Ben, Clay, a SolVelox on a tank and our customer Chris Allen made the front page of the Durham Herald last week. The article wasn’t really about solar but it Chris Allen of RTP Solar is interviewed about starting his solar installation business.

All atmospheric solar
storage tanks are constructed of an outer layer to withstand environmental conditions, an inner layer of some type of insulating material to reduce heat loss, and an inner liner to reduce corrosion and extend the life of the tank. However, atmospheric solar storage tanks are constructed of many different types of materials.

Since large capacity tanks are difficult to maneuver through doorways, assembly of some atmospheric tanks is done at the installation site. This may reduce the shipping costs as well.

next – stainless steel tanks

Legionnaires’ disease is a form of pneumonia caused by the bacterium Legionella Pneumophila. Individuals are infected by inhalation of sprays, mists or microscopic droplets of water contaminated with the bacterium. Although Legionella Pneumophila is naturally occurring at low levels in bodies of water, it is not likely that an individual would develop Legionnaires’ disease from these sources.

What does Legionnaires’ disease and Legionella Pneumophila have to do with solar hot water heating systems?

Legionella Pneumophila may live and possibly flourish in almost any water system or equipment that distributes water as a spray or mist, including residential and commercial solar hot water heating systems. Can you be infected by the bacterium by taking a shower in your own home? Yes, it is possible, but unlikely.

Legionella Pneumophila is much more likely to be found in substantial levels in the larger water systems of workplaces and public facilities such as, but not limited to, hotels, cruise ships and hospitals. In addition to conventional and solar hot water heating systems, the bacterium may also exist in the cooling towers of industrial cooling water systems, large central air conditioning systems, evaporative coolers, whirlpool spas, ice making machines and decorative fountains.

Water systems with warm stagnant water provide the best environment for the growth of Legionella Pneumophila. The bacterium can begin to multiply at temperatures between 68°F and 122°F, with the most favorable temperature range being between 90°F and 105°F. The incidence of rust and other microorganisms can also promote increased growth. Dead legs in the water system design may provide a favorable place for the bacterium to grow.

When water temperature is increased to 131°F, Legionella Pneumophila will be destroyed in several hours. At temperatures above 158°F, the bacterium is immediately destroyed.

To prevent the growth of Legionella Pneumophila, it is recommended that solar hot water heating systems be operated at 140°F. In public water systems biocides such as chlorine are also used to eliminate the bacterium, as well as ultraviolet-C light in conjunction with specialized ultrasonic processes.

Those installing or repairing solar hot water systems should take into consideration the environmental conditions that promote the growth of Legionella and shoot to avoid those situations by cleaning all piping, fittings and other equipment before assembly. Since many solar systems operate with the solar tank pre-heating the water going into a back-up heater that is set high enough to destroy the bacteria it should not be a concern.

This is the time of the year when the calls start rolling in. “I have a single tank solar water heating system and the water heater has stopped working.” This is not a service call you should need to run out on.

Using a standard electric water heater for both your solar storage as well as providing your back-up heating has many advantages including; reduced floor space, ability to use standard tanks, less standby losses from the tank, better heat recovery, and less cost. But now we come to the rub. Electric water heaters have a thermostatic breaker built into the top element. When the thermostat senses temperatures over 170° F it automatically trips this safety breaker. This breaker is designed as extra protection in case you have a run-away element in your tank to keep the system from getting too hot.

Frequently a solar water heating system will supply 100% of your hot water needs during May through September. If at any time during that period the top of your tank exceeded 170° F the tanks thermostatic breaker will trip. As the cooler and cloudier weather sets in the back up element is no longer able to kick in and you receive a service call. Fortunately, the fix for this problem is simple and within the reach of even the least proficient home-owner.

Simply remove the cover plate over the upper element, depress the red button with the eraser of a pencil and voila you are back and running again. (see picture)

Water Heater Reset Button

So next time you get this call don’t fret and think about the little red dot.