Drafting exhaust downhill about 2 feet

I am building a RMH in China. I made a mistake and the firebox/Jtube is about 2 feet higher than the exhaust tubing that goes through the bench. Will this work?

Also, the heating is done outside and the ducting/tubing goes into the bench inside the house which is about 2 feet below the burning chamber/J-tube.

Can the exhaust go downhill about 2 feet?

Dustin

"It depends". A system with otherwise good design can probably do this, though a good chimney at the end of the ducting will likely be a requirement. You may have difficulties with starting this system cold and need to put a little fire at the base of the chimney to establish draft. A bypass from the barrel directly to the chimney would be very useful, though probably not possible from your description. Most importantly, why are you putting the fire outside? Unless you have a positive use for the heat given off there, you are wasting a large chunk of your energy, not to mention that it will be inconvenient to feed the fire regularly. Any details of your system and situation that would explain how this is a good idea would be helpful in letting us advise correctly.

Glenn,

I built the fire portion outside because my room inside is only 3.5 meters in diameter. I wanted to save space and also use it to heat water. But that was a mistake. So I have the tubing already built into the bench in the house. So I guess I need to build 2 heaters; one for heating water outside and one for the inside. I will need to send some pictures to explain this situation more clearly.

Inside the bench there are 2 ducts that loop around, but the problem is they are only connected from one side. The place where I can put the fire is on the other side. I already cemented the system in place. Is it possible to channel the hot gasses through two separate pipes and have they exit the house at two different places? Or do I need to re-joint the two again? If so, then I think I am better off just using one of the tubes and heat half the bench.

I also have some questions about my hot water heating system. Does that need to be put in a separate thread on this forum?

Dustin

I can't tell from your description how the ducts are laid out and whether there is a good solution. Can you post a drawing or plan of the ducts? Feeding the heat into two separate ducts and giving each a chimney is not likely to work well. You might be able to balance the flows to give even heating, or you might not.

If you are using a rocket stove to heat your water, it might be simpler to keep all the discussion in one thread - the two systems may interface in ways that advisors should know about.

Glenn

For the heating system in the house, I will send a diagram in another post after I have time to draw it.

For the water heating system outside the house, you can see the basic RHM in the picture. I built a custom barrel, but I think it is too small because there is less than 2 inches space between the barrel and the riser. So I think I am going to use that barrel for the indoor system.

For the outdoor water heating system I was thinking of building a bell design or making a bigger barrel or using bricks to give me 4 inches space between the barrel and the riser.

I found an interesting design on the Facebook page for Sun Dog School of Natural Building. Attached are a few pics. They say this is the safe way to heat water.

Would it be possible to use concept of this design to heat the water and at the same time take advantage of any remaining hot gasses by directing the gasses into a bench nearby? Then I can sleep outside in the winter (it doesn't freeze here, just humid cold like San Francisco)

Alternatively, couldn't I just wrap high temperature stainless steel corrogated water tubing around the heat riser inside or outside the barrel? This would also be safe because it would feed into an open system, no pressure. Would this heat water more effectively, or is the Sun Dog School example a better design?

Dustin

Coils wrapped around the heat riser are guaranteed to boil and will expand faster than the water can move to the open tank. Stainless steel may hold longer than copper, but that means that when it does get too powerful for the tubes to hold, there will be a bigger explosion.
The Sun Dog example is a tested and proven safe method, and I would recommend you follow it.

When you said "China", I had no idea which part you meant, and was picturing bitter continental cold winters. If you indeed do not get below freezing, you may be able to get your inner bench heated sufficiently to be comfortable through the night with only an hour a day of firing. If you are comfortable spending that hour by the outside fire tending it, you would probably do fine. You will need a roof over the heater anyway, especially if your climate is humid, so it could be turned into a nice place to sit.

Back on the topic of your original question, is there any way the exit from the bench can come back near the barrel? If the chimney can be next to the barrel, it will get some heat and draft assistance which will help with the drop to the inside bench. This would also allow you to make a little bench outside just before the chimney to sit on and be warm. Finally, with the chimney near the barrel, you could put in a bypass that allows the heat to go to the chimney without going through the inside bench, enabling you to get a good strong draft going before you make the heat go through the longer path inside; and you could heat water without heating the inside if the weather is warm.


I am suggesting these modifications because not only is your climate mild, your space is so small (3.5m = 11-12' diameter) that an RMH with even a small barrel inside would very quickly overheat it while you were firing. This is an example of why we usually ask for your location or climate first, and why it is good to put that information in your profile so it shows up by your name when you post.

On the Facebook Page for Sun Dog Natural Building I found some interesting pictures of a hot water heating system. I am trying to learn more about how to build this. I posted my questions in this forum as well.

I am thinking maybe I don't need a bell for this to work. I don't need to heat the space around the stove. Why not just think of this system as a big barrel that has a water tank sunk into the top? I could make the distance between the heat riser and the barrel about 4 inches, then after the water is heated I might have enough heat left to heat a bench? What do you think? Would a bell design work better for drafting the heat down into the bench? Or should I create more of a barrel design that is taller to compensate for the water tank?

See pictures I got from the Sun Dog Natural Builders Facebook Page Below...