What Do L1 and L2 Mean In Electrical Wiring? (Explained!)

what does l1 and l2 mean in electrical wiring

L1 and L2 are relatively common labels in electrical wiring, but they may cause confusion if you’ve never encountered them.

People associate L1 and L2 with 240V systems. They both carry 120V. L1 and L2 are incredibly similar, and you will only notice the difference between them at the power source.

What Do L1 and L2 Mean In Electrical Wiring?

If you have a 4-wire cord, L1 is the black wire. You can also call it to line one. L2 is the red wire, also known as line two. The green wire is the ground. The white wire is neutral.

Many homeowners encounter L1 and L2 in switches. The configuration will depend on the type of switch:

  • One-Way switches have a COM and L1 terminal. One terminal accommodates the live wire for the switch’s input voltage, and the other is the light fixture’s output. You can ignore the L2 terminal if you’ve seen it, but you prefer to configure a one-way switch.
  • Two-Way switches can turn the same light fixture on or off from two different locations. For instance, you have one switch at the top of the stairs and another at the bottom. But they both control the light fixture above the stairs. Two-way switches have COM, L1, and L2 terminals.
  • Intermediate switches have terminals ranging from L1 to L4. If you have a light above a staircase, intermediate switches include a switch in the middle of the staircase. This is on top of the switches at the top and bottom. All three switches control the same light. Naturally, this configuration is more complicated than the first two.

You don’t have to limit yourself to one-way, two-way, and three-way switches. Many homeowners have two-way dimming switches. This doesn’t mean you can dim the lights from multiple locations.

You can connect multiple dimmers to the same light. But you will eventually create instabilities by inadvertently attempting to dim the lights below 0 percent or raise the brightness above 100 percent. Two-way dimmers pair a dimmer with an on/off switch.

In electrical networks, 3-phase 4-wire systems have L1, L2, L3, and neutral lines. The neutral line in 3-phase systems doesn’t have a current. This is the opposite of the neutral wire in the single-phase system that runs your home.

Many applications with  L1 and L2 terminals and wires include documentation that explains the wiring process. This prevents laypeople and contractors from connecting the wires to the wrong terminals.

Do L1 And L2 Have A Specific Color Code?

Color codes are safety features. They matter because they prevent contractors from making wiring mistakes by clarifying the function of each line in any given application. L1 and L2 have specific color codes. But the color codes depend on the location. For instance:

IEC (AC Power Circuit)

  • L1 – Brown (Line, 3-Phase).
  • L2 – Black  (Line, 3-Phase).
  • L3 – Grey   (Line, 3-Phase).
  • L   – Brown (Line, Single Phase).

UK (AC Power Circuit)

  • L1 – Brown (Line, 3-Phase).
  • L2 – Black   (Line, 3-Phase).
  • L3 – Grey    (Line, 3-Phase).
  • L   – Brown  (Line, Single Phase).

US (AC Power Circuit)

  • L1 – Black (Line, 3-Phase).
  • L2 – Red   (Line, 3-Phase).
  • L3 – Blue  (Line, 3-Phase).
  • L   – Black or Red (Line, Single Phase).

Canada (AC Power Circuit)

  • L1 – Red (Line, 3-Phase).
  • L2 – Black (Line, 3-Phase).
  • L3 – Blue (Line, 3-Phase).
  • L   – Red or Black (Line, Single Phase).

Once you switch to DC power circuits, polarities take center stage. The color codes identify the positive and negative lines and terminals. For instance, IEC color codes associate brown with L+ and grey with L- (2-wire unearthed DC power system).

If you use a physical book published by your country’s regulatory body to identify color codes, make sure you have a recent copy. Regulations change all the time. In other words, you can’t expect color codes to stay the same.

If you’re still using an outdated color scheme, you may start fires by wiring houses and applications incorrectly.

Are L1 and L2 Interchangeable?

Yes, L1 and L2 are interchangeable. If you have a one-way switch with terminals marked L1 and L2, you can use either line. It doesn’t matter. This is also true for COM and L1 terminals. You can distinguish them at the power source. Beyond that point, it doesn’t make a difference.

But you should identify the wire you want to use and stick to it. Otherwise, you will create confusion, not only for yourself but for electricians that must perform repairs down the line.

What Wires Go Into L1 And L2?

You typically find L1 and L2 terminals in switches. If you have a COM terminal as well, you can expect the following:

  • Both switches have a connection between their L1 terminals and the line.
  • The L2 terminals (from both switches) have a connection to the light’s terminal.
  • The light has another terminal running to the power supply’s neutral.
  • The COM terminals are connected together.


Stellar is an engineer. He has an unconventional approach to problem-solving, and is adept at devising original solutions to complex issues. He is an imaginative thinker and regularly comes up with resourceful answers to challenging problems.

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