Is your Lighting Efficient?

From MRO Insider:

"Winter solstice is now behind us, so the days are getting longer again. Yet, your facility seems drearier. Being the sharp electrical troubleshooter that you are, you grab a light meter and take some measurements.

When you review your findings against the lighting plan, your suspicions are confirmed. Light levels really have dropped. In some places where the plan shows 45 footcandles, you measured only 25. In an inspection area that requires 90 footcandles, you measured 70. How can you figure out what’s going on?

A drop in light output is hard to isolate in time, because it tends to creep up on us. As light output diminishes a little each day, we adjust to the new normal. That makes troubleshooting more difficult, but not impossible.

Light output diminishes as lamps near end of life (the output curve varies by lamp type). So, maybe it’s just be time for relamping. However, there are probably other factors to correct. Things to check include:

• Dust and grime accumulation. Are the lamps, lenses, and shades clean?
• Overloaded neutrals. A plastics plant in Kentucky solved a dim lighting problem in one building by rewiring the lighting system. Most of the neutral wires had overheated to the point of discoloration. This rewiring more than doubled some footcandle readings.
• Transient protection deficiencies. Is your surge protection (Art. 285) plan tiered so that it protects lighting ballasts from events generated from inside your facility? If not, you probably have damaged ballasts. Replace a few ballasts to see the effect. Correct the protection deficiencies.
• Bonding deficiencies. Walk down your lighting system for violations of Art. 250, Part V. You should not have connections to ground (as defined in Art. 100) anywhere in this system."