that it does condense, over time that acid and vapor will take its toll on masonry, even clay. I would imagine that a well placed condensate drain would help prolong the life of the masonry components. I'm sure I will be called for that one but I'm just going by what I know about burners and materials I've dealt with. In no way should that keep anyone from building a rocket, with the amount of material and cob in them it would take years if well built to have an effect, but for me it is a drawback.
This brings me to the choice of a masonry heater for my home. There is a little less of a footprint if built tall enough. They do not condense so the components will last longer if treated right. Now we get into efficiencies. If built right with proper sizing to the baffles and close attention to trapping as much of the heat as possible high in the heater before the exhaust leaves the bottom of the heater I think that one can achieve the same combustion numbers without the condensing. The other part of the masonry heater that appeals to me is the control over intake air, it looks to me that with the rocket there needs to be a lot of attention paid to how the fire is loaded. It's not a problem for me so much as it would be for my wife, she tends to get in a major hurry and loses focus on small details like that. As far as building experience, like I said before, I have put up a lot of brick and stone over the years. Enough to feel confident I can do it. I also just had enough brick given to me to build the outer wythe of the heater. My issue now is how the hell do i size this thing, that is where I need some input from someone who has done it.
I know how strongly folks feel about rockets on here so please don't think I'm putting them down, each type of heater has its own merits and their own draw backs. I am also looking at what I wrote above from a perspective of eating, sleeping and breathing industrial and commercial heating systems and burners every day all winter long and installing them during the warm months. Different ways of setting things on fire and seeing what happens when you throw in different air mixes and fuels runs into what I do. I hope I don't sound like a jackass, just putting out there where I'm coming from based on what I know so you folks can tell me where I'm right or wrong when it comes to this application.
 
Glenn Herbert
gardener
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Location: Upstate NY, zone 5
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Not wanting to tend a J-tube (or especially have a less-skilled person tend it) and wanting a smaller footprint than a traditional RMH bench are valid concerns.

I think both could be addressed by marrying the RMH and masonry heater, as has been done extensively at the forums at donkey32.proboards.com. You can build a batch box which feeds the RMH heat riser for complete combustion, and enclose it in a masonry bell or two for upright mass storage. I believe the design and construction of this, as long as you follow the published interior dimensions and ratios found on donkey's forum, should be less tricky than making a really good contraflow masonry stove. You can totally use all of your brick and your masonry skills to do this in your chosen material set instead of the usual RMH cob.

A batch box does not have any more possibility of smokeback than a masonry stove, maybe less.
 
Jimmy Smith
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Glenn Herbert wrote:Not wanting to tend a J-tube (or especially have a less-skilled person tend it) and wanting a smaller footprint than a traditional RMH bench are valid concerns.

I think both could be addressed by marrying the RMH and masonry heater, as has been done extensively at the forums at donkey32.proboards.com. You can build a batch box which feeds the RMH heat riser for complete combustion, and enclose it in a masonry bell or two for upright mass storage. I believe the design and construction of this, as long as you follow the published interior dimensions and ratios found on donkey's forum, should be less tricky than making a really good contraflow masonry stove. You can totally use all of your brick and your masonry skills to do this in your chosen material set instead of the usual RMH cob.

A batch box does not have any more possibility of smokeback than a masonry stove, maybe less.


I was hoping someone would mention that because that is an avenue that would merit exploration. The rocket burners themselves are really neat, like I said, getting a wood burner to condense when burning is absolutely phenomenal. Do you think with the shorter exhaust path that they would condense in a MH?
 
Jimmy Smith
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Keith Coldrain wrote:Jimmy Smith ^ ©

I'm wondering just how different your "older" lopi stove is from that newer very efficient lopi endeavor that has the secondary burn chamber? Maybe you could upgrade it with a little modification?
Just a thought.

And just a suggestion here, you might want to visit the woodheat.org website for advise on getting more out of your current wood stove.

As for your quedtion. There may be other mass heaters, but the only other one's I've looked at are at
www.mha-net.org

They have some really nice units. Some with ovens too.


Keith.


My Lopi has a single baffle for reburn with a bypass damper. Once the stove is fired up and running to temp (around 600*F to 750*f) there is no smoke, only way you know it's burning is by the heat waves coming out of it. I heat a 1500 square feet house with it with about 14 face cord a year. Not terrible as far as wood stoves go but I like to see where I can conserve and still maintain comfort.
 
Glenn Herbert
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Location: Upstate NY, zone 5
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That would depend on the ISA (internal surface area) of the bell(s) and the specific characteristics of the system. Peter van den Berg says that a batch box needs a good chimney, and presumably a somewhat higher temperature than a J-tube. That said, it is not a universal that the exhaust gases reach dewpoint, and doing so may create major problems with draft in some situations. The "emergency quick & small batch box for wofati 0.7" at wheaton labs encountered crippling issues with this.
http://www.permies.com/t/41202/rocket-stoves/Emergency-quick-small-batchbox-sq
 
Richard Wood
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Location: East coast USA
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no insulation, Kiln brick.

Sent you a pm Jimmy,

Double door, helps, but still needs upper smoke bypass. Water tank getting added soon, to transfer to radiators in house.
 
Jimmy Smith
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Richard Wood wrote:



no insulation, Kiln brick.

Sent you a pm Jimmy,

Double door, helps, but still needs upper smoke bypass. Water tank getting added soon, to transfer to radiators in house.


That's a cool idea. Your message hasn't come through, I'll check again.
 
Jimmy Smith
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Working on a design right now for a MH. So far I have figured a 3'x6'x6'H. I'll have an 18" hearth on the bottom about a foot off of the floor and supported all the way down to concrete in my crawl space. Now I have to figure the proper internal measurements. The plan is to shoot the flames strait up and split the exhaust above the white oven and send the exhaust downward, under the firebox and then up and out. Here's where the theory of which style burner will come in. I should have enough head space to create a rocket affect if I take the "tee" for the exhaust to the top of the backside of the white oven. It still wouldn't be a true rocket but should have enough turbulence if I make the passage leaving the burn chamber round to still burn off most of the flue gases before they leave the first passage of the heater.
 
Glenn Herbert
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Location: Upstate NY, zone 5
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If you just take your plan and make the firebox to Peter Berg's batch box dimensions, and the flue behind & above it to his heat riser dimensions, all insulated for heat concentration, you will have the efficiency of a RMH which you can load, start, and leave alone for an hour while it burns completely. Then just reload for another batch if the weather forecast warrants.
 
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