I think if we showed those pictures to a THHN wire manufacturer, they
would not approve of deforming the insulation to that degree. We are
also talking about load centers with the same bending space available to
the factory as we electricians have.
I also want to point out that Midnite has been very proactive with their
wire bending techniques. I posted a picture of their work as an example
of 'how to do it'. I'm now calling on other manufacturers to do the same.
Thanks,
Ray Walters
Remote Solar
303 505-8760
On 10/16/18 11:21 AM, b...@midnitesolar.com wrote:
Ray is coming at this from an electricians viewpoint. He is correct if
talking about wiring outside of a UL or ETL listed product.
The reason for wide radii in wiring is so the wires can be rerouted
and terminated a few times.
8 times the diameter is a very large bend radii and would never fly
inside a product, so why can a manufacturer do it?
Copper has the tendency to work harden when bending back and forth.
That will damage the current carrying characteristics of a wire.
Bending a wire once does not work harden them. The insulation can get
scrunched depending on the actual bend radii, but it is
only cosmetic after one tight bend. There are no actual cracks that
would jeopardize the insulation integrity.
We have investigated this and determined it to be cosmetic in nature
for a single bend. That said, I don’t like it either
because it makes installers nervous and doesn’t look good. The tight
wire bends are no different from putting tight bends
on a sheet metal copper busbar. We do this all the time and always
have. Testing shows that it does not constrict electrical flow.
If you straighten that same copper busbar and bend it again, it is
likely to break in half. That is work hardening to the extreme.
So, there is no violation from tight wire bending inside a listed box.
A listed box does not have the same restrictions as the NEC.
Believe me, I too do not like zero radii bends and we have custom made
pliers that give the wire a gradual radii, but that is cosmetics only.
The wire is not actually damaged unless you straighten it up and
re-bend it. We do not do that!
Thanks,
Robin Gudgel
MidNite Solar
On 10/15/2018 11:27 AM, Will White wrote:
NEC doesn't apply to the interior components of a UL listed device
although I do see your point. I'm assuming they designed it taking
that bend into consideration.
On Mon, Oct 15, 2018 at 1:20 PM Ray <r...@solarray.com
<mailto:r...@solarray.com>> wrote:
Greetings;
I've noticed several of the factory wired power panels over the
years from Magnum, Outback, Midnite, Etc are not compliant with
NEC 300.34 wire bending radius. (Radius should not be less than 8
times the diameter) Basically they should look like sweep bends
in PVC conduit, not plumbing. Here's a pic from a recent Magnum
system
You can see the kinks in the insulation on the inside of the
bend, and the color fading on the outside from being
overstretched. Some might think this is neat work, but its
actually permanent wire damage and a code violation. Imagine the
strain on the copper inside.
Midnite is very proactive and has improved, I ask that Magnum do
the same and soon.
Thanks,
--
Ray Walters
Remote Solar
303 505-8760
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