Peter Bergs Batch Box Beast

Ok, so I'm all focused on building a J-tube RMH. I've been hungrilly devouring every tidbit I can get about them - videos, books, forums, podcasts, etc. I'm polishing off questions and uncertainties by talking to the experienced folks here. A materials list is being compiled, measurements and layout in my home are examined. I'm SO close to taking the plunge, and BAM ! I get blindsided by the Frankenstein 8" radiant monster that was constructed at the innovators forum.

Now, I'm consumed with studying this thing. I keep looking at the pics, the sketch up files, and listening to the podcast. I want to build this too ! I'm trying to process the nuances of its ratio dimensions, scaling it down to a usable size for my application.

I am replacing my little wood stove in my dining room with an RMH, and want to put a batch box in my basement for providing the rapid heating of its large, open area.

So, Ernie, Erica, Mr. berg, and any of you others who were fortunate enough to witness this 3 barreled, bench feeding weird thing, I have questions ! I need to understand, so I can get back to J-tube RMH's.

Can we talk ?

When looking at sketch up, i thought the burn chamber was constructed just of firebrick with a cylindrical heat riser set on top. These pics lead me to think the heat riser sits on the base of the chamber, with an opening cut to allow the flaming gases to enter the rear chamber and pour upwards. Is that correct ?

On the podcast, Mr. Berg states he is sure a 3rd barrel can be added to the height. Could the height be lower tho ? Like more barrels connected together at floor level as the last barrel is , before connecting to the bench ?

Also on the podcast, there is a discussion regarding calculating how much mass is required to absorb the available BTU's, adjusted for amount used of metal and/or cob. Is the info for calculating these amounts readily available ?

Thanks for any info.

Robert Dearborn wrote:When looking at sketch up, i thought the burn chamber was constructed just of firebrick with a cylindrical heat riser set on top. These pics lead me to think the heat riser sits on the base of the chamber, with an opening cut to allow the flaming gases to enter the rear chamber and pour upwards. Is that correct ?

Yes, that's correct. The riser is behind the firebox with a narrow high access opening between those.

Robert Dearborn wrote:On the podcast, Mr. Berg states he is sure a 3rd barrel can be added to the height. Could the height be lower tho ? Like more barrels connected together at floor level as the last barrel is , before connecting to the bench ?

Yes, that is possible. Prefeably, each barrel would be connected to the next one at floor level. Mark, however, in order to give room to the higher gas velocity the top gap (the space between the riser end and the barrel lid) shouldn't be less than one foot.

Robert Dearborn wrote:Also on the podcast, there is a discussion regarding calculating how much mass is required to absorb the available BTU's, adjusted for amount used of metal and/or cob. Is the info for calculating these amounts readily available ?

No, this isn't or partly only. The maximum internal surface area is the figure to be calculated, not counting the floor of each barrel or, for that matter, whatever space there's over the riser. Due to the work of Klemen in Slovenia we know for a 6" version this would be 6 sq. m. or 64 sq ft when this surface is brick or cob. Metal ISA would be about 5 sq. m. or 53 sq ft. Brick ISA for an 8" version would be 10.6 sq m. or 114 sq ft when upscaling the numbers. When the whole of the internal surface area is metal I guessed that would be about 8.8 sq m. or 95 sq ft. That last figure happend to be almost exactly what the 8" trial set up was able to serve without getting too low exhaust temperatures. I've figured this out at the premises and got away with it much to my relief, phewww!

For all the other dimensions and their scalability, see the link Alexandre Harpin has provided.

this BATCH BOX will not do! I don't have the height either in my main room or better, the basement. the basement is only about six foot high from sand floor to joists.
Access to the chimney is 25 feet away.
the drums in the picture are 44 inches high, two of them is 88 inches. I have 72 to play with - Even still I'd need at ceiling clearance which I don't have using these dimensions.

Thomas Mierzwa wrote:this BATCH BOX will not do! I don't have the height either in my main room or better, the basement. the basement is only about six foot high from sand floor to joists.

This double barrel set up isn't mandatory, you could use 1 1/2 barrel on top of the firebox for example. You need more heat extraction further downstream but that shouldn't pose big problems. As long the top gap between riser and barrel top is at least 1 foot you're alright. Coupled to an excellent chimney you could get away with a shorter riser and just one barrel.

Thomas Mierzwa wrote:this BATCH BOX will not do! I don't have the height either in my main room or better, the basement. the basement is only about six foot high from sand floor to joists.

Would digging down some to recess your barrels partially into the sand help the situation ?

Peter Berg wrote: Coupled to an excellent chimney you could get away with a shorter riser and just one barrel.

What would the ideal chimney's characteristics be ?

Robert Dearborn wrote:What would the ideal chimney's characteristics be ?

Straight up, lowest mass as possible, insulated, round, smooth inside, the same as system size or larger, reaching two feet above the highest point of the roof, no other buildings or high trees in the vicinity, situated inside the insulated enveloppe of the building.