I know...age old question...but why are lightbulbs blowing left and right in 5 yr. old apartment bldg.?

p.s.....neutrals in subpanel and meter bank are tight

Might be a POWCO problem.

Can you put a recorder on it?

could you elaborate,Steve?

something to monitor for spikes?

A simple voltage recorder might show a problem, but won't pick up spikes.

The recorder you want is the more sophisticated (expensive) sort that records dips, spikes and what not. You can rent them, but in my area the POWCO will install one on a building free for a few days in response to a trouble report.

[This message has been edited by stevecheyenne (edited 01-12-2007).]

Thanks steve....I'm new here and I told my wife that might be my first question since she is constantly changing the bulbs{and I'm not getting them for free:{.....sitting for test this year and hope to learn alot from you knucklheads........

Vibration can cause the problem, as can high voltage problems. You can also look closely at your choice of bulbs, choose the bulbs with the 130 volt rating, they will last longer.
I had a problem with bulbs I used in my garage coach lights. The vibrations from the opener caused frequent bulb loss. I know it wasn't high voltage because the same bulbs would last forever in the keyless lampholders installed inside the garage. I changed them to edison base flourscent (compact) and solved the problem.

Overlamping in an enclosed fixture will also lead to early lamp failure.

One other suggestion would be to try a few 130 volt lamps in certain fixtures and take note of whether they last any longer than their 120 volt counter parts. This won't diagnose your problem but might help with the frequency of having to change the lamps

Roger

I seen basements that had that problem. It turned out that it was more of a structial issue. Without going into detail but you could see the joists shake when someone was walking above.

Also how long are the bulbs on every day? Are they in common areas? 1,000 or 2,000 hour bulbs may not last long enough if they are on all the time.

The 130volt bulbs make a serious difference here over the 120 volt ones (by about 50%).. My incoming voltage is only 122/123V phase/ground.

Not just panel connections or main connections being loose could cause issues. Loose or arcing connections anywhere in the circuit path could do the same. Even, and especially the ones right at the bulb.... An A-19 for instance with a med. base not firmly screwed in will arc at the hot connection inside, and blow pretty quick. I see this problem often in worn, or 'inexpensive' lighting fixtures all the time. People screwing in the fragile bulb in hand are fearfull of giving it a good twist. Or most often are afraid to do so due to the cheap or old fixture falling apart in thier hands.

Really appriciate the input....gonna start by seeing what voltage shes using......because you know my feelings are hurt when shes looking for an answer:}

I would really like to hear a reason why

"Loose or arcing connections anywhere in the circuit path could do the same. Even, and especially the ones right at the bulb.... An A-19 for instance with a med. base not firmly screwed in will arc at the hot connection inside, and blow pretty quick."


would have any effect on lamp life.

I have heard it said by quite a few people but I have always doubted the facts of this.

Bob, I always heard the rational as being the glue around the base of the bulb melts due to the heat, thus letting the gas out of the bulb, which makes the filament blow pretty much instantley
-Will

iwire:

Theory of Why Lightbulbs In Arcing Circuits Blow Faster

- Fact: A lightbulb has a metal filament inside (let's only talk about those at the moment).
- Fact: This filament has a very low resistance when cold (dark). Take your multimeter and measure the resistance...! When it's hot, the resistance is much higher.
- Switching on thus causes a very large current to flow thru the filament in the moment of power on.
- This high current vaporizes a minuscule amount of the filament at each power up due to the very rapid heating. The filament is literally getting thinner - of course, not over the entire length, but at the potential defect spot(s).
- As soon as enough of the filament is vaporized, the filament breaks; usually in my experience at power up. This process is accelerated by vibration, the filament usually consists of tungsten and osmium, this alloy is very brittle and will crack with vibration.

Arcing is just fast and random switching off and on of the power, causing many power cycles. Even if they're not full on/offs, they do put a significant stress on the filament.

Supporting evidence:
- Lightbulbs in well-constructed blinking lights usually have a "keep-alive" resistor which prevents the filament from going cold between the "on" cycles.
[Sideline to ElectriKid Ian A.: This (the keep-alive resistor) is the way to use normal bulbs in blinking applications such as traffic signals at home and still get a decent lifespan out of them.]


Plausible?


