Other candidates for temperature measurement include the feed and return of the
auxiliary systems, the feed and return of space heating distribution loops, and the
points measured by differential thermostat sensors.
Pressure measurement is necessary in the collector loop of closed-loop systems. It
is the only practical way to confirm that there is adequate solar fluid for proper
Measuring the pressure on each side of a pump makes it possible to determine the
flow rate through the pump. This process is explained in Section 3.1.4 in the
Differential pressure measurements can also describe flow rates through heat
exchangers, collectors or other components, if the manufacturer can supply flow
rate vs. pressure drop information. (Figure 2-53)
Specialized flow setting devices use a restriction of known characteristics with
pressure measurement ports on each side. A differential pressure gauge is
normally used to determine and help set the flow rate.
Occasionally, a draindown system will have a pressure gauge in the drained portion
of the collector loop. On cold nights, one look at the gauge tells whether or not the
water has drained.
2.7 COMPONENT OPERATION