What color wire goes in L1 and L2 on a light switch
There isn’t a single universal color for L1 and L2. In the UK and much of Europe, L1 and L2 are the two “strapper” or “traveler” cores between two-way switches and are typically the black and grey conductors in modern 3-core-and-earth cable (with brown used for COM); in older UK cable they’re usually yellow and blue (with red as COM). In the United States and Canada, standard switches aren’t labeled L1/L2—travelers are commonly red and white (re-identified) or red and black, with the common on a black screw. Neutrals (blue in EU, white in US) do not connect to L1/L2 on a traditional mechanical switch.
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What L1 and L2 mean on a light switch
On many two-way (3-way, North America) mechanical light switches, you’ll find three active terminals: a common (marked COM or C) and two terminals marked L1 and L2. The common is the feed or the switched output, while L1 and L2 carry the two “traveler/strapper” connections between a pair of switches so either can turn the light on or off. On a simple one-way switch, you typically use COM and L1, leaving L2 unused.
Typical terminal markings and roles
The following list explains the usual terminal labels you’ll encounter and what they do on a standard mechanical switch.
- COM or C: The “common” terminal, which is either the permanent live feed (line) or the switched live to the light.
- L1: One traveler/strapper terminal (or the switched live terminal on a one-way switch).
- L2: The other traveler/strapper terminal (unused on many one-way installations).
- Earth/ground: Green-yellow (EU/UK) or bare/green (US/CA) protective conductor to the metal back box and/or switch if required.
Although markings are widely used, manufacturers may vary layouts, so always check the switch’s diagram molded or printed on the device.
Wire colors by region and cable era
Color codes depend on your country and, in some places, the age of the wiring. The guidance below covers the most common standards you’ll see today and how they map to L1 and L2.
UK & Ireland (post-2004 harmonized colors)
In modern UK/Ireland “3-core and earth” cable used for two-way switching, the cores are brown, black, and grey, plus a bare earth (green/yellow sleeved). Here’s how they’re typically used.
- COM: Brown is commonly used as the permanent live feed (or the switched live to the lamp on the second switch).
- L1 and L2: Black and grey are used as the two strappers between switches; both must be sleeved/taped brown at terminations to indicate they are live conductors.
- Earth: Bare copper sleeved green/yellow to the back box and metal switch (if applicable).
- Neutral: Blue does not appear at the switch in a traditional loop-in-at-ceiling configuration; never put neutral on L1/L2.
There is no electrical difference between L1 and L2; just use black and grey consistently on the same terminals at both switches so the travelers match.
UK & Ireland (pre-2004 legacy colors)
Older UK/Ireland 3-core-and-earth used red, yellow, and blue, with a bare earth. The typical convention is as follows.
- COM: Red is commonly used as the permanent live (or switched live on the second switch).
- L1 and L2: Yellow and blue act as the two strappers; sleeve them red (or brown) at terminations to show they are live.
- Earth: Bare copper sleeved green/yellow.
- Neutral: Black (neutral) does not connect to the switch in traditional layouts; do not land it on L1/L2.
As with modern colors, which strapper goes to L1 versus L2 doesn’t matter as long as both ends match.
Continental Europe (harmonized colors)
Across much of Europe, harmonized colors mirror modern UK practice. In a two-way circuit, you’ll usually see these assignments.
- COM: Brown (phase) as the feed or the switched phase to the luminaire.
- L1 and L2: Black and grey commonly used as travelers/strappers; mark them as live where required.
- Earth: Green-yellow to ground terminals and metal boxes.
- Neutral: Blue neutral normally bypasses the switch; it must not be placed on L1/L2.
Local practices can vary; always follow the device’s diagram and any national wiring rules.
United States and Canada
North American switches are typically not labeled L1/L2. Instead, a 3-way switch has a common (black screw) and two traveler screws (usually brass). Colors follow these norms.
- Common: Usually the black (hot feed) or the switched hot to the light on the black screw.
- Travelers: Often red and white (re-identified with tape/ink to indicate hot) or red and black on the two brass screws.
- Ground: Green screw to green or bare copper ground.
- Neutral: White neutral typically does not connect to a standard mechanical switch; do not land it on travelers or common unless the device is a listed smart switch requiring neutral (and then follow its instructions).
