After the circuit breaker trips, whether we plan to carry out repairs or attempt to reset it, we must know the reason for the last trip to narrow down the scope of the fault. The circuit breaker has two main protection functions - overload (short circuit is a special form of overload) protection and leakage protection. So how can we tell if the circuit breaker tripped due to overload or leakage? In fact, by observing the circuit breaker after it has tripped, we can identify it at a glance.
(PS: This article is only applicable to leakage circuit breakers. If the circuit breaker does not have leakage protection, it can be determined that the circuit breaker tripped due to overload after it has tripped.)
Reset button
If there is a line of small text on your circuit breaker that says "Press to reset when closed," you need to observe the button indicated by the arrow next to this line of text; this button is called the "reset button."
This button is normally flush with the entire circuit breaker panel. When a leakage occurs in the circuit, the reset button will protrude and cannot be reset (it cannot be moved). In other words, if the reset button is protruding after a trip, it indicates that there is a leakage in the circuit; if the reset button is not protruding after a trip, it indicates that there is an overload in the circuit.
The existence of the reset button serves two purposes: on one hand, it shows the user the reason for the trip; on the other hand, it prevents personnel from incorrectly operating the circuit breaker, which could harm the users of the circuit.
Display screen
There is also a type of circuit breaker that does not have the "preventing personnel from misoperation" function and can only display the reason for the trip; it looks like the one below.
The position of this display screen is also not fixed; each brand of circuit breaker has its own position. Some brands will install it at the position of the reset button, while others will install it on the handle for switching on and off.
When the circuit breaker is functioning normally, manually switched off, or tripped due to overload, the color of the display screen remains unchanged, always blue or green. When a leakage occurs in the circuit, the display screen will turn red to alert the user to the reason for the trip.