Why do light bulbs blow out?

[leehljp]

I have been back in the States for 3 weeks and leave for Japan in two days. While here at our home, where our middle daughter lives and works nearby, I have been doing some general maintanence on our home. I am seeing one unique problem that I haven't noticed that much before - light bulbs blowing out rather quickly.

The room my daughter is in - has a 3 light ceiling fan with tear drop looking bulbs. Those bulbs were blown and had blown within minutes to days after putting new bulbs in. This happened over the winter. She used two lamps in that room - until I returned and could check the switches. I replaced the blown bulbs and it worked but one blew within two days.

Two other rooms, including the master bed room have 4 and 5 bulb ceiling fans that use regular bulbs. 40 watts on the 5 bulb and 60 on the 4 bulb. Two to three bulbs were blown in each when we returned three weeks ago, and I replaced them with new GE bulbs (not the bottom of the line cheap bulbs). We were gone for 14 days for traveling while back here - and returned this past week to find at least one new bulb in each burned out in each, and at least one more burned out in each in the past 4 days. What could be causing even new GE bulbs to blow within a few days to weeks? They are acting just like cheap cheap bulbs!

I need to add in that some bulbs blow when turned on and others blow after having been on for 20 to 30 minutes or so.

This past Friday, I bought about 20 flourescent bulbs and replaced the bulbs in all multi light fixtures. Any comments and insight on the possible reasons for this, and the changing to the lower watt flourescent?

Thanks!

[os1kne]

I don't have any revelations, but I have also noticed that ceiling fan light fixtures (particulary those with 3+ bulbs) tend to go through light bulbs pretty rapidly. I'm not sure why, it's just something that I've noticed over the past few years.

[WayneJ]

Ceilinmg fans tend to vibrate . Thats why there is a special bulb made just for them. My fan has five bulbs in it and is used every day, have'nt changed the bulbs in over a year. My driveway light used a lot of bulbs till I tried the fan light bulbs. HD sells them. Look for ceiling fan bulbs.
wayne

[Hellrazor]

Check the voltage at the fixture. Sometimes you need to install 130v bulbs rather then the standard 120v.

Another big reason bulbs can blow frequently is a problem with a neutral. Make sure all the wires and wire nuts are ok. Do you have any noticable flickering of the lights when the A/C or other large electric users kicks on? It might be work tightening the lugs and everything in your panel, if you feel safe playing in a panel.

[steve-norrell]

I second Hellrazor's suggestion to try 130v bulbs.

We installed a bunch of dimmer switches in a remodel area and the original 120v bulbs produced an audible buzz. Something was vibrating enough to produce the audible noise. The electrician suggested the 130v bulbs and all has been fine since.

(Just had a stray thought; Could the speed control on the fans may have the same effect as the dimmers?)

The 120s weren't in long enough to die, but the vibration could not have been good for bulb life.

Regards, Steve

[ragswl4]

We bit the bullet several years ago and replaced all bulbs with flourescents. Haven't lost a bulb yet (including 3 ceiling fans) and by now I think the 17Watt flourescents have more than paid for themselves in energy cost. Replaced about fifty, 60 to 100Watt bulbs including all exterior bulbs that are in enclosed fixtures.

[LCHIEN]

Ah, a question for electrical engineers!

Fan use: You need to get Appliance bulbs or Fan bulbswhich are designed for vibration use. The vibration fatigues the filament which causes short life.

As for Hanks question:

Bubs wear out due to heat and oxidation. While the bults are designed to have a vacuum, no vacuum is perfect and contaminents in the bulb space itself surrounding the filament lead to failure when they oxidize the filament. Also some mechancial shock and even voltage transients can lead to multiple, seemingly clustered failures. Beyond that, just a statistical distribution makes it seem that bulbs fail together. The phenomena of clusters always appears. If you pick a number from 0-9, six times, you might think that no number will appear twice but in reality, statistics say that some number will come up twice in the group of 6.
that leads to the appearance of clustering but it is quite normal. So when bulbs fail truly randomly, some will fail so close together in time as to appear related, but they are not.

Now, what are the tradeoffs to making bulbs last longer?

Bulb brightness goes up exponentially with voltage, bulb life goes inversely exponentially with voltage.

