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My hot water system


Solar Enthusiast
Oct 22, 2022
Heliodyne panels, some approaching 30 years old. Closed loop glycol system with stainless plate heat exchangers, and PV pumped as a controller and a power source for the circ pump all in one. The hot water panels were attached to steel backframes, using "HelioClips" that slide into the edge extrution so no holes need to be drilled, while still on the ground, and then lifted with my boom truck into place. The back frames are strong enough to require the fewest roof penetrations possible, and those are steel pipe and standard roof jacks like your plumbing vents pass thru. They work equeally well for structural steel pipe as they do ABS pipe it turns out.

The 6 panel array feeds the shops radiant floor heat system, via the plate HX, no storage tank involved. All the heat goes into the 5" slab as soon as it's produced, and the exchange rate/pump rate is fast enough to keep the max temps low as possible, 100 or so, after realizing that at the end of the day you reap more BTU's making LOTS of warm weather then you do smaller amounts of cery hot water. I used to have a 500 gallon tank at my first place years ago, and I wouldn't heat the floor at all during the day, just try to get the 500 gallons hot as possible for night time use. IKeeping the loop temps low as possible, counter productive though it sounds, gathers a lot more BTU's. Especially when the final goal is largely rad floor space heating anyway, where 89-90 water is plenty hot enough.

The 3 panels on my small but very well insulated home work all year. A 120 gallon storage tank with a 3000 watt element halfway up, and a built in heat exchanger at the bottom is the first recipient of the hot water after it goes thru the plate HX. That way I heat 120 gallons of using solar, but when it's cloudy and the electric thermostat (set at 120) kicks on, I'm only heating 60 gallons. The tank has a timer, and I've found 4 to 6 pm for any possible needed backup heat works perfect for when I use most of my hot water domestically. I don't want to start a day that is going to be sunny, with a tank full of 120 degree water because the element just clicked off at 7:00 AM.

After the water goes thru the tank's heat exchanger, it passes by an aquastat that is set at 120 degrees, if the water is that hot, meaning my domestic tank is hot enough,a circ pump kicks and passes it thru another plate heat exchanger plumbed to the house radiant floor system. We get a lot of sun in the winter here, (when it's not snowing...) and at nearly 6,000' the sun is intense. A typical winter day may reach high 20's/mid 30's, and then upper teens to low 20's at night. The 3 panels will not only heat the entire 120 gallon tank up to 120 degrees (and hotter), but it also heats the house. It may be a tad on the cool side, air temp wise, first thing in the morning, but the floor itself is still warm, and if it looks like another sunny day, I'll just switch on a 750 watt radiant panel electric heater that's right by the snack bar where coffe is drunk etc. A smaller one in the bathroom assures I have a warm place to "go", no matter what, radiant heat beats hot air!

In the summer, when my production overcomes my usage, I flip a couple valves, unplug 1 circ pump and plug in another. The same aquastat, now set at 140, pumps water thru under ground insulated lines to my shop's 200 gallon home made stainless water tank 85' away. This keeps the home's 120 gallon from overheating, plus, as I have the main laundry room in the shop bathroom (big shop, small home) another pump exchanges water from the 200 gallon shop tank, to the shop's bathroom's 80 gallon tank, with it's built in HX. Suffice it to say I have plenty of hot water in the summer. It sounds more complicated then it is, actually it's MORE complicated then described, but I've built it up over the last 15 years, and had a similar system on other property for a few decades before that. Part two will cover the shop's wood boiler.


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I forgot to add that there is also a 5 KW Electro Industries electric boiler in the house system, controlled by a simple timer not a thermostat. It handles the base heating loads during winter, operating about 5 hrs a day. If it's been a sunny day, with the thermal system at it's optimum performance, the house will be warmer then needed, but I can also have the boiler skip a firing with a simple flick of a switch to preclude that. If it's been a real cloudy day, the house may be on the cool side but at least the tile floors are warmish, and that's where the thermostatically controlled electric radiant panel heaters take up the slack. I've found that just taking the chill out of the floor, makes any aux heat much more effective in getting the temps up in the t-shirt zone. There is also a centrally located highly efficient small wood stove, (I had to really search to find a model that wasn't too big) that uses outside air for combustion, pre-heated as it runs alongside the exhaust stack. It's rarely used, just in single digit temps and during a windy storm, and if I've been gone and the boiler has been out of service AND it's been cloudy. I can heat the house entirely with just the e boiler, the radiant panels, just the wood stove, or just the thermal system, usually a mix is what gets the job done. If I have no time, it's just the e heat and whatever solar, if home, I use the shop boiler, that brings us to part 2

The 40x40 shop is also very well insulated, with large south facing window for plenty of solar passive gain, the 40x20 downstairs area is the same, less the south windows. If I know a day ahead of time I'll be doing something in the lower section, I'll divert all the incoming hot water to it's floor, there is also a wall hung 4500 watt e heater, the same principle at work there as in the house: pre heat the floor and a little aux heat quickly gets it very comfortable.

Probably a good time to mention I have free electricity, with a .9 KW hydro system, a 2.5 KW wind system, and a 6 KW PV system. All grid tied, with a utility that has a very liberal system: I get back every watt stored there, no matter how long it's there or when it was produced, all for $5.00 a month basic hookup fee. I have not paid anything above the 5 buck fee for 15 years now as I always run a large surplus, I can't use it up fast enough. I drive a plug in Prius, both the shop and house are airconditioned all summer, and there is no propane anywhere.

