Photo by Mike Forbes

Wow, what a spring. Little sun, and our heat and electricity generating systems sat idle most days. They are starting to perk up a bit and provide the hot water and electricity we hoped for. Last month, I left off finishing the mounting of the panels and installation of the tanks. That was last fall, leaving the remainder of the system to be finished in the comfort of our home during the winter.

I spent many days fishing wires and pipes through small spaces. One drawback to small homes that utilize every space is that there are fewer places to run utilities. I recommend installing some sort of chase in a small new home that connects the lowest level and the roof if you plan on installing renewable energy systems in the future, unless you mind looking at pipes and wires in the living space.

Our system utilizes two types of pipe: PEX and copper. PEX is easier to work with than copper, but can’t withstand high temperatures like copper. What is high? PEX fails at 180°, which is much higher than domestic hot water systems, but solar hot water systems can climb over 200° in full sun. Most installers recommend installing copper pipe from the panels to the tank and using PEX for runs between tanks and in the domestic supply system. In our system, I ran copper from the roof to the upper tank and PEX from there to the basement storage and domestic tank.

Once all the pipes were run and connected to each of the pumps, I began the process of installing the electrical system to tell the pumps when to turn on and off. The heart of the SDHW system is the controller. The controller has a number of sensors to detect temperature at various points in the system. Typically, you have a sensor on the panels and one in the storage tank. Our system has four: one on the panels, two in the solar storage tank (high and low), and one in the domestic hot water tank. Since our system has two tanks, we have to control not only pump-flowing water in the panels, but also the water that circulates between the two tanks. We used a controller made in Germany called the Delta Sol. I highly recommend it, as it lends itself to many designs and even offers the ability to collect information via your computer. The way our system work is as follows: If the sun is shining and the collectors are warm, the solar pump kicks on and circulates water through the panels and the storage tank. Once the storage tank is 120° and the domestic tank is less than 110°, the pump that circulates water between them turns on. Once the water in the domestic tank reaches 155°, the pump turns off, and once the water in the storage tank reaches 165°, the solar pump turns off. I should mention that the water that is in our domestic tank doesn’t ever touch the water elsewhere in the system. It is isolated from it by heat exchangers because the fluid in the system has a mild, non-toxic anti-freeze solution in it. We sure wouldn’t want that mixing with our water, would we?

It is a relatively simple system and has been working well for several months now. After about 4-6 hours on a sunny day, both of our hot water tanks are 155°. On a partly sunny day, the system will cycle on and off and will bring all the water in the system to about 130°.

One thing I wasn’t aware of with a drainback system is that the water that returns from the solar panels does so in a forceful manner, creating a loud coffee percolator effect in the tank. I’m use to the sound now, but have plans on putting sound deadening around the tank to minimize it. Installing the sound deadening ahead of time would have been very easy to do. Most solar hot water systems don’t have to worry about this noise issue since they are typically a pressurized glycol system.

Mike and his family are enjoying the longer days and mild temperatures of springtime.