Overcurrent Protection and Methods

Overcurrent Protection and Methods

By Drew Ihle

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?

Fill in the Blank

_ is the flow of electrons in an electrical circuit.

Multiple Choice

A method of overcurrent protection would _ the circuit if there is too much current.

• close

• start

• open

• brace

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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Multiple Choice

The number on a circuit breaker indicates the maximum _ of that circuit.

• Voltage

• Amps

• Ohms

• Hertz

Multiple Choice

What will happen to a wire if too much current flows through it?

• Melt

• Freeze

• Amps

• Rot

Wiring and Protection Chart

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Multiple Choice

True or False Fuses are reusable

• True

• False

Multiple Choice

True or False Breakers are reusable

• True

• False