In cold weather climates, such as ours here in Central Wisconsin, solar hot water heating systems use one of two systems to prevent freezing in winter.
One is the drainback system that collects all the loop fluid in a tank situated within the thermal envelope of the building when the system shuts down. If this is the type of system you have, the installer likely charged the loop system with an anti-freeze solution to help prevent the loop fluid from freezing. If this is the case, and you intend to use the system during the winter, it is imperative that the protection level of the loop system fluid be checked and adjusted, if need be.
The majority of solar hot water heating setups in Wisconsin use the standard closed loop anti-freeze system. In this type of system the loop fluid remains in the pipes and collectors whether the system is running or not. . During the hot summer months the loop fluid, typically a mixture of water and propylene glycol, can break down, losing its effectiveness. It can also become acidic.
To protect your investment and ensure the optimal performance of your solar heating system you should have your system checked prior to the onset of freezing temperatures.
Two tests are recommended. One is the anti-freeze protection level of the loop system. To properly test the protection level afforded by propylene glycol anti-freeze, a special tester is used. An automotive anti-freeze tester will not work with propylene glycol. This is likely due to a difference in specific gravity between ethylene and propylene glycols. The correct type of tester can be found at solar equipment supply stores, at some auto supply stores and certainly on the Internet.
The second is a pH test that will warn you if the solar loop fluid is becoming too acidic. A pH meter or a litmus paper test will provide the pH level of your loop system fluid. The pH level should not fall lower than 7.5. Running with a pH level that is too acidic could result in premature failure of system components. If the loop system fluid is too acidic, the system should be drained, flushed and recharged with a fresh mixture of propylene glycol and water.
The servicing of a solar water heating system should be done by a qualified service person. A homeowner familiar with the procedures required to properly test, drain, flush and recharge the system can service their own systems. Others should contact their system installer or service provider to schedule a system maintenance check.
As a query to my readers, I would like to ask about snow accumulation on the solar collectors. Cleaning the glass on the collectors before winter helps them shed snow. Do you think a silicon based protectant spray would help? Having the car washed and waxed before winter sure helps it part with its share of that annoying white stuff!
Share your ideas and comments.