Water Hardness - Scaling
Water with a high percentage of calcium and magnesium compounds is usually
described as "hard." These minerals will deposit on piping system surfaces,
particularly heated ones. The reduction in piping diameter will cause flow rates and
heat transfer to drop.
If the system flow rates at the time of installation are known, a gradual reduction
usually indicates this scaling is occurring. It may be possible to visually inspect heat
exchanger passages. In extreme cases valves will not seat properly, and pumps
may be damaged by the build-up.
Water With Iron or Manganese
Iron and manganese usually do not greatly affect solar systems, except for their
contribution to the water's corrosivity. In extreme cases, ferric iron build-up in piping
systems may cause problems similar to hardness.
Water With Microbial Contamination
The most common group of microorganisms which cause problems with solar
systems are the iron bacteria. Although they are rare, their colonies can block flow
or interfere with component operation.
More important, any microbial contamination poses hazards to the users of the
system. Disinfection equipment must be installed as soon as possible.
Water treatment professionals are equipped to test for and treat all of these
problems. In severe cases, bringing in a specialist should be considered.
Any glycol left in a working system for over three years or in an inoperative one for
over three months may need replacement. Leaks resulting from acidic glycol are
usually spread fairly uniformly throughout the system.
Burst piping from inadequate concentrations of glycol will be most common in the
absorber plates, as these reach the lowest temperature in the system on cold, clear
Concentration and inhibitor condition should be checked. Concentration can be
determined with an optical refractometer or a manufacturer's test kit. (Figure 4-7)
Some laboratories are equipped to determine this.
4.3 TROUBLESHOOTING OPERATIONS