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-   -   Bulbs keep burning out (http://www.diychatroom.com/f18/bulbs-keep-burning-out-56612/)

joelbuckley 11-05-2009 09:55 AM

Bulbs keep burning out
 
Just wanted to share this tip with the group. I was amazed. I thought I knew how to screw in a light bulb, but it turns out I didn't.

I recently installed a new lighting circuit with six 5" Juno IC-rated cans connected to a single switch. I used Air-Loc trims in these, and the cans are covered with insulation in the attic, so there's nowhere for the heat from the bulbs to go, which probably contributes to the problem.

Anyway, bulbs in two out of the six kept burning out within just a few hours of use. I thought I must have got something wrong with the wiring, like a loose neutral, and was about ready to go digging around in the attic, when I found an ask-the-builder column that suggested a too-tightly screwed in bulb can cause this. Well, sure enough, that was it. If you screw the bulb in too tightly, it compresses the center contact in the socket too much so it loses its springiness. After a few on/off cycles, a small air gap develops between the bulb and the contact, which causes arcing, which destroys the bulb in no time.

You can use a pair of needle-nose pliers to pull up the center contact in the socket ever so slightly (after cutting power at the panel). Then install the bulb with the power on, and stop a half turn or so after the bulb lights up, BEFORE it bottoms out.

Made all the difference.

fltdek 11-05-2009 04:14 PM

Hmmm? Interesting, but my question is...How many DIY'ers does it take to screw in a light bulb?


Joking aside, thanks for the info!

frenchelectrican 11-05-2009 08:24 PM

This my tip here when I screw in any type of bulbs it can be indenscent or Compact flourscent or HID

when you screw it on when you get to the end when you feel snug back off about quarter turn to half depending on the socket itself then foward 1/8 turn and that it nothing more.

I don't get too many callback with this issue at all.
Merci,
Marc

Yoyizit 11-05-2009 09:23 PM

Quote:

Originally Posted by joelbuckley (Post 349429)
Anyway, bulbs in two out of the six kept burning out within just a few hours of use. I thought I must have got something wrong with the wiring, like a loose neutral, and was about ready to go digging around in the attic, when I found an ask-the-builder column that suggested a too-tightly screwed in bulb can cause this. Well, sure enough, that was it. If you screw the bulb in too tightly, it compresses the center contact in the socket too much so it loses its springiness. After a few on/off cycles, a small air gap develops between the bulb and the contact, which causes arcing, which destroys the bulb in no time.

You can use a pair of needle-nose pliers to pull up the center contact in the socket ever so slightly (after cutting power at the panel). Then install the bulb with the power on, and stop a half turn or so after the bulb lights up, BEFORE it bottoms out.

Made all the difference.

Some sockets have a raised land to prevent this.

Supposedly the center contact has been work-hardened by this over-compression past the spring's elastic limit and then straightening it again, but who's to argue with success?

I always screwed them in with the power on and went slightly past the point at which the bulb lights.


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