Some of the other failures were attributed to heating circuits that did not work, usually during electric utility power failures. Although they initially cost more to install, they are very simple and require little maintenance. In addition, they are not affected by power outages. The primary components of solar heating systems are the collectors, heat transfer systems, heat storage, and controls. The greatest problem in all types of collectors is leakage.
Leaks can occur from improper fabrication or installation or as the result of freeze damage.
The largest potential problem in heat transfer systems is freeze protection failure. Freeze protection tends to be unreliable in water-based systems. Freezing can even occur in the water side of the heat exchanger in systems that use an antifreeze solution as the heat transfer fluid, if the antifreeze solution thermosiphons between cold collectors and a warm heat exchanger. Another problem results when antifreeze solutions become acidic, due to the breakdown over time of the antifreeze corrosion inhibitors. This eventually results in internal damage to the pipes, collectors, and heat exchangers, which can cause leaks.