What Is Com In Light Switch

What is COM in a Light Switch? Understanding the Common Terminal

This article will explain the "COM" terminal found on many light switches and its crucial role in completing the electrical circuit. We'll delve into its function, common misconceptions, and how it differs from other terminals you might find on a switch. Understanding the COM terminal is essential for safe and effective electrical work.

What does COM stand for?

COM stands for Common. This terminal is the central point of connection in a light switch's internal mechanism. It's where the "hot" or "live" wire from your electrical supply connects. This wire carries the electrical current that powers the light fixture. Think of it as the main pathway for electricity to flow.

How COM works in the circuit:

A light switch acts as a simple on/off switch in a circuit. The COM terminal remains constantly connected to the power source. When you flip the switch to the "on" position, the circuit is completed, allowing electricity to flow from the COM terminal, through the light fixture, and back to the power source via the neutral wire (typically a white wire). When the switch is "off," it breaks the circuit, preventing electricity from flowing to the light fixture.

Common Misconceptions about the COM Terminal:

• COM is not always labeled as such: While many switches clearly label the COM terminal, some older or less expensive switches might not. Always check your switch's wiring diagram if the terminals aren't clearly marked.

• COM is not always the largest terminal: While often the largest, the size of the terminal is not a reliable indicator of its function. Always refer to the wiring diagram.

• COM doesn't inherently determine the "hot" wire: The COM terminal receives the hot wire from the power supply. The hot wire is the live wire, carrying the current that powers the circuit. It's crucial to identify the hot wire correctly before connecting it to the COM terminal. Using a voltage tester is essential to confirm which wire carries current.

Differentiating COM from other terminals:

Most light switches have at least two terminals, and often more depending on the type of switch (e.g., 3-way switches). These additional terminals may include:

• L1, L2, or LINE: These terms might be used instead of or in addition to COM, often referencing the incoming hot wire.

• NO (Normally Open) and NC (Normally Closed): These terminals are primarily used in specialized switches or relays.

• LOAD: This terminal is where the wire running to the light fixture connects.

Safety Precautions:

Always switch off the power at the breaker box before working with any electrical wiring. Using a non-contact voltage tester is a crucial safety precaution to ensure the power is off before touching any wires. If you are not comfortable working with electricity, consult a qualified electrician.

In conclusion, the COM terminal in a light switch is the key connection point for the "hot" wire from your electrical supply. Understanding its function and how it interacts with other terminals is crucial for safe and correct wiring. Always prioritize safety and consult professional help when in doubt. Remember to always refer to your specific light switch's wiring diagram for accurate information.