Passive overheating protection measures employ some mechanism that reduces the collector temperature during non-standard use (stagnation). However, if the collector is operating in normal mode (again), one has to make sure that the passive overheating protection is “turned off” again, for example, thermotropic coatings need to return to their transparent state or the venting mechanisms need to close again.
Thus, we recommended looking for criteria or test procedures that allow assessing proper functioning of the collector after one or more cycles where the passive overheating protection was “turned on.”
Possible approaches can range from simple visual inspection (also during final inspection) to detailed measurements of the “passive overheating protection components” (e. g., transmissivity measurements of thermotropic covers) or an additional thermal performance test after exposure of the collector.
