Interrupting & Isolating Devices

Guidelines apply to interrupting and isolating devices such as the following:

• Circuit breakers
• Fused cutouts
• Equipment isolating means

Circuit Breakers

Circuit breakers located indoors must be made of metal-enclosed or fire-resistant, cell-mounted units and located in a place that is only accessible to qualified personnel. There must be a way to indicate if the circuit breaker is in the open or closed position.

Fused Cutouts

Fused cutouts installed in building or transformer vaults must be identified for the purpose and readily accessible for fuse replacement.

Equipment Isolating Means

There must be a way to completely isolate equipment for inspection and repairs. Means of isolation that do not interrupt the load current of the circuit must be either interlocked with a circuit interrupter or be marked with a sign warning against opening them while under load.

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