Can thickness be added to a stove?

[kevinmoelk]

Okay, the experts here are probably tired of me asking dumb questions, but here's another one. Can you simply add stone or steel plate to a stove for added thickness and hence greater capacity to "hold" the heat?

Seems to me that welding steel plates or welding a channel to add soapstone would be easy enough. Has anyone done this? Is this dangerous? If it has been done, what have the results been?

 

[MrGriz]

I'm sure the experts will be along to weigh in on this one for you. In the mean time, here's my .02.

Stoves and inserts are engineered and then tested as designed. I assume that they are put together a certain way for a reason. I'm usually not opposed to modifying anything from the original manufacturers specs, however, I think I'm going to draw the line when it comes to something that could esily burn my house down.

Of course, if I had years and years of burning, along with additional knowledge under my belt, I might just haul out the welder.

 

[Roospike]

I'm sure you could add mass. getting it right the first time might be a chore or maybe not.
Pictured below is an Englander wood stove with a soapstone slab added to the top.
One would think it would work but i dont know on the picture , maybe Craig could fill us in on the picture , unknown to me who own this stove.

You could also add steel plate to the top and it would do the same idea as to hold heat but the original size of the stove will make a difference too.

What make/model of stove is in question ?

 

[kevinmoelk]

Well I do plan to upgrade, but for now the stove would be a Frontier 1980 model. The top is split level with the higher platform being towards the rear. It's made of 1/4 inch sheet steel. Putting it on top is certainly easier than placing it on the sides, which frankly, wouldn't be too difficult either.

In terms of material failure due to overheating or lack of proper heat dissipation, well I suppose that could be a long term problem. Unlike the photograph however, I would not cut a hole to go around the entire permimeter of the flue collar. I'd be more inclined to simply cut a channel so that the soapstone could be easily removed, and the stove inspected. Like any furnace, I'd inspect the stove annually.

It would be nice to talk to the guy who added the soapstone top to see how it has worked in terms of efficiency and if it's caused any pre-mature deterioration of the stove.

A big pot of water? Am I getting that right?

Thanks guys, keep 'em coming.

-Kevin

 

[wg_bent]

I gotta agree with G. Increasing the thickness will decrease the RATE of heat transfer through the designed thickness and hence, MIGHT lead to material failure.

IMNSHO. the easiest way to add thermal mass to your stove (though it, TOO, is subject to the shortcoming mentioned above) is to fill that pot in which you boil those lobsters with the Universal Solvent, and place it atop the stove.

Yes, a big pot will be a thermal mass, but try filling your bath tub with HOT water and see how well it heats your house. Not very well actually.

Yes it decreases the overall rate of transfer of heat, a perfectly fitting peice of soapstone will also suck heat out of the steel, so will actually pull heat out of the stove faster than air will. I'm sure there is an interesting curve that describes this.

 

[suematteva]

Another thing to think of may be to add to your hearth and or surround to store heat...As the Elkmeister answer to soapstone...16" of granite stones for under the hearth and the length of the wall..probably want to check your floor first.

 

[Andre B.]

Yes it decreases the overall rate of transfer of heat, a perfectly fitting peice of soapstone will also suck heat out of the steel, so will actually pull heat out of the stove faster than air will. I'm sure there is an interesting curve that describes this.

Only true while the system is heating up, after you get to equilibrium it could still be true if the external surface area of the soapstone (fins on a heat sink) is enough greater then that of the steel it covers and the thermal resistance of the soapstone and the steel soapstone interface are low enough.

We are talking heat sink design and that's not always simple, there are a lot of variables to account for.
http://www.coolingzone.com/Content/Library/Tutorials/Tutorial 4/Thermal Resistance.html

An interesting side note. Under some conditions adding insulation can actually increase the rate of heat loss, but those conditions are normally difficult to meet.
______________
Andre' B.

 

[kevinmoelk]

What if one were to add 1/4" spacers between the top of the stove and the soapstone? That way the soapstone would still heat up, but have a "safety" air space between the two surfaces allowing both materials to essentially cool off independantly.

 

[Rhone]

If you put a slab of soapstone on top, you won't need the 1/4" washers the metal top will warp all by itself and raise the soapstone.

