What is Circuit Breaker

NEC defines and overcurrent as any current in excess of the rated current of equipment of the ampacity of a conductor. An over current is the result of an overload, short circuit, arc or ground fault. Effects of overcurrent include fires, conductor insulation damage and equipment damage.

According to NEC, an overload is the operation of equipment in excess of normal, full-load rating, or of a conductor in excess of rated ampacity that, when it persists for a sufficient length of time would cause damage or dangerous overheating. An overload is NOT a short circuit, ground or arc fault.

A short circuit is an overcurrent which greatly exceeds the normal full load current of the circuit. Also, as the name infers, a short circuit leaves the normal current carrying path of the circuit and takes a short-cut around the load and back to the power source. A short circuit is an overcurrent but not an overload.