Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were clearly
visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked" insulation
tape with a small area of something red and hard at the end where the
wires went in and the end of a screw sticking out of the other end of
this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed the gripping) the conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I had
never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being held
by that wirenut.

BTW, I think the white stranded wire must have been the ground wire to
the metal "frame" of the switch. The wirenut fell off the ground wires
before I had a chance to take careful note of where the other end of the
white pigtail went.

Perce

Percival P. Cassidy wrote:
Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were clearly
visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked" insulation
tape with a small area of something red and hard at the end where the
wires went in and the end of a screw sticking out of the other end of
this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed the gripping) the
conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I had
never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being held
by that wirenut.

BTW, I think the white stranded wire must have been the ground wire to
the metal "frame" of the switch. The wirenut fell off the ground wires
before I had a chance to take careful note of where the other end of the
white pigtail went.

Perce
prob didnt twist the wires together like u r supposed to

On 08/25/08 09:23 pm Bob wrote:

Pulled a switch to replace it and noticed that
(c) there was a charred black mess that seemed to be "cooked"
insulation tape with a small area of something red and hard at the end
where the wires went in and the end of a screw sticking out of the
other end of this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed the gripping) the
conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I
had never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being
held by that wirenut.

prob didnt twist the wires together like u r supposed to

The advertising for some wirenuts (don't recall which) says that
twisting isn't necessary. But I have no idea whether it really does vary
from brand to brand.

Perce

On Aug 25, 9:51 pm, "Percival P. Cassidy" wrote:
The advertising for some wirenuts (don't recall which) says that
twisting isn't necessary. But I have no idea whether it really does vary
from brand to brand.

Let's say wires are not twisted. Then the only reliable connection
between wires is the 'spring' inside a wire nut. If spring wires
makes contact with every copper wire, then no problem. But with heat,
expansion, oxide of copper surfaces, etc, only that wire nut spring
carries most (too much) current. Now the wire nut gets hot and wire
connection create voltage reductions.

Normally that still is not a problem ... if a wire nut 'spring' has
enough turns and makes contact with each wire in enough locations (if
wire nut does not require tape to hold it on wires). Sufficient
connection does not always happen. A hot wire nut is not a code
violation. But you don't want a hot wire nut. Potential for fire or
electrical failure increases.

With copper wire, this rarely causes a fire. With aluminum wire,
this same poor workmanship too often causes fire. See pictures and
technical explanation in:
http://www.inspect-ny.com/aluminum/pl2p8.htm
We don't want wire nuts getting hot even if the manufacture says it
is OK. If wires are twisted together, then all wires touch each other
in multiple spots without a wire nut. Then add a wire nut to make a
good connection better. Wire nut does not get hot by conducting all
current IF wires are properly twisted together.

Wire nuts on copper wire should be properly twisted as if the wire
was aluminum for a best conducting, low loss, no heat connection.

Does not matter whether code requires wires to be twisted together.
All wire connections should be sufficient without the wire nut. Then
we add a wire nut to keep that connection sufficient no matter how
much corrosion or heating might compromise the connection 80 years
from now.

w_tom wrote:
On Aug 25, 9:51 pm, "Percival P. Cassidy" wrote:
The advertising for some wirenuts (don't recall which) says that
twisting isn't necessary. But I have no idea whether it really does vary
from brand to brand.

Let's say wires are not twisted. Then the only reliable connection
between wires is the 'spring' inside a wire nut.

The contact is wire-to-wire.

With aluminum wire,
this same poor workmanship too often causes fire. See pictures and
technical explanation in:
http://www.inspect-ny.com/aluminum/pl2p8.htm

With aluminum wire surface oxide may prevent wire-to-wire contact. The
wirenut spring is not intended to be a major current carrying element.

Not seen - requirements from any manufacturer, or UL or the NEC that
wires be twisted. Apparently none of them are as smart as w_.

As with many other issues all you have is w_’s certainty.