Elviscat:
The glue is just to hold the metal socket cap to the glass. The glass itself is hermetically sealed (the glass in its molten state is pressed around the wires going into the bulb), no gas gets in or out.


Dilydalyer:
Get heavy-duty lamps if you can or maybe some of those energy-saving lamps. They last MUCH longer than anything that glows! [Of course, your "better half" will maybe have to approve of the new lightning ]

Nice theory, er...except that a bulb is switching off and on 60 times a second anyway, in harmony with any arc.
Most likely reason is crap chinese bulbs from Walmart at 15c each.

Alan

Exactly what I had in my mind.

Also how does a modern dimmer 'dim' a standard incandescent lamp?

It chops the heck out of the sine wave.

These dimmers prolong the life of the lamp.

I really do not think you will be shortening the life of a typical incandescent lamp unless you switch it off long enough for it to substantially cool down. I would think of and on periods of a couple of seconds would shorten the life.

Cheap lamps.

Try a known brand and see if it lasts longer.

Also a 130 Volts lamp will last longer too as already suggested

Try 120 times a second...

The voltage goes to zero twice in each cycle.

*smacks self in head* I've seen at least half a dozen bulbs seperated from the base, that were dangling from the wires, one of which was after I hit it with my head! (oonly 6' clearence in basement, I'm 6'2, not a great job)

Will *sticks foot in mouth again*

Tesla,

And how do you work that one out?.
Are you telling me that with a frequency of 60Hz, the real cycles per second are 120?.

Alan, iwire


The keyword here is thermal inertia. A filament takes a bit longer than 1/120s to cool down significantly. That's why with bulbs you usually do not have the stroboscopic effect (that's the one that makes some car wheels on TV stand still or go backwards).

A dimmer prolongs lamp life by operating the filament at lower temperatures (= less light, color is yellow/orange). The filament does not care about the horrible waveform feeding it. I've used small bulbs as load devices for all kinds of waveforms, even true power spikes, they don't care as long as you don't exceed the rated power dissipation (the integral of voltage times current over time). Not to say that these bulbs didn't suffer from being "switched" on and off by low-periodicity spikes...

starting at zero, the sine wave goes up to ~200v, back to zero, down to ~-200 and back up to zero. that is one complete cycle. The average voltage is 120v. 60hz is 60 complete cycles, or 120 zero crossings per second.

The way that solid state dimmers work is that the SCR (or triac) delays the turn on point for
some time after the zero crossing, reducing the average voltage, at the expense of a clean sine wave. better dimmers add a inductor to clean up the sine wave.

Let me try and reason my argument. If a piece of metal, say a bulb filament, be heated to a high temperature by means of an electric current; when the current ceases to flow the cooling rate of the metal must be a function of the dimensions, alloy and surface condition of the filament, in the radiative, convective and conductive conditions appertaining. The heating-up rate is constrained by slightly different conditions, ie the material properties as outlined above, plus the filament's resistance/temperature curve, the voltage applied over time, the original temperature and the ongoing heat losses as the temperature rises. As far as I can see these are the only conditions which appertain, and must embrace "thermal inertia". To cause premature failure of a filament would require a change in at least one of the conditions, and the only base variable is the voltage, which I think, intuitively, needs to increase.
$64000 Question: Does an arc produce higher voltages in a circuit?

Alan,

You're absolutely correct about the inertia thing, I use this word as a "lump sum" of all the various parameters that you described.

The change you are looking for that leads to filament failure is mostly in the mechanical dimensions of the filament. Over time, part of it vaporizes and the imperfections in it make it weaker until it burns out.
Take the time and check out this internet page, found googling for +light +bulb +failure: http://invsee.asu.edu/nmodules/lightbulbmod/burnout.html
Have a look at the pictures of the aged filaments - you can see the "corrosion".

Frequently switching a bulb on and off will accelerate this process, arcing is nothing else than a fast, more or less random switch that additionally switches to on - usually not at zero crossing but at substantial voltages (that can gap the bridge between the two contact surfaces) so the inrush current is even higher than usual, accelerating the evaporation process even further.

And, to conclude: In a lighting circuit, arcing should not produce high voltage spikes. Please PM me the $64,000 check and thanks for the interesting discussion!

Here's a non-technical possibility. A few tenants may be replacing their burned out bulbs with good ones from public areas of the building.