RMH for floor heating - advice please

[abuls]

Hi, I'm new here and have no experience with RMH, nor I have any knowledge in hydrodynamics or hydraulics.

I plan to buy new unfinished home which have just roof and walls. So I have an idea to use RMH for heating.

My wife does not like how look drums and barels, so I choosed that stove can be built entirely from bricks. I liked the construction I've seen on youtube
by 1mandocu.

so I plan to dig all earth (sand from the house in depth about 70cm (28"), put exaust flue pipes in order to heat the floor. Pipes will be covered with sand about 25-30cm (10-12") above pipes. That will be the mass what I plan to heat.

on to sand I'll put some brick columns in order to support wooden beams that will support the real floor of room. Near the wall under windows I plan to left about 15cm (6") space for warm air to escape from under floor. Around this space under windows I plan to makes tin box and fasten to floor in order make little chimney to air circulate and not to allow small things to fall from floor to underfoor. These boxes/chimneys look like ordinary radiators.

stove will be build on floor, or at least on the level of floor. But I am afraid, that smoke, flue gases will not want to go more than 0.5m (20") under the level there actual burning of wood happens.

another concerns I have - how I'll clean ash from pipes, and how to make ash to collect on the level above floor, but not deeper. Probably I have to make something (cone) that will do the function or cyclone. see. en.wikipedia.org/wiki/Cyclonic_separation

but this needs also some space and adds some obstacles to flue gases to go under floor.

[abuls]

I've added picture of idea. Possibly my english is too poor to understand fully.

[stovol]

abul, put a cleanout , T shaped somewhere... if your run is not too long, put it outside the wall and clean with a shop vac or a chimney sweep... i d like to know if you get accumulation in the elbow just below the sand

[mintcake]

Aug 22, 2011 4:03:59 GMT -8 abuls said:

I've added picture of idea.

I read rectifier's post #7 here: donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=226&page=1 just after reading your post.
Having checked your picture, when I see how much of your gas flow is down, rather than up, I am scared for you and your family. I think you should not build it in that way. It looks like it would be very easy for the gas flow to reverse, (e.g. at the end of the burn cycle, as the riser cools), and throw ash/flame into your home.

[peterberg]

abuls,
The underfloor heating you want has been done before. The first one I am aware of has been realized in a yurt. The yurt itself isn't very portable anymore because the whole rocket and gravel bed has been covered by a wooden floor.
www.flickr.com/photos/fishermansdaughter/sets/72157625122351115/

P.S.,
Here's a description of the ins and outs of this stove, written down by the woman in the pictures.
www.permies.com/bb/index.php?topic=5937.0

[rectifier]

Notice a couple things in fishermansdaughter's stove.
- The firebox is the same level as the floor
- there is a slight rise on the exhaust pipes (maybe 2-3 feet)
- The firebox is outdoors, so if it does reverse they don't have to eat the smoke.

If not for these facts, this stove would be at great risk for reversal, especially at the point of fuel exhaustion - which means you get to breathe odorless CO gas coming off the remaining embers in the firebox.

Donkey himself has built a stove of a similar design, I managed to track it down donkey32.proboards.com/index.cgi?action=display&board=discuss&thread=103&page=1

Note the firebox is sunk into the floor and the external air intake (which isn't strictly necessary and was scrapped in the final build)

My recommendations would be, dig the stove down into the floor so the firebox is level with the flue pipes in the floor you are going to heat. At the end of the run, turn it upwards into a chimney instead of exhausting at ground level. Then you should have no real issues.