 

[Roospike]

If you put a slab of soapstone on top, you won't need the 1/4" washers the metal top will warp all by itself and raise the soapstone.

1/4" Steel warping at under 800° ?

 

[Rhone]

I should've taken a picture of my steel stove, I don't think it's too far fetched that there can be an overfire situation and I'd love to see what the metal top looks like with soapstone slowing down the heat transfer in a unit not designed with it in place.

My steel stove, the top had a 3-4" bulge after many years, including several overfires.

 

[kevinmoelk]

I should've taken a picture of my steel stove, I don't think it's too far fetched that there can be an overfire situation and I'd love to see what the metal top looks like with soapstone slowing down the heat transfer in a unit not designed with it in place.

My steel stove, the top had a 3-4" bulge after many years, including several overfires.

3 or 4 inches! Wow! That's a tremendous amount of movement for a steel plate. The soapstone slowing down the transfer... that's exactly my point for the spacers (not washers). I'd probably choose small 1x1" tiles, maybe 5 in an "X" pattern to support the soapstone.

With the air space in between the 2 different materials would be less subject to the issues associated with having them lay right on top of the other. However, the soapstone would heat up, add thermal mass and dissipate longer than the steel would, so me thinks.

-Kevin

 

[BrotherBart]

The top is split level with the higher platform being towards the rear.

Just to be in-the-know, that type of stove design is known as a 'step-stove'.

I just learned that in September, after heating with wood for twenty years.

Ok language inspector: It is 'step-top' stove.

 

[BrotherBart]

I should've taken a picture of my steel stove, I don't think it's too far fetched that there can be an overfire situation and I'd love to see what the metal top looks like with soapstone slowing down the heat transfer in a unit not designed with it in place.

My steel stove, the top had a 3-4" bulge after many years, including several overfires.

3 or 4 inches! Wow! That's a tremendous amount of movement for a steel plate. The soapstone slowing down the transfer... that's exactly my point for the spacers (not washers). I'd probably choose small 1x1" tiles, maybe 5 in an "X" pattern to support the soapstone.

With the air space in between the 2 different materials would be less subject to the issues associated with having them lay right on top of the other. However, the soapstone would heat up, add thermal mass and dissipate longer than the steel would, so me thinks.

-Kevin

I knew a guy that put thirty gallon drums of water on both sides of his cast stove to soak up the heat and release it slowly later. It actually worked.

It is happening here now that I replaced my insert with a hearth stove. The fireplace firebox and the bricks on the front of the hearth are warm and releasing heat for hours after the stove dies down. And with the new stove being fire brick lined where the old one wasn't, even the stove stays warm a heck of a lot longer.

Put some fire bricks on top of your stove and give it a try. Heck, surround it with'em. Just don't pack insulation around an insert. I did and almost melted the old sucker down.

 

[Roospike]

I should've taken a picture of my steel stove, I don't think it's too far fetched that there can be an overfire situation and I'd love to see what the metal top looks like with soapstone slowing down the heat transfer in a unit not designed with it in place.

My steel stove, the top had a 3-4" bulge after many years, including several overfires.

Yes , Well HELLO ! You talking over firing your stove several times and after many years.
Thats operator error in the first place.

Thats like you saying one shouldnt put a turbo on there car engine because you blew up your last two non turbo cars motors over reving the past red line.

 

[BrotherBart]

I knew a guy that put thirty gallon drums of water on both sides of his cast stove to soak up the heat and release it slowly later.

WOW, sounds like a real party animal.

NOW, on the subject of language, do we "burn stoves" or do we "burn wood"????

I knew ya would get even for that remark.

 

[Roospike]

I should've taken a picture of my steel stove, I don't think it's too far fetched that there can be an overfire situation and I'd love to see what the metal top looks like with soapstone slowing down the heat transfer in a unit not designed with it in place.

My steel stove, the top had a 3-4" bulge after many years, including several overfires.

3 or 4 inches! Wow! That's a tremendous amount of movement for a steel plate. The soapstone slowing down the transfer... that's exactly my point for the spacers (not washers). I'd probably choose small 1x1" tiles, maybe 5 in an "X" pattern to support the soapstone.

