According to NFPA 70E, what is considered an acceptable flash protection boundary for a 480V motor control center with a fault clearing time of 0.025 seconds?

The acceptable flash protection boundary for a 480V motor control center with a fault clearing time of 0.025 seconds is determined based on the calculated incident energy, which is assessed using NFPA 70E guidelines. According to these guidelines, the flash protection boundary is the distance at which a person could be exposed to incident energy levels not exceeding 1.2 cal/cm², which is considered the threshold for the onset of a second-degree burn.

For fault clearing times of 0.025 seconds, the calculated incident energy level is relatively high, which corresponds to a larger flash protection boundary. The appropriate distance for a 480V motor control center meeting these specifications is established to provide a safe working environment and to minimize the risk of injury from arc flash incidents.

In this case, 60 inches is the correct choice as it aligns with the requirements detailed in NFPA 70E for this specific scenario, ensuring that the boundary is sufficient to protect workers from potential exposure to hazardous energy levels during maintenance or troubleshooting activities.