Do European soapstone stoves really function as masonry heaters? I.E. SCAN and RAIS

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MountainStoveGuy

MountainStoveGuy

Minister of Fire
Hearth Supporter
Jan 23, 2006
3,665
Boulder County
I almost hijacked a thread, i decied to post it in a new topic instead.

I wonder how well the soapstone stoves by scan hold heat. Like the KOJO for expample. You have a woodburning insert sitting in a soapstone shell. There is a air space between the forebox and the stone for convection, and you also have a schmoll lining in the insert, ( a very reflective vermiculite type of firebrick). SO the heat has to penetrate the schmoll, then the airspace, then get into the stone. Not to mention that all those tall stoves are designed as convection heaters. My scan rep back in the day once told me that the soapstone on most euro heaters is decrative, and that you have to have a direct contact appliance like tulikivi of hearthstone to realy have a true masonry heater. Im not shure if i belive him, but it almost makes sense. Any one agree or disagree?
 
My two cents, I do not believe they are alike.

Masonry heaters are designed to handle enormous amounts of heat, as masonry can whereas metal stoves/inserts can't handle repeated amounts without being damaged. That's one of the reasons an insert/stove has less burn efficiencies than a masonry heater. Masonry heaters also run the exhaust through channels, and you should have all the rooms in your house share a wall with the masonry heater. Depending on what you make your masonry heater from, will determine how fast it releases its stored heat. Pulling numbers out of nowhere just to make a point, a brick masonry heater releases heat slow, soapstone fastest. Brick masonry heater will absorb say 80,000 btu's from a fire and spread the heat over 24 hours. A soapstone masonry heater, will absorb the same 80,000 btu's of heat but it releases the heat fast and will release it over 12 hours. In the end, same amount of heat was absorb and released but one spreads it out longer than the other, the other gives one more control over how fast it takes to heat a place up.

I'm a little unsure of how well an insert surrounded by a soapstone shell can work. You couldn't burn it at the burn efficiencies of a full masonry product, and I would feel the soapstone above would leach heat into the flue and it wasted. I would imagine a soapstone stove would operate closer to a masonry heater over an insert with a soapstone convection shroud. My insert is soapstone, but rather the reverse situation. My insert is soapstone surrounded by cast iron, which is surrounded by steel, which is placed in a brick fireplace. I would rather the soapstone on the inside to protect the metal of my insert from getting too hot and warping, but this brick you mention on the inside of them may do similar. Even with soapstone protecting the inside and stainless on top, I can't burn my soapstone insert at the same temperatures of masonry heaters, so I can't get the same burn efficiencies. Hmm... neither can soapstone stoves, so I'd assume neither can this insert. I guess it would depend on how hot the fire can be inside without damaging it and can it handle repeated fires at extreme temperatures. I'm not an expert on the topioc to be sure though. Is it possible for you to post a link so we can see what you're referring to? I've not been able to find anything.
 
I agree with dylan i've had serious questions about the supposed incredible efficiencies of these masonry heaters, i've even looked over some of the designs that i could find on the internet, and looked at the materials, and having a background that allows me the knowlege to be a decent judge of reality when dealing with things combustion and masonry related, i've become fairly skeptical of many claims by this industry.
 
I dont have a link, sorry. i just look at them everday, i see these tall euro stoves made out of steel with soapstone sides and tops. I would be willing to bet that the soapstone sides are lukewarm to the touch. Like i said before, you have a firebox, a very reflective liner in the firebox, a large airspace, then stone. I like the responces here. They make sense. Now to there defense, RAIS and SCAN do not claim that they have masonry heaters. But the KOJO shure looks like it should be. And it isnt.
 
I don't think they function like masonry heaters... although I am also part of that camp that believes the whole masonry heater concept is somewhat suspicious, for reasons mentioned above.
I think the Scan Kojo would probably act like a large Hearthstone... heat up a bunch of stone and it radiates heat out over time, big deal, where's the rocket science in that? Its just a stove in a big piece of rock. Hell, my Jotul heats up my 8' wide granite fireplace surround, and that thing radiates heat after the insert has cooled down...again, no miracle there, its expected.

Here's a link to the Kojo:
(broken link removed to http://www.fireplaceproducts.com/site1/Fswood/Scan/kojo_soapstone_freestanding.htm)

By the way, didn't Jotul just purchase Scan?

