Defective Bulb Tripping Ckt Breaker: How Possible ?

[Robert11]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

 

[Laurence Taylor]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.

This often happens. It's because when the filament breaks, it falls
across part of the wire nearer the mounting points, thus horting them
out. That's why there's a bright flash, and the fuse/breaker goes
because of the increased current through the much lower than normal
resistance.

--

rgds
LAurence

...."I forgot to increment the counter" said Tom, nonplussed
---*TagZilla 0.059* http://tagzilla.mozdev.org

 

[Meat Plow]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the
hall lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there. Was the el-cheapo
brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

Might have a problem with the base of the bulb or the socket.

 

[N Cook]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

I'm only going by memory and may have it a bit wrong.
A tiny part of the filament wears to the point it creates a hot-spot which
rapidly gets worse causing the first part of the intense flare. In that
super-heated process a plasma state is formed within the bulb. In a plasma
state the effective conductivity across the 2 filament suspension end points
becomes orders of magnitude less than the original filament resistance so
for very short duration , can pass tens or hundreds of amps.
It is the same mechanism whereby a lightning discharge through air can pass
millions of amps through a channel that is only about 1/2 inch in diameter
which no metal could pass. The same discharge passing into the right soil/
conditions leaves a yards long but same 1/2 inch wide hollow tube punched
through the ground, see keyword fulgurite.

 

[Homer J Simpson]

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Sure. There should be a fuse in one of the leads inside the bulb, but China
???

 

[Yukio YANO]

I'm only going by memory and may have it a bit wrong.
A tiny part of the filament wears to the point it creates a hot-spot which
rapidly gets worse causing the first part of the intense flare. In that
super-heated process a plasma state is formed within the bulb. In a plasma
state the effective conductivity across the 2 filament suspension end points
becomes orders of magnitude less than the original filament resistance so
for very short duration , can pass tens or hundreds of amps.
It is the same mechanism whereby a lightning discharge through air can pass
millions of amps through a channel that is only about 1/2 inch in diameter
which no metal could pass. The same discharge passing into the right soil/
conditions leaves a yards long but same 1/2 inch wide hollow tube punched
through the ground, see keyword fulgurite.

This all sounds nice BUT the two strands of the broken filament limits
the current to ~ current to less than 1 Amp. !

More likely the Light-bulb in question was mounted Socket-Down and a
portion of the broken filament dropped down and shorted across base
conductors. The short length of filament's Resistance would be much less
than the nominal ~ 200 ohms of the intact filament. The resulting arc
would vaporize in the Argon Gas of the light-bulb and create a miniature
MIG (Metal Inert Gas)Welding condition at which time, the Circuit
Breaker would Open due to the excessive current draw. A photographic
Flash-bulb would be a good analogue. Source Impedance and Current
Limiting of Household wiring were engineered to safely harness
electrical energy!

Yukio YANO

 

[Dave Plowman (News)]

Wife turned on a hall light switch last night, big flash by one of the
hall lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker?

Have you recently changed from fuses to circuit breakers? A bulb blowing
and tripping one isn't uncommon.

 

[Lionel Sharp]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

G'Day

This has happened to me. The bulb was a "Reflector Lamp Type R80" with
an Edison Screw Base". It was used in a "down light" and they have a
very short life (6 months or so). In the process of removing it the
brass base and the glass globe separated and I had to get the base out
of the socket (with power turned off of course.) with a pair of pliers.

Recently purchased a couple of bulbs from China and on the side of the
box it says:-

For your added safety every globe has 2 built-in safety fuses.

Seems like the some manufacturers are aware of this problem

Lionel L Sharp

 

[James Sweet]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

This is common, the filament breaks and an arc strikes in the fill gas
between the ends, this quickly vaporizes what remains of the filament
and will sometimes melt a good portion of the filament support wires
before the fuse in the stem blows. If the fuse is poor quality or not
present (as may be the case in a cheap import bulb) it can easily trip
the circuit breaker. This arcing is what kills most dimmer switches and
touch lamps, the triac is destroyed before the fuse can react.

This is one more thing I like about compact fluorescents, when they fail
they don't blow with a bright flash and a pop which is always a
startling experience when you flip on the only light in a dark room.

 

[Meat Plow]

This is one more thing I like about compact fluorescents, when they fail
they don't blow with a bright flash and a pop which is always a startling
experience when you flip on the only light in a dark room.

I saw flames shoot out of the side of the base of a screw in fluorescent.

 

[Ancient_Hacker]

This is one more thing I like about compact fluorescents, when they fail
they don't blow with a bright flash and a pop which is always a
startling experience when you flip on the only light in a dark room.

Right, they blow with a considerable BANG and a bad smell. The CFL in
my wife's bedside lamp did that. Of course I had to open it up and see
what happened. The first capacitor of the voltage-doubler ( a tiny
10uf cap ) had popped. Really popped. It spread black goo all over
the insides of the thing.

