fixture problem

[iwire]

Me too - found this to be the case in many older fixtures - and one of the more puzzling troubleshooting mysteries. The arcing contacts while seem to light the bulb just fine eventually kill the lamp life to ~50% or <.

How is it shortning lamp life?

Please explain.

 

[R Bob]

Personally I have a real hard time believing that a loose connection in a lamp socket will shorten the lamp life.

How is it shortning lamp life?

Please explain.

Good question!

It would seem to me that a poor connection/poor contact would result in reduced voltage(voltage drop) to the lamp, thereby actually extending the life of an incandescent lamp. :-?

I'm not quite sure what impact the arcing issue would have.

 

[USMC1302]

The arcing caused a hole to be burned into the base. That'll cause the lamp to fail quickly. Correct me if I'm wrong.

 

[R Bob]

The arcing caused a hole to be burned into the base. That'll cause the lamp to fail quickly. Correct me if I'm wrong.

Of course you're correct.

However, all instances of poor contact don't necessarily result in arcing.

If arcing is taking place, there will be evidence of it on the base of the lamp or in the socket, such as; carbon deposits, or the condition that you cited, which would be quite apparent on inspection.

 

[mxslick]

How is it shortning lamp life?

Please explain.

The arcing caused a hole to be burned into the base. That'll cause the lamp to fail quickly. Correct me if I'm wrong.

Burning a hole in the base is one possible failure mode, but I feel that the arcing of a loose connection is the same as turning the lamp on and off thousands (millions?) of times very rapidly.

Incandescent lamp filiments have very low resistance when first energized, which results in high current flow.

Try an experiment on your own: Take two lampholders, one switched, one unswitched, powered from the same circuit. Leave one lamp on all the time, and turn the other one off and on several times a day. See which one lasts longer.

 

[boboelectric]

fixture has 5 lamps in it. 3 of the lamps keep burning out within 2 weeks of installation everytime. the other 2 lamps remain energized and fine. problem persists whether incandescent or mini compact flourescent lamps are used. any clue on what would cause this.

Buy a new fixture.

 

[ohmhead]

Well just thinking a little bit ,

Heres why a standard bulb burns out if it has a bad contact in the base the ac voltage applied to that lamp element internally has a higher frequency now its not 60 cycles it can be higher this vibrates the metal to the point of breaking that element .

That on /off is a higher freq your eyes can not tell its going off /on 1000 times per second bad contact makes the contact a oscillator metal heats up and vibrates .

Have you ever put your ear near a bulb you can hear the ringing of the 60 cycles if you hit the bulb they usally blow out same thing bad contacts .

 

[e57]

How is it shortning lamp life?

Please explain.

Not completely sure - BUT IT DOES!!!!

My theory on it.... The arcing contacts while not seemingly intermittent causes an imperceptible switching. This 'switching' causes the tungsten, or in the case of the POS CFL - to have recurring starting currents. These starting currents in the CFL is just destroying the POS little ballast in there. In the case of the regular lamp it constantly bounces the filament until it gives way by way of metal fatique... Well that's just what I think...

But proof be positive - getting better contact on the lamp itself with a clean firm contact - corrects the ridiculously short lamp life phenomenon. Go figure....

 

[hurk27]

Not completely sure - BUT IT DOES!!!!

My theory on it.... The arcing contacts while not seemingly intermittent causes an imperceptible switching. This 'switching' causes the tungsten, or in the case of the POS CFL - to have recurring starting currents. These starting currents in the CFL is just destroying the POS little ballast in there. In the case of the regular lamp it constantly bounces the filament until it gives way by way of metal fatique... Well that's just what I think...

But proof be positive - getting better contact on the lamp itself with a clean firm contact - corrects the ridiculously short lamp life phenomenon. Go figure....

So we are saying that a 120 volt bulb will last 60 times longer powered by direct current (DC) than if it were powered by alternating current?
remember on AC it already turns on and off 120 times a second.

The filament in a lamp does have a lower resistance when power is first applied, but after it has reached the temperature of luminescence's not much would change until the filament were to cool off, this should mean that a lower frequency would be required for it to do this, very much lower in fact, but at the same time the filament would receive a very much lower RMS voltage, thus counteracting the extra starting cycles, many two position dimmers just use a diode to cut the sine wave in half, thus only providing a 60hz pulse instead of the 120 pulses the filament would normally see, as far as I know this has not affected the bulb life and maybe extended the life of the bulb in most cases, so I cant see where a higher or lower frequency would shorten the life of a bulb unless it so low that it allows the filament to cool below a certain temperature? which would mean it would be so low it would pulsate.

What I can see is a high resistance connection in the base causing a higher temperature on the wire holding the filament, this could cause a failure?

 

[LazyS]

Are the bulbs rated for 130 volts? Could a higher voltage, say 123volts burn out a 120 volt lamp quicker? Not sure what cfl's are normally rated.

 

[mivey]

fixture has 5 lamps in it. 3 of the lamps keep burning out within 2 weeks of installation everytime. the other 2 lamps remain energized and fine. problem persists whether incandescent or mini compact flourescent lamps are used. any clue on what would cause this.

Any reason that these 3 bulbs would be getting bumped/handled? Are they exposed to some sunlight that does not hit the others? Is there an A/C vent that hits some but not the others?

Personally I have a real hard time believing that a loose connection in a lamp socket will shorten the lamp life.

I have seen the solder melted on the base of the bulb from over-heating.

Arcing cannot be good for the bulb. While the A/C is already cycling, and dimmers cut the waveform, I would think arcing is more violent.

I think I read something on that. I'll look when I get a chance.

 

[e57]

So we are saying that a 120 volt bulb will last 60 times longer powered by direct current (DC) than if it were powered by alternating current?
remember on AC it already turns on and off 120 times a second.

~~~~

Edison was shooting to promote DC.... Who knows? And while AC and even dimming does go off and on rather quick - they do so pretty gently in the sceme of things...

Any reason that these 3 bulbs would be getting bumped/handled?

Arcing cannot be good for the bulb. While the A/C is already cycling, and dimmers cut the waveform, I would think arcing is more violent.

I think I read something on that. I'll look when I get a chance.

Sure I have also had the up-stairs neighbor knock 'em out...

And if you find anything post it....

Anyway who could forget these from when they were trying to ram AFCI's down our throats....

Again - not trying to say that's the reason - but better contact on the lamp does equate to normal lamp life.... Why? :roll: Go figure?

 

[bhalp]

fixture problem

Thanks for the input to everyone. I have not seen the fixture yet. I was told of this problem and was asked what could be the problem. My guess was the 3 lamps were getting to much current causing them to burn out faster. its possible that a homeowner rewired the fixture wrong. i like the one with the arcing causing the lamp contact to go bad. the guy says its an old fixture and the best solution is replace it, but i'd like to disect it to see what the problem is. just curious to increase my knowledge. thanks to everyone.