If ungrounded conductors of a multiwire circuit are on the same phase, what could happen?

When ungrounded conductors of a multiwire circuit are on the same phase, they share a common path for the current, leading to a situation where the neutral conductor carries the sum of the currents from all the ungrounded conductors. If these conductors are carrying current in the same direction, the neutral wire can experience an overload. This happens because there is no cancellation of the currents, as would be the case if the conductors were on different phases where the currents could potentially offset each other.

In this case, the rating of the neutral conductor can be exceeded, which could lead to overheating and, in worst-case scenarios, pose a fire hazard or damage to the wiring. The design of multiwire branch circuits typically seeks to balance the loads across different phases to prevent such scenarios, making it crucial to ensure that ungrounded conductors are correctly arranged. Thus, the correct answer highlights the important consideration of load balancing and circuit safety in electrical design.