Pressure and Temperature Relief Valves
Pressure and temperature relief valves must be used on pressurized storage tanks
and other city water lines of all systems. Look for evidence of leakage or blowoff,
and properly installed discharge piping. Local code may require piping of discharge
to drains or outside the building, and the system should be in compliance.
A temperature and pressure relief valve must not be used in the
collector loop of closed-loop systems. The valve will inevitably
open at some time, causing a loss of solar fluid.
Check expansion tanks with diaphragms in closed-loops by very briefly depressing
the Schrader valve. If any fluid comes out, the diaphragm is leaking and the tank
must be replaced. (Figure 3-9)
Repeated testing of diaphragm-type expansion tanks as
described above will eventually release enough air to interfere
with proper operation. Whenever the fluid is removed from the
loop, the air pressure of the tank should be measured and
necessary air pumped in.
Whenever an expansion tank is installed in a loop with a pump,
it must be on the suction side of the pump. Installation of an
expansion tank on the discharge side of the pump can result in
pump cavitation and damage.
3.1 INSPECTION PROCEDURES