With the air space in between the 2 different materials would be less subject to the issues associated with having them lay right on top of the other. However, the soapstone would heat up, add thermal mass and dissipate longer than the steel would, so me thinks.

-Kevin

I'm think your going to need a lot more soapstone mass than some 1" tiles on top to make that much of a difference. If my understanding of soapstone stoves are correct they have an inside and out side layer of soapstone and there is a lot of soapstone in the stove. two walls of 2" per the sides or 1.5" thick x 2 maybe?

 

[kevinmoelk]

I should've taken a picture of my steel stove, I don't think it's too far fetched that there can be an overfire situation and I'd love to see what the metal top looks like with soapstone slowing down the heat transfer in a unit not designed with it in place.

My steel stove, the top had a 3-4" bulge after many years, including several overfires.

3 or 4 inches! Wow! That's a tremendous amount of movement for a steel plate. The soapstone slowing down the transfer... that's exactly my point for the spacers (not washers). I'd probably choose small 1x1" tiles, maybe 5 in an "X" pattern to support the soapstone.

With the air space in between the 2 different materials would be less subject to the issues associated with having them lay right on top of the other. However, the soapstone would heat up, add thermal mass and dissipate longer than the steel would, so me thinks.

-Kevin

I'm think your going to need a lot more soapstone mass than some 1" tiles on top to make that much of a difference. If my understanding of soapstone stoves are correct they have an inside and out side layer of soapstone and there is a lot of soapstone in the stove. two walls of 2" per the sides or 1.5" thick x 2 maybe?

I think we've got our wires crossed here. The 1x1x1/4" tiles woud only serve to create a 1/4" air space below the soapstone slab, which could be anywhere from 1-2".

 

[Roospike]

Ah , .............. As it is written tho i didnt read it that way. got-cha . I-C

 

[cbrodsky]

I gotta agree with G. Increasing the thickness will decrease the RATE of heat transfer through the designed thickness and hence, MIGHT lead to material failure.

IMNSHO. the easiest way to add thermal mass to your stove (though it, TOO, is subject to the shortcoming mentioned above) is to fill that pot in which you boil those lobsters with the Universal Solvent, and place it atop the stove.

Yes, a big pot will be a thermal mass, but try filling your bath tub with HOT water and see how well it heats your house. Not very well actually.

Actually, our experience is pretty good in that regard - if we fill our jacuzzi tub in the winter, I leave it overnight and have notices the master bath is a little warmer than normal in the morning. Probably a combination of the humidity and the bath heat.

All these things are easy enough to estimate... just take (mass)*(specific heat capacity)*(temp. difference to room temp) and you can figure out how many BTUs you'll load it up with.

That tub holds (80 gal)(8.33 lbs/gal)*(1 BTU/lbF)*(105-70F) = 23324 BTUs when we're done.

In the morning, the tub is about 80 F, so it's left with 6664 BTUs, meaning about 16,660 BTUs were released into the bathroom overnight. That's a pretty nice load of heat to recover in a small space. (almost equivalent to leaving a 600W space heater on full blast all night, for example)

-Colin

 

[cbrodsky]

I realize that there exists a long queue of those who will attest to the heat holding capacity of soapstone, but this quality has relevance only when one's fire has gone out. IMNSHO, it should be understood that IF the thermostatically controlled air supply remains OPEN at that time, a significant portion of that stored heat will be lost to incoming air and will warm THE CHIMNEY.

Point being: the heat capacity of materials NOT comprising the stove is often overlooked.

Absolutely right. In fact, I think I've posted elsewhere making that point - soapstone is not by any means magical in terms of heat capacity - only incrementally higher - the numbers clearly show that. It is more the design of the stove's heat transfer rate that lets you moderate heat output and get longer heat cycles. This can be similarly accomplished by putting a iron or steel stove next to huge thermal heat sinks. The only drawback in that case is you won't keep the coals as long since you're pushing the steel stove hard to load the surrounding thermal mass, which means it will die out earlier, leaving the thermal mass to radiate. In a soapstone stove, you just never reach the same peak output, but you keep the stove itself hot longer, which does make for good coaling and easy restarts.

-Colin

 

[Andre B.]

