Bulb Life to short

[GerryB]

The customer has recess lights over the counter, it's a cafe. She said the bulbs don't last long. They are par 20's and she keeps them slightly dimmed. (read 102 volts at socket). According to the box they are only good for a year at 3 hours a day, she has them on 10-12 hrs every day. Would you recommend LED's? The par 20's are about $7 each, that style LED is probably at least $20. I know I might also need a new dimmer. I hesitate because I don't think all LED's are "created equal". Another question does dimming of lights affect the life of the lamp? I'm thinking no on that one. Thanks in advance for any advice.

 

[ptonsparky]

Replace with LED. Only way to go. Get the ones that include the trim.

Dimming should extend the life of an incandescent lamp with heat shortening them.

 

[mgookin]

Well that's interesting. I just pulled up some GE & Osram Par20's and they are 3k and 1.5k hours, respectively. That's not much for a bulb.

Keep in mind if you do this changeout, it's possibly going to be a totally different lighting effect with respect to color, beam angle, etc.. With these over a counter in a café, that may be a real big deal to her. Just a heads up.

Maybe get one (if they're local in stock) and do a swap out and say "Do you want all of them like that?"

 

[ptonsparky]

Make sure she installs all the same K and if she dims them anyway the lower lumen output may be better.

I agree take a sample in and let her try it. My wholesalers have no problems with doing that, but they all know where I live and the names of my children and some of the grandchildren.

 

[gar]

151317-0835 EST

The typical incandescent bulb is designed for an average bulb life of 750 to 1500 hours.

Reduced bulb voltage can greatly improve bulb life. Reduced sine wave voltage is somewhat better than a phase shift dimmer waveform.

I have hall lights on a phase shift dimmer that have been on for about 1/2 of 40 years with only about 2 failures from about 16 bulbs. These are low wattage fine filament bulbs. Almost all the time these are at very low intensity.

For my bathroom night light I use a 757 28 V pilot lamp operated at 14 V. I have never had to replace this bulb.

Search the Internet. Some results:
http://www.lamptech.co.uk/Documents/IN Voltage.htm
https://en.wikipedia.org/wiki/Incandescent_light_bulb
http://donklipstein.com/bulb1.html#mll
https://www.google.com/search?q=inc...7NesPuHSM:&usg=__8Y50W3fCz1zqfRFP7hQI1noSocI=

.

 

[GoldDigger]

An exception to the normal extension of bulb life at lower voltages is Halogen incandescents. Their normal operation relies on a chemical recycling of evaporated tungsten back to the filament. The process in turn depends on the walls of the quartz envelope reaching a minimum temperature.
When run continuously dimmed the bulbs may blacken and burn out prematurely.
You can minimize this effect by running the bulbs at full power for an hour or two regularly to get the lost tungsten back into circulation.

 

[tom baker]

CED locally has par floods Sylvania for $10.

 

[GoldDigger]

Dimming effect on Halogen bulb life: see http://www.topbulb.com/blog/dimming-alters-halogen-cycle/

The critical point for lowest overall life appears to be about 20% dimming, just the condition that the OP reports.
If the outer bulb is clear, then the OP would be able to see the blackening and see if it is reversed by high temperature operation for awhile.

 

[big john]

...Reduced bulb voltage can greatly improve bulb life....

Agreed, which is what makes this a little odd.
Running a tungsten at 17% of its rated voltage is supposed to improve life by several hundred percent.

So for a lamp with a 3 month expectancy I wouldn't be surprised if she got a year of service out of them.

How many lamps are there? Is this a case where one out of 12 burns out every month and she just notices that a lightbulb always seems to be out, even though it's not the same lamp?

 

[K8MHZ]

Agreed, which is what makes this a little odd.
Running a tungsten at 17% of its rated voltage is supposed to improve life by several hundred percent.

So for a lamp with a 3 month expectancy I wouldn't be surprised if she got a year of service out of them.

How many lamps are there? Is this a case where one out of 12 burns out every month and she just notices that a lightbulb always seems to be out, even though it's not the same lamp?

It seems the PAR 20s were halogens, they don't behave the same way as incandescent.

