Connecting wires to the correct screws when wiring a light switch, outlet, or other electrical device is crucial for safety and proper functionality. While wiring standards provide guidelines on wire and screw color pairings, the specific connections can vary based on the device, the country’s electrical code, and other factors.
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Quick Answer
As a quick answer, here are some common wire to screw color pairings:
- Black wire – Brass or gold colored screw
- White wire – Silver or light colored screw
- Green or bare wire – Green screw
- Red wire – Brass or gold colored screw
However, this can vary depending on the type of device, wiring system, and national and local electrical codes. Always check diagrams and instructions for the specific device.
Wire and Screw Color Conventions
In general, wire and screw color pairings follow certain conventions and electrical codes:
- Black wire – Hot or live wire that carries current from the electrical panel. Connects to brass or gold colored screws.
- White wire – Neutral wire that returns current to the panel. Connects to silver or light colored screws.
- Green or bare wire – Grounding wire for safety. Connects to green screws.
- Red wire – Hot or live wire, typically used for a secondary live circuit. Also connects to brass or gold screws.
However, variations do exist:
- In older constructions, black can be used for neutral and white for hot.
- In switch loops, white is used for hot and black for switched hot.
- Green can be used for grounding or as a hot in some multiconductor cables.
Typical Wire and Screw Connections
Here are some typical wire and screw connections for common electrical devices and wiring systems:
Electrical Outlets and Receptacles
- Black wire – Brass or gold screw
- White wire – Silver or light colored screw
- Bare or green wire – Green screw
Light Switches
- Black wire (hot) – Brass or gold screw
- White wire (neutral) – Silver or light colored screw
- Green or bare wire – Green screw
- Black wire (switched hot) – Brass or gold screw
3-Way Switches
- Black or red wire (common/hot) – Dark or brass screw
- Red or black wire (traveler 1) – Brass screw
- Red or black wire (traveler 2) – Brass screw
- Green or bare wire – Green screw
Ground Fault Circuit Interrupter (GFCI)
- Line hot – Brass or gold screw
- Line neutral – Silver or light screw
- Load hot – Brass or gold screw
- Load neutral – Silver or light screw
- Bare or green wire – Green screw
240 Volt Circuits
- Black wire (hot) – Brass or gold screw
- Red wire (hot) – Brass or gold screw
- White wire (neutral) – Silver or light screw
- Bare or green wire – Green screw
Identifying Screw Terminals
If you are unsure which screw terminal is which, look for these identifiers:
- Brass or gold screws – Hot or live terminals
- Silver or light colored screws – Neutral terminals
- Green screws – Grounding terminals
- Labels like “Line”, “Neutral”, “Hot”, “L1”, “L2” – Can indicate hot/live terminals
- Labels like “Load” or “Switched” – Can indicate switched hot terminals
Additionally, refer to any wiring diagrams or labels on the device. Use a multimeter to test and verify connections if uncertain.
Typical Screw Sizes
While screw sizes can vary, here are some typical screw sizes for electrical devices:
- Outlets and switches: #6 or #8 screws
- Appliances and motors: #8, #10 or larger screws
- Ground screws: #10
- Neutral and ground bars: #6 or #8 screws
- Lug terminals: Vary in size depending on wire gauge
Matching Wire Gauge to Screw Size
When connecting wires, it’s important to match the wire gauge to the correct screw size:
| Screw Size | Recommended Wire Gauge |
|---|---|
| #6 | #10 to #14 AWG |
| #8 | #12 to #14 AWG |
| #10 | #14 to #18 AWG |
Using too large or too small of a wire for the screw connection can lead to loose connections, damaged conductors, overheating issues, and other hazards.
Special Considerations
Here are some other factors to keep in mind when wiring electrical devices:
- Twist-on connectors – Many devices use push-in twist-on wire connectors instead of terminal screws. Ensure you twist wires clockwise to properly seat connections.
- Stranded vs solid wire – Stranded wire may require crimping ferrules for screw terminals designed for solid wire. Use compatible connectors.
- Aluminum wire – Requires special treatment and compatible connectors due to oxidation and expansion/contraction issues.
- Double-check connections – Verify that all bare wire is trimmed, connections are tight and wires are matched to the correct screw or terminal.
Following Electrical Codes
Always follow relevant national and local electrical codes for all wiring and connections, such as:
- National Electrical Code (NEC) in the US and Canada
- BS 7671 in the UK
- AS/NZS 3000 in Australia
Code violations can lead to fires, electrocution hazards, and problems getting electrical inspections approved. When in doubt, consult an electrician.
Conclusion
Matching electrical wires to the proper screw or terminal is crucial for safety and correct functionality. While there are conventions for wire and screw color pairings, always check the specific device instructions and wiring diagrams. Other important factors include screw sizing, wire gauge compatibility, and adhering to all electrical code requirements. With attention to detail and safer wiring practices, you can help reduce electrical faults and risks.