My husband has always wired a switch to break the neutral wire to turn a light on and off. I can remember for 40 years he has said to "break the neutral". However, our son worked as an electrician for 2 years and he said you always "break" the "power" wire (black one) Who is correct? Thank you!!
6i wonder why in the world anyone would break the neutral to turn off power?– jsotolaFeb 4, 2019 at 19:07
8Break the hot, not the neutral. That way it is possible to de-energize the lamp in case of a problem. I once detected some internal hot-ground arcing in a lamp, so I ran over and shut the switch off. If the guy had switched neutral, I would have been sunk. More routinely, you want to de-energize the fixture so you can change the bulb or extract a broken bulb without getting nailed. Being stunned when you are on the top of a ladder can mean being killed.– Harper - Reinstate MonicaFeb 4, 2019 at 19:16
@jsotola: Some kinds of switching arrangements could benefit from being able to break hot and neutral separately. For example, in a darkroom one might want to have a switch at each workstation that will turn on a "normal" light if a master light switch is on, but turn an indicator light that's small enough to avoid fogging paper in any case. Switching the neutral of the main lights, if it were allowed (which it isn't) would considerably reduce the amount of wiring required as well as the need for double-pole switches.– supercatFeb 4, 2019 at 22:38
There was a time when switching the neutral was a common practice, but it was way more than 40 years ago. It's no longer permitted:
NEC 404.2(B) Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit.
(In the case of your home, and in most cases, the neutral is grounded so the neutral wire is the grounded conductor.)
This way when receptacles, light switches, etc. are switched off, they do not carry any voltage to ground, making them safer for light bulb changing, etc.
Listen to the electrician. If you break the neutral, there is still power going to the fixture or the outlet, and if you contact a hot surface, you can get a serious shock.
Code requires breaking the hot (power) and always maintaining a connected neutral. (110 volt US systems)
3This was also a problem with non-polarized, 2-prong plugs: if you plugged it in "backward", the on/off switch would break the neutral rather than hot, and your bulb's screw shell would remain "hot" even with the switch off, creating an unnecessary risk of shock to anyone unscrewing that bulb.– UpnorthFeb 6, 2019 at 19:59
@Upnorth Hence the requirement that any plug-in device that has metal parts that might be energized and accessible have a polarized plug. Only "double-insulated" devices can use non polarized plugs.– bibFeb 6, 2019 at 20:11