# HPS bulbs and premature failure



## Electric_Light (Apr 6, 2010)

Dnkldorf said:


> I didn't know this about HPS bulbs.
> 
> I quote:
> 
> ...


It's like blocking vents. The lamp converts energy to light and when you trap the light and reflect it back, it will overheat the arc capsule. 

Use a fixture intended for the specific type of bulb and avoid ghetto retrofit attempts.


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## 10492 (Jan 4, 2010)

Electric_Light said:


> Use a fixture intended for the specific type of bulb and avoid ghetto retrofit attempts.


 
Ummmm.......OK, if you say so.

The new bulb came with the new fixture.

Jump back jack.


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## Electric_Light (Apr 6, 2010)

Dnkldorf said:


> Ummmm.......OK, if you say so.
> 
> The new bulb came with the new fixture.
> 
> Jump back jack.


If the fixture is used with the specified lamp and the fixture manufacturer followed the design guideline, this shouldn't be an issue.


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## 10492 (Jan 4, 2010)

Electric_Light said:


> If the fixture is used with the specified lamp and the fixture manufacturer followed the design guideline, this shouldn't be an issue.


You need some listening skills. Quit jumping to conclussions.

I had no idea that this "phemon" if you will, existed.

I'm curios if this happens to MH, Fluro, and LED?

FWIW, the fixture and bulb I am referencing is the A-typical post light that most everything here is using. They must be listed for use with both 100W and 150W HPS, because the identical post frame uses both different
ballasts and bulbs. 

The bulb is mounted vertically in the lid. Same thing with every street light I've seen. 

I'm thinking how to properly calculate how much of the "quoted" life hours HPS bulbs have, and how much to subtract for vertically mounted bulbs.


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## Electric_Light (Apr 6, 2010)

Dnkldorf said:


> You need some listening skills. Quit jumping to conclussions.
> 
> I had no idea that this "phemon" if you will, existed.
> 
> ...


I don't remember specifically if there is orientation restrictions on 100 & 150W HPS lamps. I know that MH lamps come in a few variations and not every type is available in every variant. Horizontal +/- x deg, base up, base down, vertical and universal/non-orientation specific. For the orientation sensitive lamps, operating outside the range is misapplication.

If the lamp supports the mounting position you're using, there should be no need to derate. The "quoted" life means the hours until failure at standard cycle rate and usually means until half of a large sample fails. It follows a mortality curve that looks like a reverse "s". 


For maintenance purpose, it depends on how you're relamping (spot, group, or combo?) and the amount of acceptable failure rate. If you're group re-lamping, you probably don't want to wait until half the lamps are out, so you'll see yourself relamping them before the rated life.


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## LightsRus (Sep 12, 2010)

Dnkldorf said:


> I had no idea that this "phemon" if you will, existed.
> 
> I'm curios if this happens to MH, Fluro, and LED?
> 
> ...


This matter is true with devices that radiate infrared; that is a cooling mechanism. 
If the bulb and fixture are furnished together, a reputable fixture manufacturer has most likely already accounted for this.

To your question about LEDs, they don't radiate IR so having reflectors aiming back on the LED is not really a problem; although it would really mess with efficiency.


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## 10492 (Jan 4, 2010)

LightsRus said:


> This matter is true with devices that radiate infrared; that is a cooling mechanism.


Do MH, Fluro, including cathode radiate IR, or is it a unique characteristic to the sodium bulb?




LightsRus said:


> To your question about LEDs, they don't radiate IR so having reflectors aiming back on the LED is not really a problem; although it would really mess with efficiency.


 
Yeah, heat at the junction seem to be the dilema with LED.
That and surge protection.


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## LightsRus (Sep 12, 2010)

Dnkldorf said:


> Do MH, Fluro, including cathode radiate IR, or is it a unique characteristic to the sodium bulb?


IR radiation is characteristic to filament bulbs, Halogen, MH, LPS and HPS. 

Fluorescent bulbs retain most of the IR. Some IR does escape, but most of their cooling is convection, with air flow around the bulb.


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## 10492 (Jan 4, 2010)

Good info.:thumbsup:


Cheers.


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## Electric_Light (Apr 6, 2010)

LightsRus said:


> IR radiation is characteristic to filament bulbs, Halogen, MH, LPS and HPS.
> 
> Fluorescent bulbs retain most of the IR. Some IR does escape, but most of their cooling is convection, with air flow around the bulb.


A 25W LED "bulb" would run hotter than a 25W incandescent. Since LED doesn't gives very little IR, the balance of energy that isn't radiated out as visible light must be removed by conduction and a large heat sink.


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## LightsRus (Sep 12, 2010)

Electric_Light said:


> A 25W LED "bulb" would run hotter than a 25W incandescent. Since LED doesn't gives very little IR, the balance of energy that isn't radiated out as visible light must be removed by conduction and a large heat sink.


