USA Electrical Wire Colors (AC/DC): Line, Neutral, Ground

Electrical wiring is a crucial aspect of any building or structure and understanding the different wire colors and their functions is crucial for both electrical professionals and homeowners alike. In the United States, the standard wire colors for both AC (alternating current) and DC (direct current) electrical systems are line, neutral and ground. These colors are used to identify the different wires and their functions within the electrical system and it is essential to understand the significance of each color to ensure the safe and efficient operation of any electrical system.

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 connections 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)

Neutral (N)

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

Positive (+)

No recommendation (Red)

Negative (-)

No recommendation (Black)

2-wire grounded DC

Positive (of a negative grounded) circuit (L+)

Red

Negative (of a negative grounded) circuit (N)

White

Positive (of a positive grounded) circuit (N)

White

Negative (of a positive grounded) circuit (L-)

Black

3-wire grounded DC

Positive (L+)

Red

Mid-wire (center tap) (N)

White

Negative (L-)