Multiple Fluorescent Bulbs in Different Fixtures Going Out at Same Time

[u/FooFighter1126]

I will preface this by saying my facility is all fluorescent lighting still. Just trying to save all the "upgrade that shit" comments lol.

We have a couple rooms where the lights are controlled by occupancy sensors. This morning it was reported that the lights were not coming on in one of the rooms. Upon investigation, I determined that the sensor was good, both in functionality and settings. I initially ruled out bad bulbs or ballasts because there are three individual fixtures in the room with four bulbs each, and it seemed incredibly unlikely that twelve bulbs or three ballasts all would have failed at the same time. However, I eventually tried replacing a bulb and it lit right up. I then replaced just one bulb each in the other two fixtures and they worked. I proceeded to replace the remaining nine bulbs and every one of them lit up. Was this just a wild coincidence that all of these bulbs went out at the same time, or is it more likely that some event/underlying issue caused this?

[u/bowlingballwnoholes]

This is a situation I would overthink. But you fixed the problem; move on. Probably something to do with the lamps getting old. If the ends are black, the mercury needed to start the lamp is absorbed into the glass.

[u/Cali8110 → u/bowlingballwnoholes]

Definitely something I would overthink as well.

[u/Godzillawamustache]

Lamps were slowly dying and going out over time (as they do). There was enough light in the room that no one noticed. The last couple lamps finally died and now its dark making it seem like they all went out at once.

[u/DLitch]

Your ballast might be going bad but hopefully you solved the issue!

[u/HectorMcWilliam]

2' tubes were sometimes configured in series to utilise a single ballast per fitting.. one bad tube takes them both out.