Closing the Circuit: Installing The Solar Water Heater
(Page 2 of 3)
January/February 1986
By Mother Earth News Editors
THE EQUIPMENT
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Besides the solar collector panels (you'll probably want to use two 3' X 8' units for a family of four), you'll need a pump, a controller, the sensors, and an expansion tank, which is used to absorb the increase in volume of the closed-loop fluid when it's heated. The parts list below indicates those components we used in our system, and Solar Components Corporation, P.O. Box 237, Manchester, NH 03105, offers a full line of hardware in its catalog, which is available for $1.00 to those who write saying they got the address from this article.
In addition, you'll need an ample supply of 1/2" copper or polybutylene pipe, enough elbow fittings and couplers to complete your site-specific installation, ultraviolet-protected insulation jacketing for the exterior plumbing and an interior-grade equivalent, air vents for the highest points in the system (these can be purchased . . . or you can use simple condensers fabricated inexpensively with a 1/2" pipe T or cross to suit your plumbing plan, a 1/2" nipple, a 1/2"-to-1/8" pipe reducer bushing, and a 1/8" pipe plug), a check valve for the closed loop, a hose cock, and several shutoff valves. We'll assume that your existing plumbing is to code and already has a vacuum relief valve and a temperature-and-pressure relief valve installed if required.
Finally, you'll need two 8' and four 2' treated 2 X 4s, four 1/8" X 2" X 9" sections of angle iron, eight 1 /4" X 2" machine bolts, an equal number of 1/4" X 2" lag bolts, and eight 1/4" X 3-1/2" carriage bolts to complete the roof mounted collector racks.
THE HEAT EXCHANGER
Your choice of heat exchanger will depend largely upon how much you're willing to invest. In many professional installations, a combination heat exchanger and water heater is used as a single unit to replace the existing hot water tank. Because such a unit has intricate exchange coils, electric elements and thermostats, and a special lining, it costs about $500 . . . twice as much as a standard tank.
As an affordable—but admittedly less efficient—alternative, we adapted a scrapped 30-gallon gas water heater to serve as a separate exchanger for a total cost of about $12.
The gas-fired models, you see, have a central exhaust stack that runs right through the reservoir itself. So turning one into an acceptable heat exchanger involves nothing more than welding a 2" pipe coupling into each end of that stack (after you've removed the gas burner and controls), threading 2"-to1/2" pipe-reducer bushings into the openings, and installing 1/2"-pipe-to-sweat fittings into the bushings. The tank should come with a pressure relief valve (or a new one can be added if necessary), so it's ready to be safely used as a hot water storage reservoir, once it's plumbed in and wrapped with insulation.
A DIRECT ROUTE
Although the illustration included with this article shows how we set up our system, it's not necessarily representative of how you might put yours into service. Nonetheless, it'll provide anyone with basic guidelines for component location, routing, and panel mounting.