So a bulb intended to be run at 120V, say you run it at 10% more, or 132 volts. The brightness will increase about (1.1) cubed. or 1.38 times as bright. (actually its the 3.4 power)
But the life will be 1/(1.1) to the 16th power or about 1/21 of the life.

Comversely, if you run the bulb at 10% less (a 120V bulb at 108 volts, or even a 130V light bulb at 117 volts) then you will get .72 of the birghtness but a life expectancy 4.5 times as long.

So buying and using 130v bulbs extracts a significant light loss penalty although the bulb will last 4.5 times as long.

If you line voltage is a little high, like 4%, then your bulb life will be halved.

Incandescent bulbs are very poor anyway in light efficiency, a 100 W bulb puts out 95 watts of pure heat and about 5% light energy.

Also you note looking at the packages within the same manufacturer's line, the higher the watt bulb, they chose to design lower life expectancy.
So you might see 100W, 850 hours, 60W 1250 hours, and 40W 2000 hours.

So my point here is that are tradeoffs, you can buy long life bulbs with less ouput but longer lives.

My final point is that I buy light bulbs, usually 4 for a $1. But the cost of lighting a $0.25 100W light bulb for its rated life is $11. That's based on 850 hour life, and 13 cents per KWH. The cost of electricity used in a bulbs life far outstrips the cost of the bulb itself. Paying more for a long life 100W bulb, but getting less useful light of the 100 Watts is poor economy. You'd be better off buying a 60W standard life light bulb and paying less for the electricity! Or even getting a 100W light bulb and paying 25 cents for a new one to get 30% more light for your $11.
(we're assuming it doesn't take an act of congress to replace the bulb in an inaccessible place). A timer or darkness sensor could save a major amount of $$ over a bulb left on 24/7.

The cost of lighting 5% efficient bulbs is hidden, that's why some localities (read California) are considering outlawing Edison's legacy, incandescent bulbs.

Fluorescents and LEDs are much more efficient but not as cheap for the base item. Typically flourescents will last much longer hours than incandescents and will also put out the same rated light for about 1/3 or 1/4 the power... so for the lifetimes of say 2 100W bulbs (2x 850=1700 hours), you will have saved around 14 dollars in electricity and $0.50 in bulbs for around $10 for a spiral fluorescent bulb - a good tradeoff. IF you like the light character and the brightness really does compare (which the ones I bought, don't seem to have the claimed same light output). It should r4eally outlast more than 2 bulbs by the way, so your savings will only increase.

Interesting dilemma:
Car makers are wanting to go to 48V systems in cars replacing 12V systems. Cheaper and lighter wiring is one reason, Motors and electronics will be cheaper and lighter too. But, one major stumbling block is light bulbs, the filament for 12V bulbs use heavier and thicker filaments for a given light output at 12V than at 48V. The filaments in todays 12V cars last pretty well. but 48V bulbs will fail much more often because of vibration and shock.

[docrowan]

Bubs wear out due to heat and oxidation. While the bults are designed to have a vacuum, no vacuum is perfect and contaminents in the bulb space itself surrounding the filament lead to failure when they oxidize the filament.

Loring,

I almost always read any of your posts that I see because I know in advance I will find a detailed, thorough, and accurate response. No exception in this case, but I have to point out that modern incandescent bulbs use an inert gas rather than a vacuum to protect against oxidation of the filament. I believe it's usually nitrogen, although krypton or argon is used as well.

Lee,

We switched to all compact fluorescents about four years ago. We dropped our electricity bill at least $60.00 a month. It's not just the energy savings of the lights themselves, they also generate far less heat, resulting in lower cooling bills in the summer. One summer cooling season in Mississippi generated enough savings to payback our investment. They last several years. We've moved three times and took our light bulbs with us in every move. We have a large variety of them, of differing wattages, shapes, and size, to try and match the right bulb with the right size fixture and how exposed it will be. Also once you install a bulb, you usually don't have to worry about it again. Some ceiling fan fixtures point down, so there's no avoiding that coiled look, but we try to get the most compact one possible. When it comes down to it, who walks in a room and stares at the light bulb?

[leehljp]

I want to thank each of your for the input. It has been very helpful!

The same as DocRowan stated, we changed our incandescent bulbs in our Japan home three year ago for fluorescents. It dropped our bill by an average of (the equivilent of) $60 to $75 a month and with much less heat generated.

