Masonry heaters....

[tsodak]

Evening all,


I am wonderin if any of you have any knowledge of or experiance with Masonry Heaters, aka Russian or Finnish heaters.

I have been reading about them for years, and have been able to find many answers  to many questions. But one has come up that is really giving me a headache, and I thought someone else might have some insight if I could bounce it off there heads.

These heaters use small fireboxes often found in series to gasify wood and burn with very high efficiency. The exhaust gases are then routed through the large mass of masonry in a downward direction (they are also known as contraflow heaters). It is this long path through the masonry before going to the flue in conjunction with the hot fire that gives such high efficiency. It appears that generally these are formed on a slab with an ash cleanout below.

My home is a two story ranch on a walkout basement. Our main living area is on the upper floor, with utilities, storage, kids rooms and a small den in the basement. The designs that I have been able to find with the heater on the second floor usually include a simple cement block column with a large concrete pad on the top upon which the heater is constructed. Often the slab is pierced by a hole allowing ashes to be dumped into the block column as a long term dump. When you get to the heater, the firebox sends its gases upwards into a channel which splits and flows downwards almost to the slab then back upwards to exit the top of the structure into the chimney. Sometimes they have long horizontal runs that serve to warm masonry benches or a chamber that works as a stone oven. Before someone asks the question, these firechambers are designed to burn very hot, so little creasote is created, although any channel has access built in for cleaning them.

My question is this. I want the fire upstairs, by my deck doors for easy access and in the living room where we spend our time. But I also want a lot of the heat downstairs. So instead of building on a slab, why could I not build the entire heater two stories high with the firebox in the upstairs, and the contraflow channels running downwards for 15 feet instead of five. This would dramatically lengthen the total lentgh of the heat exchanger, and give me one hell of an efficient heater I would think. I could insulate and isolate the portion penetrating through the floor, and since my floor is made of web trusses instead of I beams I could tie them into the structure as well.


Has anyone seen a design like this, or do you have any thoughts??? I would incorporate a water heating coil in as well..... maybe in the area of floor penetration. That would serve to cool that portion very well, and help keep heat away from the floor.

Thanks in advance for any thoughts,

http://mha-net.org/

Tom

[Don P]

No experience, I've read and dreamed a little bit, we have one heck of a footing under the house  :D. I switched gears and went another direction with ours when I had to get things finished enough for my wifes mom to live with us. She passed away a year ago so I guess I could make a mess again. I'd better build a nice dog house first though. I'd appreciate you taking us along on your's.

For good reason building codes require you header the floor system around the masonry keeping the framing at least 2" off of it.
From my understanding the draft has to be able to overcome the contraflow, which you're tripling, I don't have a clue how to figure the needed stack height. I'll bet there's a stall point in there somewhere where you lose draft if its too efficient. Maybe think along the lines of making the lower drop tuneable  ???
I've thought along the same lines with water, make sure you have some pop offs in the lines, blue steam inside a building is better'n dynamite.

I've got a 30' piece of  6" sch 40 pipe for a flue in a steel stud "chimney" frame covered with durock and plaster now. I've debated wrapping the pipe in a coil of water pipe or trying to figure out some form of series thermocouple to run a light or 2 while the stove is going. When I did the pipe and stud arrangement I left a hole into the crawlspace and a intake near the top inside. The plan was to suck air into the sealed crawlspace plenum from the high intake along the hot steel pipe. The possibilities if the pipe failed and the fan was on have kept me from hooking the fan up  :-\.

[tsodak]

Should have said, we thought farenough ahead to put an 18" overthickened portion in the foundation under this spot, sttrengthened with rebar on 6" centers.

I would have some concerns cooling the pipe on a regular wood stove too much, or on a regular fire place. But from the research I have done, if you can make the fire hot enough, through one of a couple of methods, there should not be much creasote left when she heads up.

I see your point and that is where I am questioning. I see some of these with auxilliary dampers that allow you to vent  right up the pipe until you get the flue warmed up, then shut  it to reoute the flow of gases down and around. Since the lift would be back up the same distance as down and then on out the roof, why would overal draft be affected??

I can imagine the downward leg would be warmer, since it is closer to the fire, so it will want to resist going down a little more than the other side going up. Part of the whole idea is to have a system with no motors of anything, so a draft inducer should be out of the question.  But a good chunk of triple wall going out the top should be more than enough I would think.

Anyone knwo a good source for firebrick???

[TW]

I doubt it will work to have the downdraft flues going into the storey below. Those owens i have seen have never had any downdraft flues going lower than about a half metre below the firebox. Though many things are possible if you can find a mason who is skilled with this kind of work.

There are basicly two kinds of owens with downdraft flues

1 Finnish owens. they are not common in my part of Finland, but further east and north they were and are common. They are hugely big, and built from brick as you mentioned. The bottom may be two by two metres and the owen may be 2.5 to 3 metres high. In the middle of it is a firebox and there are flues going from the firebox to the top and down to the bottom and up again and out to the chimney.  The mortar is always clay mortar because no modern mortar can cope with the movements cased by heat when the huge oven is fired hot. The outside is plastered with clay mortar(clay+sand+water). Once the owen is hot it stays hot all the day, they say. I think the finns call them "uloslämmittävä uuni". In Russia and Estonia there are owens built on the same principle, but theirs are said to be less developed than the Finnish ones.
I have no own experience of theese owens, but i have seen a couple of them.

This type with an open fireplace for cooking is oldfashioned (read outdated) but you get an idea what it is all about.
http://www.kirjastovirma.net/museot/taivalkoski/kokoelmat
A small one
http://restaurointikuvasto.nba.fi/restkuvasto/asp/rakosakuvahaku.asp?kuvaus_id=68
The two pictures to the right at the to of page
http://www.koskipirtti.net/virtuaalimuseo/uunit.html


2 Kakelugn or plåtugn in Swedish, kakluuni or pönttöuuni in finnish.
http://www.tiilirakenne.fi/uunit.html Shows different types of plåtugnar by a maker in Finland. the outer cover of a plåtugn is covered with iron sheets, but the inside is filled with brickwork. the smoke goes up in the middle and down in a flue on each side and back up through one or two flues in the back and out. The fire is on top of a cast iron grating(correct word?) in order to get good draught. A kakelugn is similar in principle, but the outside is made from a special kind of glazed tiles.

Nowadays most houses have central heating around here, but the oldfashioned owens are becoming popular over again as emergency heating, because the cirkulation pumps stop when the power is out.

[olyman]

Nowadays most houses have central heating around here, but the oldfashioned owens are becoming popular over again as emergency heating, because the cirkulation pumps stop when the power is out.
[/quote]  ande that TW--is the whole cruz of the matter--newer heating is nice--till the power goes out--power was out in our town for 23 hrs last year--people were in mourning!!!!!! ;D ;D  we werent---wood furnace in basement--back basement of house full of wood--and ours is set for natural draft for heat--no blower!!!! quiet--and who cares if electric goes off---but did have backup gene in case was off too long--to cool frig and freezer back down--

[isawlogs]

 You should look into making two stoves in to the same cheminy with two flews ....  Would be much more efficient and would give you the opportunity to make a fire either below or abve or both ... 

[Blue Sky]

We have been heating our cathedral style Post and beam addtion with a masonary heater since 2000.  Works fantastically.  Ash works BEST for fuel.  Burn from top down, not the bottom up
                                                 Enchanted Forester