 

[mopowr steve]

What most people don't realize is that when you find what appears to be an incandescent bulb on the store shelf now-a-days it's probably really a halogen (read the fine print and you may also notice how sucky the average lifespan is too in comparison to the old tungsten filament bulb you used to get) it's those government energy guidelines the manufacturers are trying to meet.

 

[big john]

It seems the PAR 20s were halogens, they don't behave the same way as incandescent.

D'oh! I didn't realize PAR 20s were usually halogens; I thought we were just spit-balling.

 

[GoldDigger]

It seems the PAR 20s were halogens, they don't behave the same way as incandescent.

Halogens are 100% incandescent. The light source is a glowing filament.
But the differ from the earlier inert gas filled (or even vacuum filled) incandescents through the addition of a specific chemical process.
The lifespan curve will look like that of a basic incan at the high voltage end since the halogen cycle cannot repair the filament fast enough or uniformly enough. And at the very low voltage end they also look like incans in terms of the expected life increasing as voltage decreases.
It is just in the middle ground where filament temps are still higher than basic incans but low enough that the lifespan enhancement of the halogen cycle is failing.

 

[James L]

The customer has recess lights over the counter, it's a cafe. She said the bulbs don't last long. They are par 20's and she keeps them slightly dimmed. (read 102 volts at socket). According to the box they are only good for a year at 3 hours a day, she has them on 10-12 hrs every day. Would you recommend LED's? The par 20's are about $7 each, that style LED is probably at least $20. I know I might also need a new dimmer. I hesitate because I don't think all LED's are "created equal". Another question does dimming of lights affect the life of the lamp? I'm thinking no on that one. Thanks in advance for any advice.

I would try a 3000k PAR20 l.e.d.
Are these flood or spot bulbs?
Are they in a baffle trim? Beam angle may not be critical
How many on one dimmer? l.e.d. maximum is usually only 1/4 of incandescent max - a 600w incan/l.e.d./cfl dimmer is only rated for 150 watts of l.e.d.

 

[ptonsparky]

I would try a 3000k PAR20 l.e.d.
Are these flood or spot bulbs?
Are they in a baffle trim? Beam angle may not be critical
How many on one dimmer? l.e.d. maximum is usually only 1/4 of incandescent max - a 600w incan/l.e.d./cfl dimmer is only rated for 150 watts of l.e.d.

Advantage is 150 watts of LED is a lot of light.

 

[kwired]

My home is now just past 10 years old (construction began in 2004 moved in early 2005)

I have can lights around a lot of the perimeter with 75 W PAR 30 halogen lamps that are on a photocell and dimmers. They all still have the original lamps that were installed when new, and have run all night nearly every night for 10 years. And all day at one time for a few weeks when photo cell had failed.

I probably run them at about 30% level or so and only occasionally have turned them up - not to recycle halogens, though I may think about that now.

 

[James L]

Advantage is 150 watts of LED is a lot of light.

It is, for sure. But it's easy to not think of the maximum wattage in that way.

Just three months ago i wired a basement with 14 cans on 3 switches (8, 4, &2 respectively). Homeowner said he wanted dimmers, no problems.

Until said homeowner bought his own can trims.
22 watts each x 8 =176 watts

When's the last time anyone thought 8 can lights would overload a dimmer?

 

[James L]

My home is now just past 10 years old (construction began in 2004 moved in early 2005)

I have can lights around a lot of the perimeter with 75 W PAR 30 halogen lamps that are on a photocell and dimmers. They all still have the original lamps that were installed when new, and have run all night nearly every night for 10 years. And all day at one time for a few weeks when photo cell had failed.

I probably run them at about 30% level or so and only occasionally have turned them up - not to recycle halogens, though I may think about that now.

I've had standard light bulbs last 8 years with regular use. I'm about 80% convinced that most problems of bulbs burning out too fast is user error.

It's a strange phenomenon to meet people who actually know how much to screw in a bulb. Center tab in the socket gets smashed, then it's never a good connection after that. And it makes bulbs burn out faster.

It's exactly like the old 3-handle shower valves that had rubber washers on the ends of the stems. People cranked on them til they wouldn't turn and it smashed the washer out of whack