Overcurrent Protection and Methods

What is overcurrent protection?

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An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor.

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Without current, you can still have voltage (potential)​

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​*A 60 watt light bulb on a 120v circuit will draw .5 amperes, or amps. ​

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​First...Current

​​The purpose of overcurrent protection is found in the NEC [240.1], which states: “Overcurrent protection for conductors and equipment is provided to open the circuit if the current reaches a value that will cause an excessive or dangerous temperature in conductors or conductor insulation."

Overcurrent Protection

​What are some methods of overcurrent protection?

A fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit.

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Fuse

Breakers work as a fuse to open the circuit, but are reusable. The breaker uses thermal energy and magnitism to open the circuit.

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The number indicates the maximum ampere rating. ​

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Breakers

Too much current can cause electrical wiring insulation to melt, and potentially the conductor if the wire is too small to carry the amount of current loaded on the circuit.

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​What happens if...?

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If the wire and breaker/fuse are sized correctly, but the current exceeds the breaker/fuse size, the breaker and fuse will safely open the circuit without damaging the wiring. ​

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​What happens if...?

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Wiring and Protection Chart

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