And you can demonstrate that by placing paper in contact with both light sources.

The 25W incandescent bulb will start a fire, the LED will not.


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## Paulusgnome (Mar 28, 2009)

The effect that the OP is referring to is called _photon return_, and it can have a detrimental effect on the life of an HPS or non-phosphor MH lamps. 

Geeky Technical Explanation :
What the lamp is normally doing is spitting out photons as excited electrons give them up and drop to a lower energy level. When a photon re-enters the lamp it raises a low-energy electron up to a high energy level, and this causes a small jump in the lamp terminal voltage. If lots of photons are returning, it will increase the lamp terminal voltage. The net effect is that the lamp runs hotter than it should, with predictable effects on its lifetime.


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## Electric_Light (Apr 6, 2010)

LightsRus said:


> And you can demonstrate that by placing paper in contact with both light sources.
> 
> The 25W incandescent bulb will start a fire, the LED will not.


If you build a clam shell heatsink that will fit over a 25W bulb and make the surface area comparable to what you would use for a 25W LED, it wouldn't. 

a 25W LED array driven at 25W without any heat sink will smoke and start a fire too, if it doesn't fail open before getting that hot.


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## LightsRus (Sep 12, 2010)

Electric_Light said:


> If you build a clam shell heatsink that will fit over a 25W bulb and make the surface area comparable to what you would use for a 25W LED, it wouldn't.
> 
> a 25W LED array driven at 25W without any heat sink will smoke and start a fire too, if it doesn't fail open before getting that hot.


I was referring to your statement:


> A 25W LED "bulb" would run hotter than a 25W incandescent. Since LED doesn't gives very little IR, the balance of energy that isn't radiated out as visible light must be removed by conduction and a large heat sink.


Which simply isn't true. 
Now it seems you are modifying a lightbulb to make your statement work.

None of this has anything to do with the original post or topic, but merely a way to say something negative about LEDs.


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## Electric_Light (Apr 6, 2010)

LightsRus said:


> I was referring to your statement: Which simply isn't true.
> Now it seems you are modifying a lightbulb to make your statement work.
> 
> None of this has anything to do with the original post or topic, but merely a way to say something negative about LEDs.


LEDs have to reject excess heat through its mounting base using a heatsink. They simply run "cool" since you use a massive heat sink.

Incandescent lamps don't reject that much heat at the base, because it can reject energy through IR radiation. 

25W LED or 25W incandescent, if you prevent the light from leaving, they'll produce the same amount of heat. 

LEDs produce less total radiant power (including IR range) than incandescents.


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## LightsRus (Sep 12, 2010)

Dnkldorf said:


> I didn't know this about HPS bulbs.
> I quote:
> " Using this lamp in a fixture that redirects a substantial portion of it's light toward the arc tube will cause premature failure"
> This is from the _Caution _notes on a box carton the bulbs come in.
> Any guesses why? and how to compensate for this in maint calcs?


A reputable fixture manufacturer that provides or recommends a bulb, and provides a warranty, has addressed and accounted for this fault potential in their design. The caution note you found is simply a disclaimer for the bulb maker.

*This post now gets Geeky....*

Reasons for this early failure have been suggested here, twice. One of them as follows...


Paulusgnome said:


> The effect that the OP is referring to is called photon return, and it can have a detrimental effect on the life of an HPS or non-phosphor MH lamps.
> 
> Geeky Technical Explanation :
> What the lamp is normally doing is spitting out photons as excited electrons give them up and drop to a lower energy level. When a photon re-enters the lamp it raises a low-energy electron up to a high energy level, and this causes a small jump in the lamp terminal voltage. If lots of photons are returning, it will increase the lamp terminal voltage. The net effect is that the lamp runs hotter than it should, with predictable effects on its lifetime.


This previous 'Geeky Techy Explanation' isn't accurate, but that matters not; The "premature failure" problem is real.

Photon Return usually involves lasers, and requires quite a large number of coherent photons to make a difference. This won't make much of a measurable difference with even a 10,000 watt HPS.

I am grabbing the following from the WWW -
_'The highest luminous efficacy possible on this planet is 683 lumens per watt, even the best HID lighting source produces over 70% heat for the power consumed; at best 15% is light, and the remainder is UV and/or electrical losses.' _
Of course, if it's from the Internet it must be true. 
"_Light_" refers to the visible portion of the EM spectrum. 

Physics tells us:
Just generally speaking, a typical light source produces over 7 watts of heat for every 10 watts used. Even in 2010, lights are still pretty good heaters.
With a 150 watt HPS bulb, that's 105 watts. If a reflector sends 10% of that heat, for example, back into the bulb, it is no longer being cooled to the manufacturer's requirements. 

You can do the rest of the math, but I am not aware of an algorithm that helps with predicting _this_ bulb's end of life.


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