The shop boiler is my design, a buddy who is a pro welder did the work. It's my second, my first was used for 28 years, and then when I moved I sold it for what it cost me to make, $350.00. This more recent one is tweaked a bit, and cost about $900.00. It's just a large steel pipe (the firebox) inside a 4" larger dia. pipe, not centered but offset a bit, so that the bottom only has 1" of water in it, the top 3". The back of the firebox is also offset so it has water behind it also. The firebox smokestack pipe passes thru the 3" of water on it's way out. The combustion air enters from the rear via a 3" steel pipe, it runs along one side the length of the firebox, getting pre heated along the way, and then exits about 12" from the front door and at about a 10:00 position. The intent and seemingly resultant effect being to cause the flame path to swirl up the opposite side before traveling along the length of the 4' long firebox. With my first very similar boiler (the air intake being the biggest difference) I used to load it up with nearly 4' long pieces of wood, light the fire, and ignore the heavy smoke as I had no neighbors to complain! It eventually would quit smoking, but over the years I have discovered that I can get a smokeless burn by using 12 to 16" lengths of firewood, and keep the fire as far forward as possible, the rest of the firebox is just heat exchanger, not for firewood. The X amount of hot water I get for X amount of wood is much greater, and smokeless. Unlike other wood boilers I see, I'm not after massive amounts of stored water, I start a fire while doing other things in the shop, load it, go do other stuff, and 3 or 4 hrs. later, before the embers die, load it a second time and that's it. That will heat the house (85' away, underground insulated lines of course) for a day or more, in conjunction with the house thermal system and e boiler, or not. It's all fairly crude but it works! If the house doesn't need heat, the shop gets it, also while, or instead, depending on the weather that day, the solar thermal system does it's thing. If the house gets occasionally overheated, an open window will let out the (free) heat.

An aquastat controlled circ pump (set at 100 degrees) moves the heated boiler water up into the 60' of coiled 1" soft copper tubing that is suspended in the 200 gallon stainless tank, built by the same welder friend. The boiler water is a closed loop:boiler to the HX, back to the boiler. The tank water is "open", and is the same water that then goes thru the home or shop floor, as needed. Circ pumps near the storage tank click on at 80 degrees, sending the water to either building, as the burn cycle continues the tank temp is constantly being held in check somewhat by water being cycled thru it, it's rare to see over 125 degrees in it. I can read the shop's tank temp in the house, with a remote digital indicator. The intent is not to store the hot water for long periods in the insulated tank, rather to put it in the floor ASAP, the tank is just a buffer for the boiler. It's feed water is a standard boiler valve, it reduces the incoming 45 PSI water to 15 PSI, and there is a check valve to prevent it from mixing with the "regular" water. Also a blow off valve on top of the boiler. In addition, PEX was used in some areas, so in case of a over pressure event, before the boiler would build up dangerous pressures, blowing steel shrapnel all over, the boiler valve would release the pressure, the blow off valve being the second backup, and the finally the PEX line would rupture. In operation, I usually see 20 PSI tops. I like having it IN the shop, not outside, at the same time the shop is pretty bulletproof for any leaks etc., plus it has a floor drain if needed. Check valves thru out the entire system, locations determined by trial and error, prevent the hot water from going where it's not needed.

With rad floor heat, the mass involved makes it all move in slow motion, (a good and a bad thing) today, at 8 AM, it looks like another snowy day, and it's 20 degrees, while the house is still 71 (that's air temp, but it feels warmer as the floor isn't cold) in a bit I'll go out to the shop and fire up the boiler for tonight's heating cycle. A certain amount of anticipation is involved, practice makes nearly perfect. With the multiple ways I have to heat, I don't have all my eggs in one basket, which turns out to be a pretty fail safe way to heat. I should mention also that as part of my crane service business I am on construction sites all the time, literally tripping over wood, 75% of my wood is obtained that way. The rest comes from downfall on my own property that would be picked up anyway. There is no schematic for the system, anyone looking at it would be baffled, sometimes, I am baffled by it, especially in the winter/summer changeover! But a few 3x5 note cards to my future self with explicit directions solve that. When I sold my previous place, the last thing I did was put in a conventional propane boiler for the new owners, so they could have "conventional" heat (and a propane bill every month.) All I know for sure is that I'm not going to be cold, ever, and it won't cost me a dime. I'll add a picture of the boiler in a bit.
Water jacketed woodstove with 200 gallon tank above.


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It would be wonderful to sit down with you next to the wood stove in the shop and talk systems. I inherited the responsibility of caring for a system with hydronic panels connected to rad floor heat system. The solar loop is moved by 3 ElSid pumps that control things by only working when the sun shines. The man who built it in 2001 would be your soul mate, sadly he died and left us the system with no instructions. I've been reverse engineering the system since 2016, all the elements are way out dated. It's in a community building in the backwoods of the Arkansas Ozarks, so most of the time no one is observing and tinkering with it. Mostly I've learned through fixing mistakes. It is amazing it has kept going all these years, but it is only used for heat in the winter. Plumbers and electricians are scarcer than hen's teeth around here so DIY is the only way to go. A knowledgeable person to talk to would be so sweet. Hoping for connections here on the forum. Fun to hear how much you enjoy your system.
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Very interesting
I'd like to learn more about heat storage too.
And radiators and plumbing for systems....

Is there a DIY wood boiler or heating forum?

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