Lamps blowing

[mivey]

It didn't make sense at the time to me either but if your neutral is reversed on an incandescent fixture it can be a big surprise when you re lamp.

Agreed. The part that did not compute was the reversal causing the lamps to blow.

Nobody said what kind of light bulbs were being used.

From#1:

...These are pendant mount incandescent fixtures with 60watt lamps...

If the unbalanced current was leaving through the tip and the current was entering through the screw shell the area of the screw shell is more. More area to heat up. No limiting values of only entering through the point of the lamp base. The heat translates into shorter life of the lamp. My solution was to wire the fixture correctly.

How do you get unbalanced current an a two wire circuit?


Add: Whoohoo! #2000. I'm am still page 2 scum.

 

[GUNNING]

Got me. It was just a guess. They were getting hot though and the screw shell was energized. Maybe it was bad metallurgy. What would make the base of a lamp heat up to such an extent that the bulb would plop out. Loose connection? No, these were tight. The limiting value would be the area of the tip in contact with the point of the lamp. The energy used was in excess of the melting point of the glue holding the bulb to the screw base. Heat is a limiting factor of the lifetime of the lamp. Got a better solution? The only thing I could find was the fixture was reverse wired. This might not be what is making their fixtures blink out lamps.

 

[mivey]

Got me. It was just a guess. They were getting hot though and the screw shell was energized. Maybe it was bad metallurgy. What would make the base of a lamp heat up to such an extent that the bulb would plop out. Loose connection? No, these were tight. The limiting value would be the area of the tip in contact with the point of the lamp. The energy used was in excess of the melting point of the glue holding the bulb to the screw base. Heat is a limiting factor of the lifetime of the lamp. Got a better solution? The only thing I could find was the fixture was reverse wired. This might not be what is making their fixtures blink out lamps.

Could just be cheap fixtures or lamps. I have had some lamps just fall apart and I just wrote it off to poor quality.

I know some sockets get very hot. I have seen some cans that cause lamp failure more than others. Could be ventilation, could be a bad socket.

FWIW, if the tip gets hot enough, the solder will soften, giving more contact area, up to a point. I have seen them soften so much that the solder flows away from the spring, causing the lamp to go out because it loses contact. The lamp would still light up when voltage was applied.

It can be strange sometimes.

 

[kbsparky]

I am assuming these are fixtures with medium base lamps, if that is the case, look up inside the sockets and see if the little brass rivets that make contact with the metal tab and screw base have signs of arcing (black carbon residue) I have run across this quite a bit. They can arc and cause incandescent lamps to fail prematurely.

Bad sockets. Replace the sockets with some good grade porcelain ones, and I'd wager your problem disappears.

 

[iMuse97]

Bad sockets. Replace the sockets with some good grade porcelain ones, and I'd wager your problem disappears.

I'm with the thought here. Had tabs in the center of the socket that didn't provide great contact and the lamps apparently got very hot as a result of a continual "mini-arcing" in the base.

I had one that wouldn't keep a lamp for more than two hours before burning it up. Pulled the tab forward with a screwdriver (made sure power was off), and never had a problem again--it's been two months.

This lamp holder was part of a fixture assembly that came straight off the shelf. Quality isn't always job one, apparently.

 

[elvis_931]

I went back to work on this. I found that these are cheap fioxtures woith poor quality materials. The tabs in the sockets were flimsy at best, making poor contact with the lamp. I touched one with my screwdriver and it broke off! I could tell where thay had been arcing a little. I also got a case of 130v 60w lamps for them to replace as they go out. Thanks for the input. And by the way: the more surface area, the better the heat dissipation!

 

[iMuse97]

I went back to work on this. I found that these are cheap fioxtures woith poor quality materials. The tabs in the sockets were flimsy at best, making poor contact with the lamp. I touched one with my screwdriver and it broke off! I could tell where thay had been arcing a little. I also got a case of 130v 60w lamps for them to replace as they go out. Thanks for the input. And by the way: the more surface area, the better the heat dissipation!

thanks for the report back.