The color of electrical wiring provides important information about the purpose and function of the wire. Black wire is used for power in most electrical wiring systems.
Common Uses of Black Wire
Here are some of the most common uses of black wire in electrical systems:
- Hot wires – Black is used to denote the hot wire in single phase 120/240 volt AC power circuits. The hot wire carries the power from the electrical panel to the device or outlet.
- Line wires – Black can denote the line wire in a 3-phase system that uses multiple hot wires. Line wires carry power from the electrical service to the electrical panel.
- Load wires – Black wires are often used as load wires that carry power from switches to lights and other devices that are being controlled.
- Ground wires – In some older installations black was used for ground wires though this is no longer common practice.
Black Wire in AC Power Circuits
In standard AC power circuits in the United States, black wire is used for the hot wire that carries the power from the circuit breaker panel or fuse box to the device or receptacle being powered.
The hot black wire is paired with the neutral white wire which returns current back to the service panel. The black hot wire normally connects to the brass screw terminal on outlets and switches. The white neutral connects to the silver terminal.
220 Volt Circuits
In 220 volt circuits two hot wires are required. One hot is black and the other hot is usually red. The neutral in 220 volt circuits is white or gray, while the ground wire is bare copper or green.
Black Wire for Switches and Lights
For basic lighting circuits, black wires typically connect the switches to the lights. A black wire will run from the switch to the hot terminal on the light fixture. A white neutral wire provides the return path for the current.
For a switched outlet, one black wire will run from the switch to the hot terminal on the outlet. Another black wire will connect the hot feed from the panel to the outlet. This allows the outlet to be turned on and off by the switch.
Black Wire for Receptacles
General use receptacles are usually wired using black hot wires paired with white neutral wires. Typically in a branch circuit a black wire will feed power to multiple outlets connected in a daisy chain configuration.
The black hot connects to the brass screw and the white neutral connects to the silver screw. On a 20 amp 120 volt circuit, 12 gauge black wire is normally used to connect 15-20 amp receptacles.
Is Black Required for Hot Wires?
While black is the standard hot wire color in the United States, it is not necessarily required by code. The National Electrical Code (NEC) mandates color markings for power conductors, but allows some flexibility:
- A black covered conductor can legally be used for a grounded (neutral) or grounding conductor as long as it is marked with white or green tape or paint at the termination points.
- Any color wire can be used for an ungrounded (hot) conductor as long as it is consistently used for hot throughout the installation.
Even though any color is technically allowed, electricians strongly prefer to stick with standard color coding for safety and ease of inspection.
Common Black Wire Gauges and Sizes
Black electrical wire is manufactured in a range of standard sizes or gauges. The gauge refers to the diameter of the wire. Some common sizes of black building wire include:
| Wire Gauge | Conductor Diameter |
| 14 AWG | .064 inches |
| 12 AWG | .081 inches |
| 10 AWG | .102 inches |
| 8 AWG | .129 inches |
| 6 AWG | .162 inches |
| 4 AWG | .204 inches |
| 2 AWG | .258 inches |
| 1 AWG | .289 inches |
| 1/0 AWG | .325 inches |
| 2/0 AWG | .365 inches |
| 3/0 AWG | .405 inches |
| 4/0 AWG | .450 inches |
Larger gauge wires can carry more current. For example, a circuit with a 15 amp breaker would normally use 14 AWG black wire. A 20 amp circuit would use 12 AWG wire. Important note – always follow code requirements and use properly rated wires for the circuit amperage.
Buying Guide for Black Electrical Wire
Here are some tips for selecting and purchasing black wire:
- Choose the correct wire gauge and insulation type for the application and environment.
- Buy from reputable electrical supply stores that stock quality wire from top manufacturers.
- Purchase UL-listed and CSA approved wire when possible.
- Make sure the insulation colors match the standard electrical wiring color code.
- Buy spools of wire for large jobs or pre-cut lengths for smaller tasks.
- For wire with very fine strands, ferrules may be needed for secure connections.
Conclusion
Black wire is an essential component of electrical systems, used primarily as the hot wire carrying power in circuits operating at 120 or 240 volts. Understanding the proper function and termination of black wires is important for safe and code compliant installations.
While black is the standard hot color, the NEC allows flexiblity when other colors are available. Electricians should always clearly identify and mark wire colors to avoid confusion. Choose quality copper wire in the appropriate size and insulation for the installation. With sound wiring practices, black wire provides years of safe, reliable service.