I'm a long-time lurker that just joined the site. Also, I've been running a standard 6" RMH for 2 years now with good success.
So here is why I signed up, after feeding the stove for 3 or 4 days, at a pretty healthy rate, I noticed a new smell... my floorboards pushing out combustible vapors.
I know I know but I'm sure someone will still chime in and chastise me anyway.
I shut it down and waited for the mass (sand) to cool and excavated with the shop vac. Originally it was built over a 2 inch thick 1.5 PCF fiberglass blanket. This had compressed down to about 1/4 inch since first installed. To this, I just added an additional 20mm of pyrogel to the areas that will see the most heat.
Now for the question. While I have everything excavated, should I add a copper water coil between the pyrogel and the loose sand? Everyone always seems to want to add them to the barrel or stack but I'm just trying to keep waste heat out of the crawl space.
This coil would tie into our, currently inactive, oil furnace and radiant (pex in joist) flooring system.
Hi Troy; Big Welcome to Permies! Glad your not lurking any more!
Well, I won't chastise you about your floor.
I will however remind you that sand is not a very good mass.
Very easy to install or remove though!
However it has worked for you for two years so that's good enough.
Your question) I think you will be fine running coolant pipes to carry away excess heat.
Will it protect your floor from overheating? I would guess it should.
It certainly will not hurt anything, so I say give it a go!
For all your Rocket Mass heater parts.
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My RMH cores where they must be over wooden floors are usually built in a barrel lined on the bottom inside with at least an inch of ceramic wool then that barrel is set on a tripod of stacked bricks at least two high with a piece of sheet metal the full size of the barrel between the brick layers as a heat shield, all over a code-approved hearth board over the wood floor. Please leave a big air space you can reach into to check for hot spots on the floor.
I should have laid rows of 6 inch c channel the whole length before I built it but with steel at such a high cost right now... Over the summer I'll probably tear everything down and do a post mortem.
For now I think I'll just lay a 25 foot coil of 1/2 copper and tie into our radiant circuit in the kitchen. If I run the coils in a series all the stove heat will go to the kitchen then dump into the furnace water jacket. plus I get all the safety features afforded by the furnace's pressure relief and auto fill.
I'll try to document along the way, this place is a treasure trove of layman's science.
You can thank my dental hygienist for my untimely aliveness. So tiny:
Morgan Superwool Plus non-ceramic fiber blanket for Rocket Mass Heaters