What should be the basis for determining the rating of the service disconnecting means?

The determination of the rating for the service disconnecting means is fundamentally based on the protection and capacity required to handle the maximum expected load safely. This involves considerations related to the characteristics of fuses and circuit breakers in a system.

In this context, the appropriate basis for selecting the rating of the service disconnecting means is the largest fuse that can be installed. This criterion ensures that the disconnecting means has a rating sufficient to handle the maximum load without exceeding safety limits, thus preventing potential overcurrent conditions. Larger fuses indicate the ability to withstand temporary overload conditions without tripping unnecessarily, which is significant during equipment startup or transient conditions.

While other options might seem relevant, they do not appropriately address the safety and operational capabilities required in a service disconnecting means. The smallest device rating, combined ratings of devices, and continuous current trip settings do not take into account the maximum potential load that could be imposed on the disconnecting means during operation. Therefore, selecting based on the largest fuse provides a clear guideline that aligns with NEC requirements, ensuring reliability and safety in the electrical distribution system.