Never Switch a Neutral

What do you mean by switch?

I am referring to using the neutral as the breakpoint in a switching circuit. A light is the simplest example. When you flip the switch, your light turns on. Normally this is done by having the switch between the hot wire and the light fixture. This is also the safe and proper way. The problem is, that electricity does not care about you, your codes, your safety, or the proper way to do things. It follows the laws of nature, not the laws of man. That being said, it is physically possible to switch a neutral and achieve the same effect, turning a light on and off.

What's the big deal?

The problem occurs when there is a problem or work to be done on the circuit. This is especially true if the person performing the work assumes things are proper. Never assume things are right, always test and verify everything. It's for your own good. Also, practice LOTO.

When you go perform work, such as changing a ballast you know how a very dangerous condition. With the light off, there should be no power flowing and no chance of shock or electrocution. However, in a switched neutral situation the light and ballast are always energized. This is because the circuit is broken after the load instead of before it. Now if you cut a wire or remove the wire nuts, you have a live wire next to bare metal. This leads to a situation where sparks can easily fly, you could be shocked, knocked off a ladder, burned, or even killed.

This is especially bad if the light is in a commercial or industrial setting. While your home lights are normally 120V, many lighting circuits in buildings are 277V. When a voltage that high hits metal, it'll seriously take your picture with how bright that arc flash is. Hopefully, you never encounter this situation.

If you do encounter it, exercise caution. LOTO. Do what you have to do to correct it. Get the switch off the neutral and onto the hot. Save yourself and the person who comes after you from having a shocking surprise.