Knowing the proper wiring color coding is essential when performing electrical work and designing complex circuits. Each color serves a different purpose and you should be aware that all wires can carry a current at some point so they should be handled carefully. Colour coding helps to reduce hazards while implementation and troubleshooting. Let’s have a look at the USA wiring color codes. (Both AC and DC)
USA wire colors (AC)
USA Single Phase wire colors
Line (L): Black or Red
Black insulation is always used for hot wires and is common in most standard household circuits. The term “hot” is used for source wires that carry power from an electric service panel to a destination, such as a light or an outlet. Red wires are used as the second hot wire in 240 Volt installations. Another application for red wires is to interconnect hardwired smoke detectors so that if one alarm is triggered all of the others go off simultaneously.
Neutral (N): White or Gray (alternative)
White or gray indicates a neutral wire. When examining a white or gray wire, make certain that it has not been wrapped in electrical tape. This would indicate a hot wire. Older wires sometimes may lose their electrical tape wrapping. So, if the box has a loose loop of tape inside of it, there is the possibility that it may have come off of the neutral wire.
The term neutral can be deceiving as it appears to imply a non-electrified wire. It is important to note that neutral wires may also be carrying power and can shock you.
Protective Ground (PG): Bare, Green, Green-Yellow
Bare copper wires are the most common type of wire used for grounding. All electrical devices must be grounded. In the event of a fault, grounding provides a safe pathway for electricity to travel. The current passes back to the ground or earth. Bare copper wires connect to electrical devices, such as switches, outlets, and fixtures, as well as metal appliance frames or housings. Metal electrical boxes also need ground connection because they are made of conductive material. Plastic boxes are non-conductive and do not need to be grounded.
Green and green-yellow wires are sometimes used for grounding. Never use a green or green-yellow wire for any purpose other than grounding.
USA Three Phase wire colors
Line 1 (L1)
Black or Brown (alternative)
Line 2 (L2)
Red or Orange (alternative)
Line 3 (L3)
Blue or Yellow (alternative)
White or Gray (alternative)
Protective Ground (PG)
Bare, Green, Green-Yellow
USA wire colors (DC)
Protective ground (PG)
Bare, Green, or Green-Yellow
2-wire ungrounded DC
No recommendation (Red)
No recommendation (Black)
2-wire grounded DC
Positive (of a negative grounded) circuit (L+)
Negative (of a negative grounded) circuit (N)
Positive (of a positive grounded) circuit (N)
Negative (of a positive grounded) circuit (L-)
3-wire grounded DC
Mid-wire (center tap) (N)