Longest mass run for a mass heater

I am working on plans to build a rocket mass heater for my home. I plan on putting the mass in the crawl space. My question is how long of a mass is effective and at what length does it start to lose it effectiveness.

What size rocket do you anticipate? The larger the rocket, the longer the flue before it runs out of heat.

Not quite sure on the size of the rocket. I would like the mass to be between 45-50' loop. That will run under the largest rooms in the house. The mass loop I have imagined will be from the rocket 19-20' make a 90 degree turn run 5' make a 45 degree turn run 10' bend run 10' to the stack that is already there through the roof. I will try to get a drawing up of my plan as soon as I can.

Well a 12 inch system will go about 100 feet a ten inch about 75 feet and 8 inch about 50 and a six inch about 45 maximum.

Quoted from Ernie.

Duane Camilletti : Yes you can! Though that would certainly be at the maximum for a 6'' system. I do have a few questions about why you would want to?

Starting with getting up to a warm house everyday your 1st task is to decide how you want to portion out your day, usually the decision is whether to have
1 or 2 burns during the day, dividing up the 5 - 8 hours of burn time to cover a 20 -25 hr period.

If there is a mad dash for everyone to get out of the house in the morning, and No one will be home all day, your house will have cooled some by the time
you get home, and start your 1st Fire!, the afternoon/evening fire becomes the single burn of the day, if some one is home during the day every day this
is much simpler to get in some ,most, or all of the days Fuel consumption/storage as heat energy in your Cob Thermal Mass.

I often compare learning to Tend to your Rocket Mass Heater to a Potty training your two year old, 1st you train the parent and then you train the child, The
1st rule is to be there, something that comes naturally to most parents, but something they must learn to be successful ! A 2-yr old off by himself will never
learn to potty train himself, the Adult needs to be in the same room with the child !

It is exactly the same way with a Rocket stove, any attempt to place a Rocket into an out of the way corner, Will result in Constantly missing the signals that
tell you when your RMH needs attention! Just like the Child !

If you bring the RMH into the heart of your home where it can be tended to auto Magically without any Conscious thought as you do other chores or just enjoy
its heat It will be like a Treasured member of the family that you want to spend time with!

Located out of sight and mind, you miss the clues to keep it running smoothly, and Stopping what you were in the middle of, Getting up one more time, to go
tend to 'that wood hungry monster' be comes a Drudges task, and you find excuses to not tend it, as a result it serves you only as well as you serve it!

Wood stoves left untended in remote locations like kids is never a good idea ! Think of your RMH like a well endowed Bank account into which you make
regular deposits of Small Very dry wood and Receive Automatic Disbursements in the form of heat, Warm gentle and relaxing heat, always there to give you a hug!

If your plan provides for you being able to tend to the immediate needs of a co-located RMH -And flow heat thru crawl spaces to warm your floors*, then by all
means comeback here with sketches outlining your plans and your fellow members will help you refine them to extend the comfort zone and the warmth though
-out your house! For the good of the craft ! Big AL !

*for your Rocket mass heater to heat your floors first it has to heat the air within the Crawl Spaces, and then the floors, this means that the interior or exterior
walls of the crawl spaces must be well insulated with No insulation between floor joists, even just carpet will retard heat transfer ! You are heating a lot of non
living space, Tons and tons of mass to eventually receive heat in your living space, it will take some time, days perhaps to charge the whole mass, If you go
away for a week, the whole house will be mostly warm for the first 3 days, and take nearly that long to charge up again when you come home !

This is my first draw up. It is not the complete layout of my house. It is just the rooms affected by the mass. With it now on paper instead of my head I have some changes in mind. But, I would love the input of any who will help.

Allen Lumley: The J tube will be centrally located in the main section of the house. I will pipe the exhaust down to the crawl space. This is a very old house under the siding it still has the original wood siding, and looking in the attic you can still see the wood shake. I want to do as little changes to the interior. Where I will be placing the heater itself is where our current furnace(which has died) is located. I also understand how the heating will work in the crawl space. I was looking into a radiant heat system, but, at $10000 for parts and install it is well out of my range. Plus, there are far too many points for failure that if one thing went bad the whole system would stop producing heat. From what I have read and watched with a mass heater once it is in place it has far fewer points of failure.

Duane Camilletti : By now you should be looking to find Locally sourced materials free or cheep for your build. Traditionally the initial trials are done outdoors or
in unheated spaces where the materials can be laid out to make the several practice fits necessary to get a working unit before you dis-assemble the Rocket
Mass Heater to move it inside for final placement !

Now would be an excellent time to crawl under your house to investigate the Amount of space you will have to work in and to look for obvious problems that must
be solved before committing yourself to final budgeting of time for the build, Any signs of past presence of water must be investigated, and dealt with before any
other actions, both to allow for the best operation of your Thermal mass with minimum heat loss and for the structural integrity of your house and foundation.

This should include looking at the existing insulation and placement, the condition of the sill plates and sill plate pockets, and the tightness of the fit where the sill
plate or logs meet the foundation walls, This is best done with inch by inch inspection of that area being alert to cracks, crevices, insect and rodent tunnels, feeling
for any air exchange, and checking with the smoke from incense sticks,not forgetting to turn out your light at regular intervals to look for tell tale light where
foundation and sill logs no longer fit tight !

As you will be attempting to seal this area up to be able to retain the heat from your Crawl Spaces Thermal Mass Any sign of ground water penetration must be
dealt with first ! While this can be done by the homeowner, A certain amount of knowledge and skills set is needed, most of what you need to know is available on
You Tube!

Here is where I recommend going to rocketstoves.com to Download a PDF Copy $18. of the Brand New 3rd edition of Ianto Evans' Great Book " Rocket Mass Heaters "
With over 100,000 RMHs made world wide, most of them were made following 'The Book' and over 95% of the 1st builds ( That Worked 1 ) were made from
' The Book '. Full disclosure, I do not make a nickel off of recommending this!

This will allow you to come to this Forum and use the same vocabulary to describe and understand parts of,and their shape, size, and orientation toeach other, And
the ratio of height to length to height of the Feed Tube, Burn Tunnel, and Heat Riser, and the need to maintain a Constant Cross Sectional Area, C.C.S.A. for the size
Rocket Mass Heater you decide to go with! This requires no more than 5th grade Math that the book talks you through - When you can explain it to a second party
you know you understand it ! For the Good of the Crafts ! Big AL