Under what condition can Class 1 circuits and power-supply circuits be in the same raceway?

Class 1 circuits and power-supply circuits can be in the same raceway if the equipment powered is functionally associated. This means that the circuits need to serve equipment that is designed to work together or is part of the same system, ensuring that they operate effectively and safely. Functional association implies that the circuits work in tandem, which maximizes efficiency and minimizes potential interference or complications between systems.

Using raceways for circuits that are functionally linked is important for maintaining organized and manageable installations, especially in low voltage communication systems. These provisions help in adhering to safety regulations and ensuring that all components are compatible with one another when installed.

The other conditions may not guarantee safety or effectiveness when combining different types of circuits in the same raceway. For example, the size of the conductors alone or the voltage level does not specifically address issues related to functionality and compatibility between the circuits. Local code variations might allow for different practices, but they do not inherently provide the reasoning necessary to combine circuits based on their operational relationships.