The NEC requires illumination for all working spaces about electrical equipment [110.34(D)], but does not define what's adequate. Theoretically, a single 40W incandescent lamp or a flickering fluorescent fixture 10 ft away is sufficient because it meets the "letter of the law." However, it would be pointless for the NEC to include this requirement if the intention were not to ensure that those working around electrical equipment have sufficient light to work safely.
How much light is sufficient, and how do you provide it?
The NEC answers that question only indirectly. For example, we can imply from Sec. 90.1 that the lighting must be enough to make the installation essentially free from hazards that could arise from lighting deficiencies.
We also get some guidance from OSHA, which provides a minimum footcandles table in 1926.56, Table D-3. You could strictly apply this table if your idea of safety is meeting legal minimums, regardless of actual conditions. But if your goal is to ensure safe working conditions, use this table as a starting point.
However, footcandle readings don’t tell the whole story. For example:
- Given where people must stand to perform maintenance or repair, will shadows interfere with visibility?
- Is the color rendition appropriate?
- Should task lighting supplement general illumination?
- Is the lighting branch circuit on a different source from the equipment so the light is available when the equipment is de-energized?
