Lateroo
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| Why do some manufacturers recommend switching off HID bulbs in continuous use from time to time? What is the benefit of this cooldown period? As a test, I have run a MV bulb 24/7 for over half a year now and have not noticed anything out of ordinary.
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sol
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| HID lamps can suffer from non passive EOL, meaning a violent arc tube rupture. This can come with all its obvious consequences. However, the rupture is way more likely upon startup at which time it tends to be the least violent. By switching off weekly, you give the lamp a chance to go EOL peacefully, so to speak. If this is not respected, the lamp has no chance to fail peacefully, increasing the chance of disastrous consequences. Of course, there are other protection means like completely enclosed lamps and protected lamps, but insurance rules ask for that wording. In other words, it has happened enough to warrant the warning.
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Multisubject
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"The only stupid question is the one left unasked"
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| MV lamps very rarely fail non-passively, but of course if they do you don't want to be very close to it. Like sol said cycling it should make the rare possible non-passive failure less severe. If it were me I personally wouldn't bother, cycling it will surely wear out the electrodes a little more. Your choice. When we say "non-passive" what we mean is the arc tube exploding (among other far less common things I'm sure).
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Public Lamp Spec Sheet | More Info
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SoxFtw
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"Respect my authoritah!" —Eric T Cartman, c. 1997
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| Definitely true for metal halides at least, the quartz can't take all that stress over a long period of time.
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Vive la révolution, the reign of the LED must come to an end. Archaic forms of lighting deserve not to be phased out; but to be preserved for generations to come. HID lighting is the absolute pinnacle of technology--on this hill shall I die, and the full price, pay.
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James
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| This advice to switch off the lamps was added to HID lamp packagings after a Sylvania Super Metalarc lamp exploded and the hot quartz fragments caused damage to one of the space shuttles in a NASA hangar. The resulting legal case became quite messy and almost bankrupted Sylvania. Since the risk of explosion is amplified when the lamp is left running continuously, all manufacturers decided to minimise their liability by adding a warning to the packaging. Switching off the lamp at least once a week for at least an hour is sufficient.
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AgentHalogen_87
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Long Live SOX!
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| Never heard that story before, that's interesting!
Other places say to switch lamps off to allow the control gear to cool, but that's clearly less important than a detonating lamp.
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dor123
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Definitely true for metal halides at least, the quartz can't take all that stress over a long period of time.
The internal pressure of MH lamps is way higher than that of MV lamps. Also, the halides corrodes the quartz arctube. |
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.
I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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Richmond2000
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120V 60HZ
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| I had read about the once a week and wondered "why" partly because there is a HPS AEL 115 outside the works yard for the power utility that I work near that has been powered on constantly for nearly 7 years now at least except the occasional storm related power cut
it is a weird situation of being on the roadway lighting not the converter station power and is positioned as a roadway light and was left alone when all the mates were taken down and replaced and those replacement taken down and replaced again yet it piles on the hours never being shutoff or serviced at the entrance to the hydro works yard for the mainline transmission works
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sol
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| I don’t believe HPS poses the same risk as metal halide. However, manufacturers likely put the warning on every HID lamp type just to be sure and to make it less confusing to people who have a hard time differentiating HPS from MH (I know some people like that who worked in facility management).
As for the day burning HPS in the power company yard, that is not too much surprising. Ever heard of the cobbler’s children’s shoes ?
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dor123
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@sol: HPS can't explode because the internal pressure is lower than atmospheric. Instead, the arctube would leak. HPMV lamps also operates in was lower internal pressures than MH lamps.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.
I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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sol
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| You are correct, but manufacturers want to avoid liability at all costs so they put the warning on all HID packages. Also, since it is in the standard text, it can eliminate the risk that it would be forgotten on some packages.
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