A tenant of mine had an outlet start sparking after trying to plug a
lamp into it. There is an air conditioner on the same circuit as
well. The sparking was bad enough to melt the side of the outlet
where the wire get screwed in. Shouldn't the circuit breaker have
tripped? Do cicuit breakers go bad such that they do not trip when
they need to?

Circuit breakers do go bad and fail to trip on overloads, but it is unusual.
More commonly they trip unnecessarily when they fail.

But, they will not trip on arcs unless there is also an overload. Arc fault
circuit breakers were invented for precisely that reason; to protect against
arcs that did not involve overloads.
They outlet was probably damaged, and that is what caused the problem. The
breaker is "probably" okay, but unless you want to test it, you might rest
easier replacing the breaker. Hey, why not replace it with an arc fault
breaker?!

"balboni" wrote in message
om...
A tenant of mine had an outlet start sparking after trying to plug a
lamp into it. There is an air conditioner on the same circuit as
well. The sparking was bad enough to melt the side of the outlet
where the wire get screwed in. Shouldn't the circuit breaker have
tripped? Do cicuit breakers go bad such that they do not trip when
they need to?

This is Turtle.

They sure do !

Replace the I.T.E. breaker for just good measure to be safe.

TURTLE

I would also add that replacing the breaker might be a good idea if
it's very old. Older ones aren't as reliable as newer ones. They
sometimes go bad slowly with age.

"balboni" wrote in message
om...
A tenant of mine had an outlet start sparking after trying to plug a
lamp into it. There is an air conditioner on the same circuit as
well. The sparking was bad enough to melt the side of the outlet
where the wire get screwed in. Shouldn't the circuit breaker have
tripped? Do cicuit breakers go bad such that they do not trip when
they need to?

You can not afford to test an molded case circuit breaker. Here in Phoenix I
know of only one company that has MC CB testers. And they can not test every
brand.

Call a pro and have the circuit checked out. If you can "weld" with the
circuit there could be something wrong with the grounding for the circuit.

For the ~15 bucks replace the offending unit. When you replace it. Force all
of the breakers off and on a couple of times. Sometimes they will "freeze"
into an ON position.


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On 13 Sep 2004 20:36:38 -0700, (balboni) wrote:

A tenant of mine had an outlet start sparking after trying to plug a
lamp into it. There is an air conditioner on the same circuit as
well. The sparking was bad enough to melt the side of the outlet
where the wire get screwed in. Shouldn't the circuit breaker have
tripped? Do cicuit breakers go bad such that they do not trip when
they need to?

The circuit breaker only trips if you have an excessive amount of
current flowing through it. In this case the outlet failed internally
but the only current flowing was to the other devices on the circuit
so the breaker was not overloaded.

This is a problem and current code requires the use of arc fault
breakers in bedrooms that would trip if this were to happen. I
wouldn't be suprised to see the arc fault breakers become a code
requirement for all convenience circuits in the next few years.

Steve B.

"toller" wrote in message ...
Circuit breakers do go bad and fail to trip on overloads, but it is unusual.
More commonly they trip unnecessarily when they fail.

But, they will not trip on arcs unless there is also an overload. Arc fault
circuit breakers were invented for precisely that reason; to protect against
arcs that did not involve overloads.
They outlet was probably damaged, and that is what caused the problem. The
breaker is "probably" okay, but unless you want to test it, you might rest
easier replacing the breaker. Hey, why not replace it with an arc fault
breaker?!

Could the arc have been caused by bad wire? The outlet was only one
year old, but the wiring is very old. Someone suggested that the wire
is too old and needs to be replaced. If it is charred, can it just be
cut back and used again?

Could the arc have been caused by bad wire? The outlet was only one
year old, but the wiring is very old. Someone suggested that the wire
is too old and needs to be replaced. If it is charred, can it just be
cut back and used again?

Without seeing I can't really answer that, but it seems unlikely.
Since the arc happened when you plugged the light in (right?) the problem
had to either be the outlet or the connection between the outlet and the
wire. A defective hot wire does not need anything plugged in to short, and
a defective neutral should not short unless it is completely broken.
Did the person who installed the outlet know what they were doing? If the
outlet is a year old and not abused, a bad connection sounds like the
culprit. Was the wire attached to a screw terminal or pushed through a hole
in the back. The holes in the back are very prone to failure, at least on
the $0.99 outlets.
If there is no visible damage to the wire, and it is not overloaded, it
should be safe; though some 70 year old wiring looks pretty dicey.

If you have enough wire to cut it back to a sound section, it ought to be
okay, though again, I can't see the wire so it might be prudent to get
someone to see it if you have any doubt.

On 14 Sep 2004 08:59:15 -0700, (balboni) wrote:

Could the arc have been caused by bad wire? The outlet was only one
year old, but the wiring is very old. Someone suggested that the wire
is too old and needs to be replaced. If it is charred, can it just be
cut back and used again?

The wire itself doesnt wear out. Eventually the insulation can get so
brittle that it breaks off when the wire is flexed but that doesn't
sound like what happened to you. I would guess that the outlet itself
failed (don't get the .99 home depot outlets) or, more likely, you had
a bad connection. Did you use the backstab connections on the outlet
or the screw terminals? I would suggest that you always use the screw
terminals and make sure the wire is very tight.

You can cut the wire back to the point that the insulation hasn't been
affected and the wire hasn't discolored from heat. Hopefully there is
enough wire in the box for that. If not then you are looking at a
bigger repair.

Steve B.

Could the arc have been caused by bad wire? The outlet was only one
year old, but the wiring is very old. Someone suggested that the wire
is too old and needs to be replaced. If it is charred, can it just be
cut back and used again?

OP said it went when the tenant tried to plug something into it...
My bet would be improperly installed plaster-ears shifted when
the plugh got shoved in, and either cut something, or bridged
two screw-contacts.