How do you determine the incident energy value for a given piece of equipment?

• A. By guessing based on equipment size.
• B. By performing a formal arc flash analysis or by reading the equipment label.
• C. From the color of the equipment.
• D. From the manufacturer's last service date.

Answer: (B)

Incident energy isn’t something you can guess from appearance or age; it comes from how the electrical system would behave during an arc fault. You determine it by either performing a formal arc flash analysis or by reading the equipment’s label that lists the incident energy (in cal/cm^2) or the corresponding PPE category. An arc flash analysis uses system voltage, available fault current, prospective fault duration, and enclosure geometry to calculate the energy a person could be exposed to at a given working distance. If the equipment already has a label, that label provides the actual energy value you should use to determine appropriate PPE and safety procedures. If there is no label, a qualified person should perform the analysis to establish the correct incident energy. Choices based on guessing, color, or last service date don’t reflect the electrical conditions that drive arc energy.