3-way switch at end of run


Old 10-06-00, 03:02 PM
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Okay, I need a clarification. I have learned here that the 1999 code now specifies that the black rather than the white should be used as the switched hot on a 2-way switch at the end of a run. But what about a 3-way switch at the end of a run?

Let's say I have:


Should the white, red, or black wire return power to the light? If you answer "black", the I assume you must wire black-to-white, and red-to-red in the box at the light?

But if you answer "white", then I can wire black-to-black and red-to-red in the box at the light. This seems more natural to me.

What's the code say?

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Old 10-06-00, 03:27 PM
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hello john,
u allways what a colored wire returning power to the light on any switch loop, wheather it be singel, 3way. reasion 4 this is u dont want 2 whites to hook to the light. whin power is in the light the white shuld allways carry power to the switch.
Old 10-07-00, 10:37 PM
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Previous editions of the NEC have required white be reserved for grounded (nuetral) conductors, but allowed an exception when the circuit was wired the way Sprky described, allowing the white within a cable to serve as an ungrounded conductor ('96 NEC 200-7 exception #2). The thinking was that generally any competent electrician would know what they were dealing with in terms of color coding and would wire accordingly. The '99 NEC eliminated the exception. Any ungrounded conductor must now be colored something other than those colors reserved for grounded or grounding conductors (white, gray, green). In response to John's question regarding a three way at the end of a run, the white must now be re-identified no matter how you use it. The days of hooking the white up as Sprky describes are over, at least in terms of code-compliance. The thinking behind all of this was to idiot proof the color coding since nowadays the unfamiliar are regularly doing their own wiring. That's progress guys!
Old 10-08-00, 09:51 AM
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There is an exception in the 99 NEC that allows the power to be in a light box and a 12/2 switch leg to be run to the single pole switch. The only stipulation is that the white wire runs the power from the light box to the switch and the black wire must run the hot switched back to the light fixture. This white wire must now be reidentified with black tape at both ends.

Now as for the three way switch the black and red of your 12/3 now must be you travlers and the blacks must be the commons and the whites must be the grounded.

You have an example that is a mix of a single pole switch and a three way switch because you only have a 12/3 going from the light fixture to the last three way switch. You must reidentify the white as an ungrounded conductor by running any color tape at each end of that white except grey tape, green tape, or white tape. This would reidentify the conductor as an ungrounded conductor. See the copy below of that section in the NEC

Good Luck


200-7 NEC

2. Where a cable contains an insulated conductor for single-pole, 3-way, or 4-way switch loops, and the conductor with white or natural 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 natural gray insulation or with three continuous white stripes shall be permanently re-identified to indicate its use by painting or other effective means at its terminations and at each location where the conductor is visible and accessible.

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