-- Mike
 
Gentlemen, gentlemen:

Comparing a woodburning metal stove having some masonry (soapstone or other) panels and a masonry heater is not comparing apples-to-apples. They are very different.

The major difference involves understanding the concept of "thermal mass" heating. Masonry heaters are thermal mass (storage) heaters. Woodburning stoves are not. It is this significant weight (mass) of masonry that determines, along with the temperature of the mass achieved by the burned fuel load, the amount of heat that can be stored by a true masonry heater (definitions below) and then slowly released into the room. The addition of masonry panels on a metal stove help delay the heat loss a little.

Another major difference in the two heaters is the fire. Masonry heaters have the technology to be able to burn wood at high enough temperatures (1800* - 2000* F) to allow quite complete and clean combustion of wood and simultaneously store the heat in the body of the stove for "long term dissipation". The masonry heater is designed to burn a "load" of wood without baffeling down the incoming air, and then go out. Again, these are major differences with woodburning metal stoves which would be severely damaged by so firing.

The Standard Guide for Construction of Solid Fuel Burning Masonry Heaters ASTM E   1602-94, published by the American Society for Testing and Materials, gives the following definition:

 Section 3.2.14 – masonry heater – a vented heating system of predominantly masonry construction having a mass of at least 800 kg (1760 lbs), excluding the chimney and masonry heater base. In particular a masonry heater designed specifically to capture and store a substantial portion of the heat energy from a charge of solid fuel mixed with a adequate amount of air to burn rapidly and more completely at high temperatures in order to reduce emission of unburned hydrocarbons; and be constructed of sufficient mass and surface area such that under normal operating conditions, the external surface temperature of the masonry heater (except the region immediately surrounding the fuel loading door(s), does not exceed 110°C (230°F).

As far as emissions are concerned, to meet the EPA requirements a masonry heater must conform to the following:

1. A masonry heater is a solid fuelled heating system of predominantly masonry construction having a mass of at least 800 kg (1760 lb) (excluding chimney and foundation), and having an overall average wall thickness of not more than 250 mm (10 in.). It achieves heat storage by the routing of exhaust gases through internal heat exchange channels in which the flow path downstream of the firebox includes at least one 180 degree change in flow direction, usually downward, before entering the chimney. The shortest distance between the firebox exit and chimney entrance is not less than twice the largest firebox dimension. It is equipped with doors that are intended to be in the closed position during the burn cycle. Its combustion air supply system is configured to produce a burn rate greater than five kilograms of fuel per hour. The chimney has a maximum flue size of 8 in. x 12 in. (200 mm x 300 mm) nominal rectangular dimensions, or 8 in. (200 mm) round.

2. The masonry heater is constructed by a person who holds a valid certificate of qualification issued by the Masonry Heater Association of North America, or the holder of such a certificate verifies in writing that the heater complies in all respects with item 1. above. Proposed language is for the acceptance of masonry heaters in sensitive airsheds.

Comparision on Masonry Heaters with Other Woodburning Appliances

1998 “Best Professional Judgement” Emission Rates (EPA-600/R-98-174a):

Appliance type Smoke g/kg
Conventional fireplace 17.3
Conventional Stove 18.5
EPA certified non-catalytic stove 6.0
EPA certified catalytic stove 6.2
Masonry heater 3.0

References
1. J.E.Houck and P.E.Tiegs Residential Wood Combustion Technology Review, Volume 1. Technical Report, EPA-600/R-98-174a, December 1998. http://mha-net.org/docs/rwc01.PDF

2. R. Jaasma, J. W. Shelton and C. H. Stern, Final Report on Masonry Heater Emissions Test Method Development, Wood Heating Alliance, Washington, 1990

3. www.vermontwoodstove.com/planning

4. Oregon, Interpretive Ruling No. 93-47, Masonry Heater Radiant Heating Systems (rev 05/01/00, ed. only)

Aye,
Marty
 
Would you agree that the kojo looks like a masonry heater? im not confused on what is and what isnt, i just think the marketing of these companies is questionable.
 

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Guys:

Instead of throwing dirt or clay balls at each other, read this from the Masonry Heater Association website:

"Other Refractories:
Soapstone is a unique refractory and masonry material. Compared to a pound of concrete, a pound of soapstone can store approximately 20% more heat. Its main distinctive thermal property is that it has about 4 times the conductivity of concrete or about 6 times the conductivity of soft clay brick. Another way of saying this is that its R value is 1/4 that of concrete. It is somewhat similar to a metal in this respect. This means that a soapstone heater of equivalent mass will heat up faster on the outside surface and reach a higher surface temperature, due to the high conductivity. On the other hand, the higher rate of heat transfer to the room also means that it cools down faster than other masonry materials."

