Marco Ernst

Thanks for the advice all. Tonight is feeding time again I will try insulating the chimney as well and maybe add another meter of hight. Will make the first load tonight only thinner logs before going for a few thicker ones. I will also start looking at a gravity feed system since the greenhouse is way outside and it is really hard to go outside to feed when I am all snug in bed!! Was thinking of a expanded metal tube as not to form a chimney but still keep the wood in place. Will keep posting what the dragon does. It is like a living thing that fire!

Yes, I was a bit cryptic when explaining my setup. A little more detail. The horizontal flue runs from the drum straight for 9m with no bends. Then a 90 degree bend horizontally and immediately another 90 degree bend vertically where the 3 meter chimney follows. The area of the gap between the drum and the horizontal flue is about 1.5 times the area of the flue pipes (8"). So no bottleneck there. In fact, all the dimentions adhere to the specifications as set out in the RMH "bible" pdf .
I started burning the stove again and again and it looks as if you were right allen, the mass needs to dry out. The longer I burn the better the draft gets as the bench starts heating up. Yes it is a large bench. It is 9 meters by 0.7 meters by 0.42 meters. The flue as right at the bottom of the bench so it is covered on top with 220mm (8.6") of mass. The sides are covered by about 250mm a side of mass. I went overboard I think.

I did some temperature measurements. I have sensors touching the top of the bench in 3 places. Starting the fire the bench temp was closest to the heater 15 degrees C. After around 3 hours it went up to 22 degrees. It then slowly cools down through the night after the burn finished and reaches about 15 degrees again round about 6am. I will do some more tests and post some measurements later. The temperature last night in the clivia area (shadenet covered with greenhouse plastic, very poorly insolated) went down to 2.88 degrees with the outside temperature drommping to -1.5 degrees. I only need the Clivias to remain above 0 degrees or slightly below, not colder. So so far it seems to do the job.

For those interesed I also added antracite to the feeding hole behind the last logs. The antracite all burnd out during the night, might have helped lowing the cooling of the mass during the night as well but I will have to do more tests and measurements.

I still have a problem or maybe it is just the nature of the beast. The pdf states that an 8 inch system can burn logs up to the size of one's knee. I have smaal knees and still I can not burn logs that size in my heater. For some reason the logs dont burn fast enough or maybe too fast forming "chimneys" between the logs followed by flames running up the logs instead of burning sideways into the burntunnel. Using smaller logs is fine (or better). The wood I am burning is wattle, very hard and difficult to chop. Takes a lot of effort to get it going as well.

Hi all,

I built a RMH for my greenhouse, an 8" system with 9 meter horizontal flue run followed by 3 meter vertical chimney at the end. I used an old water heater tank steel drum to cover the insulated heat riser. I test burned the MRH and it worked amazingly well. I then started boxing the horizontal flue and added mass (concrete, mud and gravel). The total mass is around two cubic meters (calculated at about 4 tons). Ever since I added the mass and fired up the heater again it is as if the heater is struggling to form a decent draft. Nothing changed except for adding the mass. Why is this? Could I have added too much mass? The horizontal chimney at the end almost does not even heat up (exhaust gasses are very cool but still escapes). Is this due to the mass absorbing the heat so fast that a decent draft does not start? Do I have to wait for the mass to heat up before the stove will start performing as expected?

Thanks!

Baxter, thanks for the very nice post. I am all on fire again to dust off that Arduino of mine and get monitoring! Planning to use a site like cosm.com to publish the data realtime. I stated covering my exhaust with mass this past weekend and man am I sore! But non the less, feels good to do something!

Hi Baxter

This is a very cool project you have going here. I love the fact that you are using your Arduino as well! Suddenly I have a few new idea for mine! I am at the point of building my heat battery and was playing with the idea of using concerete. So this might be the solution afterall! Would love to see the pictures and videos of how you did the bench.

Looks great so far! Cant wait to see the rest!

Looks fantastic! Thanks for the info and reply. All the best with the rest. Will start covering my exhaust this weekend with mass. Will see what I come up with. Also need to cover the growing area with plastic this weekend. We are also located next to a river, gets real cold. I have a second hoop house as well that will need a heater soon!

Hey Amos, have you fired up the rmh yet? I am also busy with a heating project and my system is very similar than yours. My only headache is the thermal mass. What to use! My rmh is on top of the ground so I am building a box around the exhaust that I need to fill with mass. I do not have access to clay so cob is out. I was thinking 13mm stone aggregate. Give some feedback on how the soil works as mass.

Cheers
Marco