Re: Effect of starting on lifespan of general-lighting HID lamps?



Travis Evans wrote:
I've done some searching a number of times in the past on exactly how
adverse an effect on life frequent starting has on various (otherwise
properly installed/operated) types of lamps, general-purpose-lighting
HID lamps in particular (or more specifically, HPM, HPS, and MH lamps
around the 50-100 watt range; the kind usually available in common
"home center" stores in the US), but without much luck. I've seen at
least one website or document say that HPM lamps are the most
tolerant of frequent starting, but no cited sources or any actual
figures.

As a hobby/for fun, I have some fixtures/lumiaires of these types
intended to be used as dawn-to-dusk "security lights" that I instead
switch manually and use indoors in my home. As such, the "operating
hours to starts" ratio tends to be quite a bit lower than the 10 that
HID lamps are typically spec'd at. I have no way of knowing how low
exactly, but I very roughly estimate the average is probably somewhere
in the range of maybe 40 minutes to around 4 hours per start, give or
take. The thing is, I haven't been able to get an idea of how much I
really need to worry about how often the lamps are started, if at all.

The most heavily used light is a 100-watt MH (ANSI M90). The ballast,
ignitor, and original lamp, used almost daily for approaching 3 years
now, still appear to be holding up well to this pattern of usage so
far. A 50-watt HPS lamp used over a slightly longer period of time
still works well, and a Philips H38 phosphored HPM lamp (used
somewhat less, though I'm unsure by how much) also seems fine.
Finally, my 70-watt HPS and 70-watt MH units still work, though I
haven't yet had these two for very long. All of these are on
conventional iron ballasts (with ignitors for the HPS and MH ones),
except for the 50-watt HPS Lights of America fixture which instead
appears to use some sort of electronic ballast circuit on a board
(mostly discrete components with maybe an IC or two).

On the other hand, I've had a clear H38 mercury (the one shipped with
my particular corresponding luminaire) mysteriously no longer start
without warning after operating apparently perfectly normally the
last 2-3 years, despite almost certainly not having had 6000 hours,
if half that; a couple of HPS ignitors fail prematurely (though this
perhaps was just a bad manufacturing run as both were installed in
fixtures bought the same day from the same store (one died on the
very first startup; the one in the exchanged unit lasted about half a
year); and a dirt-cheap Lights of America 50-watt HPS luminaire's
ballast electronics fail after around 9 months [though in my
experience, this seems to be the rule rather than the exception with
LOA products, so no big surprise there :-) ], though the lamp itself
was fine (the original lamp and replacement luminaire, since
reinstalled outside the house and returned to dusk-to-dawn operation,
currently still work after a little over 2 additional years). But as
with various CFLs that I've seen fail early over the years, I just
have no way of knowing whether or not failures like these could have
directly or indirectly had anything to do with number of starts.

Does anyone have any experience with using these kinds of lamps on
fairly short cycles like this over their entire lifespan [and perhaps,
whether the end-of-life behavior tends to be any different from the
"normal" 10 or more hours per start usage, just to satisfy my
curiosity :-) ]?

The lighting companies usually publish survival curves for x hrs/start for all HIDs. For this, you'd need to get a hold of an engineering catalog for the corresponding company.

Because of sputtering and other side factors during the start, the ideal performance is usually one lighting-continuous, and all other modes, such as x/y hrs/start fall below the curve for continuous burning, in terms of overall population survival.

However, understand that the published curves are probability distributions showing only survival of 50% of the sample, as such they cannot be taken as individual indicators, as they apply to the average/mean samples and not to every single individual from the population.

The above means that you can have severe exceptions on either side of the game: Individuals which may survive longer than those with continuous burning and individuals which may fail unpredictably in shorter times than expected samples.

This has to do with manufacturing error tolerances related to the sample population construction, as such, single individuals may not display published expected behavior.

Examples include (to my experience) HPM/HID lamps which fail to start for all sorts of side reasons, such as sudden de-gassing of the internal burner, loose internal connections, unpredictable and terminal falls in internal pressure and various other factors which cannot be perfectly controlled during the manufacturing.

When you read the published survival curves on engineering catalogs for x hrs/start, you can expect such behavior _on average_ from single individuals, but this is not a guarantee that a specific individual will behave according to the published curve.

If the individual has tolerated side errors during the manufacturing process, this individual may display aberrant behavior despite what you'd expect and may fail unpredictably sooner than expected or last 20000 hours for some obscure reason.

The manufacturing process for HID lamps is extremely complicated, as such the final behavior can only be described probabilistically using a large sample.

This means that there is considerable variation in the expected behavior of specific individuals, so expecting an individual to comply to published standards is a bit optimistic.
--
I.

.



Relevant Pages

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