Converting a double fireplace

[abe]

Hello everyone!

I have built a couple of J tube rocket mass heaters in the past. One was a 6" system, the other an 8". Both worked great, and are still in use to this day. (The 6" one is now over 10 years old).

A few years ago, we moved to a small place in Texas, and this house has a double brick fireplace. What it looks like to me is that there was a single brick fireplace on the edge of the original small farmhouse, which is typical for this area. Some time after, the house was expanded, and for some weird reason, they added another brick fireplace to the backside of the first one. So, what we have now is a giant monstrosity in the middle of the house.

It doesn't work, even barely. Light a fire on one side, and over time, it'll draw in smoke down the other chimney. We've tried all sorts of modifications to get it to work. We're now at the point where we closed the top of one of the chimneys. We can run the other side now without the smoke coming down, but it still smokes into the house until it warms up the brick chimney, and honestly, it's kinda a pain to keep it running smoothly without smoking up the entire house.

As you can tell, I'm pretty frustrated with this thing and now 5 years with it and it still doesn't contribute anything to the house. It does take out a lot of space. It really makes me miss my rocket mass heaters and appreciate what good design can do for you in the long run.

So, I've been thinking about converting this thing into something useful. Reading through this forum and others, rocket stoves have advanced quite a bit since I built one. The batch rockets, the vortex designs, the double shoe box designs, and the Walker riserless designs all are new and exciting developments that give me hope that we can turn this into something useful.

Before I go down the road too much, I'd like to ask you experts here what you would do with what I have.  I don't want to tear the house apart to do this, so no benches, and nothing extending too far out from the hearth.

Here's what I have:

• 2 giant brick chimneys right in the middle of my house
• House floor is a concrete slab
• 2 standard brick fireplaces (the opening is 3.5 ft wide by 30 inches tall)
• Endless supply of nice oak firewood
• Lots of skills - I can weld, very proficient with masonry, very handy (I've built 3 houses myself)

We currently use a propane furnace to heat the house. Luckily, we live in a mild climate, so we don't run it all that much, but I'd really like to get away from it if possible. We have lots of oak trees and lots of firewood here.

What would you do if you were in my position?

Here's what I'm dealing with. It's got a tile facade on the outside of the double brick core:

[abe]

I made a rough mockup of the internal spaces in the fireplaces, so you can see what I am dealing with.

As you can see, each fireplace is divided into 3 main chambers. The bottom fire box, the pyramid top transition above flue to the chimney, and then chimney itself. The bottom fire box and the pyramid are made from brick. The chimney has an internal terracota liner, the cross section is 12 inch by 10 inch. It's surrounded by brick all the way up and out of the house. I'm not sure the height of the chimney, but it's at least 4 meters.

The gray "plate" in this image represents the ceiling to living space.

Just looking at each fire box and pyramid (everything below the chimney), the ISA is 3.3 m3

The footprint of each fire box is 36 inches wide and 28 inches deep, and then 30 inches tall until the flue plate.

[Dan (Upstate NY, USA)]

I'd knock it all out except for the chimneys and go from there.

Seems like there is some kind of column in there supporting the floor above.

[abe]

Dec 25, 2022 14:09:10 GMT -8 Dan (Upstate NY, USA) said:

I'd knock it all out except for the chimneys and go from there.

Seems like there is some kind of column in there supporting the floor above.

The whole thing is a brick column that goes up through the roof. Removing it would be a massive project.

[abe]

I'm thinking of some sort of batch rocket setup on just one side, possibly a DSB3 or Walker riserless inside the brick bell. The exhaust could be an insulated stove pipe with an insulated plug in the chimney.

The face plate would likely be metal. I'll probably figure out some sort of the heat exchanger for the face, as well.

Here's DSB3 and walker riserless core mockups in that space. It would be nice if I could design the face to be able to remove the core relatively easily.

[fiedia]

I am afraid that your bell walls are too thick to radiate any heat.

You will probably have to destroy part of the existing chimneys, either inside or outside walls.