On a 3-phase, 4-wire delta system with a high leg, what color is that high-leg ("wild leg") conductor required to be identified with?
Not quite. The answer is B: Orange
110.15 requires the high leg of a 4-wire delta system with a grounded midpoint — the conductor with the higher voltage to ground (about 208 V on a 120/240 V system) — to be marked orange or by another effective means. The panelboard rules in Article 408 also place it in the B (center) phase position. The marking matters because someone assuming all legs read 120 V to ground could connect a 120 V single-pole load to the high leg and destroy it.
Reference: NEC 2023 110.15 (High-Leg Marking)
Checked against multiple published sources
Two independent secondary sources agree on the requirement; neither is the code text. The ECM article is based on the 2011 NEC; 110.15 reads the same in later editions as far as the sources show.
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