Within the wall switch box, there is a single black wire, neutral wire, and ground wire. I'm installing the Lutron Caseta dimmer (doesn't require a neutral wire connection). On the Casetas, there are TWO black wires. How do you recommend I connect the two components?
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The white is likely the hot, black the switch leg. Can you use a voltage meter measuring voltage on white to ground and black to ground? A picture would also be great.– NoSparksPleaseCommented Dec 31, 2020 at 19:26
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Welcome. Please take the tour.– isherwoodCommented Dec 31, 2020 at 21:37
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What makes you think that is a neutral wire?– Harper - Reinstate MonicaCommented Jan 1, 2021 at 4:03
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1 Answer
Actually, what you called a neutral wire (I assume colored white) is actually the hot coming from the light box (technically, there should be a black stripe of tape or paint near the end, but this is often omitted) and the black is the switched hot going back to the light. This is called a switch loop.
If you had a true neutral in the switch box, it would either be a non-connected white or two whites connected together.
Connect one black from the dimmer to the black wire, the other black from the dimmer to the white and ground to ground.
answered Dec 31, 2020 at 19:27
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Marked or unmarked the white being switch load would be an NEC violation. The configuration of using white for hot prevents polarity confusion presented by two whites connected to light fixture. Commented Dec 31, 2020 at 19:29
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@NoSparksPlease Wouldn't using /2 NM-B as a switch loop require using the white as switched hot? Assuming it was pre-code requiring neutrals in switch boxes. Commented Dec 31, 2020 at 20:09
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@DoxyLover -- white is supposed to be always-hot in /2 (old style) switch loops to make it identifiable as a hot -- see NEC 200.7(C) point 1 Commented Dec 31, 2020 at 20:18