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 For shutoff purposes, gate valves or ball valves should be used. (figure 2-27) Globe
valves, because of their high resistance to flow, should never be used in any part of
the system.
Tanks, heat exchangers, the cold water supply, and banks of collectors are typical
candidates for shutoff valves. Pumps can be isolated as well, using either separate
valves or isolation flanges
Isolation valves should not be used on solar collector arrays unless a pressure relief
valve is in the piping between valves.
Balancing Valves
An ideal collector array is piped so that all the collectors receive an equal flow
automatically. However, sometimes it is necessary to install balancing valves in the
collector piping to accomplish this.
FIGURE 2-27
A Gate Valve (left)
and a Ball Valve
(right)
Balancing valves should be ball valves, and should be installed in the inlet line at the
top of a group of collectors. Every group of panels should also have a thermometer
or the equivalent installed in its outlet. (Figure 2-28) When all the outlet piping
temperatures are equal, the flows are properly balanced between collector groups.
Check Valves
Check valves allow fluid flow in only one direction. They are used in closed-loop
and draindown systems to prevent heat loss at night by reverse thermosiphoning.
OPERATION
34
2.7 COMPONENT OPERATION
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