The rating of any one cord- and plug-connected utilization equipment not fastened in place shall be a maximum of what percentage of the branch-circuit ampere rating?

The correct answer is that the rating of any one cord- and plug-connected utilization equipment not fastened in place shall be a maximum of 80% of the branch-circuit ampere rating. This rule applies to ensure the safe operation of electrical equipment and to prevent overheating of the circuit wiring.

The rationale behind this percentage is rooted in maintaining a margin for safety while ensuring that the circuit can handle the load without tripping the breaker. When multiple pieces of equipment are connected to a single branch circuit, it is crucial to account for the total load that will be drawn. By restricting the individual equipment's rating to 80% of the branch-circuit capacity, it allows for additional equipment or unexpected surges in demand without exceeding the circuit's limit.

This practice also conforms with general guidelines from the National Electrical Code, which emphasizes safety and the prevention of potential electrical fires or electrical equipment failure. Understanding this percentage is vital for electrical inspectors to ensure compliance with electrical codes during inspections and ensure the safety of electrical installations.