--
bud--

On Aug 27, 11:33*am, bud-- wrote:
The wirenut spring is not intended to be a major current carrying element..

Which is why wirenuts do not have that metallic spring inside? Wire
nuts using only grooves in the plastic cannot be used. Wire nut uses
a metallic spring sufficient sized to conduct major currents.

Bud is not posting to provide useful facts. Bud is my troll who
routinely posts only to insult.

That wire nut spring must have sufficient gauge and turns to carry
current without fire risk. And then copper wires also must be
sufficiently twisted so that wire without a wire nut will also safely
conduct that current. Bonding by twisting wires and using a wire nut;
both must carry current.

If wire nut is not intended to carry current, then a wire nut would
only have grooved plastic. Wire nuts use a metallic spring that cuts
into (makes electric contact) with each copper wire. Wire nut also
must be able to conduct current between copper wires. Spring must be
sufficiently sized so that this fire cannot happen:
http://www.inspect-ny.com/aluminum/pl2p8.htm
Bud knows this. But a troll always seeks reasons to post insults.

Twist theose wires together so that sufficient contact exists
without a wire nut. Then install the wrie nut so that connection is
even better. No reason for a wire nut to get hot if properly
constructed and installed. Learn from a worst case reason for wire nut
fire in:
http://www.inspect-ny.com/aluminum/pl2p8.htm

"Percival P. Cassidy" wrote in message
...
Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were clearly
visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked" insulation
tape with a small area of something red and hard at the end where the
wires went in and the end of a screw sticking out of the other end of this
mess.

As I cut away the insulation tape, it became clear that this was a "fried"
wirenut, and that what had looked like screw threads was the wire spiral
that was gripping (or was supposed the gripping) the conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC approved.
So what would cause a wirenut to "fry" like this? Note: I had never
noticed any problems with the lights that the switch was controlling, or
with any other circuits fed through the wires being held by that wirenut.

BTW, I think the white stranded wire must have been the ground wire to the
metal "frame" of the switch. The wirenut fell off the ground wires before
I had a chance to take careful note of where the other end of the white
pigtail went.

Perce

If the wirenut is not twisted on tight there will be a high resistant joint
and it will heat up. How hot depends on how much current is being used and
how much resistance is in the joint.

I work as an electrician in a large plant and there are thousands of wire
nut joints. Most work just fine. We very seldom have any problems with
them.
We almost never use any tape on them. Sometimes I will put some tape on the
motor leads or other devices that have some vibration.

Percival P. Cassidy wrote:
Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were clearly
visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked" insulation
tape with a small area of something red and hard at the end where the
wires went in and the end of a screw sticking out of the other end of
this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed the gripping) the
conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I had
never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being held
by that wirenut.

BTW, I think the white stranded wire must have been the ground wire to
the metal "frame" of the switch. The wirenut fell off the ground wires
before I had a chance to take careful note of where the other end of the
white pigtail went.

Perce

Is the wire aluminum vs copper ?
This can and does happen with AL wire. Twice in my house. :-(

Warm cover plates are first clue. Flames are second clue.

On 08/25/08 11:43 pm Reed wrote:

Percival P. Cassidy wrote:
Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were
clearly visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked"
insulation tape with a small area of something red and hard at the end
where the wires went in and the end of a screw sticking out of the
other end of this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed the gripping) the
conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I
had never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being
held by that wirenut.

BTW, I think the white stranded wire must have been the ground wire to
the metal "frame" of the switch. The wirenut fell off the ground wires
before I had a chance to take careful note of where the other end of
the white pigtail went.

Is the wire aluminum vs copper ?
This can and does happen with AL wire. Twice in my house. :-(

All conductors are Cu.

Warm cover plates are first clue. Flames are second clue.

I'd never noticed that the cover plate was warm.

Perce

On Tue, 26 Aug 2008 05:15:04 -0400, Percival P. Cassidy wrote:
All conductors are Cu.

