Conductors in Tunnels

Conductors in tunnels must be installed in one or more of the following ways:

• Metal conduit or other metal raceway
• Metal-clad type cable
• Another suitable multi-conductor cable

Multi-conductors must be located or guarded in a way that protects them from physical damage. Multi-conductor portable cables can supply multi-conductor equipment. An equipment grounding conductor must be run with circuit conductors inside the metal raceway or inside the multi-conductor cable jacket. The equipment grounding conductor can be insulated or bare.

In order to prevent accidental contact with energized parts, certain bare terminals must be enclosed, such as those on:

• Transformers
• Switches
• Motor controllers

These enclosures must be drip-proof, weatherproof, or submersible as required by the environmental conditions of the tunnel.

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