But mostly, my point was/is that unless someone is available to close the air intake at the start of said cycle-decline, heat will be supplied to 'combstion' air when there really is no combustion taking place....and will, thus, NOT be available to the living space. OBVIOUSLY, this flies in the face with soapstone stove marketting propaganda. I've been making this point for some time....I date my involvement with HearthNet to 1998....but with very little acceptance. However, it DOES seem as though there is a little less resistance (here) to that thinking ....perhaps, some folks are 'coming around'.

You may find this an interesting addition to your cache of Odd-Knowledge.
http://eig.unige.ch/cmefe/Publication/2005-CleanAir05-paper-EIG.pdf
I have not read it all so it may be BS but what I skimmed looked good.
________________
Andre' B.

 

[Rhone]

[quote author="Roospike" date="1164861335]Thats like you saying one shouldnt put a turbo on there car engine because you blew up your last two non turbo cars motors over reving the past red line.[/quote]

Your example, it implies over-reving the engine on purpose and having damage be the result. You imply anyone who overfires do it purposely... I don't find that funny. More people than not will overfire. It takes is the door gasket to slip ajar unnoticed, an ember or twig to get in the way of the door unnoticed, to not latch the door properly, a weld to fail, the phone to ring while you've got the door ajar, or you leave and forget to turn down the air. Chances are someday you will overfire, I won't think it intentional.

 

[Roospike]

[quote author="Roospike" date="1164861335]Thats like you saying one shouldnt put a turbo on there car engine because you blew up your last two non turbo cars motors over reving the past red line.

Your example, it implies over-reving the engine on purpose and having damage be the result. You imply anyone who overfire do it purposely... I don't find that funny. More people than not will overfire. It takes is the door gasket to slip ajar unnoticed, an ember or twig to get in the way of the door unnoticed, to not latch the door properly, a weld to fail, the phone to ring while you've got the door ajar, or you leave and forget to turn down the air. Chances are someday you will overfire, I won't think it intentional.[/quote]

No , Implying one can over rev an engine easily making/doing/asking/forcing the engine to do more that it set up to do.

Just busting your chops Rhonemas , got 2 rib-ya once in a wile. its all good brotherman. ;-)

 

[cbrodsky]

I realize that there exists a long queue of those who will attest to the heat holding capacity of soapstone, but this quality has relevance only when one's fire has gone out. IMNSHO, it should be understood that IF the thermostatically controlled air supply remains OPEN at that time, a significant portion of that stored heat will be lost to incoming air and will warm THE CHIMNEY.

Point being: the heat capacity of materials NOT comprising the stove is often overlooked.

Absolutely right. In fact, I think I've posted elsewhere making that point - soapstone is not by any means magical in terms of heat capacity - only incrementally higher - the numbers clearly show that. It is more the design of the stove's heat transfer rate that lets you moderate heat output and get longer heat cycles. This can be similarly accomplished by putting a iron or steel stove next to huge thermal heat sinks. The only drawback in that case is you won't keep the coals as long since you're pushing the steel stove hard to load the surrounding thermal mass, which means it will die out earlier, leaving the thermal mass to radiate. In a soapstone stove, you just never reach the same peak output, but you keep the stove itself hot longer, which does make for good coaling and easy restarts.

-Colin

I disagree a bit here. Though I agree that soapstone is not magical, I feel that a typical soapstone stove's heat capacity is enormous, especially considering that its walls are upwards of two inches thick AND all walls meet at RIGHT ANGLES, ie, excess mass exists here, purely out of the shortcomings of working/machining the material. On the other hand, mass positioned next to a cast or steel stove is unlikely to reach two hundred degrees in temperature...far less than the five hundred degrees that the soapstone can attain prior to its decline portion of the cycle.

But mostly, my point was/is that unless someone is available to close the air intake at the start of said cycle-decline, heat will be supplied to 'combstion' air when there really is no combustion taking place....and will, thus, NOT be available to the living space. OBVIOUSLY, this flies in the face with soapstone stove marketting propaganda. I've been making this point for some time....I date my involvement with HearthNet to 1998....but with very little acceptance. However, it DOES seem as though there is a little less resistance (here) to that thinking ....perhaps, some folks are 'coming around'.