Solar System Design Guide
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Collector Cooling Function with SCU 124 / 224 / 345
The solar circuit pump will be switched off when the
maximum tank temperature is reached. The control will
allow the collector temperature to increase until it reaches
a user defined temperature. Then the solar circuit pump
will be switched on long enough to enable the collector
temperature to fall by 9ºRa (5ºK). This process will
continue until the solar tank temperature increases to a
maximum of 203ºF (95ºC).
Tank Cooling Function with SCU 124 / 224 / 345
Information Regarding the Collector Cooling and Tank Cooling Functions
Ensure the intrinsic safety of the solar thermal system,
even if the collector temperature continues to rise after
the system has reached all limit temperatures,
by accurately sizing the diaphragm expansion vessel.
Where stagnation occurs or for collector temperatures
that rise further, the solar circuit pump will be blocked or
stopped (emergency collector shutdown) to avoid thermal
overloading of the connected components.
This function is only available if the collector cooling
function has been enabled. If the maximum tank
temperature has been exceeded, the solar circuit pump
will be enabled once the collectors are cooler than the
solar tank. The pump will run for as long as required
to cool the solar tank, to the selected maximum tank
temperature. The reduction in tank temperature will come
from the thermal losses via the collector array and piping
(works best with flat plate collectors).
Solar Control
