The 3rd question is for Peter or who ever else knows. What mortar was used for the fire bricks on the inside wall of the bell heater posted on 4-25? Can I make my own high temp. mortar cheaper using our local Lincoln 60 fire clay as one of the ingredients and if so I need a proven recipe?
If I had seen this design when building my hybrid horizontal water tank bell heater I would have used this simpler method instead. Nice clean design -. no tanks, no cob, small footprint, looks good,
Alan Mikoleit wrote:What mortar was used for the fire bricks on the inside wall of the bell heater posted on 4-25? Can I make my own high temp. mortar cheaper using our local Lincoln 60 fire clay as one of the ingredients and if so I need a proven recipe?
The mortar consisted of clay and sand, bagged and brought to the place. The whole of the heater was in fact built with that because after the workshop all the heaters built there were tore down.
Best way to build with clay mortar: thin joints just to keep the bricks apart. When built with a cement-based hi-temp mortar it's possible to stick the bricks together but they will expand and contract, causing cracks. Clay mortar is much more flexible and the cracks are very thin then, all over the place. Please note: in this bell design cracks are very sparse.
Lincoln 60 fire clay is excellent for this application, use it with fine sand 1:1 and try how it feels. I don't know this particular type of fire clay but it's always possible to vary with proportions to find out best.
My best guess is you will need to subcontract a master mason ( vetted, bonded, etc ) to do the firebox-critical work. Sell it to the insurance company as a Masonry Heater ( which in my opinion it is, provided you are making a batch-style, as per Peter's design ) and start researching them, perhaps beginning with ASTM-E1602-03 (reapproved 2010; Standard Guide for Construction of Solid Fuel Burning Masonry Heaters) a document with which I believe we should all be familiar anyway.
Then with drawings in hand, you may be able to find an architect or engineer who will sign off on a more suitable footing design for a modification based upon more typical RMH arrangements, which as we know have a much larger footprint than most masonry heaters ( less weight per square foot; smaller footer to be poured )
You can then either do the non-firebox work yourself or subcontract that too.
Bottom line as I expect it to boil down to is who/how is the exposed neck of the insurance company going to be covered? Stamped plans, based upon ASTM standards and safe building practices of the masonry heater trade will be the first step. Then the build being done by a professional mason with lots of experience is the second step. If you are lucky, you may be able to get away with passing a fire-safely inspection, if your county has such a thing, and is any good at doing them.
This area of county inspection and getting insured is a sticking point right now. Not many have done it. Do look up the thread(s) in which the Wisner's discuss their efforts at getting a permitted build done in WA (Seattle? Portland? I forget where). And please post back if you clear these hurtles successfully!
1. Permitting and/or county inspection is one hurtle.
2. Getting insured in another.
3. Building it is another.
Start with a safe design, sold as a type of masonry heater. Don't use new vocabulary. The thing has tons of mass, it burns wood, and with minimal modification, I cannot imagine why it cannot be a type of masonry heater. After all, isn't a batch-style RMH really just a subset of masonry heater? If it is not, why not?
Perhaps because we tend not to like outside fresh air intake? Then build one of those into the system. What else? Because many prefer cob over brick? Then build the core in brick and just use the cob as a heat/fire-safe exterior finish treatment. What else?
Glenn Herbert wrote:I think that the critical distinguishing feature between a masonry heater and a RMH is the firebox. If it has a J-tube or batch box with a verticalish heat riser, it qualifies as a RMH. It's the combustion zone that is the unique factor. The way the heat gets into the mass is interchangeable. And some RMHs could be considered as a subset of masonry heaters (ones built largely of cob with horizontal bench mass might be disavowed by the masonry heater trade.)
You may or may not be correct in these definitions, however if speaking to an insurance company or a permitting/inspection agency for the government, keeping as close to the age-old technology is the safest bet, and I feel confident the better chance of obtaining the results one wishes (insurance, getting permitted/passing county inspection, etc). That was my main point.
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