New to rocket stoves. . . . Can I fork the exhaust pipe/thermal mass?

Hi I am developing a design for a rocket mass heater, but have no experience whatsoever. I am wondering if it is possible to "fork" the exhaust pipe and then have them merge again into the main exhaust pipe. In other words, I am essentially looking to have two thermal mass benches. Is this possible?

R.W. Possible ? Yes ! Likely No!!! , Even with carefully balanced identical systems one branch is dominate. You should NEVER create a system where it is possible
to close off MORE THAN ONE branch at a time !

The possibility of closing off more than one Duct at a time raises the possibility of closing both off Both at the same time ! A possible consequence is both being closed
at the same time and killing everybody exposed !

While possible this is a skill set left to the professional builders, and generally not considered safe or worth the practice/energy involved ! Big AL ! Hope this helps
and is timely, For the good of the crowd ! Big AL

Allen, thanks for the reply. I am, however a little confused and am wondering if you can elaborate a little so I might understand the basic principles behind this. What exactly do you mean by "closed off". What I am trying to do is just basically have two exhaust pipes coming from one single combustion chamber into two separate thermal batteries, and then merge into a single exit flue (just making sure I'm being clear here). Neither duct would ever be closed. And by "killing" do you mean a possible explosion? Or exhaust leak? I just need to get straight here so I don't make any horrible design flaws.

Robert Woden : Sorry, That was unclear and unhelpful on my part ! It is possible to have a damper inline in one pipe to pinch off the air flow a little fractional bit at
a time, They are often found As part of the ductwork in Fossil Fuel Fired, Forced-air Furnaces, and put inside ductwork where the ducts run to 'The Spare Room',
Generally the ductwork damper is closed until one 'of the children come to visit and the damper is then opened up so it will be warm back there for the 'little dears'!

As part of a well thought out plan this can be a way to balance different heating/cooling loads during the flow of the seasons !

Done wrong, your end up exchanging cold spots (or too warm spots ) from one place in the building to another !

My point which I seem to have lost in mid thought, was anyone who puts in Two Dampers one in each pipe and creating the possibility of both getting closed at one
time, Has just entered the lottery to suicide and decrease the Gene Pool ! Because the Rocket Mass Heater must run as an open system OR backdraft, Carbon
Monoxide would be your gift for yourself with any system with dampers, if it can get closed it will get closed, Sorry' I will be amazed if you get any support for
your plan !


If you get anyone who wants to encourage you in this idea, ask them if they have ever seen a single example, I only know of one example of a successful twin
exhaust type and it isn't possible to make your system compatible !

For the good of the Craft ! Big Al!

Late note : It might be possible to install a gee whizz electrical gadget to monitor and run two separate infinitely variable speed fans, one to a pipe, such a custom
piece of equipment would Start at ~$5,000 ~require Electricity 24 / 7 thru out your heating season, and make your ability to use your RMH during a winter power
outage unlikely ! A.L.

Robert Woden : From The Rocket stoves Forum You can Select The listing of all the Rocket stove Forum Threads, new ones at the top. Scroll down to, and
Clickon>

''video : great rocket mass heaters in upstate New York and Quebec ''. It is the 1st video I want you to look at !

This is only one example of what can be done without forking your exhaust path and has been in basically trouble free service for 2 heating seasons over 16
months, this video has made about ~5-6~ months after the Build as part of a Sustainable Living Project / Workshop taught by Ernie and Erica Wisner, the
Moderators here at the Rocket and Wood Stoves forums !

This SHOULD put a more positive spin on things ! For the Good of the Craft ! Big AL

Allen, you definetely cleared up a lot and I really appreciate your guidance. However I still feel like I maybe haven't explained what I'm looking to do well enough. Here's a little paint pic I whipped up. My system would be entirely open, no dampers, nothing but open duct work. It would also be built only for one room/one space ( you can get somehwhat of an idea of its scale by comparing the size of the combustion chamber with the duct work in the pic).

The duct work would be placed in-floor. The idea behind the forking was to surround a small seating area in the center.

My question concerns what happens to the exhaust path/heat distribution in this situation?

Robert Woden : O. K. why the difference in the size of the ductwork, it is an unnecessary complication If you can design a system that has nearly everything the
same one section of ducting will always assume domination, and i doubt there are 10 people in the United states who could tell you which one before Hand, After
they all could give you 4 reasons why !

If I were going to attempt something like this I would probably run each identical leg with 6'' pipe and combine the final part as an *'' but This is something I would
never attempt !

On Top of this you want to bury it in the floor. the floor of what ? It is one of those simple rules that for your first Rocket Mass Heater, you go as conventional as
you are able with the materials you have on hand ! Again you have picked a build that is mostly an unnecessary complication that most instructors who teach at
Rocket Mass HeaterRMH workshops have never even attempted ! This is also a very complicated build made even more complicated by site-ing!

I feel tired thinking about the endless ways these two modifications to a simple D.I.Y. project that any one can do, can create problems almost impossible to
diagnose without tearing the system apart !

Here is where I discuss the ideal working relationship between you and your Rocket Mass Heater! Your RMH should be a piece of hand sculpted fine built- in-
-furniture located in the very heart of your home, some thing to be enjoyed and watched by the whole family, something to be passed down through the
generations, never more than an easy arm reach away but easily tended to, with barely a conscious thought, like having an old friend of the family in the room
good company!

It should never be hidden out of site where every stick of wood you feed it becomes an endless drudges task,a chore that you quickly find reasons to ignore or
skip, serving you as well as you serve it !

As a faithful servant close to your elbow and easy to command it will be like a Well Endowed Bank Account, into which you add regular deposits of very dry small
split wood and Receive Regular, timely withdrawals in the form of relaxing, comforting, Gentle, Bone Warming, Heat !

If you can look deep in your soul and swear that it is your intention to welcome your own fine crafted pice of treasured family ART, and not just expect it to work
like a rented mule with little or no input from you. Then we can Talk about how to get ready to build the rocket burner outside, test that for its performance,
giving it small tweaks if necessary And combining to make a working plan to welcome your own RMH into the heart of your home ! (which is what the word Hearth
originally meant, not just an architects term ! )


Come back here often, if there is a rocket stove in your future we will help you find it ! BIG AL !

Robert, can you do it like this?