If you're wiring up a lighting circuit, where the power enters at the lighting outlet. According to the National Electrical Code, which wire should be "hot" and which should be "switched hot"?

Question in graphical form:

Graphical Representation of Question

Bonus points if you can reference relevant code section(s).

  • 5
    Personally, I make black the always hot, and white with black tape the switched hot. – BMitch Sep 13 '13 at 13:42

It doesn't matter, it's in the past

In the old days (pre 2011 code adoption), National Electrical Code said that if a wire with white or gray insulation or a marking of three white or gray continuous stripes is used as part of a switch loop to single-pole, 3-way, or 4-way switches. The conductor should be permanently reidentified, and should be used for the supply to the switch but not the return (200.7(C)(2)).

National Electrical Code 2008

Chapter 2 Wiring and Protection

Article 200 Use and Identification of Grounded Conductors

200.7 Use of Insulation of a White or Gray Color or with Three Continuous White Stripes.

(2) Where a cable assembly contains an insulated conductor for single-pole, 3-way or 4-way switch loops and the conductor with white or gray insulation or a marking of three continuous white stripes is used for the supply to the switch but not as a return conductor from the switch to the switched outlet. In these applications, the conductor with white or gray insulation or with three continuous white stripes shall be permanently reidentified to indicate its use by painting or other effective means at its terminations and at each location where the conductor is visible and accessible.

So before 2011 NEC adoption, the wiring should look like this.

Proper switch loop wiring

The future

According to the 2011 code...

National Electrical Code 2011

Chapter 4 Equipment for General Use

ARTICLE 404 Switches

I. Installation

404.2 Switch Connections.

(C) Switches Controlling Lighting Loads. Where switches control lighting loads supplied by a grounded general purpose branch circuit, a grounded circuit conductor shall be provided at the switch location.

A grounded (neutral) conductor is now required at each switch location (see code for exceptions), which means the circuit would now have to look like this...

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enter image description here

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  • 1
    So you leave the neutral capped off in the box? – Chris Cudmore Sep 13 '13 at 18:55
  • 5
    @ChrisCudmore, yes or used in lighted, smart, etc. switches that require power. – Jason Sep 13 '13 at 18:56
  • Either is correct but it's sort of a convention to, when an always-hot and switched-hot are present, make black always and red switched. I even put a piece of red tape on the black lead from the lamp, so it really is "match color to color". – Harper - Reinstate Monica Jan 27 '18 at 21:03

It is still in the 2017 Code. 200.7 (C) (1) requires the white used as ungrounded (hot), in a switch loop, to be re-identified with another color.

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