National Electrical Installation Standards

Standards as High as Your Own

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Friday, April 10, 2020

Question:

Good Day, we are hoping you might provide some clarification about the NEC requirements for identification of the high-leg conductor installed in a 120/240 delta high-leg system. The utility says it needs to be red in color and the "C" phase is the high leg. What does the NEC say? Thanks for your help.

Jerry Blair

A

Answer:

Hi Jerry, thanks for participating. The NEC does specifically address your question. Section 110.16 indicates that on a 4-wire, delta-connected system where the midpoint of one phase winding is grounded, only the conductor or bus bar having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is orange in color or by other effective means. Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present. Section 408.3(E) indicates that the B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other bus bar arrangements shall be permitted for additions to existing installations and shall be marked. Note that there is an exception that allows the high-leg phase to have the same position as the metering equipment, which usually aligns with some utility company requirements.

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