Boy this one took a long time. Not so much actual time to work on the project, rather, being able to work on the project, rainy weekends, summer vacations, taking delivery of the solar panels, et cetera. However, today at almost 12 noon, I flipped the switch, the little red light came on and I was greeted by the sound of rushing water. Since it is mostly cloudy out today, I wasn’t sure if there would be enough heat in the collectors to turn on, but apparently there is. When the system is running it sounds a little bit like a coffee pot percolating.

So I watched as the return water came back down the loop and the thermometer rose up to 80 degrees F. That is not too shabby considering the incoming water is 47 degrees F. That gives me a 32 degree temperature rise over 80 gallons of water, which is about 21,350 BTU. A BTU is the amount of heat required to raise the temperature of one pound of water by one degree F. Water weights 8.34 pounds per gallon, 80 gallons X 8.34 pounds equals 667 pounds. 667 pounds times 32 degrees is about 21,350 BTU.

Since the solar tank is only 80 degrees F today, which is way too cold for domestic hot water supply, it will get heated the rest of the way in the auxiliary tank.

This project was not without it’s ups and downs. Last night when I though I finished soldering all of the plumbing connections, I turned the water back on. Now, when you are soldering pipes and you go to re-pressurize the system, the last thing you want to hear is SSSSSSSSS. And yet, at 5 PM when I wife was coming down stairs to tell me she had ordered Chinese take out for diner and would I please go pick it up, I hear SSSSSSSS. After I minute, I looked down and saw a small spray of water coming from the bottom connection on the 80 gallon solar tank. The other thing about soldering, it is best done before you put water into the pipes. Any amount of water in the pipes will cool the joint enough that the solder will not stick, making all efforts to solder a good connection futile. I decided I had had enough and hooked up the hose to the drain spigot and let all the water drain out overnight.

Today, I went and got a few 1/2 inch unions, cut the tubing, removed the whole unit and soldered it again. This time, all went well. By 11:00 am the solar tank was filled. Then it was making three electrical connections for the temperature sensors and flipping the switch. I also spent a good deal of time insulating all of the pipes. I need one more piece of pipe insulation to finish the job. I filled the drainback tank up with distilled water. One of the solar contractors around here recommended putting a couple of gallons of propylene glycol which is a non-toxic antifreeze (among other things). I will pick some up tomorrow at the hardware store just to be safe.

Here are the AET AE-40 solar collectors mounted on the roof of the master bedroom. This is pretty much a south facing roof, the azimuth is about 192 degrees true, the collectors are tilted at 52 degrees. Man, the gutter is crooked. I will have to fix that before winter.

This is the basic system, the solar storage tank is a Sears Miser 12 80 gallon conventional electric hot water tank. The electric heating elements are not connected. Cool water is pulled off the bottom of the tank and circulated through a heat exchanger in the drainback than, then returned to the top of the tank solar tank. Basically this system acts as a water pre-heater.

Even on a cool cloudy day there is enough heat gain by the collectors to turn the pumps on. The water in the bottom of the solar tank is a chilly 47 degrees F. The water coming back from the solar loop is 80 degrees F. Even though this is too cold to use as domestic hot water, this water will be heating in the auxiliary electric hot water heater to 130 degrees F for household use. Bringing the water temperature up, even a few degrees will save electric in the long run. On sunny days, I would expect the water coming back from the solar loop to be much warmer. The flow rate is a little less than 5 gallons per minute, which is a little higher than it should be for optimum collector performance. I will have to slow the pump down a little bit to get it to around 3.6 GPM.

This is a list of parts I used to build the system. I was going to include cost for each part, however, most of this equipment is made from copper, which has been spiraling upward for the last several years. Any price I list today will likely not be valid in a few months.

That’s it. Finally done, now I can get back to my regularly scheduled fall events like splitting fire wood and raking leaves.

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