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Friday, January 8, 2021

Question:

Thanks for this Code Forum. I check this out each morning before heading to work. I have a 3-inch rigid conduit for a 4160-Volt circuit installed in a tunnel. Can the conduit serve as the equipment grounding conductor or should I install a wire-type EGC inside the raceway?

Thanks,

Armand Stern 

A

Answer:

Hi Armand,

Thanks for the comments and the great question. Part IV of Article 110 addresses tunnel installations over 1000 volts. There is a specific requirement in Section 110.54(B) that "an equipment grounding conductor be run with the circuit conductors inside the metal raceway or inside the metal jacket of a multiconductor cable assembly. The EGC can be a bare or insulated conductor. We don't see an exception here.  In this case, it appears that the EGC has to be a wire type and the types mentioned in 250.118 (including rigid metal conduit) are superseded by the provisions in 110.54(B). Sizing the EGC is addressed in 250. 190(C)(3) which refers to Table 250.122. 

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