Mark Price
Member
- Location
- United States
mountain cabin every visit one or two bulbs have blown sometimes the same bulb suggestions to the problem:?
blowing bulbs
- Thread starter Mark Price
- Start date
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most common occurrence I have found is folks using lamps rated a 120v on systems where the voltage tends to run 130+. Second most common for me has been poor neutral connections causing higher voltage on one leg.
- Occupation
- Licensed Electrician
What augie said times two.
ptonsparky
Tom
- Occupation
- EC - retired
X3. Then add vibration and the 10 for a $1 factor. Overlamping.
big john
Senior Member
- Location
- Portland, ME
Three things will kill incandescent lamps prematurely: Vibration, over-voltage, and cheap construction.
While I can't swear by the accuracy of it, there are a lot of tungsten lamp life charts similar to this that show a ~50% reduction in life for a 5% increase in voltage, so I agree with the other guys, that's a good starting point.
And while this doesn't sound like it's the case here, in places with a lot of light bulbs try to keep track of which ones you change: The customer only remembers that they're constantly calling you to replace lamps, they don't remember that it's not actually the same lamps blowing repeatedly.
While I can't swear by the accuracy of it, there are a lot of tungsten lamp life charts similar to this that show a ~50% reduction in life for a 5% increase in voltage, so I agree with the other guys, that's a good starting point.
And while this doesn't sound like it's the case here, in places with a lot of light bulbs try to keep track of which ones you change: The customer only remembers that they're constantly calling you to replace lamps, they don't remember that it's not actually the same lamps blowing repeatedly.
kwired
Electron manager
- Location
- NE Nebraska
One thing not mentioned yet that I used to get a lot of calls about is poor connection in the lamp socket. Often is created by overlamping, over tightening the lamp in the socket or both. Look into lamp socket and if there are burn marks around the rivet that connects the center pin or the shell to supply conductor - it is loose and excess heat developing there does shorten lamp life. Aluminum shell lamp sockets are the worst for this.
big john
Senior Member
- Location
- Portland, ME
I've often heard this, and have trouble understanding it. A lamp filament operates at more than 4000?; based on that, I just find it very hard to imagine that the relatively little heat created by a poor connection at the lamp base would have a serious impact.
Maybe the poor connection is more likely to cause flickering, which would stress the filament and shorten lamp life?
kwired
Electron manager
- Location
- NE Nebraska
I kind of fee the same way - does it add that much heat to make a difference, but experience has shown that fixing those bad sockets makes a difference yet I have no real good technical reason as to why. Many times have had a multi-lamp fixture where only one socket goes through more of same lamps then others - every time have found bad connection in that socket and replaced it and problems were greatly diminished.
I lived in an apartment a while back where the light inside the front door would blow every week or so.
We left the light on most of the time so it wasn't pitch black when we got home from work.
Ruled out vibration by putting in a CFL - those kept blowing too.
Didn't want to buy an LED bulb only to have that blow too.
Every time I metered the voltage, it was around 125.
Eventually, got a contractor pack of 130V bulbs off of Amazon for about $10.
Put one of them in, and it never blew again!
So, I'm guessing the voltage was spiking, probably a loose neutral somewhere. The landlord was a moron, and I was moving out anyway, so I never investigated.
I'd recommend getting the 130V bulbs, and then checking for loose wires somewhere if you've got the motivation.
We left the light on most of the time so it wasn't pitch black when we got home from work.
Ruled out vibration by putting in a CFL - those kept blowing too.
Didn't want to buy an LED bulb only to have that blow too.
Every time I metered the voltage, it was around 125.
Eventually, got a contractor pack of 130V bulbs off of Amazon for about $10.
Put one of them in, and it never blew again!
So, I'm guessing the voltage was spiking, probably a loose neutral somewhere. The landlord was a moron, and I was moving out anyway, so I never investigated.
I'd recommend getting the 130V bulbs, and then checking for loose wires somewhere if you've got the motivation.
kwired
Electron manager
- Location
- NE Nebraska
Was a good solution 15 years ago. Today it is getting harder just to find 120 volt incandescent lamps.
electricianexpress
Member
- Location
- Gaines, MI
I agree with the loose connection at the socket. Ive never heard of the extra heat theory, but assumed it was causing flickering and wearing out the filament. I also change out many of these. Usually the wires connecting the socket is a little toasted. Also I've had customers use those screw shell photo controls. There is a time when it is just enough light to make these flicker some times and I have found that they are rough on bulbs sometimes.
- Occupation
- Licensed Electrician
Just have to know where to look and what to ask for. Rough Service bulbs are easy to get and most are 130V.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
You just have to be willing to pay the price of less light per watt when the voltages are down around the 120 nominal.
Still saves money over replacing bulbs when the voltage is actually high, but the light is yellower.
kwired
Electron manager
- Location
- NE Nebraska
If flicker is bad enough to be noticeable customers would complain about that, otherwise they flicker anyway at 60Hz but is a fast enough rate it isn't noticeable but also isn't a full off/on flicker either.
A dimmer kind of does same thing, but one difference is any heat produced in the dimmer is remote from the lamp. I don't know that there is that much heat produced compared to the heat in the filament, but where it is applied is different.
electricianexpress
Member
- Location
- Gaines, MI
I agree, it does cause heat and also damages the wiring at the sockets. Just not sure if that's what causes the filament to go bad. Im not really sure if my theory is correct either. I just know that a socket change seems to correct the problem. Sometimes when asked, the customer does recall some flickering, sometimes not. Often they only mention what is the problem to them, which is constantly changing bulbs.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
It's not noticeable in incandescents more for the second reason than the first. The heat inertia of an incandescent filament is high enough that the difference in its temperature (and therefore its light emission) between a voltage maximum and zero crossing is very small. Even in ultra slow-mo you probably wouldn't see a flicker.
- Location
- Illinois
- Occupation
- retired electrician
The heat at the socket melts the solder used on the bottom of the lamp, breaks the seal, and oxygen enters the lamp. The filament burns up very quickly as soon as you have oxygen inside of the lamp.
kwired
Electron manager
- Location
- NE Nebraska
Best explanation I have heard for this.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Except that the solder on the bottom of a light bulb is not the air seal. The extruded glass piece inside the bulb that supports the filament standoff is the bottom of the envelope.
kwired
Electron manager
- Location
- NE Nebraska
I have to say I doubt solder would seal glass very well and should have seen that. Maybe still a possibility that the real seal sees too much heat and is compromised though.
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