Electricity – What’s the Difference Between an Overload and a Short Circuit?

Electrical wires also called conductors come in many sizes and current ratings to power everything from a simple small appliance to heavy-duty industrial equipment. Protection and control of electrical systems are essential to preventing overloads and short circuits. So what’s the difference between the two?

Overloads – Electrical conductors are sized to specific equipment based on how much current the equipment will draw. In order to ensure the conductors do not exceed their current rating (measured in amps), a protective device, usually a circuit breaker is installed within the circuit with a current rating matching that of the conductors. In an overload situation, the current flowing to the load exceeds the current rating of the conductor and therefore the circuit breaker. If prolonged, the circuit breaker protecting the circuit will heat up and “trip” opening the circuit to prevent damage to wiring or equipment. For example, too many appliances plugged into the same outlet and running and at the same time could overload the circuit by exceeding its current rating. Without a circuit breaker, the conductors in the circuit could potentially heat up to a point in which the insulated coating on the conductors melt creating a fire hazard.

Short-circuits – When a circuit path is disrupted, usually by accident, current does not flow to the load and a short-circuit condition occurs. For example, if a table lamp is plugged into an electrical outlet and its cord is suddenly cut with wire cutters, there is little or no resistance in the circuit. This causes the current to reach a very high value causing the circuit breaker to trip instantly.