It was a loose connection. Power dissapation at the connection is equal
to current squared times resistance. Let resistance get to be more than
milliohms, and the connection burn up.

On 08/25/08 09:05 pm Percival P. Cassidy wrote:

Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were clearly
visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked" insulation
tape with a small area of something red and hard at the end where the
wires went in and the end of a screw sticking out of the other end of
this mess.


And I forgot to mention (d) the back of the switch body looks to have
had a hot (temperature-wise) insulated wire pressing against it.

Perce

"Percival P. Cassidy" wrote in message
...
Pulled a switch to replace it and noticed that

(a) the switch brought one black wire with it but left two other wires
(one black solid, the other white stranded -- the bare ends were clearly
visible) in the box;

(b) the temperature in the box seemed high -- decidedly warm;

(c) there was a charred black mess that seemed to be "cooked" insulation
tape with a small area of something red and hard at the end where the
wires went in and the end of a screw sticking out of the other end of this
mess.

As I cut away the insulation tape, it became clear that this was a "fried"
wirenut, and that what had looked like screw threads was the wire spiral
that was gripping (or was supposed the gripping) the conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC approved.
So what would cause a wirenut to "fry" like this? Note: I had never
noticed any problems with the lights that the switch was controlling, or
with any other circuits fed through the wires being held by that wirenut.

BTW, I think the white stranded wire must have been the ground wire to the
metal "frame" of the switch. The wirenut fell off the ground wires before
I had a chance to take careful note of where the other end of the white
pigtail went.

Perce


Most likely a loose connection caused the conductors to arc which generated
the heat.

On 08/26/08 07:33 am John Grabowski wrote:

Pulled a switch to replace it and noticed that
(c) there was a charred black mess that seemed to be "cooked"
insulation tape with a small area of something red and hard at the end
where the wires went in and the end of a screw sticking out of the
other end of this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed to be gripping) the
conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I
had never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being
held by that wirenut.

Most likely a loose connection caused the conductors to arc which
generated the heat.

Shouldn't the arc-fault breaker have caught
this? And wouldn't the lights and other devices fed from that circuit
have behaved erratically?

Perce

Percival P. Cassidy wrote:
On 08/26/08 07:33 am John Grabowski wrote:

Pulled a switch to replace it and noticed that
(c) there was a charred black mess that seemed to be "cooked"
insulation tape with a small area of something red and hard at the end
where the wires went in and the end of a screw sticking out of the
other end of this mess.

As I cut away the insulation tape, it became clear that this was a
"fried" wirenut, and that what had looked like screw threads was the
wire spiral that was gripping (or was supposed to be gripping) the
conductors.

The first time I ever saw a wirenut, I thought "What kind of a Rube
Goldberg kludge is this?" but I now understand that they are NEC
approved. So what would cause a wirenut to "fry" like this? Note: I
had never noticed any problems with the lights that the switch was
controlling, or with any other circuits fed through the wires being
held by that wirenut.

Most likely a loose connection caused the conductors to arc which
generated the heat.

Shouldn't the arc-fault breaker have caught
this? And wouldn't the lights and other devices fed from that circuit
have behaved erratically?

AFCIs until this year would only detect a "parallel" arc - H-N, H-G.
Starting 1-1-2008 they were required to detect a "series" arc you describe.

If there is an arc you will probably see flickering lights. Some other
loads there may be no indication.

As others have said, a loose connection can also produce damage (with no
flickering). An arc should give you more heat.

If there was a lot of tape I suspect workmanship. There should be no
need of tape with a wirenut. May also have been the wrong size wirenut
or a junk wirenut that was not UL listed.

There are a lot of wirenuts I won't use. They are hard plastic outside
the spring. The kind I like allow the spring to expand over the wires
and have more contact area.

There is no requirement I know of (manufacturer/UL/code) to twist the
wires before using a wirenut. It may be a good idea, particularly with
the springs that don't expand.

--
bud--