National Electrical Installation Standards

Standards as High as Your Own

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Thursday, April 15, 2021

Question:

Hello Code Friends,

I've installed a 1-inch metal conduit (EMT) for a 3-phase, 100-ampere circuit that is sized at 2 AWG copper. The conduit is too small for (4) 2 AWG copper wires (THHN). Can I install the forth conductor (neutral) outside the conduit and using cable tie wraps to fasten it to the outside of raceway? Is there a Code that applies in this situation.

Thanks in advance. 

Arnold Ford

A

Answer:

Hey Arnold.

The short answer is no. Section 300.3(B) requires that all conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cable bus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4). We suggest replacing the conduit with the appropriate Code-compliant size EMT or reduce the wire size for the circuit, along with reducing the rating of the overcurrent device protecting the circuit. We don't have all the information or details needed that would address your complete scenario. It is also advisable to have the installation inspected by the authority having jurisdiction. 

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