What should be done if a branch circuit supplies devices from different voltage systems?

When a branch circuit supplies devices from different voltage systems, it's essential to ensure safety and clarity regarding the circuit's operation. Labeling by phase and nominal voltage serves multiple critical purposes. First, it ensures that anyone working on or interacting with the electrical system can easily identify the voltage levels involved, reducing the risk of accidental contact with a live circuit. Correct labeling is a critical aspect of maintaining safety standards and compliance with the National Electrical Code (NEC).

Additionally, such labeling helps to prevent confusion among technicians, electricians, or maintenance personnel who might assume that all components within a given circuit operate under the same conditions. By indicating both the phase and the nominal voltage, it provides clear guidance on operating limits and informs users about potential hazards associated with different voltage levels. This practice helps in avoiding dangerous situations that could arise from improper connections or maintenance activities.

While color coding and utilizing a single voltage source may seem beneficial in some contexts, they do not provide the same level of detail and clarity required for safe operations across different systems. Labeling remains the most effective method for communication of critical information in complex electrical environments.