Using a white or gray wire as a hot conductor
On circuits of 50 V or more, a white or gray wire may serve as a hot only within a cable assembly or flexible cord. In a cable, it must be re-marked in another color at terminations and wherever visible and accessible.
What the code requires
On circuits of 50 V or more, white, gray or three-stripe insulation may be used for something other than a grounded (neutral) conductor only in the two situations described in 200.7(C)(1) and (C)(2).
200.7(C)(1) covers cable assemblies. The conductor must be permanently re-identified as an ungrounded (hot) conductor with tape, paint or another effective means at its terminations and at every location where it is visible and accessible. The marking must go all the way around the insulation and be a color other than white, gray or green.
For single-pole, 3-way and 4-way switch loops, a re-identified white or gray conductor may be used only as the supply to the switch. It may not be the return conductor from the switch to the outlet it controls.
200.7(C)(2) covers flexible cords. A cord with a white or gray conductor may connect an appliance or equipment as 400.10 permits, even if the outlet's circuit has no grounded conductor.
On the job
- An unmarked white wire used as a hot in a switch loop or a 240 V cable circuit does not meet this rule. It must be re-marked at its terminations and wherever it is visible and accessible.
- Using the white wire as the switched return to the light fails the switch-loop rule.
Related sections
- NEC 200.6: How neutral wires must be identified
- NEC 404.2(C): Neutral wire required at light switches
- NEC 400.10
- NEC 400.22
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