Metal-Halide Lighting Fixture In-Rush

[GotShocked]

We just wrapped up a painful multi-year troubleshooting marathon trying to understand why fuses were constantly blowing on exterior lighting circuits using Lithonia TV1000M-GP6 fixtures. In a few cases, the fuse failures were catastrophic to the point of blowing up the fuse holders and adjacent conductors and equipment. See attached photos. Here are some of the key lessons we learned:

1. Despite what the lighting manufacture states, there is significant short duration in-rush current, our 2.35A nominal operating current fixtures drew 20-40A each during in-rush. See attached power quality recording. The in-rush current duration was generally short, 5-10mSec +/-.
2. We elected to use circuit breakers instead of fusing for lighting circuit protection. We selected C-curve breakers based upon a couple manufacture recommendations. Yet another mistake, we are replacing them with D-curve breakers to survive the short duration in-rush. We obviously should have rented the power quality meter much sooner in this evaluation.
3. According to their Fuseology Selection Guide, Littelfuse recommends that their fuse holder be operated at no more than 60% of their nominal rating for operation at 77deg F. We also learned not to use fuse holders with rejection clips.

Hopefully this information will help someone on this forum, thank you.

GotShocked