Hi,, i'm wanting to use rmh's in a couple of simi dugouts in the mountins and the largest is 12x16 inside,,i want to use with a bench but think the 6 in i have plans for is way to much for them,,does anyone know of a rmh with bench system useing 4 or 5 in pipe insted of 6 and for a smaller dwelling ?? thanks for any info.. Ed
I don't see why you couldn't make a bench for a 4-inch system it may have to be a smaller bench you could get away with a larger one but you would need an assist fan and it would take a very long time to warm up the bench
Ed, you don't say whether it is a J-tube or batch box you have plans for, but my feeling is that it is a J-tube. 6" is about the smallest size that is likely to be highly reliable when built by a first-time builder. Smaller sizes are inherently less efficient as it is harder to get the concentrated heat and dwell time that drives a complete burn. As long as you can fit the system in your space, a 6" J-tube can just be run as often as you need to keep the space comfortable. You would probably want to minimize the exposed barrel so as not to overpower the space with instant heat.
A batch box is a different kind of combustion core, and is what Aki gave numbers for. That can be scaled down quite small and still be effective. It is a more technical style of core and requires closely following the specs to work well. Lots of info at http://batchrocket.eu/en/
So we need more information on how you expect to use these systems before we can give the best advice.