Light/Switch wiring

11 years ago

Here is the scenario. Have a kitchen light that needs replacing. Upon removal, I have 3 "cables". One is the continuing circuit, one is a junction to feed a switch directly below in the basement and the 3rd is to a switch. How should the light be wired to have the switch control the light but not interrupt the other circuit?

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Comments (3)

ionized_gw
11 years ago
For the continuing circuit and the switch down stairs, hot to hot and neutral to neutral. For the switch loop and light, connect the neutral directly to the light and connect the hot to the switch loop in the ceiling box. Connect the returning hot from the switch to the hot connection in the light. Connect all the grounds properly.
greg_2015
11 years ago
If you're replacing a light, then just wire it up the same way that the old one was. Or am I missing something?
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User
11 years ago
last modified: 11 years ago
The white wire is not supposed to be used as the return conductor from the switch to the light.

NEC

200.7(C) Circuits of 50 Volts or More.

The use of insulation that is white or gray or that has three continuous white stripes for other than a grounded conductor for circuits of 50 volts or more shall be permitted only as in (1) through (3).

(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.

Before tying any wires together, you permanently color or tape the white wire that goes to the switch (wrap it in black electrical tape) on BOTH ends. Then I take the two black wires that are not going to the switch and the black taped white wire, and wire nut them together and fold them into the back of the box because you should never need them again to change a light fixture. You could tie all the grounds together first and pigtail out a lead to hook to the light, but with only 3 grounds and a fixture with a ground wire and not a screw, I do the grounds second. Third, tie the (only two) remaining white wires together. These will also be the neutral for the light. Last, you are left with only the one black wire coming back from the switch that also (and only) hooks up to the light.