I noticed that you are using a PE cube cage for your hot water storage. Be warned that PE loses strength rapidly with increasing temperature. Black PE pipe, used as a rooftop pool heating application can melt. Google polyethylene pipe derating temperature.
If you are only heating it to bath temperature, this isn't an issue. If, you are heating for use in radiant heating, and are running water temps of 160-180F it may well be an issue. If the plastic ruptures you are going to have a flood of instant burns surging across the floor, and that water will be hot enough to instantly fill the room with fog.
Note too, that PE creeps when hot. So this is a situation that you could be fine for a long time. (Months, Years) then have a sudden catastrophic failure of the unit.
In an application where the RMS is also used as a building heater, you may have a cold period, where you run the stove more than usual, and end up with a tank of water that is too hot for the PE.
you should see the IBC container as an example of how to very easily expand and adapt (water) mass to one's needs
one could connect a battery of IBC containers, thus the mass is limitless
I don't intend to heat the water over say 20-25°C (68-77°F) as this would be lethal for the fish
in my case even less: 15-18°C (60-65°F)
the water will also run in and through the plant growing media, heating this instead of the air
extra mass + warmth for the plants roots the air is heated indirectly
I am guessing plants will be better off with this "floor heating", just like we humans are
a few degrees less is much healthier to live in
overheating is as good as impossible
anyway: 160°F (71°C) is nowhere needed for any heating, especially not for floor heating
not for showers either, and you will not keep your hands very long in 45°C (113°F) water
of course this system is also applicable for these temperatures,
but then indeed a plastic container is not the best choice
and all combinations stay possible: the water in the primary tank of the RMH can be allowed to rise, even to boiling point
still temperature in secondary tanks can be kept much lower at will
I was aware that your project wasn't going to be that hot, but you provided the nice diagram, I was was concerned over the possibility that people MIGHT use PE containers for HOT water storage. This is esp. true if they are reading new posts, but not reading/remembering the context.
I have a small urban greenhouse that I'd like to heat. It's l8' x 12' (long width runs east-west), made of very heavy-duty aluminum, sits on a dwarf wall, and is peaked, and built against a tall masonry wall (on its north side). It has a single door in the west wall under the peak. There is no concrete base: the floor is clay/subsoil. We don't get serious cold here, on the south-east coast of England. Min temp mid-winter -5C (23F), av. winter 5-15C (40-60F). The heater is needed at night, but more particularly during the long weeks of gloom and cool temps that we usually get in July, just when the heat-loving fruit is gearing up to ripen. Loads of blight and mold in this cool moist clime (very like NW USA). Funny, I'm from NY State where I never felt the absolute need for a greenhouse, because we had reliable HEAT in the summer...
Anyway, I can erect a small shelter on the leeward side (NE corner), against the 9' masonry wall. Here's where the fire box could be, along with a box full of dry tinder. I'd like to make as big a firebox as is possible since I won't be sitting next to it to stoke it every twenty minutes. If I stoked it twice, running it for an hour in the evening, that would probably be enough for this tiny space. (?) The burn chamber could run into the greenhouse through the wall (recently built, and the guy who built it is still around, can cut the hole for me). The riser would be just inside the NE corner. I'm thinking ceramic pipe, say from http://www.schiedel.co.uk, for the innermost flue of the riser? If it was ceramic would I still need to insulate it? As for the barrel, I'd like to try to avoid metal in that very damp environment. Maybe I could make it out of soft brick or fire brick? The pipe leading the warm exhaust gases away could be of clay sewer/drain pipe, available here with every possible join and and angle. The pipe could lead west through the center of the raised (2' high) bed on the north side, buried 2' deep or more in the soil. Before reaching the west wall it would make a left turn under the steps leading down from the doorway (currently just stacked bricks) into the raised bed along the south wall; then head back to the east wall of the greenhouse, through it and up to the roof. I'd need some sort of clean-out system, and maybe some form of insulation over the clay pipe, at least when it's running under the north bed, so it doesn't burn the tomatoes' and melons' toes, and also so there's some heat left for the south bed where the peppers and eggplants grow.
I've read the original Evans/Jackson book and have just ordered the third edition in case it can give me some new ideas. I'm considering the use of ceramic pipe for the burn chamber, but I guess fire brick would work as well. We have a small stack of it, left over from the masonry heater we had built inside the house four years ago.
Any thoughts? Is anyone aware of such a construction having been built anywhere near here, or the London area? No help from my English partner who thinks the whole project is a waste of time and money. Then again, she thought the same of the masonry heater, but the fact that we now use a single basket of wood per day to heat most of the converted sandstone barn we live in has gradually won her over. ; ) Thanks in advance for any suggestions.
Hello, I'm sharing these links to pictures of some of my greenhouse rockets. They work. Putting the heater outside the greenhouse or using sand for insulation or mass doesn't work because sand is a lousy insulator and the air between the grains of sand is a lousy thermal mass.