So Ive been looking into building a rocket stove boiler to tie in with my infloor radiant heat and help cut back on my gas bill.

In all my research there have been a few hold backs.

1. the fact that these stoves are very hot and if anything went wrong it would only take a few minutes for a system to become a steam pipe bomb.
2. Being a non CSA approved device if my house burns down I have no insurance
3. I work out of town, I am home in the evenings but I would not want to leave watching a fire to my pregnant wife as she has enough other things to do.


I have come up with solutions to these issues I will post them here and see what you more experienced people think about them.

Problem 1 the steam pipe bomb
webpage
I have come across a product used in High Performance race machines and heavy diesel trucks. It is called EVANS WATERLESS COOLANT this product is an antifreeze solution good to -40, and up to +375F but the real benefit of the product is that it has no water and even when it boils it does not create pressure. Im not suggesting that this would replace any in floor fluid, simply that the boiler would heat this then run through a coil in the thermal mass tank and transfer that heat to the water or antifreeze already in the in floor system. This way a gallon of $60 coolant goes farther and you can run the stove hotter and safer for less time to get the heat built up in the tank.
I have talked with the rep for Evans in Canada and he tells me that below 212f standard coolants will work more efficiently to transfer heat but above that is where the there product shines as it dosen't boil and therefore keeps better contact with the walls of the pipe and carries off that heat without creating pressure


Problem 2 the no insurance thing
I plan to put this boiler in a 8x14' shed and the back of my city yard, this way if I do somehow burn it down my house is safe and I'm only out a shed. I will pipe the water in through large diameter insulated pex lines then tie into my manifold inside to reduce my heat loss outside. In summer I will bury the lines to limit the heat loss more.

Problem 3 limited time and attention.
Since the Evans coolant should be much safer, I will be able to run the stove hotter and peel off more heat to stock pile in a shorter time, maybe burning the stove for an hour or 2 a day while i am in the shed working on other projects. I would never want to leave a fire like this unattended but I think I should be able to build up a good about of heat in a fairly short amount of time.

What are your thoughts? and are there any proven designs for a rocket water heater?

Ill figure out the image attachment thing soon but for now ill describe it.
My heater would be a 4" setup with an secondary combustion air. built like a standard mass heater i will have an insulated stainless riser tube and then a mild steel barrel around that which will have an incorporated water jacket (also insulated on exterior) the top of the barrel will have a small radiator above the surface to prevent to quick of a heat loss on the exhaust gasses but still allow for the heat on top of the barrel to be used.
this system would be an open loop and dump its cool fluid back into a pail above the heater to recirculate through and eliminate the possibility for pressure buildup completely.
After the fluid is heated it will flow through a coil of copper pipe inside a 275 gallon chemical tote which is again insulated to reduce heat loss and from there the standard in floor glycol mix will be piped into the houses system.

Would a bigger system be better, or should a 4" produce enough heat to get the reserve up to temp?

thanks for your help and advise in this matter

If you are in Canada, it is likely that you will need much more heat than a 4" system can provide. This of course depends on how big an area you are trying to heat. Also, even experts find it tricky to make a system as small as 4" run well. A 6" system is the smallest you should attempt for your first build, and depending on the heating load you may want an 8" system. We need detailed figures about your house heating load for the experts to advise on what system would be best for you.

Then a steel heat riser of any kind is doomed to quick failure in any properly functioning rocket mass heater. The combustion core will see temperatures up to 2000 degrees F or more, and the required insulation around it will keep the heat in and the active combustion gases attacking the steel. The barrel around the heat riser sees much lower temperatures and only inert complete combustion products like CO2 and water vapor.

From your limitations I wouldn't advise doing a rocket mass heater with water/coolant heating.

Will a solar hot water heater, trombe wall, or masonry heater work for you?

Don't know if this might help, but in many high-temp applications, salts are used as the heated fluid. Some knifemakers have built home-scale systems for heat-treating blades, and the results are very cool. Salts that liquefy around 400f are available, which might be realistic for a rocket setup.

The advantages, from what I understand, relate to the way the sale are totally inert, immobile, and safe when not heated, and the very high evaporation temperature (I don't recall what temp that was, but not something you'd reach accidentally.)

Just another avenue to investigate!

Glenn Herbert wrote:If you are in Canada, it is likely that you will need much more heat than a 4" system can provide. This of course depends on how big an area you are trying to heat. Also, even experts find it tricky to make a system as small as 4" run well. A 6" system is the smallest you should attempt for your first build, and depending on the heating load you may want an 8" system. We need detailed figures about your house heating load for the experts to advise on what system would be best for you.

Then a steel heat riser of any kind is doomed to quick failure in any properly functioning rocket mass heater. The combustion core will see temperatures up to 2000 degrees F or more, and the required insulation around it will keep the heat in and the active combustion gases attacking the steel. The barrel around the heat riser sees much lower temperatures and only inert complete combustion products like CO2 and water vapor.

Ok my house is 2 storeys plus a basement, each level is 800 sq ft and it was built in 1910 so has no insulation other than the 2" styrofoam I installed on the exterior. My house is an old modular cat agog house so its walls are a dual sheeted panel with a 2" dead air space inside each section so that does give some r value.

I am located in the metropolis of Moose Jaw Saskatchewan in Canada.

As to the riser, my cousin has a fab shop and a good selection of metal forming tools, if we make a 8" system and use stainless would it stand up long term, or would you recommend I go a step further and have it ceramic coated to prevent the gasses getting to the metal?

Adam Dombowsky wrote:

Glenn Herbert wrote:If you are in Canada, it is likely that you will need much more heat than a 4" system can provide. This of course depends on how big an area you are trying to heat. Also, even experts find it tricky to make a system as small as 4" run well. A 6" system is the smallest you should attempt for your first build, and depending on the heating load you may want an 8" system. We need detailed figures about your house heating load for the experts to advise on what system would be best for you.

Then a steel heat riser of any kind is doomed to quick failure in any properly functioning rocket mass heater. The combustion core will see temperatures up to 2000 degrees F or more, and the required insulation around it will keep the heat in and the active combustion gases attacking the steel. The barrel around the heat riser sees much lower temperatures and only inert complete combustion products like CO2 and water vapor.

Ok my house is 2 storeys plus a basement, each level is 800 sq ft and it was built in 1910 so has no insulation other than the 2" styrofoam I installed on the exterior. My house is an old modular cat agog house so its walls are a dual sheeted panel with a 2" dead air space inside each section so that does give some r value.

I am located in the metropolis of Moose Jaw Saskatchewan in Canada.

As to the riser, my cousin has a fab shop and a good selection of metal forming tools, if we make a 8" system and use stainless would it stand up long term, or would you recommend I go a step further and have it ceramic coated to prevent the gasses getting to the metal?

Neither. Use refractories.

Check this! Stainless eaten in one heating season.

https://www.youtube.com/watch?v=7RyvsZD1_CU

I've embedded the video for you.

Ah yes, I see what you mean. That is some intense heat.

what are your thoughts on his steel caged brick riser? i would like to be able to grab this unit with a bobcat and move it if need be and that seems to be a good solution to stabilize it.

A RMH combustion core made of refractory materials is not likely to stand up well to being moved as a unit by a bobcat. If it is really important that you be able to relocate it, you could make the lower part of the J-tube combustion zone as one unit with some extra binding around it, and a separate heat riser to set on top of that, which is common practice anyway. These parts could be made to be picked up by one or two people. The whole RMH needs to be far more massive and larger than you could move as a unit; you would have to disassemble it to move it.