Recessed Lighting - Thermal Cut-Off or Electrical Short

Reply Sun 22 Dec, 2013 12:27 pm
I've got a fairly standard covered, recessed lighting fixture in an upstairs bathroom, where there are in fact, two of these fixtures on a single circuit.


Although both fixtures are equipped with the correct watt light bulb (Max: 75W), periodically I have noted that the bulb in one fixture or the other will seemingly fail, but then after a period of time, will illuminate again.

This sort of not-easily-explained electrical "behavior" always seems to freak my wife out, since she seemingly never met a risk (real or imagined) that she didn't want to obsess about (evidenced by a prior posting on Outdoor Lighting, to ward off imaginary burglars she felt were lurking in the backyard . . .). And for the record I try to accommodate some of that paranoia, up to a point (. . . I only acknowledge that publicly, since she won't ever see this due to concerns about the NSA spying on her on-line . . .). http://i195.photobucket.com/albums/z319/CGDobyns/smile_zps830dc23c.gif

Consequently, my wife is convinced that one or both light fixtures have a dangerous "shortage" in them (I don't correct that use of terminology, only because it's always entertaining to hear her say it). My belief is that both fixtures must have some sort of thermal sensor built into them, which shuts off the flow of current to the bulb, when the temperature within the fixtures reaches a certain level. I'm happy if that's the case, because the predominant mass of the fixture does extend up into the attic, presumably anchored to one of the ceiling joists.

I've noted that the fixtures don't shut off that frequently, and typically only after they've been left on for an extended period of time (2-3 hours). Since we've correctly concluded that there's nothing wrong with the bulbs, or the switch, and eliminated the likelihood of gremlins, elves, and even prank-playing burglars (thanks to the outdoor lighting now . . .), does this theory about the integrated thermal limiter sensor in the fixture sound right?
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Reply Sun 22 Dec, 2013 12:37 pm
CD I'd agree your theory about thermal shutoff sounds good, very technical and all, but if you're wrong then your Better Half is indeed Better. Maybe the problem is a manufacturing defect in the socket or you need to screw in the bulb a bit further; either shortcoming potentially hazardous
Reply Sun 22 Dec, 2013 05:32 pm
Since I was making my seemingly 4,237th trip this year to Lowe's this afternoon (wait, that would be more than 10 trips per day . . . never mind . . . as apparently this is just my imagination), I thought I would try to clarify the recessed lighting question.

The lighting/electrical representative at Lowe's confirmed that most recessed lighting fixtures today, do include a thermal protector, in the form of a thermocouple, which interrupts the flow of current to the bulb, if the temperature in the fixture reaches a certain level. So for us, there appears to be no danger, except when the light is left on too long - since the thermal sensor is apparently doing its job. Prudence would seem to suggest that we might want to "step down" the wattage on the bulbs to the 60W range - just to be on the safe side (or just not leave the light on endlessly).

So, with regard to this question . . . how does the famous quote from the movie go: " . . . this is not a boat accident, and it wasn't any propeller, it wasn't a coral reef . . . and it wasn't Jack The Ripper. It was a shark".

Jack The Ripper ≠ Electrical Short / Shark = Thermal Cut-Off.
Reply Sun 22 Dec, 2013 05:40 pm
Well thanks CD, not everyday…….
Reply Mon 23 Dec, 2013 01:56 am
The trim will not tell you if you have the correct fixture installed. If these fixtures are not listed to be in contact with insulation and there is nothing holding the insulation away from the recessed fixture can, they will overheat. If you have attic access where the fixtures are located you could check the fixtures and move some insulation if needed. If you do not have access you can remove the lamp and then the socket assembly and then the recessed can will also come out so you can see what is there.
Reply Mon 23 Dec, 2013 12:05 pm
Wow thank you Bah, that's 2 days sequentially…...
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