First Rocket Mass Heater Going In My Basement

allen lumley wrote:Again Buy the best brick you can afford, though there is little reason to go above 2000dF !

matthew boersma wrote:i chose to not stack the bells, but to rather lay them out in series horizontally along the floor. i feel this will be better for my floors weight handling ability as i stack the bricks up. although i will probably still reinforce my floor with support jacks anyway just to be on the safe side. my basic plans in mind are having the total dimensions be around 30"x 60" giver or take a few. let me know if this design makes sense to anyone with experience.

Peter Berg wrote:For a given space to act like a bell, the inlet and outlet should be at floor level. Directly behind the inlet there should be enough room to slow the gases down nearly to a standstill in order to allow the forces of gravity do their thing. In effect, the hot gases will rise almost immediatly behind the inlet, thereby pushing other gases out. Since the exit opening is also at floor level, the cooler gases would be pushed out. Don't make it complicated, just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.

allen lumley wrote:Think like Fire, flow like a Gas, Don't be a Marshmallow, As Always, your questions and comments are Solicited and Welcome ! Big AL

matthew boersma wrote:i think/hope this is what are saying i should do?

Erica Wisner wrote:As to the 3" or 4" marked on the manifold part of the diagram:
If you are connecting a barrel to exhaust ducting, and you have less than 3" gap between the barrel and the heat riser where the exhaust duct joins in, then there will be a flow constriction at that point. In general I want a gap that is about 1/2 the diameter of the exhaust ducting at that point, on the assumption that the main flow of gas has to pass through the top of this gap into the duct, and there will be some turbulence there. This minimum gap can be tricky to achieve when making the manifold out of the same standard 55-gallon drum, so I point out the possible constriction in our diagrams. The reason we allow 3" instead of 4" is that it has worked for certain projects - for an 8" diameter system, 4" would be the theoretical minimum, but 3" has sometimes worked out OK in practice (especially if the gases can flow down around more than half of the opening and enter from the lower sides).

Under the barrel where Allen mentioned, above the heat riser, the exhaust is free to flow away from the heat riser in all directions. So the minimum is about 1/4 of the diameter or 2". If your heat riser has a big flat top where fly ash can build up like snow, allowing more space in this area may be wise.

If you don't use a metal drum at the base for the manifold, but instead build the hollow base out of masonry, then it's much easier to build adequate flow space. It's also easy to constrict it too much, however. Bears attention.

My biggest concern with the plan as originally described would be the damp factor in the basement. Basements can be large, poorly-insulated spaces, and putting the heater in the basement commits you to effectively increasing the size of building you are heating. Having the heater in the occupied spaces gives you much better return for the investment, in terms of long-term fuel efficiency and achievable comfort.

I would look at bringing a cinderblock, brick, or concrete footing up from the basement floor, and cutting and re-framing a hole in the floor with a 2" gap on all sides to allow the masonry heater up into the main room. This will make feeding it more convenient, improve your draft situation, and get better effectiveness and efficiency from your fuel.
(You can insulate that 2" gap with non-combustible insulation, such as Roxul or mineral wool. It is important as it allows for the different types of movement in a building without the wood and masonry trying to tear each other apart, as well as reducing heat transmission that might over-heat the wood. At the base I'm not terribly concerned about the heat problem, but around the firebox you definitely want masonry-heater type clearances, at least 8" thickness of masonry plus 4" air gap to combustibles.)

Peter Berg wrote:

matthew boersma wrote:just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.

your talking about total volume of the bell space not a certain dimension worth mentioning are you? i have already noted that all the inlet/outlets need to be the same size as the last exhaust point.

-matt

Peter Berg wrote:

matthew boersma wrote:just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.

your talking about total volume of the bell space not a certain dimension worth mentioning are you? i have already noted that all the inlet/outlets need to be the same size as the last exhaust point.

Peter Berg wrote:

Peter Berg wrote:

matthew boersma wrote:just remember the ratio of inlet opening and bell space should be at least 1 to 4, the more the better.

your talking about total volume of the bell space not a certain dimension worth mentioning are you? i have already noted that all the inlet/outlets need to be the same size as the last exhaust point.

This is not about the total volume of the bell, of course. To make matters clear: immediatly behind the inlet opening into the bell there should be a sudden widening in the horizontal plane at the same height as the inlet, not counting the space above (or under) it. This widening will slow down the velocity of the stream, so the hotter and lighter gases are allowed to rise.

The space above the inlet is where those lighter gases can go. Hope this is clear.

Peter Berg wrote:My understanding of the English language is too limited, I"m afraid. But I'll try again.

Your side view is more or less correct when applied to coupled bells. However, the inlet of the first bell and the exhaust of the second bell need to be smaller as compared to the cross section srea of the bell floor. Normally, the chimney is the same as system size so both of these holes would be system size as well.

Try to see it like this: picture a 55 gallon barrel with two holes in it of 6" for example. Both these holes are at floor level opposite of each other. This is how a simple bell should look like. When the holes are beside each other there could be a shortcut effect, so in that case one would place the inlet opening a little higher.

Byron Campbell wrote:You may find the following of value, a ton of photos of a complete masonry rocket style all brick stove constructed from the ground up:

http://www.mha-net.org/docs/v8n2/wildac12g.htm

Erica Wisner wrote:If you don't use a metal drum at the base for the manifold, but instead build the hollow base out of masonry, then it's much easier to build adequate flow space. It's also easy to constrict it too much, however. Bears attention.
Erica W

Satamax Antone wrote:Barrel wise, there's other options, like square barrels

http://donkey32.proboards.com/thread/1017/pure-genius

The idea is, that you can stack bricks around and leave some bare metal, so you have a mixture of quick heat and accumulation. In the second example there, the plan is to use the home heating oil tank, as a flat bell and cover it with mass. That saves me from thinking about loosy massonry joints.

HTH.

Max.

Satamax Antone wrote:Matthew, i'd say i'm no expert.

But the downdraft can be skipped. I'm not even that sure it contributes much to the rocket draft.

For example, when you have a free standing J tube in the backyard for testing purposes, with no barrel, it draws real well. Then you plonk a barrel on top, and trouble arises, up to the point that you need, more often than not; to put a chimney on this system to make it work.

To me a barrel is an excelent radiator to shed heat quickly into one room.


Which brings us to he next question, if you don't shed heat quickly, what will happen?


Well, in your case, since you have raised the question about normal mortar. If your exhaust gases are hotter than 200C° out of the first bell, you won't be abble to use a mortar based on cement, or your joints will start spalling.

HTH.

Max.

Byron Campbell wrote:For masonry heater hardware, a quick Google of "masonry heater bake oven doors" will bring up lots of links. Be sure you're comfortably seated before viewing prices! Here's one source I was looking over a while back when contemplating a masonry heater construction project:

https://mainewoodheat.com/shop-maine-wood-heat/bake-oven-doors/