I am currently building a rectangular one bell, 6 inch batch box Rocket Mass Heater out of soapstone that I am looking to use to heat my home and water this winter. I live in Virginia Beach. Winters are cold and wet but mild compared to other states to the north.
I have purchased a hilkoil stainless steel hot water loop to circulate water in and out of my heater. If you are not familiar with this device, visit http://www.hilkoil.com . I am trying to figure out the best place to put the coil to get consistent hot heat. I have ruled out putting it in the woodbox itself. Should I embed it in the top cap slab of my heater that sits above the riser (I am building the heater out of soapstone) and let the radiant heat of the stone heat it? Should I put it into the bell cavity toward the top of the rocket mass heater where it will be suspended in the space? Should I put it lower? They say that a consistent 800 degree temperature around the coil would be best. I know if I put it in the wrong place, the heater will eventually destroy it.
So, I am trying to figure out different temperatures in the stone and in the bell in order to figure out where to put this.
My goodness, 25 years ago. How come I didn't know about this until now. I need hot water!
My question is, Permies talks a lot about heat shock explosion or boom squirt, When the RMH too hot all of a sudden bring water up to boiling in too quick cause explosion in copper coil. Or when power is out and the pump doesn't work to put water, too hot water cause steam burst as well. Is Thermo-bilt solve that problem? Do I still get boom squirt with thermo-bilt if power out or heat shocl?. Is this coil for RMH?
Stainless steel is a poorer conductor than copper, and is also much stronger, so you would be less likely to get a sudden steam burst inside the heater. You would still have to be concerned abut too much pressure in the rest of the system. You would always want to design the system for gravity circulation so the hot water would be carried out of the coil even without power, and either an open system that cannot build up pressure or one equipped with a professionally set up pressure relief valve.
posted 3 years ago
the system is designed to continuously recirculate and does have a built in pressure relief valve along the way from the masonry heater to the water heater.
Any thoughts on coil placement? Has any research been done on temperatures in the rmh whether in the cob of the thermal mass or in the bells?
Location: Upstate NY, zone 5
posted 3 years ago
People with standard RMHs have found that the top of the barrel surface can get up to 1000 F, and the sides over 500 down to maybe 300 near the base. Every one is its own thing, of course; this is just an upper ballpark. The gases inside the barrel will be hotter than these temperatures, depending on precisely where you measure.
A bell will be hottest at the top inside, but there is no way to say what the temperature will be until there is an actual setup to measure. The mass around the bell cavity will mostly not get hotter than a few hundred degrees, again depending on where exactly you measure. A bell designed for maximum internal temperatures will probably get up to 500-800 F near the top.
Not in or resting against the soapstone, the thermal shock of cool water coming in will crack your stone.
Heating coils and water jackets are tricky things. So are RMH's. Marrying the two has way too many variables to give you a reliable or even safe answer up front.
I have a water jacket in my cookstove. It has been a learning curve.
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