If your device is labeled L1/L2 in North America, verify it’s suitable/listed for your market and follow its specific diagram—terminal names may differ from typical US/CA markings.
How to confirm the correct conductors in your installation
Because colors can be repurposed and older homes may not follow today’s conventions, verification is important. The steps below outline a cautious approach.
- Isolate power at the breaker/fuse and lock out/tag if possible.
- Remove the switch plate carefully and take clear photos of existing terminations.
- Note terminal labels (COM/C, L1, L2) on the new and old switches.
- Identify cable type and colors; look for any sleeving/tape indicating re-identified live conductors.
- Use a two-pole tester or continuity meter (with power safely controlled) to identify the common and the two strappers between switches.
- Reconnect consistently: permanent live to COM, strappers to L1 and L2 at both switches, and switched live from the second switch’s COM to the light.
- Sleeve/mark any repurposed conductors per local code (e.g., sleeve black/grey or yellow/blue as brown/red in UK).
- Reinstate power and test operation from both switches.
These checks help ensure function and safety regardless of the cable colors present.
Safety and code notes
Working on electrical circuits carries risk. The following points summarize key safety and compliance considerations.
- Always de-energize and verify the circuit is dead before touching conductors.
- Follow your national wiring regulations (e.g., BS 7671 in the UK, NFPA 70/NEC in the US, local EU standards).
- Do not connect neutral to L1/L2 on a conventional mechanical switch.
- Re-identify conductors where required (e.g., sleeve blue/black/grey/yellow used as lives).
- If unsure, hire a licensed/qualified electrician—especially where colors don’t match expectations or multiple cables occupy the box.
Adhering to local rules and safe isolation procedures is as important as choosing the right colors.
Summary
L1 and L2 are the two traveler/strapper terminals on a two-way switch and don’t have universal colors. In the UK/EU, use black and grey (modern) or yellow and blue (older) as L1/L2, with brown (modern) or red (older) on COM; sleeve live cores appropriately. In the US/Canada, switches typically have a common and two travelers rather than L1/L2, with the common usually black and travelers red and white/black. Neutral does not go on L1 or L2. When in doubt, identify conductors by function, not just by color, and follow the device diagram and local code.
What wire goes into L1 and L2?
Connect the black wire coming from the first switch to the L1 terminal, connect the grey wire to the L2 terminal and connect the brown wire to the C (common) terminal. Again, don’t forget to connect the Earth conductors to the Earth terminal provided.
Which color wire is L1 and L2?
In a 120/240V single-phase system, L1 (Line 1) is commonly Black and L2 (Line 2) is commonly Red. For three-phase systems in the US, L1 is typically Black, L2 is typically Red, and L3 is typically Blue. It’s crucial to always use a voltage tester to confirm wire function, as colors can vary by location, system type, and age of the installation.
Why Colors Vary
- Location: Different countries have different national electrical codes, leading to different color standards.
- System Type: Single-phase and three-phase systems use different color codes.
- Age of Installation: Older installations may use different color codes than modern ones.
- Voltage: Higher voltage systems, like 277V or 480V, can also use different colors.
In the United States:
- Single-Phase:
- L1: Black
- L2: Red
- Neutral: White
- Ground: Green or Green/Yellow striped
- Three-Phase (120/208V or 120/240V):
- L1: Black
- L2: Red
- L3: Blue
- Neutral: White
- Ground: Green or Green/Yellow striped
Important Safety Note:
Always turn off the power to the circuit at the breaker before working on any wiring. Use a non-contact voltage tester or a multimeter to verify the function of each wire before making connections. If you are unsure or uncomfortable with electrical work, always consult a licensed electrician.
What does L1 L2 mean on a switch?
The L stands for line. For example, a 1-way switch has a common line (C) and line 1 (L1) terminal. A 2-way switch has a common line (C), line 1 (L1) and line 2 (L2) terminal – line 1 is off when line 2 is on, and vice versa, depending on the switch position.
What is L1, L2, and L3 on a light switch?
The important point is that terminals L3 and L4 are used as a pair for connections to one switch, while L1 and L2 are similarly used as a pair to the next switch. © Dowsing & Reynolds 2023 – release 1.0a.
