Courtesy of Marsh Instrument Co.
To make an adjustment, let all the system pressure out, and turn the calibration
screw until the needle indicates zero.
Pressure Relief Valves
When replacing pressure relief valves, be sure the release pressure of the
replacement is the same as the system designer specified. Repipe discharge piping
following local code requirements.
Never use a temperature and pressure relief valve in the
collector loop of closed loop systems. The valve will open at some
time, due to normal temperatures, causing a loss of solar fluid.
5.2 REPAIR PROCEDURES