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Rocket mass heater capacity

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Hi everyone!
I'm very new to RMH and I feel that I'm about to ask silly questions, but I'd rather sound silly than never know the answer!
So we're very interested in RMH in a project where we would have to heat several rooms (3-4), and we were wondering if it's realistic, and how the design should perhaps be changed. The idea would be to build the stove in a central room, and heat 2 or 3 rooms aligned around it. So we also wonder if it is possible to have two "exhaust" pipes (or one that would divide in two after) going in opposite directions, with two different evacuations ?
And also how the size of the fuel feed, burn tunnel, heat riser etc would be impacted. I've read that 8" were a pretty common size, but I guess it would be better to make it larger if one wants to have a longer heat exchange mass ?
Thank you very much for any feedback you could give!!
Posts: 3124
Location: Upstate NY, zone 5
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I think your goal is quite realistic, though the details you proposed are problematic.

First, do you actually live in or near Buenos Aires? The 8" RMH system is generally recommended for heating a whole average house in a moderately cold climate, and the BA climate which seldom gets below freezing would be easy to handle. With several rooms to heat, I would not go to a smaller system, though. An 8" RMH is said to be able to support up to 50'/15m of horizontal duct, minus 5'/1.5m per 90 degree elbow. With four elbows, you could only have 30'/9m of duct.

Splitting the exhaust to go in two directions with two chimneys has never been demonstrated to work that I know of, and would require skillful balancing if it would work. It is possible to have two or more alternate routes for the exhaust which come back together and feed one chimney, but again this requires skillful balancing. It would be easier and probably better to have the duct make a loop through the rooms and come back near the feed, then go up the chimney. This is if the rooms are so separated that radiant heat from one area cannot warm the rest. What can work well if you are building new, or can rebuild walls, is to have the mass in a shared wall that heats two or more rooms.

More details of your situation, with plan drawings or sketches if possible, will help us give the best answers.
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