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Continuous copper wire to earth ground Fpbear II 01-13-2007
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Posted by Steve on January 14, 2007, 6:09 pm



> hallerb@aol.com wrote:
>>
>>> Why would sharp bends do anything? As long as the wire is continuous
>>> the electrons will flow whatever shape the wire is.
>>>
>>> I had someone tell me that making sharp bends in romex was bad too.
>>> Thats bullshit. Electricity follows the copper. Bends dont matter.
>>> When I wire something I always like to make it look neat bu bending
>>> the wires around corners and keeping the bends tight to the structure.

Perhaps the worry is grounding for a lightning strike. At that kind of power
level, the current can do all sorts of strange things. It might decide to
spark across the gap as well as flowing around the corner.

OT: Bending radius is a significant concern for coaxial cable. Bending the
wire deforms the outer shielding layer away from the desired cylinder. A
sharp bend deforms the cylinder significantly, making one side closer than
the other to the signal-carrying center conductor. This does "funky things"
to the signal. Don't ask me to define that technical term. I'm doing well to
remember my installation training at all. I remember the trainer putting a
meter of some kind on the line and showing how the needle moved when the
cable was bent severely.



PexSupply Full Banner
Posted by Tom Horne, Electrician on January 14, 2007, 9:31 pm


George E. Cawthon wrote:
> hallerb@aol.com wrote:
>>
>>> Why would sharp bends do anything? As long as the wire is continuous
>>> the electrons will flow whatever shape the wire is.
>>>
>>> I had someone tell me that making sharp bends in romex was bad too.
>>> Thats bullshit. Electricity follows the copper. Bends dont matter.
>>> When I wire something I always like to make it look neat bu bending
>>> the wires around corners and keeping the bends tight to the structure.
>>
>> you create future fail spots, the bend stresses the metal and has a
>> good chance of it cracking or similiar in the future. cracked wires
>> overheat and cause fires
>
> I agree you shouldn't bend it to tight like a near perfect 90 degrees
> but you don't need to bend it that much to get good looks. Bending
> copper work harden it and further bending operations can make it break,
> but exactly how many bends before it breaks. When you wrap a 12 gauge
> wire around a post, tighten down the screw, and bend the tail to make it
> break off, how many bends (back and forth motions) do you make? For me
> it is at least four each way at a very sharp angle. But when you
> install romex, you bend it and then how much additional bending do you
> do, and how sharp are the bends compared to a single stripped wire? My
> guess is that you would have to do a lot of very sharp bending to get
> the wires work hardened enough to crack.

When the acceptance testing was done on type NM cable by Underwriters
Laboratories; low these many years ago; the incidents of conductor
insulation damage went up sharply at bend radii of 3 cable diameters.
The US NEC requires bends of five cable diameter in radius as a safety
margin. The problem isn't conductor fracture but rather that the
insulation will fail over time if it is bent too sharply. Since there
is a bare EGC run inside the jacket of type NM cable the possibility of
arcing which can cause a fire is real.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

Posted by Ralph Mowery on January 14, 2007, 11:36 am



> On Sat, 13 Jan 2007 06:51:56 -0600, Dean Hoffman
>
>
> Why would sharp bends do anything? As long as the wire is continuous
> the electrons will flow whatever shape the wire is.
>
> I had someone tell me that making sharp bends in romex was bad too.
> Thats bullshit. Electricity follows the copper. Bends dont matter.
> When I wire something I always like to make it look neat bu bending
> the wires around corners and keeping the bends tight to the structure.

Bends in wires that have low frequency or DC will not have a noticable
effect in most cases. When you get to higher frequencies it will. A
lightning strike is a very steep pulse. It will not follow the bend in the
wire. It may jump off at a bend and go to something else. Also it will
act like an inductor in the wire and in effect you are disconnecting the
wire at the bend.

Sharp bends in wire may or may not be bad as far as the physical routing
goes.



Posted by Steve Barker on January 14, 2007, 11:36 am


You obviously haven't been advised properly. LIGHTNING does not turn
corners well. It will NOT follow the copper if it has sharp bends. The
best way to protect a piece of equipment from lightning is to tie a knot in
the cord. You'll also notice on houses with lightning rods, the cable
coming from them will have nice big easy bends where it comes around the
gutters and down the side. Lightning will blow right out the side of a
conductor that has too tight a bend in it. NOW, back on the topic of the
ground cable in an electrical panel, the tight bends don't matter, because
that ground is not for lighting protection anyway.

--
Steve Barker



>
> Why would sharp bends do anything? As long as the wire is continuous
> the electrons will flow whatever shape the wire is.
>
> I had someone tell me that making sharp bends in romex was bad too.
> Thats bullshit. Electricity follows the copper. Bends dont matter.
> When I wire something I always like to make it look neat bu bending
> the wires around corners and keeping the bends tight to the structure.



Posted by Thomas D. Horne, FF EMT on January 14, 2007, 3:03 pm


Mike Ryan wrote:
> On Sat, 13 Jan 2007 06:51:56 -0600, Dean Hoffman
>
>>
>>> I am extending the ground for the service panel with two 8' rods because the
>>> pipes were re-done in PVC. I plan to attach #4 wire to the end of the
>>> existing #6 wire with two copper split-bolt connectors and make the
>>> connection real tight. I have been reading that the copper ground wire
>>> should be one continuous wire. However I pefer not to mess with high
>>> voltage and take apart the service panel to make it one continuous ground
>>> wire. Are the split bolt connectors sufficient or is there some "physics"
>>> reason it must be one wire? Or is it to prevent someone from accidentally
>>> un-screwing the bolt?
>> It's due to the destructive power of a lightning strike.
>> The idea is to make it as easy as possible for the lightning to get to
>> ground without damaging anything. There aren't supposed to be sharp
>> bends in the wire to the ground rod either. The wire isn't supposed to
>> be wrapped around anything. It's supposed to be as straight as
>> possible. #6 is specified since a ground rod can handle only so much
>> current anyhow. Going to a larger size wire won't help a whole bunch.
>>
>> Dean
>>
>> ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet
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>
> Why would sharp bends do anything? As long as the wire is continuous
> the electrons will flow whatever shape the wire is.
>
> I had someone tell me that making sharp bends in romex was bad too.
> Thats bullshit. Electricity follows the copper. Bends dont matter.
> When I wire something I always like to make it look neat bu bending
> the wires around corners and keeping the bends tight to the structure.

A bend made any sharper than a curve with a radius five times the
diameter of the cable holds the real possibility of breaking the copper
conductor. That is why the code specifies that as the tightest bend
permitted in type NM cable
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.

Page 6 of 8       < 1 2 3 > last >>
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