What criteria must be met for a common neutral to be used effectively in branch circuits?

Using a common neutral effectively in branch circuits relies on the principle of balancing loads to avoid overloading the neutral conductor. When circuits are scheduled for different phases, they can draw current in a way that allows the currents to cancel each other out. This cancellation is particularly important in a multi-wire branch circuit where two or more circuits share a neutral.

When circuits are on different phases, it ensures that when one circuit is drawing current, the other may be returning current through the neutral, thus maintaining a balanced load. This configuration helps to prevent an excessive amount of current from flowing through the neutral wire, which can cause overheating and pose safety hazards.

In contrast, if circuits are on the same phase, the currents will add together in the neutral, potentially exceeding its safe carrying capacity. Therefore, scheduling circuits on different phases is critical for the effective use of a common neutral in branch circuits.