Blowing light bulbs

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Yeah, I know, not this topic again... But this is getting ridiculous.
I have a string of about 6 pot fixtures in the basement with BR30 bulbs. The fixtures are switched by a pair of 3 way switches. The fixtures are open to the air - the ceiling hasn't been drywalled (yet).
The bulbs are burning out at a very high rate. Within a week of getting them all working again, at least one goes out, within another month, usually all of them are dead.
As far as I can remember, these have all been Sylvanias, some "extended lifetime" (hah!).
Most of the time, a bulb expires when we "flick" (as opposed to "sloowwly presssss" ;-) one of the threeways. The threeway switches are relatively newish decora type switches. Probably cheapies - I'll bet they bounce a lot.
I'm looking for real-world experience here - has anybody solved lamp burnouts like this by replacing the switches? Are there line filters for this sort of purpose?
I want to exhaust those possibilities before going on an expensive quest for more expensive bulbs.
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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Chris Lewis wrote:

There is a gizmo, looks like a wafer, you can put inside the bulb socket, to limit the surge to the bulbs. I bet it's just a flat resistor, but it might help.
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HeyBub wrote:

IIRC they aren't just resistors, they're thermistors, which have a moderately high resistance when cold, to limit the bulb's turnon surge current. They warm up fast with current flowing through them and drop way down in resistance so that most of the power gets used by the bulb.
Jeff
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Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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Blowing lightbulbs is a felony.
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Matt wrote:

So is screwing in one:
http://home.comcast.net/~jwisnia18/temp/screwing.gif
Jeff
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Jeffry Wisnia

(W1BSV + Brass Rat \'57 EE)
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Chris Lewis wrote:

you can try installing a dialed dimmer switch. or see if you can find any of those devices that go in the socket that are supposed to extend the life of the bulb, not sure what they do.
could it be the room temperature is too low? Soft starting of lights definitely extends the life.
--
Respectfully,


CL Gilbert
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in part:

Usually not much (there are some exceptions), despite lightbulbs typically blowing during a cold start.
What usually happens is that cold starts do surprisingly little damage to the filament, while a filament that is approaching end-of-life (due mainly to operating hours and filament temperature during steady operation) becomes unable to survive a cold start a little before becoming unable to survive steady operation.
A filament that has suffered uneven evaporation to the extent to become unable to survive a cold start is already in bad shape, and this condition is accelerating at a rate that increases worse than exponentially while the filament is running.
Now a bit of specific data: I actually got one of those soft-starting "buttons" to attach to the bottom of a lightbulb to supposedly double its life. I managed to get an indirect reading of voltage drop across the "button" and the lightbulb while the "button" was in place and fully warmed up, and it turns out the "button" dropped enough voltage to dim the lightbulb enough to extend its life 50%. Also: Using the usual rules of lightbulb performance as a function of voltage, light output went down 11% while current consumption (and power consumption, counting watts dissipated in lightbulb and button combined) went down 1.7%.
- Don Klipstein ( snipped-for-privacy@misty.com)
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Don Klipstein wrote:

yes. Its kind of playing a game. Like using something thats broken, but using it very gently so as to keep using it...

Nice. We do the same thing to car headlamps when possible.
--
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CL Gilbert
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Don Klipstein wrote:

Lots of nice info there. Thanks. I am wondering what the effective voltage drop would be for a dimmer that is full on.
It has been my experience from work with tungsten heating coils in a vacuum system that unused tungsten can be bent into small radius turns, BUT, after it has been used into the dull red heat range the same wire will break if that same bending is attempted. I guess it has to do with annealed or not annealed and work hardening, but I can never remember how that goes!
My point is that a USED bulb filament is mechanically fragile, AND when standard service bulbs are turned on with a switch, there are MECHANICAL forces due to the start up of magnetic/electric fields. These mechanical forces on the filament may be demonstrated by the ringing sound some filaments will make when a dimmer is set low. Sound is due to a mechanical phenomenon, so that would mean the filament is vibrating!
I continue to be convinced that using an up/down dimmer (one with no abrupt on/off) slows down bulb burn out, and that mechanical actions will also do it for bulbs. For example, rough service bulbs last longer in mechanically rough service, and if we look at the guts of such bulbs, we see extra filament supports which minimize vibration. --Phil
--
Phil Munro Dept of Electrical & Computer Engin
mailto: snipped-for-privacy@cc.ysu.edu Youngstown State University
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I've never found a rough service bulb whose light color wasn't ugly. I wonder why?
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Doug Kanter wrote:

I use clear glass fan bulbs (which are a form of rough service, I think) and some "rough service" bulbs for a trouble light. I have not noticed "ugly" color. What does "ugly" mean? --Phil
--
Phil Munro Dept of Electrical & Computer Engin
mailto: snipped-for-privacy@cc.ysu.edu Youngstown State University
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Other than some Philips frosted fan bulbs I mentioned elsewhere in this thread, my experience with rough service bulbs has been those labeled as "Good for trouble lights". Weird, overly warm color, more so than your run-of-the-mill light bulbs. Doesn't matter so much in a trouble light, but there have been some other instances over the years when I could've used them, in basement fixtures, for instance, where foot traffic above seemed to be causing early bulb failure.
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Doug Kanter wrote:

