Epic Seven Stove Patch Notes

[Harcourt Ordonez]

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PS, I have a top loading wood stove, and know the amount of smoke that can escape when loading.

With a large firebox like the one shown, side loading may be a better option than end loading.

Another thought, CO2 is good for plants, so if the CO2 from the flue could be cooled, and drawn into the greenhouse, without the particulate, its free fertiliser.

Hey Nik. Good idea regarding the small fire at the end of the run to support the now cooler air in rising out of the exhaust column. Definitely could be added as an optional control tool. And the side loading firebox makes good sense too based on the dimensions in this heater.

Have not seen anyone who captured the final exhaust and routed it back into the greenhouse. Have you? Good idea however. Thanks for your thoughts Nik.

What a great undertaking! My hat is off to you folks for this idea.

Would it help to have the whole exhaust pipe in a channel with a grate over it and not surround it with rock? It seems the direct heat transfer to air would be more efficient. Just an opinion.

With a grate James you would get more heat during the time of the burn but then nothing beyond that. The system would cool down immediately when the fire goes out. The purpose of the thermal mass is that it slowly gains and stores excess heat which is released later so that one does not have to have a fire burning 24/7.

Built one almost the same as yours in length but with a front load door on my uncles farm. To make the heat spread out more we used steel recycled drainage grates on the bottom and on top of the pipe that is buried with stone in one green house but not the other. The one with the grates heated the stone up far greater and is a lot warmer in the mornings. Note the grates you do want them in direct contact with the pipe. Also cast iron grates work better than steel. They take more heat and spreads it out faster than plain steel grates on a future build. Yes it is much better to insulate the flue pipe for draft and you could end up needing to clean it more from sap build up if it is to cold.

Do you anticipate problems with any part of our plan? Would preheating incoming air with exhaust air using a heat exchanger be of significant benefit? Replacing stove pipe at some point in the future is a concern. What do you think of surrounding metal stove pipe with chicken wire coated with ferrocement? If metal pipe rusts out would the ferrocement surface be too rough for decent air flow?

Hey guys, nice site.

One little thing I noticed, maybe you have a reason for doing this but

the 2100 degree stainless steel packed pipe on the flue in some of your

photos is installed upside down. This allows creosote to drain back into

the mineral fiber between the inner and outer layers of steel pipe,

increasing fire danger.

Probably never be a problem but just thought you should know.

Justin

So, Justin is correct. These insulated chimney pipes are designed to stack with the rounded end up and the cupped lip down. As Justin observed, this is to allow creosote to drip all the way back to the stove without filling the space between the pipes.

I love this process. And now that we have been doing this for well over a decade, I know for sure that I will never learn it all. There is just so much detail and mystery contained within every opportunity. As such, I have learned to really appreciate what knowledge and experience others have and to value their input.

So, maybe we could allow 1/2 of the exhaust gas into the greenhouse and still maintain a good draft by having the dedicated inflow pipe and an exhaust pipe going out of the greenhouse. But still, this would have to be carefully monitored for any people who end up working in this space. Too much CO2 is toxic to humans.

Keep the rmh as is. Take the flue off altogether. Continue the trench outside the greenhouse. Existing exhaust/thermal mass allows cool co2 to fill the new trench. Co2 is heavier that air so if cool it will simply collect there. The trench can be populated with plants and could then be dug in a U shape back into the greenhouse?

Bill, I did a test run on my RMH without any mortar or lid.

Some of the Flames burned sideways but a lot burned straight up. Does the lid solve that?

Once I am confident that it is going to work I think I will mortar everything. I am using repurposed cinder blocks so there would be a lot of gaps.

Hi, I love the design! I have two quick questions. One, did you have to provide an outside source of combustion air? It does not appear so in the photos, but I am curious as to the possibility of cold air being drawn in to replenish air loss and causing aforementioned crop damage. Two, did you keep track of how much fuel wood was consumed over the duration of use so far.

