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I have a light that is plugged into a double gang wall recepticle. One plug is controlled by a light switch. When I went to move the receptacle I noticed that the wired plug had a red wire going to it and the brass tab was removed leaving the other 3 plugs hot. The mystery is that when I removed the light switch it was only connected to a two wire (black and white) romex, not a three wire as I expected. How is this possible and is it safe. I want to move the plug and keep it switched but would have to use 3 wire. Confused. Any help? Thanks.

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    Can you post photos of the insides of the boxes involved please? Aug 14, 2021 at 0:03
  • How many separate cables go into the box with the two duplex receptacles? Is there only one cable and does it have one black, one red and one white plus a bare copper ground? If so, this cable probably goes to another receptacle which is fed by a /2 cable. The B of this cable is connected to the B of the cable going to the 2-gang receptacle and to one wire in a /2 going to the wall switch. The switched hot from the switch is connected to the R going to the 2-gang. Aug 14, 2021 at 0:11
  • Look for a receptacle near the switch which is on the same circuit as the switched receptacle. It might be on the other side of the wall from the switch. Turn off the breaker to the switched hot and see what other receptacles are turned off too. Aug 14, 2021 at 0:19

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If you have a switch with only one /2 cable going to it, it is wired as a *traditional "switch loop". The two wires in the switch loop are

  • Always-hot (hot at all times)
  • Switched-hot (hot when the outlet should be energized)

Normally the cable's white wire is reserved for neutral. In this application it >>WAS<< allowed to be used as always-hot, if the white wire is marked with a few wraps of electrical tape to mark it as a hot.

However, as of NEC 2011, you are required to also bring one more wire:

  • Neutral (actual neutral)

This is required so that smart switches, motion sensors, and other such "powered switches" can be supported. The switch connects its own circuitry between always-hot and neutral, and uses the switched-hot wire to control the lamp.

This requires /3 cable, white becomes neutral, and black becomes always-hot.

Since this is a modification of the circuit, and since you have access to the cable route, you must bring that switch loop up to current Code.

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  • Would the obligation to provide a neutral when "modifying" a circuit be strict enough to require opening up a wall that otherwise would not have to be? If one is modifying one small part of a multiroom circuit, is there an obligation to provide these neutrals everywhere on the circuit? Aug 14, 2021 at 12:43

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