Red yellow and black wires in the distribution box

In most electrical systems, black wires are hot (live), red wires are secondary hot or switched hot, and yellow wires are often used as live wires in three-way switches or for specific circuits.

Black Wire

The black wire is almost always a hot or live wire, carrying current from the breaker panel to outlets, switches, or fixtures. It is the main power line in a circuit and should always be treated as energized until verified otherwise.

In A

C systems, black wires connect to brass-colored screws on outlets and switches, and in DC systems, black is typically the negative wire.

Red Wire

The red wire is also a hot wire, often used as a secondary live wire. Common applications include: 240-volt appliances like stoves, dryers, or water heaters, where it works alongside black to provide higher voltage. Interconnect wiring for ceiling fans or three-way switches, allowing separate control of lights and fans or multiple switches controlling one fixture.

In D

C systems, red usually indicates the positive wire.

Yellow Wire

The yellow wire is less common in standard residential wiring but is often used as a live wire for switch legs, travelers in multi-way switch setups, or for specific circuits requiring identification separate from black or red wires. In some regions following IEC standards, yellow may also indicate a phase in three-phase systems.

Safety Notes

Always turn off the breaker before working in a distribution box. Use a voltage tester to confirm wires are de-energized. Never assume wire color alone guarantees function; older installations may not follow modern color codes.

Green, green/yellow, or bare wires are used for grounding, and white or gray wires are typically neutral in AC systems. Understanding these color codes helps ensure safe installation, maintenance, and troubleshooting of electrical circuits.