 

[Ancient_Hacker]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Plasma, most likely, from the internal arc. Light bulbs are filled
with argon gas which can conduct quite nicely once started.

Or the floppy wire ends had enough magnetic attraction to attract each
other, which makes the field stronger, attracting each other some
more...

 

[James Sweet]

James Sweet wrote:




Right, they blow with a considerable BANG and a bad smell. The CFL in
my wife's bedside lamp did that. Of course I had to open it up and see
what happened. The first capacitor of the voltage-doubler ( a tiny
10uf cap ) had popped. Really popped. It spread black goo all over
the insides of the thing.

Interesting, well I suppose it could happen, in 8 years of using them
almost exclusively mine so far have all just failed to turn on, save for
one that made a soft buzzing noise and let out a puff of stinky smoke.

 

[Meat Plow]

Plasma, most likely, from the internal arc. Light bulbs are filled with
argon gas which can conduct quite nicely once started.

Or the floppy wire ends had enough magnetic attraction to attract each
other, which makes the field stronger, attracting each other some more...

Also could have caused a momentary neutron star.

 

[default]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

Happens more than a lot - depending on the circuit breaker.

Magnetic beakers trip faster than thermal ones.

Filament opens - the tungsten is in a partial pressure of nitrogen as
a rule - not a vacuum just inert gas at low pressure. The filament
separates and sparks an arc in the bulb. The ionized gas is a dead
short.

Low pressure gas conducts electricity better than high pressure gas -
until you start approaching a total vacuum. Ionization gauges are
used to monitor vacuum pressures in lab instruments - put 200+ volts
on it and it conducts until you get to near perfect vacuum.

That failure will trip a magnetic breaker and not phase a totally
thermal breaker - event is over before the breaker heats.

Solid state relays are toast - if they drive an incandescent lamp that
opens.

 

[Sjouke Burry]

Hi,

Boy, this is a funny one.

Wife turned on a hall light switch last night, big flash by one of the hall
lights, and the ckt breaker tripped.

Was about 2 days since putting in a new bulb there.
Was the el-cheapo brand picked up at CVS, and made in China.

Replaced the bulb with a GE one, and so far everything seems O.K.

Question: I can't imagine how anything, like e.g., a broken filament
perhaps, can short out the circuit.
But, perhaps ?

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Or, might this be just a coincidence ?

Thanks,
Bob

The filament in the bulb vaporises at the point
where it breaks, and produces a nice hot plasma
and a dead short across the input.
If you want to see such a plasma cloud, put a
defunct bulb in the microwave oven(for a few seconds
only).

That in turn can vaporize the connections
to the base of the bulb.
I have had lamps producing a pop sound close to
an explosion that way, and sparks flying.
On checking, the base of the lamp was looking burned
around the attachment point of one of the wires.
It works much better with 240 Volts

 

[Eeyore]

Can anyone think of a bulb failure mechanism that might trip the breaker ?

Yup.

If there's an arc, which it sounds like, that has negative resistance and the
fault current can be very high.

Graham

 

[Sam Goldwasser]

I'm only going by memory and may have it a bit wrong.
A tiny part of the filament wears to the point it creates a hot-spot which
rapidly gets worse causing the first part of the intense flare. In that
super-heated process a plasma state is formed within the bulb. In a plasma
state the effective conductivity across the 2 filament suspension end points
becomes orders of magnitude less than the original filament resistance so
for very short duration , can pass tens or hundreds of amps.
It is the same mechanism whereby a lightning discharge through air can pass
millions of amps through a channel that is only about 1/2 inch in diameter
which no metal could pass. The same discharge passing into the right soil/
conditions leaves a yards long but same 1/2 inch wide hollow tube punched
through the ground, see keyword fulgurite.

You've got it about right. And in response to the other post, it's
rarely a matter of the filament falling across the terminals.

http://members.misty.com/don/bulb1.html#wbs

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Sam Goldwasser]

Nope, he's got it right. Once the arc forms, it may not stay between
the broken ends. Because the arc is a negative resistance, increasing
the current lowers its resistance. So, it can grow towards the ends of
the filament in an instant and then it's nearly a short circuit.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[Sam Goldwasser]

This is common, the filament breaks and an arc strikes in the fill gas
between the ends, this quickly vaporizes what remains of the filament
and will sometimes melt a good portion of the filament support wires
before the fuse in the stem blows. If the fuse is poor quality or not
present (as may be the case in a cheap import bulb) it can easily trip
the circuit breaker. This arcing is what kills most dimmer switches and
touch lamps, the triac is destroyed before the fuse can react.

This is one more thing I like about compact fluorescents, when they fail
they don't blow with a bright flash and a pop which is always a
startling experience when you flip on the only light in a dark room.

But they may blow with a puff of smoke and a acrid smell....

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.