Aye,
Marty
 
MSG:

Your kojo is a joko if you think it is at all similiar to a masonry heater.

It doesn't look like it weighs anywhere near the minimum 1750 lbs. Nor does it look like the shortest distance between the firebox exit and chimney entrance is at least or more than than twice the largest firebox dimension. And I doubt it can burn wood with air wide open throughout the burn and produce a burn rate of greater than 5 Kgs of fuel per hour.

No. This is a metal stove with some masonry facade. It clearly is not a masonry heater.

Aye,
Marty
 
Its not my Kojo, i agree its a joko, when i did handle scan, i can guarentee it weighs every bit of its stated weight. I was using this as a example. If you read my initial post. You will see that we agree.
 
MSG:

You said:
My scan rep back in the day once told me that the soapstone on most euro heaters is decrative, and that you have to have a direct contact appliance like tulikivi of hearthstone to realy have a true masonry heater. Im not shure if i belive him, but it almost makes sense. Any one agree or disagree?
Click to expand...

I'm not sure what you mean by "direct contact appliance" (flame contacts masonry?) but I do understand what "I'm not shure", "almost makes sense" and "Anyone agree" means. I do not agree (like Dylan, almost catagorically). There are more considerations than whether or not an appliance has "direct contact" features to qualify it to be a true masonry heater.

Actually, internally masonry heaters do have a small space created for expansion of the very hot core in the firebox and flame path channels vs the facade so as to eliminate, or minimize, cracking of the facade. However, this space is not intended to be for convection heat to the room.

Aye,
Marty
 
Dylan said:
MountainStoveGuy said:
Would you agree that the kojo looks like a masonry heater? im not confused on what is and what isnt, i just think the marketing of these companies is questionable.
Click to expand...


What's a kojo cost, BTW??
Click to expand...

bout 6500.00

Small Tulikivi territory. (I'm sure install of a Tulikivi is more, but if you have 6500 to spend on a wood stove, what the hay)
 
Interesting. I had assumed the Scan products were contra-flow designs, like most of the Tulikivi products. Looking at the drawings, I see they are not.

( (broken link removed) )

I also note that Tulikivi is now making what appear to be 'stoves' similar to the Scan products. They must be trying to reach the consumer with a normal income that just wants something that burns wood and is pretty, rather than their traditional audience that must surely be wood worshipers with fairly deep pockets.

( (broken link removed to http://tinyurl.com/khc4n) )

The Scan stove seems more closely related to the Austrian and German tile (and other) stoves. Many of those have metal fireboxes with surrounding thermal mass of various materials, usually including ceramic tiles on the exterior. But those are usually much larger and custom built on site with the living quarters designed around the stove. My brother-in-law had a tile stove in Austria. It was very interesting. I was never sure if it was burning or not, but I never seemed to feel very cold in that room. If I can ever dig up the photo and get the scanner working, I'll post it.
 
Thanks for the link Marty.

Why is everyone standing so far back? They look nervous.

That stove appears to have a single offset baffle with no side vertical baffle channels redirecting the smoke downwards. It looks like a very simple design. I would assume it isn't nearly as efficient as using side channels, but probably a lot cheaper and easier to build. In fact, they make it look almost like you could build one yourself.

Do you know if the regular looking bricks are just normal bricks like you find on houses, or are they something special? I couldn't find any references to the materials they used except the doors and hardware they sell.
 
Mo:

You see what you see.

Red bricks are red bricks. Basic fired clay refractory units (the red comes from iron impurities).

Did you know that when you say "brick" that implies the material is fired in a kiln (read: saying "fired brick" is redundant)? Note these are solid which is good for a masonry heater (adds mass - when hot, thermal mass).

No fancy high tech super-duper industrial quality firebrick is being used since just good 'ole brick can withstand temps much higher than this measly stick fire will produce. This is why I recommend replacing your metal woodburner firebrick, when needed, with just good 'ole brick and not the higher priced spread (firebrick, the whitish units with no iron ---> higher melting point).

Yogi Bera says, "You can see a lot just by observing." I think he quoted that one from Grandma, maybe Grandpa. It doesn't matter.

Aye,
Marty
 
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