Looking at 75W bulbs, the rough service bulb is 62% of the light output of a normal bulb. Part of this is losses from more filament supports. But they probably run the filament at a lower temperature to make it more shock resistant. Lower temperature shifts the spectrum toward the red.
Bud--
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Outright true, but for most lightbulbs this stress is within the "endurance limit" (threshold of causing metal fatigue), and less than the stress of having people dance or dribble basketballs on the floor above or slamming nearby doors. And yes I do know that a lightbulb experiencing a cold start can have its filament mechanically jolt enough to produce a "ping" sound that is often audible within a foot or two away. NOTE - the filament is much weaker when hot, and the main mechanical stress of a cold start occurs when the filament is not so hot, and much stronger than a hot filament whether it is ductile or brittle.

Most dimmers when turned all the way up will reduce RMS voltage to a lightbulb roughly 2-3 percent, and that reduces light output about 3 times that and can account for a life extension of 20-40%.
In general, "rough service" bulbs have much longer life expectancy than "standard" bulbs even where there is no damaging vibration present due to the filament being designed to run cooler, since most such bulbs are used where labor has to be paid to replace them. Also, they are less efficient to such an extent that a 60 watt "standard" bulb usually outshines a 75 watt "vibration resistant" or "rough duty" one. Over 1,000 operating hours, 15 watts of electricity usually costs more than a lightbulb does.

- Don Klipstein ( snipped-for-privacy@misty.com)
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On Tue, 26 Jul 2005, snipped-for-privacy@nortelnetworks.com (Chris Lewis) wrote:

What is the wattage of the bulbs? What is the rated maximum wattage of the fixtures?
Don <www.donwiss.com> (e-mail link at home page bottom).
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Not familiar with BR30 bulbs. Are they incandescent or fluorescent? If incandescent, is it possible that foot traffic from above is causing enough vibration to ruin the bulbs? If fluorescent, never mind....
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Chris Lewis wrote:

Heat, vibration, water and over voltage are common problems for short life.
Heat? (are the fixtures rated for 45W or more?
Vibration? Anything causing a vibration of the fixtures?
Water? Anyway they could have water drip on them; condensation maybe?
Over voltage? This is my guess. The power coming into you home could be too high or if you have a floating ground (usually one loose wire, and not always near the lights) that could account for it. Do the lights brighten and dim sometimes? Do you have any aluminum wire anywhere in the house?
--
Joseph Meehan

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Joe... Interesting possibilities to ponder......... How does aluminum account for overvoltage? If it has an inherent higher resistance, I would expect the opposite. What about a floating ground? It would have a lower differential to the mains. Please qualify how this would work. Thanks
Les KA9GLW I agree with the overvoltage as a consideration, but I can't see how this could happen in practice. My other thought is that these bulbs are not the tungsten variety, but the halogen type. It's known that the ion exchange between the halogen envelope, the gases and the filament are tuned to work at specific temperatures. If you try to alter the optimum operating temperature, they fail much quicker. So, don't dim halogen bulbs. It doesn't extend their life, but shortens it. A soft start would be an exception, I'm sure.
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les wrote:

The power to your home is supplied at 240V. It is split 120V on either side of the neutral. The neutral is connected to the ground, but it is not a ground. Each 120V circuit is one one or the other side of the neutral. If you had two 120V circuits with exactly the same load (say 5 100W lamps) then the they would be balanced and current would flow only on the two hot wires and nothing on the neutral leaving your home (you have three wires and maybe a ground coming into your home.) however if one of the lamps went out, you would have about one amp more going through one side than the other so the difference would flow through the neutral OK I am getting to your question. With aluminum wire, connections tend to get flaky so it is possible that the neutral may not make good connection so the set of 5 good lamps would get less current and be a little dimmer and the side with 4 good lamps would be brighter.
If you have aluminum wire coming into your home from the street, that's OK they use special designed fittings to eliminate the problem, but if you have it inside your walls running to outlets, it can be a hazard because of the bad connections.

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Joseph Meehan

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either
not
Joe... I never thought about this before, but in the 2 phase system as you describe, where does the transformation occur? On the pole down the street? If so, the utility company has me and many other costumers experiencing possible imbalances due to the communal sharing. How do they account for these potential problems? (no pun intended) I uinderstand your explaination, but I think in a low impedance system as the power grid, you would need a large current difference in the 2 legs to see anything measureable. Does it really happen in the real world? I'm aware of brown-outs, but this isn't it..........
(and speaking of grounds, what defines a ground? That's a relative thing)
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