For my Mississippi home and for my daughter I changed out the main lights that she uses. I should have bought some extra's but I am sure that she will just use ordinary ones for replacements in others because of the cost. With the information many of you gave, I will tell her to look for the 130V or ceiling fan bulbs, if she doesn't find the fluorescent bulbs locally.

I suspect voltage regulations problems, and one light does flicker quite a bit, but the light is recessed and hard to get to the wiring; we will just leave it off until I return again and have more time to check it out. It is only used rarely and I will jsut put tape over the switch. I have checked several lights for the connections, and needed to tighten the connections on most. On bathroom vanities, I found that several of the screws that hold the socket to the frame to be loose, indicating that the heat is causing lots of expansion and contraction, which lead to loose wiring joints also.

That alone has been a wake up call, and while I can't get to every light in my house this time, I have been maticulous with the ones that my daughter uses.

Thanks again everyone.

Loring, thanks for the clustering information also, that was helpful!

[Uncle Cracker]

Popping bulbs within days of replacement is definitely a sign of an electrical problem. If the problem is localized to one fixture, suspect wiring, switch or the fixture itself. If localized to a single circuit, but multiple fixtures, wiring or bad circuit breaker is probably the culprit. If the problem exists in your whole house or if your neighbors are having trouble too, then get your power company involved. Vibration can be an issue, but you shouldn't be popping bulbs if they're fan rated. Low or high voltage is more likely at the root of the problem.

And on a related note, for those folks who have one of those Intermatic digital timer/switches (found in practically every Lowe's and HD) replacing a standard wall switch, and perhaps operating several outside 120V lights, you are likely to notice that your bulbs burn out more often than they should, even if you stay well within the advertised wattage ratings. You should also never use the flourescent minis with this type of timer/switch. Intermatic has sold a gozillion of these timers, and has been very quietly trying to downplay the HUGE problems they've been having with them.

[blame]

now i know you have this figured out but to me the first thing i thought of was your circuits are overloaded and that would cause them to burn out when you turn the switch on

just my 2 cents
blame

[LCHIEN]

...

And on a related note, for those folks who have one of those Intermatic digital timer/switches (found in practically every Lowe's and HD) replacing a standard wall switch, and perhaps operating several outside 120V lights, you are likely to notice that your bulbs burn out more often than they should, even if you stay well within the advertised wattage ratings. You should also never use the flourescent minis with this type of timer/switch. Intermatic has sold a gozillion of these timers, and has been very quietly trying to downplay the HUGE problems they've been having with them.

Got a link or reference on that????

[gaj1967]

Yup, definitely check the wiring especially in older house. That's one reason electrical fires start.

I installed CFL's when I moved into this house two years ago and only had a couple go out. Those were in a ceiling fan that has a slight wobble that I need to work on one day.

I also use LED flashlights because they use fewer batteries.

Anything that helps lower electric bills and produce less undesired heat is great with me.

[LCHIEN]

Loring,

I almost always read any of your posts that I see because I know in advance I will find a detailed, thorough, and accurate response. No exception in this case, but I have to point out that modern incandescent bulbs use an inert gas rather than a vacuum to protect against oxidation of the filament. I believe it's usually nitrogen, although krypton or argon is used as well.

Doc R you are absolutely correct about filling with an inert gas (to prevent oxidation). It keeps the tungsten filament from boiling off, extending life and preventing the tungsten from darkening the inside of the glass. I guess they haven't used a vacuum since early in the 1900s and I stand corrected (and learned a little).

This article is very informative:
http://en.wikipedia.org/wiki/Incandescent_light_bulb

[Uncle Cracker]

Got a link or reference on that????

Nope. They're not being publicly forthright about it. I've had direct dealings with Intermatic, and they've admitted "re-engineering" these things twice already, and a third re-work is in the offing. They've also replaced considerable product to me thus far, as well as to two electricians I know. Has to do with too much resistance in the switching electronics, causing low voltage to the loads, and also causing some failures within the control unit as well. Coach lights on my home burned for five years before I had the units installed. Since then, units replaced three times, and double-life bulbs last about 3 months. Intermatic promises that the NEXT one they send me will hold up, but they're not in production yet. As for the mini-flourescents, it's stated inconspicuously on the packaging that you can't use them. My BIL didn't see that, and had one mini on his porch. The timer failed within 6 weeks.