Balancing must be done on a sunny day when the system is operating. Reduce the
flow slightly through the array with the lowest outlet temperature. Wait three or four
minutes, and recheck all the array outlet temperatures. Continue balancing and
waiting until all the temperatures are within five degrees of each other.
Close the balancing valves as little as possible. Reducing the flow
rate through the collectors reduces their efficiency.
Never install valves in a way that could allow the isolation of the solar
collectors from pressure relief valves and/or expansion tanks.
Collectors have been completely destroyed by bursting in this way.
Pressure Gauges and Thermometers
Broken, leaking or inaccurate pressure gauges and thermometers are almost
always replaced. The only practical exception to this is the occasional pressure
gauge which can be recalibrated.
A recalibratable pressure gauge has a removable glass lens and ring (to hold the
glass on). It also has a screwdriver slot in the center of the gauge needle or
elsewhere on the face (Figure 5-13).
5.2 REPAIR PROCEDURES