Just have to jump in here with personal experience:
In our bedroom we have a deLonghi radiator heater which uses an extension
cord (high cost UL approved) heavy guage #12 wire to power it - when it's
used. This extension cord plugs into a "multi outlet" adapter, also heavy
duty UL approved. At the time of the incident there was no power being used
from this outlet.
I was in another room, my wife was sitting on the edge of the bed watching a
news blurb on TV when she heard a funny sound, a scritch, scritch. She
called to me to come listen. Scritch, scritch, scritch got louder. As I
arrived, flames started lapping up the wall from the outlet while still
making arcing sounds. The flames were less than 6 inches from curtains. I
reached into all this and unplugged the extension cord which luckily stopped
the fireworks display. Imagine, if we had not been there.
Upon examination, it appeared that an arc had formed between the blades of
the extension cord (remember no power at the time). That arc was not
sufficient to drop the 15A breaker to the outlet, yet was sufficient to
carbonize the UL approved material which further sustained the arc.
I posted this to the newsgroup alt.home.repair where a fireman jumped in
describing how this exact mechanism is what starts most home fires! Isn't
that an encouraging thought!
Anyway, a little damn fuse in the plug would not have helped in this
circumstance, complete waste of time, much like the main breaker was.
- Robert -
Robert A. Macy, PE m...@california.com
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-----Original Message-----
From: Roman, Dan <dan.ro...@intel.com>
To: emc-p...@majordomo.ieee.org <emc-p...@majordomo.ieee.org>
List-Post: emc-pstc@listserv.ieee.org
Date: Thursday, October 25, 2001 7:41 AM
Subject: RE: skinny power cords.
>
>I agreed completely with Scott. A 6 to 9 foot 18AWG cord will handle well
>in excess of 20A for a short period of time without starting to smoke
(heck,
>it'll handle close to in excess of 60A for a very very short time without
>bursting into flames--not that it was a good experience finding this out).
>Point is, the cordage will handle a fault either indefinitely or long
enough
>for the branch circuit breaker to trip provided you are connected to a 15A
>or 20A branch circuit.
>
>Another data point, you routinely pass more current through the cord when
>doing the earthing test and that uses more current than the cord is rated.
>Leave the tester on for awhile and the cord does not really heat up either.
>
>What this list needs is a power cord manufacturer or agency safety engineer
>that does power cords to settle this once and for all!
>
>Dan
>
>-----Original Message-----
>From: Scott Lacey [mailto:sco...@world.std.com]
>Sent: Wednesday, October 24, 2001 7:43 PM
>To: Gary McInturff
>Cc: emc-p...@majordomo.ieee.org
>Subject: RE: skinny power cords.
>
>
>
>Gary,
>I believe the answer is that the power cord rating of 6 or 10 amps is the
>operating current, at which it will have minimum temperature rise. Under
>fault conditions it will experience a rather dramatic temperature rise that
>is still well below the melting temperature of the insulation. The breaker
>or fuse should clear well before the cord is "cooked" to the point of
>failure.
>
>Scott Lacey
>
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