Using an old fireplace as bell for a woodstove

Hello,

I am quite new to this forum, but found a link in the book 'the rocket mass heater builder's guide'. I was planning to build one, but since there is quite some work involved, I wouldn't be able to make it for a couple of years. We found an old soapstone woodstove and are planning to use it for the time being. I hope it is ok if I ask some advice here, as I have never built a heater of any kind before.

Below is a picture of the woodstove we are planning to use. It weighs about 600kg and is 130cm high. We have dismantled it and needs to be rebuild again.
- The woodstove has a double wall, but no downdraft. Only a 'zigzag' channel. I assume the lenght of this channel is not long enough to extract enough/much heat.
- The woodstove needs to be connected to the old fireplace of the house. The exit of the woodstove is higher than the entrance of the existing fireplace.

I tried to combine a few things in a design, but maybe it is not the best idea or there are just better ideas. So please give me your thoughts if you have the time.
For now, we prefer not to break down the existing wall around the fireplace of the house. So a vertical downdraft was the only solution I could find for that. The space of the old fireplace (about 50x50x50cm), I want to use as some sort of a 'bell'. It might not be ideal, but I want to use it to extract some extra heat since the space is there anyway. The drawing (see below) has the front of the fireplace covered with a stainless steel plate (with a ceramic blanket between bricks and steel as a seal).
My main question is: would this setup work and is it likely to make things better (or even worse)?

Thanks for your help,
Patrick

Hi Patrick.

Very good idea.

Well, i have been saying this for years.  "use old chimneys and fireplaces as bells"

Your plan seems to be the only one. Tho.

This big fireplace wall around a tiny firebox, owes to be empty. I would drill a hole in the left hand side of the firebox, to see if it is really empty. If yes, you have gained a real bell. Just mater to knock off the wall. Even if you have to rebuild it later.

I would bet it works!

I would note that it appears that 1 1/2 or 2 of the sides of the brick mass are exposed to the outside, and a bell would be throwing half its heat to the outdoors. If it is hollow and usable, I would put a good insulation layer on the outer surfaces of the bell. Then it may function well.

Thank you Satamax for your reply. Do you have experience with using/building fireplaces as bells?
Great idea for the big fireplace wall! I went downstairs right away to check it. When knocking on the walls (inner and outer) there is a noticeable echo, so I think you are right about the empty space inbetween. Although this would make a huge bell, I doubt it is very usefull though. The photo shows the curtains. Half the walls are outside. So I would need to insulate that part, which might be a huge project in itself.
But thanks for mentioning it, I will keep it in mind, maybe for something else. Who knows.

Haha, sorry Glenn, I was typing while you posted the same remark. Thanks though. Yes, you are right about the exterior walls. Insulation from outside might be a better option indeed. But I think for now, I prefer not to break the old fire place. I can always do that at a later time. Something tells me such a huge bell, might be a little too much or this type of woodstove and I might run into draft problems.

Patrick, i walked one guy through the retrofiting of a batch in  a fireplace. Using it as a bell. He was kind of happy. Even thought it was a small thing.

http://donkey32.proboards.com/thread/1274/rocket-heater-fireplace-design

What are the KW of your stove?

If you could manage somehow to insulate the back of the bell and ceiling. It would make a fantastic one for a Six incher rocket!

Your stove made me think of this!

http://www.ecologieforum.eu/viewtopic.php?f=3&t=4610

Thank you for your links. Had seen the last one in my search for examples. Nice one.
I have no idea of the KW of the stove. The dimensions are 130x50x50cm. I think it's a bit small for our living room during cold days, but we always have the central heating of the house as backup. And we don't mind wearing an extra sweater and are usually comfortable with 18 degrees C.
Yep, my dream is a rocket, but I have zero experience in building heaters (and not the time at the moment). If I start with a rocket, I would make a garden model first to gain experience (and see what my wife thinks, haha). Though, I would prefer a bench over a vertical bell though.

I am considering to add vermiculite plates to the interior of the woodstove. I hope this will insulate the hearth better than the soapstone and will increase the temperature for better combustion. Has this been successfully tried before with some measured positive differences? I searched the internet and this forum, but couldn't find anything more than just some basic instructions about replacing.

Supra, in France, does this type of firebox lining with vermiculite board. What is it worth?

I don't know.