Overcurrent

Smoke rising from electrical outlet
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Definition: Overcurrent is a condition in an electrical circuit when the current (amperage) in the circuit exceeds the rated amperage capacity of that circuit or of the connected equipment on that circuit. Overcurrent may be caused by excessive circuit load, a short circuit, loose electrical wire connection, ground fault or surge power draw from a motor start up.

Overcurrent protection is a term given to circuit breakers or fuses.

When more current (amperes) runs through a circuit than the wire size of the circuit was intended to accommodate, the circuit breaker will trip to interrupt and open the circuit.

Short circuits occur when the hot wire (usually black or red) touches another hot wire or comes in contact with a neutral wire (white). Shorts can also happen if there is a break in a wire in the circuit. Short circuits can be difficult to diagnose since they can be caused by your home's wiring or a load plugged into an outlet.

Ground faults are a type of short circuit. They happen when the hot wire touches the ground wire or the side of a metal outlet box (when the metal box is connected to ground).

Loose terminal connections can also trip overcurrent protection. When a connection is loose, it creates resistance and results in heat. Sometimes the heat can get so hot that the plug will melt and wires can get so hot that a fire can start in a wall.

Surge power draw is another reason a circuit protection device can trip. When a motor starts up it draws more power (higher amperes) than when it is running. When this happens the circuit may be temporarily overloaded and the overcurrent protection device will trip due to excessive circuit load for that fraction of a second.

Also Known As: short, short circuit