Yeah, I could get the new copy but then I would have to walk all the way
over to the other desk. Thanks
-----Original Message-----
From: Kealey, Doug [mailto:[email protected]]
Sent: Monday, March 13, 2000 6:53 AM
To: 'Gary McInturff'; '[email protected]';
'[email protected]'
Subject: RE: derating of conductors.
Gary's reference to NEC 250-95 is from the 1996 code. It
has been
re-numbered 250-122 in the 1999 code.
Doug
-----Original Message-----
From: Gary McInturff [mailto:[email protected]]
Sent: Friday, March 10, 2000 6:37 PM
To: '[email protected]'; '[email protected]'
Subject: derating of conductors.
Ran across a new wrinkle on this issue.
The NEC in section page70-162 and table 310-17 does describe
derating of
ampacity capacity for conductors with temperature
That is for normally current carrying conductors. - hot and
neutral.
How about for grounding and bonding conductors?
I see section 250-95 basically says that the ground wire
shall be the same
size as the feed wires. It also says that if the feed wires
are adjusted in
diameter for voltage drop the equipment ground conductors
shall be adjusted
proportionally - but no reference (here at least) for
temperature.
I am wondering if the fact that the ground wire is not
intended to be a
normal current path but rather a short term 'emergency
cutoff mechanism', if
you will. As such it won't have current flowing along it
long enough to be
adversely affected by a higher than 30 degree ambient and
therefore required
to be derated for ambient.
Make sense to anybody.
Gary
PS I also have a question for a non-member. He is wondering
if anyone has a
source for shielded power supply cords? I am also thinking
that Europe hates
those things because many countries many not have a grounded
outlet, or that
outlet is so far from earth ground that there is a
significant impedance
along that path.
You can respond directly to [email protected]
<mailto:[email protected]>
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