Re: Insteon Observations

["TKM" <nomail@xxxxxx>]

"Bud--" <remove.BudNews@xxxxxxx> wrote in message
news:cf341$4585a877$4213ea40$4617@xxxxxxxxxxxxxxxx
> TKM wrote:
>
>> "G. Morgan" <alarmpro@xxxxxxxxxxx> wrote in message
>> news:cnt6o2p66td2u9s7k2pntcrjg8v6voadrr@xxxxxxxxxx
>>
>>>On Fri, 15 Dec 2006 21:24:59 -0700, AZ Woody <reply@here> wrote:
>>>
>>>
>>>>Dave Houston wrote:
>>>>
>>>>>G. Morgan <alarmpro@xxxxxxxxxxx> wrote:
>>>>>
>>>>>
>>>>>>Anyway,  I have never experienced what you describe (a circuit breaker
>>>>>>trip) on failure of a bulb.  My common sense tells me the arc (air gap
>>>>>>resistor) would be a great, sudden, resistance that would indeed draw
>>>>>>a large current spike.  Part of me thinks the opposite is true - for
>>>>>>which I have no basis!
>>>>>>
>>>>>>I was not aware that common bulbs had a fuse either, I thought the
>>>>>>filament IS the fuse.
>>>>>>
>>>>>>My interest in this has nothing to do with Insteon devices, it has
>>>>>>more to do with what I can do to protect the circuit for devices I
>>>>>>install, if the theory is true.  It may explain some anomalies I've
>>>>>>experienced with security devices.
>>>>>
>>>>>The tungsten-arc is for real. The built-in fuse is also. If you hear a
>>>>>"pop"
>>>>>and see a bright flash, you're buying cheap bulbs. If you hear a "poof"
>>>>>and
>>>>>notice a bit of a flicker before darkness descends, your bulbs are
>>>>>fused
>>>>>(even if cheap).
>>>>>
>>>>>The inrush current for an incandescent is about 10 times the current
>>>>>once
>>>>>the filament has warmed to its normal temperature. For a 100W bulb this
>>>>>means an inrush at turn-on of +8A. The "fuse", if any, built in to the
>>>>>wire
>>>>>leading from base to the filament should withstand the inrush but blow
>>>>>before a 15A breaker is tripped by a tungsten-arc.
>>>
>>>
>>>>Come on...  This is all like discussing how many angels can dance on the
>>>>head of a pin...
>>>>
>>>>In reality, don't most folks buy light bulbs at Home Depot, Lowes,
>>>>Target, Walmart, (or at their local food store if they ran short)!
>>>>
>>>>I doubt that 99.9999% of the folks would buy "fused bulbs" vs "unfused
>>>>bulbs" but will buy what's on sale..  Do you all not have a life?
>>>
>>>
>>>The fundamental question for me is whether or not light bulbs can
>>>cause equipment damage.  And no, I have no life.
>>>
>>>
>>>
>>>--
>>>
>>>-Graham
>>
>>
>> Yes, a failing incandescent lamp can cause a current surge if the
>> filament arcs as it falls apart.  That's been well known for years.
>> Incandescent dimmer manufacturers usually handle the situation by
>> inserting a small impedance in the output circuit to protect the solid
>> state parts which, of course, act faster than the thermal fuse in the
>> lamp.
>>
>> General service inandescent lamps are gas filled and fused.  That's
>> because when gas-filled lamps were developed in 1913, manufacturers
>> learned quickly that an arcing filament was bad for business as it caused
>> lamps to shatter, bases to melt and sparks to fly around.
>>
>> Terry McGowan
> I knew that UK bulbs at 230V would arc and had fuses but until recently I
> didn't think it was a problem in 120V bulbs. Where is the fuse hidden?
>
> --
> bud--

The fuse is in one of the leads in the "stem" or glass support structure for
the filament.  If you take a lamp apart, you will see that there are
different kinds of wire going from the base or cap up to the filament.  The
filament, of course, is tungsten.  The support wires are Molybdenum, but
they are welded to a wire of nickel-iron alloy covered with copper called
Dumet which has the same coefficient of expansion as the glass which
surrounds them.  In one of the leads toward the cap, there is a fuse wire as
well.  It may be inside a tube surrounded with glass beads called ballotini
which helps to quench any arc as the fuse opens.  All lamps sold in the
European Union must have a fuse which complies with IEC 432-1, a lamp safety
standard.  I don't know if there is a similar standard for the fuses used in
North American lamps.

Terry McGowan