What Do Wire Colors Indicate?

Wire Color Guidelines

Electrical wire colors are standardized.  Cables containing several wires are marked or stamped on the outside casing with markings that tell the type and size of the wires inside.   When you take the sheath off you can see different wire colors.  Electricians know that each color should be used for a specific purpose.  Imagine how difficult it would be to wire a house if all wires were the same color.   Here are the most commonly seen colors and the way those wires are used.

Black – Black is always used for hot wires, and never used for neutral or ground.  These wires bring power to feed a switch or an outlet.  

Red – Red is also used for hot wires and for the second hot wire in 220-volt installations.  They can also be used to interconnect two smoke detectors.

White (or Grey) – White or grey is used for neutral wires, which are used to carry the unbalanced load on the circuit.   

Green or Bare Copper – Green wires and bare copper wires are used only for grounding purposes.  When you see a green screw on a mounting plate or a metal junction box, this is an indication that the green ground wire should be connected to that screw.

Wire Color Exceptions

In certain instances, wire colors may be used for connections that don’t follow these general rules.  For instance, sometimes a short piece of white wire is used as a hot wire (called a jumper), in a three-way switch application.  This white wire should be properly marked to show that it is being used for something other than a neutral by marking the end of it with black or red electrical tape.  That way, no one will be confused and accidentally use it for something else.

For some small jobs around the house, like replacing a light fixture, knowing these color guidelines will be helpful.   If you feel unsure about doing it by yourself, or want to have more extensive electrical work done, give us a call at (317) 659-6899.  We’ll be glad to give you some advice or assistance.

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