Electronic component end of life detection
We have here a lightning arrester circuit breaker, including a varistor (square blue component on the picture), designed to bear an overload of 40.000 volts, in case of storm.
As the device is permanently powered up in the building electrical network, it progressively ages, and it will loose its protection function, when it arrives to end of life. This end of life is defined by a temperature rising, around 100°C.
It is this temperature that the Delta Concept bimetal senses, by actuating a circuit-breaking mechanism, linked to a visual indicator for failing device information.
Note: the lack of lightning arrester may cause the building electric board be set on fire, and so the whole building itself.