I have two flourescent fixtures that keep turning on and off at random intervals.
One fixture would occassionally trip the CB so that was replaced with a used fixture that was known to function properly. The CB stopped tripping, however when installed in this new spot the previously-operable fixture also started turning on and off at random times.
I managed to catch the light while it was inoperable to put a volt meter on the branch wiring and it all reads like it should, so for some reason, the problem is somewhere in the fixture. I replaced the ballast on this newly installed fixture and even then the problem continues.
I have not begun to trouble-shoot the second light aside from re-making the fixture-to-branch connections and correcting the missing EGC. However, out of 50+ lights like this, these are the only two that exhibit this problem, and all the fixtures are identical.
All I can remember about them at the moment is that they have 40W universal ballasts, which, I think are for parallel tubes...? Not sure. All these fixtures are underlamped at 32W. I seem to recall hearing that is hard on ballasts-will shorten operational life-but I can't remember positively. Even with all the fixtures underlamped, however, those two are the only ones that have ever had a problem.
I'm thinking from the way these things turn on and off (no flickering or blinking) that it's the thermal disconnect in the ballast kicking out. But what are the odds of three ballasts all having bad thermal cutouts?
I've done the usual tightening- connections/jiggling-conductors test to see if something is loose and that hasn't yeilded any change.
Anyone have any clues?
Thanks.
-John
