Failed Hager RCBO

This video features a 6 amp Hager RCBO which had failed in an explosive, smoky fashion.

The Video

Electronic Failure

The failure on this item occured when the test button was pressed, and normally that causes a tiny current to flow which is detected by the electronics and trips the mechanical circuit breaker.

In this instance a much larger current has caused the entire circuit board to be blackened and charred, with the disconnect probably occuring due to a short circuit between line and neutral.

Due to the extensive damage it is not clear exactly what the failure was, but as it happened when the test button was pressed a likely cause is either the test resistor failed, or some arc formed between the test circuit and some other parts, possibly due to moisture.