Looking for ideas

Hi everyone, first time poster, in the research stage of my RMH build.

I'm living part time in Bulgaria and part time in the UK.

Bulgaria will be where I'll get to build my RMH, the chimneys built into the house are 130 mm (or 5.12"), I have a wood burning stove in one of 5 rooms on the ground floor of a 2 story house, (we live downstairs in the winter, as the stairs are external, and closing off the upstairs and living downstairs make more sense).

Having read enough to know that the necked down point should lay the basis for J shaped RMH, that gives me 20.588 "sq for the flues.

Fire bricks available are 230 x 114 x 75 mm (or 9" x 4.5" x 3"* just under 3"), so if I start the front of the J with a brick stood on end 4.5" wide, with sidewalls 2 bricks high, and make the feed tube and riser, 4.5" square shaped (or 20.25"sq), that will mean the 3rd layer of bricks will be interlocked, and the sidewalls can be bonded with 1/2 brick on layer 1, (at each end), and full bricks on the 2nd layer.

1) With the 20.25"sq feed and riser, and burn chamber, how long should the burn chamber be?

2) How tall should the riser be?

3) Is there a formula for the length of piping this will be able to feed heat through the mass?

4) There is also an old fireplace in one of the rooms, I don't know the diameter of the flue on this chimney, is it better to think about a build with a 6" system and vent through this chimney, or go with the 4.5" system and vent throuch the 5" flue in the wall?

Apologies for the long winded multiple question first post...so many questions, so much information, so little time.

p.s. I have the "build bible" on order, just waiting for delivery, and can't sreep for all the questions going round and round in my brain.

Hi Chrishophori;    Welcome to Permies!

First question I have is)  are regular clay bricks easily available ?  I suspect that they are. Most of your build can be regular clay bricks.
If so, rather than a piped mass a brick bell might work better for you.
A small batch box might also be a better choice with the smaller chimneys you have.
J tube rockets are recommended to be 6" minimum especially for a first build.
Building test rockets outdoors before indoors is recommended to help to feel comfortable with your building skills.

The RMH builders guide will teach you the mechanics and dimensions of a J tube rocket build.

To learn about batch boxes and brick bells , you want to check out Peter Van den Burgs site.  Here is a link to it.    donkey32.proboards.com/thread/1998/batchrocket-eu-information-site

As to your questions)  #4) I would build 6" and use the existing chimney.
#3) A 6" J tube can push 35' Horizontal, with a 5' deduction for each 90 degree bend.  An 8" can push 50'
#2) The taller the better. Mine are 48" and 60"
#1) Burn tunnel roof is on average  apx. 7-9 " long.

After you decide what size and style rmh you are building, the dimensions will match the build.

Chrishophori Ezzy wrote:

4) There is also an old fireplace in one of the rooms, I don't know the diameter of the flue on this chimney, is it better to think about a build with a 6" system and vent through this chimney, or go with the 4.5" system and vent throuch the 5" flue in the wall?.

Hello Chrishophori

Well, it all depends!

Where is this chimney against an inside wall?  Or an outside wall?

Pictures?

I love old french fireplaces, as they can make the bell and mass at once. With not much work. You might have luck there too.

So if the fireplace's chimney is big, that's worth trying.

What size house are you trying to heat?  Floor plan?

Myself, i'm partial to batch boxes and bells. J tubes are too much work for tending.

Thanks for the replies.

The chimney and the 5" flues are on internal walls, the floor plan is a simple cross, splitting each outside wall roughly in half. 3/4 of them are about the same size, the last 1/4 is split in half making 5 rooms.

The second floor has a similar but all the rooms are 1/4 the floor plan, each floor is about 1050' sq, I'll post pictures on the next post.

I don't yet know the size of the fireplace chimney, just the wall flues.