On Sun, 2006-09-24 at 17:16 -0400, John wrote:
> Please correct me if I am wrong , the 240 line should not even be extended
> with a extension cord let alone using a 110 line . John kbn2huk
By the National Electrical Code you aren't supposed to use an extension
cord for any application except one that is temporary. You are supposed
to get a permanent outlet wired so that the extension is not needed. And
an outlet strip, even if UL approved is one of those not to be used
permanently.
Commercial extension cords for 240 volt applications are in home centers
as well as hardware stores and electrical distributors.
Over the years extension cords have been given a poor rap, because they
are easily abused. In the past cords made of 18 gauge zip cord fit the
same outlets and had the same outlets as cords made of 12 gauge copper
wire. And the 18 gauge cords cost much less than the sturdy cords.
However the 15 or 20 amp fuse/breaker lets the 18 gauge cord burn if
shorted. Today the smallest in the stores uses 16 gauge which may almost
be protected by a 15 amp fuse or breaker.
Extension cords tend to be run behind couches where the legs smash them
against the wall baseboard when the people sit on the couch hard. And
sometimes get run through doors where the door pinches them or cuts them
off leading to hot spots, if not fires. Then cords sometimes get run
under carpets and traffic on top the carpet smashes the insulation off
and the thermal insulation of the carpet makes that more than fully
loaded wire run on the warm side melting the wire insulation... Carpets
burn.
I've seen 18 guage zip cord from a clock stapled to a plywood wall in a
school. I didn't leave it that way. No staple made it all the way
through the insulation on both conductors but some were close. The fire
marshal wanted that school district to close several schools unless an
engineer would certify them safe. I inspected and certified them UNSAFE.
There are gadgets sold so that neatnicks can wrap up one of those
excessively long 18 gauge cords concentrating the heat in a small space.
I cringe when I seem them advertised.
I do own outlet strips and extension cords. They are all UL approved,
and most have sturdy conductors unless the load is controlled to be a
clock or a single table lamp. Some have been in place excessively long
in this place I rent.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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