During thermal imaging of electrical equipment, the equipment should be operated at or above what percent of nominal load?

• A. Must be operating at normal capacity
• B. Must be cleaned prior to imaging
• C. Must be lubricated prior to imaging
• D. Must be at or above 40% of nominal load

Answer: (D)

Thermal imaging of electrical equipment works best when there is a meaningful heat pattern to detect. If the equipment is not loaded enough, components may stay near ambient temperature and faults like loose connections or overloaded conductors won’t stand out as hotspots. By operating at or above a practical loading level, you ensure enough current flow to generate reliable temperature differences and reveal abnormal heat sources.

A commonly used threshold is at least 40% of nominal load. This level provides a noticeable, repeatable heat signature without pushing the system into overloading. Cleaning or lubrication isn’t directly related to obtaining meaningful electrical heat patterns, and simply operating at normal capacity isn’t necessarily required for every inspection.