I posted some questions a while back and got some great feedback from the permies community while still in the planning phases of my RMH. Well, our cordwood project has since matured, and we've reached the point of building our first rocket stove that will use an earthen floor as the thermal battery. The pictures tell a lot of the story, but I'll fill in the gaps.
We pretty much stuck to the plan in the Ianto Evans book for the 8" system as far as the CSA and other dimensional aspects. I didn't insulate the feed tube or burn tunnel. There's no insulation under the stove. The heat riser is insulated with clay coated vermiculite contained in hardware cloth. As you'll see in the photographs, there's a pretty adequate transition area from the stove to the duct work (too adequate, perhaps?). The duct work exits the stove and is not yet covered in cob. We're waiting at least a few weeks until the temperatures rise above freezing regularly to resume cobbing.
So far I'm pretty excited by the three or so times we've fired it, but I'm having the same recurring problems and can't figure how to piece all the possible variables together. The stove works well for the second half of a 2-3 hour firing, but it tends to only work with the door open. For the first few minutes, it fights backdrafting. This seems normal to me, considering the fact that we're essentially cold firing it, the duct work is exposed, and it's 12 degrees out. Once we get past that phase, the system wants to "pulse", putting it self out and drawing again to reignite itself. With the door closed, it generally just puts itself out. Any ideas there? Is it just a bad idea to be firing it under described conditions?
The cleanouts aren't 100% sealed either. Apparently, I purchased components from two different manufacturers and the caps don't fit the t-shape cleanouts without taking some pliers to them. I know I can seal them with high temperature sealant but that seems to defy the convenience of having frequent access to that portion of pipe. I was running a propane space heater in the space too. There's no fan on it, but it's definitely affecting the temperature in the room. Could this affect the draw? There aren't any obstructions in the pipe, as far as I know. There's a cleanout that I embedded in the cob above the transition area, but I feel that the cob is still a bit too fragile for me to try and get this out just yet. This will obviously give me more insight on what's happening on that end of the system.
The chimney is currently only about 4 feet tall outside. I've run it higher to 8-10 feet with similar results. Will a taller chimney help me?
That's about it...sorry if it's a little stream of consciousness, as I'm just sort of spitting out the details I remember from the last few firings. Thanks to all the rockety folks around.
Theodore Axehandle : Lets start with the buddy heater and stop a whole shit load of negative comments about using an unvented space heater indoors, besides
the tip over Auto shut down your model comes with a low oxygen sensor. It looks like you got the 10 foot feeder hose rather than the 12 foot, the 12 foot one
requires a special adapter that you are recommended to change yearly, however that requirement is for overseas use where the Gass is not as clean or well
filtered ! You should never need to change the Filter adapter !
You remark on the fact that you needed to have the door open to get your Rocket Burner to 'work' and pulsing, these are both caused by and are signatures for
not enough air to your burner, Congratulations you have succeeded in building a very tight Cabin/home ! As your cord wood weathers in with shrinkage, some of
which will be seasonal, you will get better infiltration of your home, I am afraid that you will have to add additional air to your build, there is a model in the book
that lets you make a heat exchanger that uses the stratified air at the ceiling to warm the incoming air, the trick to 'see' how this will work, remember that after
the warm air of the living spaces is used as combustion air in Your Rocket Mass Heater, instead of going up the vertical chimney to be wasted, it will be transferred
into your Thermal mass, constantly being recycled !
Actually the transitional area is that small area between the Bottom of the 55 gallon drum where the vertically failing hot exhaust gases are turned at 90 degrees
to be channeled to the horizontal pipe of your thermal mass, Your first clean out and every thing down stream from there is rather part of your Thermal Mass !
All your clean outs need to be VERY Tightly Sealed! This could aggravate the symptoms you have now ! After the First elbow in your system has been covered
with cob you can- in the future use any old rag to help seal your clean out, You will need to purchase some Fireproof rope gasket material like is used to seal closed
the Door on a conventional wood stove to seal it now ! The last indoor clean out is unnecessary and should be replied with a horizontal 'T' with a cap just outside your
For the height of your chimney plan on having the stove pipe run to a height at least 3 feet above the peak of the roof ! This will be your best plan as we find and fix
your other problems ! I am interested on what other comments we get from Your other Fellow Members ! For the Craft ! Big AL !
Success has a Thousand Fathers , Failure is an Orphan
LOOK AT THE " SIMILAR THREADS " BELOW !
Location: Hawkins County, TN
posted 6 years ago
Thanks, Al. I appreciate the advice. I also appreciate you getting that indoor propane heater conversation out of the way. I feared getting an onslaught of chastising words. I'll apply the changes you suggested, try some stuff I picked up on Donkey's board, have some fires, and give an update. Happy rocketing.
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