"Jeff Liebermann" <jeffl@[EMAIL PROTECTED]
> wrote in message
news:o6jt6492nr7jm12fet7taq24rskkkhhd1e@[EMAIL PROTECTED]
> On Fri, 4 Jul 2008 01:23:49 +0100, "Arfa Daily"
> <arfa.daily@[EMAIL PROTECTED]
> wrote:
>
>>I have noticed that these new smaller bulbs run a whole quantum leap
>>hotter
>>than the older larger size, and they hot up the shade on the bench light
>>until it is unbearably hot to touch.
>
> As I understand it (possibly wrong), the higher the temperature of the
> filament, the more efficient the incandescent light bulb in lumens per
> watt. There's a bit of a clue at:
> <http://en.wikipedia.org/wiki/Incandescent_light_bulb>
> During ordinary operation, the tungsten of the filament eva****ates;
> hotter, more-efficient filaments eva****ate faster. Because of this,
> the lifetime of a filament lamp is a trade-off between efficiency
> and longevity. The trade-off is typically set to provide a lifetime
> of several hundred to 2000 hours for lamps used for general
> illumination. Theatrical, photographic, and projection lamps may
> have a useful life of only a few hours, trading life expectancy
> for high output in a compact form. Long-life general service lamps
> have lower efficiency but are used where the cost of changing the
> lamp is high compared to the value of energy used.
>
> In other words, the newer smaller bulbs are trading efficiency for
> lifetime, which is the result of running hotter. I'm not sure why the
> bulb is smaller. My guess(tm) is that it's simply thicker, which
> allows the use of a smaller bulb size, which can withstand the heat
> better than a thin bulb and can handle a higher internal gas pressure
> (which is necessary to prevent filament eva****ation).
>
> More on the subject:
> <http://en.wikipedia.org/wiki/Luminous_efficacy>
> <http://members.aol.com/ajaynejr/lumen.htm>
>
> --
> Jeff Liebermann jeffl@[EMAIL PROTECTED]
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558
Interesting thoughts. Really not a good thing though, I am thinking. It's
only been a matter of a few months that I have been using these small
bulbs,
and they have already caused a problem with a lamp that had previously
been
running daily, without heat-related problems, for years. It seems to me
that
in certain domestic applications, these could represent a significant fire
hazard. Take for instance, a 'standard' pendant room light fixture,
suspended on normal plastic cable. There is not normally enough heat
generated, to cause a problem with the insulation, but I'm sure that with
the increased temperature that these things run at, there's going to be.
Take also, a typical lampshade made from either plastic or paper based
sheet. These will typically have a sticker in them saying something like
"60
watt max lamp". Now that figure is a fire safety one, based on the heat
generated by a typical 60 watt bulb. What about when you put one of these
new ones in ? I would guess that the heat steaming off them, is at least
equivalent to what you would be expecting from a traditional-sized 100
watt
bulb. So even putting in a correctly rated 60 watt bulb, you could be
thermally overloading that shade, by 60 odd % . Potential fire hazard, or
am
I just being paranoid ? Does this need bringing to someone's attention ?
Arfa
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