Solar Pre Heater for a Hot Water Heater

[wv1720]

What you want to research is a closed-loop drain back system.

 

[jmc]

You could think about a batch system like these:
Solar Water Heating Projects and Plans

Gary (from BuildItSolar)

Careful Guys, there's enough interesting stuff on his link that you'll forget about tractors for awhile!

John

 

[machmeter62]

I am a Californian, and we get lots of sunshine nearly year around. I fell for the tax incentive in 1982 for going solar. We built a large home, and thought the tax savings, plus the free heated water for the master bath spa, and hot water system would be worth it. The system cost us $25,000 in '82. The fourteen 4'x 8' panels are located on the back side of the home facing South, which was an incentive for the system being out of sight of the front of the home.

Well, the second winter a freeze plug on one of the roof panels failed that cost us $1000 to replace one panel, because there was no insurance on the system, and the company that installed it no longer existed!

Within the next few years, apparently a frustrated golfer that must live on one of the surrounding ridges started sending golf balls off his backporch or yard, in our direction into our rural valley taking out another solar panel.

We also have two large storage tanks, one each end of the home. A special stainless steel one, that was placed in a confined area that cost $3000 to make, plus the standard hot water tanks giving us about 500 gallons of hot water, with instant hot-water too, via of special electric pumps on timers! When one of the large 250 gallon tanks was installed; there was no water-proof plate under it, and is now leaking causing "dry-rot," that has to be addressed. We still use the system, but will never recover our investment!

I would look at your project as a challenge, with the reward coming from the "learning curve?" There is no free lunch, but technology has improved however.

 

[goodlife]

It does not surprise me that you could save $50.00 per month. Solar Water Heating works even in it's simplest form.

 

[blueriver]

Stupid is what stupid does ... I bought this place in 2004 and there was a system in place ... a big solar panel, copper in lines and outlines, going into the utility room with some sort of small unit, plumbing, copper, a timer all set up ... and hooked up to the hot water heater, well stupid me had no idea what or how it worked and gave the outside unit away to a fellow who was doing some dozer work for me. The lines where cut off at ground level, no water came out so i thought it was not hooked up and or working.

A few weeks later I found what was described as an electric less pump in the barn ... searching I found a septic system in a gully supplied by a spring with plumbing, a wooded platform obviously where the pump sat.

The man who owned this place had passed, a few months later his daughter stopped in and asked if I had found the spring well ... she explained that her dad had it set up to pump spring water to the solar panel for hot water with that electric less pump ... go fiqure ... only good thing is everything except the solar panel is in place ................

 

[MtHam]

I have a 2 panel system with a 80 gal storage tank feeding the traditional propane fired hot water heater. It was purchased 2nd hand ($250) in 1991 and self installed. Previous owner's kids had left home, needed new roof installed, thus decided not to reinstall. I estimate it saves at least $50/mo in propane. Thus, savings to date = $11,400. It's a delight to be able to use hot water freely without guilt!

 

[Raspy]

Ok folks I am new to the solar world so be easy on me. I was thinking about adding a solar Pre- water heater system to my 40 gallon electric hot water heater. I was thinking this may save me a little money each month on my electric bill. I was also thinking this would be something I could build myself. I am think I can build a square box 10'X10'X8" out of treated wood painted black and mount it outside my roof above my hot water heater. Than insulated inside the box with foam board inside. Than run copper pipe or cpvc pipe back and forth inside the box to absorb the sun's heat. Than cover the box with a piece of glass. My thoughts are that if my ground water average temp of 72 degrees going into the Hot water pre-heater it may come out of the pre-heater at about 92 degrees plus ( just a guess) That would raise the temp of the water going into my 40 gallon electric hot water by 20 plus degrees there for not working my hot water heater as hard to get to the 120 degree setting it's on. Do any of you have a system like this? What kind of return could I expect on my investment. Like I said, I am new to the solar world so any information or guidance you can give me would be appreciated

What you are describing is a simple batch type heater. But in your case there is very little water stored inside and the plastic pipe will fail.

To make a simple system of this type get an electric water heater, strip the jacket and insulation off, paint it black and put it in a box with glass glazing. You can also put it under a skylight and build it in.

Or make it the way you suggested but use large copper pipe, maybe 4" diameter, to get some volume. 40 gallons would be a nice starting point.

These work and are trouble free, but they are low on efficiency. Oh, and don't let them freeze!

 

[CurlyDave]

Look these things up before you do any real work on it.

One problem is that the very same properties that make a device a good solar collector, can also make it a good heat radiator at night. The wrong design can freeze water inside the pipes at air temperatures well above freezing.

There are know solutions for this, but first attempts have been known to be pipe freezers.

 

[Raspy]

Good point about freezing!

Solar panels and piping can indeed freeze at above freezing temps.

Freeze protection is the most important design consideration when thinking about solar. It puts you into the correct category so you can begin to size and design the rest of the setup.

Batch heaters are best in places like along the coast in lower lattitudes or in Hawaii. Built into the attic under a skylight, they can be very trouble free and simple, but not very efficient.

 

[handirifle]

I am a Californian, and we get lots of sunshine nearly year around. I fell for the tax incentive in 1982 for going solar. We built a large home, and thought the tax savings, plus the free heated water for the master bath spa, and hot water system would be worth it. The system cost us $25,000 in '82. The fourteen 4'x 8' panels are located on the back side of the home facing South, which was an incentive for the system being out of sight of the front of the home.

Well, the second winter a freeze plug on one of the roof panels failed that cost us $1000 to replace one panel, because there was no insurance on the system, and the company that installed it no longer existed!

Within the next few years, apparently a frustrated golfer that must live on one of the surrounding ridges started sending golf balls off his backporch or yard, in our direction into our rural valley taking out another solar panel.

We also have two large storage tanks, one each end of the home. A special stainless steel one, that was placed in a confined area that cost $3000 to make, plus the standard hot water tanks giving us about 500 gallons of hot water, with instant hot-water too, via of special electric pumps on timers! When one of the large 250 gallon tanks was installed; there was no water-proof plate under it, and is now leaking causing "dry-rot," that has to be addressed. We still use the system, but will never recover our investment!

I would look at your project as a challenge, with the reward coming from the "learning curve?" There is no free lunch, but technology has improved however.

I built my own system during the 80's. Cost was about $200 and got it ALL back on taxes, not even counting the savings on my gas bill.

machmeter62,
You COULD pay for that system easily. With the number of panels you have and the storage, I'd add a water coil in the main plenum of your heating/AC system, and use that hot water to heat the house in winter. Even if it doesn't take care of the full load, it will pay you back. Run the water through a flat AC (ALL COPPER) coil, and turn the system on with a two stage thermostat. The first stage turns on the blower and circulating pump for your water from storage. If the solar storage doesn't give enough heat, the second stage will turn on your existing heating unit.