A Visual Guide to Wiring (in Color)

A question arose on one of the woodworking fora about electrical wiring that illustrated a fundamental misunderstanding about the role various wires play in a circuit. This was my attempt at clarifying it. I hope it helps you.

> In a 110 volt circuit you need the neutral wire to keep the circuit balanced.

Ummm, not quite. You need the neutral wire to allow current to flow. I sure wish they'd selected different words to describe the various conductors.

Hot is pretty self explanatory, but supply is perhaps even clearer.

Ground ought to be called safety or something like that, because its principal function is safety (in the National Electrical Code, NEC, it's called the grounding conductor). When it acts as a safety it happens to function much like the ground in a radio or TV, but a ground in that conventional sense is not its purpose.

Neutral (in the NEC it's confusingly called the grounded conductor, which alludes to its common connection to earth at the load center) is best thought of as return path because, from the standpoint of the electrons it performs the function that the ground or common return in a radio or TV (or your car) does, or the safety wire does when it acts as a safety.

But return path is much more descriptive (even though it's more of a DC term in an AC world) in that without completing the circuit, which is its function, electrons cannot flow.

Of course, the purist will argue that they do flow, because of the ground, but that's only because the ground is then acting as a safety.

To put it another way, there is a right way and a wrong way to complete a circuit; the right way is a hot or supply and a neutral or return path (or, for the purist, another hot of opposite phase). The wrong way is a hot or supply and a ground or a safety.

But, remember that whenever you get all your colors and terminology straightened out, be sure to include a ground or safety wire in your circuit, even if you happen to leave other things out. And if you're going to be leaving other things out, please get someone else to do your wiring.

This is also an illustration of the wire colors used in wiring.

As always, check your local code to verify anything you're not sure of.

27 January 2009

Valid HTML 4.01 Transitional Valid CSS!