What percentage of the branch-circuit ampere rating can one cord-and-plug-connected utilization equipment be rated for?

The correct answer is rooted in the National Electrical Code (NEC) requirements regarding branch circuits. Specifically, one cord-and-plug-connected utilization equipment can be rated for 80 percent of the branch-circuit ampere rating. This guideline ensures that the circuit is not overloaded, which can lead to overheating and potential hazards, while still allowing for the safe operation of the equipment connected to it.

The rationale behind allowing only 80 percent usage of the available capacity is to account for the continuous load and temporary inrush currents that can occur when equipment is turned on. This 80 percent rule serves as a safety buffer, ensuring that the branch circuit remains within safe operational limits and reduces the risk of tripping breakers or causing electrical fires.

This standard is particularly important in settings where multiple pieces of equipment may be used simultaneously, as it promotes better management of electrical loads and reduces the likelihood of exceeding the circuit's capacity. In summary, the 80 percent rating effectively balances the safe operation of equipment with the capacity of the electrical system.