Gábor Kertész wrote:On another note: I have a concrete foundation for the RMH. Is it enough if I place firebricks only under the core? Should I cover the entire foundation with some sort of bricks, or can the bell floor be the concrete?
Gábor Kertész wrote:Remembering Peter's earlier advice about the floor levels I've got the feeling that this could distract gas flow between the first bell (floor mostly filled by the core base) and the bench bell.
Gábor Kertész wrote:And yet another: I need to bridge the bell above the oven. I can by a 1000x250x60 (mm) brick bridge element rated to 700 °C. It would sit about 60 cm-s below the top of the riser and 2 cm-s above the oven. Would that suffice?
Randy Butler wrote:For the last two summers, we have been living with a small (Little Moe All Nighter) woodstove - in the cellar.
No where near big enough to heat the upstairs, but with 13" thick ICF cellar walls, nearly all the heat hangs under the wooden floor.
Not exactly a "radiant heat" floor, but it did make the place very livable. So heating the unoccupied area is not a "make or break" deal.
Randy Butler wrote:The open space in the main living space is largely kitchen and living room. And the bell will emerge between the two.
BUT - I need to keep the height below 4 feet, or the brickwork will eliminate the line of sight between the areas (wife says "no").
So while I can make a wider bell, or add a bench seat for more radiant exposure, I am limited on elevation.
Randy Butler wrote:On the 7 vs 8 inch device, can I not run an RMH at less than full load capacity?
Is it less efficient, or just more costly to build the larger size?
I have plenty of K26 Insulating Fire Brick, and so far, nearly all the red brick has been free for the taking.
What is the disadvantage of having a larger heater?
Randy Butler wrote:The site for the heater is an old cottage, 1.5 story, very little insulation, about 1200sf and open to cathedral ceiling.
I have no plans for winter usage (pipes are drained and the place is unoccupied during the cold spell), but I
do want to extend from mere summer use to three seasons.
Randy Butler wrote:The design has the firebox in the cellar with the bell extending through the floor and up into the center of the open space living area.
It allows me to have the actual firebox at a very comfortable loading level, and keep the bark and wood chips mess out of the travelled path.
I will be burning 80 to 90% red spruce - that's what grows all around us, so I figured that an 8 (which seems to have anecdotal evidence to be
the best behaved and most forgiving) would be my best bet.
Gábor Kertész wrote:That actually was my main question. I will keep the two chamber on the same floor then.
If I have to make a call however between an undersized chimney, an oversized ISA and a somewhat undersized CSA in the bench, would I still be best to go with the tighter bench? Or should I keep looking for another solution?
Gábor Kertész wrote:I'd also like to understand the physics of placing the oven. Would it be too cold further away from the firebox? Would it's top be too hot, being closer to the top of the bell, while it's floor not enough? I understand that for one the firebox itself is very hot, and two that in the bell the hotter gases are higher up.
Gábor Kertész wrote:Also: are 4 cm thick firebricks sufficient for the firebox, and can I cast a clay bonded perlite riser for it? I'm a bit more hesitant to try my hand at cutting firebricks than at casting. I would also use as little rock wool (or alternative, as with the 5-minute riser) as possible.
Gábor Kertész wrote:Should the 1:5 rule be adhered to in general however? If I lower the bench with about 10 cm from the level of the first bell I get that ratio, but I also exceed the recommended total ISA with at least 0,5 m2.
Gábor Kertész wrote:I also just looked it up: the yurt that we bought was (is) until now heated with a 3,5 kW output split air conditioner. That would indeed be in the range of an 8" batch with 2 fires per day.
Can 2 fires follow each other if the mass is sufficient, or do they have to be apart in time? (I have since found the term "double fire" on Peter's site, which I presume is exactly this.)
Gábor Kertész wrote:Edit| For the wood load above: there was a decimal error, I calculated about 0,054 cubic meters. Stills comes out to just above 4 cords per winter (averaging 20 °C delta T). It seems a tad too much, but that could be my lack of experience speaking.