On the list of fall projects, based on how well the other two water heaters have done with PV panels, I got up on the roof yesterday with the aid of a neighbor, a 35' rental lift and couple of my longest extension ladders and mounted five 245w Solar World panels I'd taken out of electrical production a while back. Ran the wires from the panels down some 2" PVC with an LB at the bottom into the basement. Inside the basement, ran to Midnite combiner box, then a 40amp breaker for a main disconnect. Yet to do is run to the 120 gallon tank with a 1200w 36v DC element in it, that will be the pre-heating tank for the propane tank we use now. Hoping to cut propane use significantly from that use.
That's a pretty good idea. I wanted to do thermal solar but have trouble coming up with something that won't be wrecked by hail or freeze and burst. That seems like the way to go. Where did you get those low volt high watt water heater elements?
I got them from Amazon, but checking just now to get you the link, it says "unavailable"......???? https://www.amazon.com/gp/product/B018S4AN42/?tag=survivalmonke-20 Did a search, and they are (along with a whole lot of others) available here: Heating element | water heater element Once you get one, go hunting for some way to connect the wires to the terminals. Terminals are TINY, and close together. I couldn't find a regular ring connector to attach #8 wire to the terminals.....like they really didn't set it up for connection to a heavy wire ! I found some odd ball connectors (below) at a local electrical supply that worked good.
Looking at that brick wall took me down memory lane...ahahhahaa......here are a couple photos of the wife and I laying that wall when we built the house in 1984. She is STILL a fox !
5 panels in parallel ? do you install a amp gauge and use relays to control the thermostat settings ? On mine from the amp meter /gauge full sun at 13:00 summer im reading 40A at 36Vdc, when it drops to 20A at 15:00 or so , the top thermo has opened the top power relay so i don't blow the over temp valve . Run the DHW for washing and the preheat tank top relay cuts back in and the Amps are back up to 40. This also lets me know if the elements are good. Sloth
120 gallon tank. Panels only get good sun after 12pm, I'm gonna try it with no thermostat and see how it goes. I'll have a temperature gauge on it to monitor tank temp. 1200w element = 4100 BTU 120gal of water ~1000lbs. One BTU will raise one pound of water 1 degree in 1 hour......so around 4 degrees rise per hour IF I get full sun on the panels and the element cranks out the full 1200w. Incoming water 55 degrees....say 65 from sitting in the tank in the basement. 5 hours of good sun, maybe 20 degree rise ? So end of day, 85 degree water....assuming we draw none out, which almost never happens....daily showers, dishwasher running, etc. My guess is this thing will simply provide lukewarm water into the propane tank but save in that the normal incoming water is 55, and the propane heater is having to bring it to 130ish. IF we ever go 3-4 days not using hot water, AND it doesn't bleed too much heat off over night, we might get into some serious water temps.....but otherwise, I think not. I think if anything, I'm gonna be figuring out how to weld another element fitting in the tank and add a second set of panels with another element !
here just the lower element is stilled being powered Tank temp is 130F so the upper is off. I use copper lines to connect all tanks so I don't get any electrolysis from PV or tanks ..ALL grounded well Sloth
You probably want some kind of temperature shutoff. I dont know, let's run the numbers. 120 gallons is 996 pounds of water. And at 55 degrees, to raise that temperature 100 degrees to over 150F or enough to pop the temperature/pressure release valve is about 99,000btu. 99,000btu is only about 29 kwh worth of power. A 245w a panel should easily be able to catch at least 1 kwh per day no problem. So safe to say 5 of those panels should catch about 6kwh. So it should heat the water about 20 degrees F per day. Should save around 1 pound of propane per day, 81 gallons per year. So yeah a shutoff is a pretty good idea. It will probably never need to shutoff, key word being probably.... or have a solenoid and pump kick on to circulate the water if the solar tank gets too hot. Just make sure the shutoff doesn't arc.
When in need for a 8ga ring connector, especially for high temp connection, go to a quality commercial provider and purchase a Nichol ring connector with a solid crimp wire connector.
Got a link got them ? Search wants to return a 'nickel' ring connector. Problem with any crimp on connectors is the hole is usually 5/16" or bigger, which is WAY oversize for these little terminal studs on the element, and the outside of the ring is too big and wants to touch over to the other side terminal unless you grind off one side of the terminal. They really didn't design the fool thing to have a large wire attached....maybe they mean for you to parallel smaller wires ?
A commercial site will have what ever you need, never bought them on line, shrink tubing will provide some protection.
Pico also handle that at any auto shop supply , look up in the pico catalog for what the supply house don't stock , they only supply off the shelf low end stuff. Home :: Pico of Canada Ltd
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Living on the desert we got snow ther too, I did 2 solar water heaters, one was a tank inside a double glassed box and the other was a coil of copper tubing in a flat 4'x8'x3" glassed box. The 5 gallon tank came to 130 degrees and the copper coil came to 160 degrees in one hours time.in the same sun. The tank worked out best, however if I had a heat exchanger I would have run antifreeze in the copper tubing and preheated the water to the tank and had more than enough hot water for the family. Both PV and thermal solar are dependent on exposure. and for the best scenario, one might best have a large reservoir of tanks in their home the heat is accumulated in, and both heat the water and home as well. This was done in a home i saw in a solar magazine. This house had a part of the structure facing south and double glassed with barrels stacked to receive the best sun exposure during the winter months. Verticle-walled windows never got covered in snow.