Did you use mortar with the big cinder blocks? It does not look so. I am almost at the point of mortaring cinder blocks and using refractory cement for firebricks.

Also, for the base of the bell, is there a continous surface of firebrick or are the regular bricks exposed to the heat travelling downward front the riser?

One last thing, the riser is supposed to be twice the length of the burn chamber (per Ernie and Erica). Is that a problem for this design?

Hi,

Just wondering how the stainless steel insulated riser has held up and what temperatures have been recorded for the burn. I keep hearing that metal is bad for the riser and will burn out FAST.

Any feedback would be appreciated.

Thanks,

Katie

Bill, I find everything about this project to be fascinating. I have one question. With all of the discussion around heat loss due to conduction into the soil and the need for ideas in the area of insulation. What would be the possibility of raising the entire thermal mass structure above ground? To me this would produce 100% radiant heat. In effect giving off a better btu to atmosphere ratio. If so you could burn slower and longer would it not result in less fuel and/or more time between loading the stove. I was behind the idea of heating the ground until it became obvious the ground will take most of the heat generated thru conduction. To me this leaves me with one conclusion. I would love to hear your thoughts.

I am planing to make a greenhouse free of frost all year round, using a rocket stove and to put the chimney underground as you do.

We consider the whole ground as a mass store of heat, and will insulate the whole block of soil outside the foundation.

Then I hope to put the chimney almost one meter under level to get enough mass for storing heat.

My plans started when I saw a greenhouse heated in the summertime by letting the hot air going through plastic pipes in the ground and storing the heat in the soil. In the wintertime the heat is leaving to heat up the air in the greenhouse.

My plan is to do as you have done, and in the summertime let the extra heat pass through the underground chimney and lift the temperature of the soil and store heat for winter. Then later in the winter when more heat are needed starting the rocket stove. Your electric fan at the end of the chimney will in the summertime work as a regulater of the temperature of the greenhouse. It can be automatic.

I also consider to place containers for fish and aquaponic systems. I plan to use ferrocement for that and place the tanks in the ground not to take to much space. Also to get a better heating of the water. The water container will also act as a mass store for heat.

We are living in Denmark and we have often freezing conditions for to-three month a year. Our greenhouse is about 4 by 4 meter, so it is not a big challenge as yours. We will insulate as much as possible. We got some two layer glass window free of cost and recycle them to the greenhouse as we do with a lot of materials for building.

I like the sounds of your design Anders. It should work well. Please let us know how your first season turns out. You will learn so much your first year it will blow your mind. ? All this stuff looks so simple but there is a good bit of nuance that much be learned as one goes along. Good Luck and have fun!

Thank you for your comment. I know that the first season will show a lot about the design. I hope very much that concrete pipes are good as underground pipe.

I is in my mind, if it is necessary to add isolating layer under the pipes so heat is not lost to deep underground.

I will let you know when I get started on the project. It might be next year, because other projects are asked for by my wife.

The temperatures will depend on how much wood you burn, the exhaust temperature after the thermal battery (and therefore the size and details of the construction), and the size and type of greenhouse you have. Typically the barrel can get 600+ degrees (at peak performance the wood burns at 2000 degrees), the mass say 80-90 some degrees, and the exhaust say 80 degrees. Of course that all depends on how you build it.

I had to see more when i found the photo of you greenhouse with a long thermal mass & how it works.

I did not think 40 feet would work, until I read fan, I want to do fish & fruit with a rocket thermal heater. But here in South Carolina our low can get as low 10 F, this year we had 13 F on Sat. then 80 F on Thursday of the same seven days. So I should be able to pull it off in this zone 8a.

Actually there is no need to insulate the stove nor the pipe it would work without. The soil will act as an insulator and you will get a much larger geothermal storage mass that way. Use the insulation in a vertical trench around the greenhouse instead. Just insure there is no moving groundwater thru the storage mass.

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