Connections and Understanding [RE-wrenches]

Matt Lafferty pvpro at attbi.com
Tue Jun 4 19:35:59 PDT 2002


William:

I have been meaning to respond to this message you posted a while back.

I do not allow unsupported cable on any of my installations.  I also don't
allow un-sleeved cables to be run outside the perimeter of the array.

The technique we use is to sleeve the cable(s) with Non-Metallic Liquid
Tight Flexible Conduit (A product that I condemned for many years but find
it to be quite suitable for this application) anywhere it extends beyond the
periphery of the array to a termination point (J-Box/Combiner).

This flex is supported by blocking and secured.  It has a normal connector
at the termination point but no connector under the array.  We then seal the
"open" end with duct-seal or splicing mastic to prevent critters and/or
moisture from entering.

So far it works well, Homeowners are pleased, Inspectors like it and we have
had no problems with it.  I have used this method for about 2-1/2 years (not
the tray cable, but sleeving of USE--2 cables).

In the case you describe, I would probably turn the Module J-boxes toward
one-another so you could run an output to a J-box between every two rows and
connect the J-boxes to the combiner with EMT.  Does that make sense?  Hope
so.  I've had a long day.

Best to all!

-Matt Lafferty
pvpro at attbi.com

William Miller Wrote:

> Friends:
>
> I am a died-in-the-wool conduit user.  I have been researching this
concept
> of using tray cable.  The samples of tray cable I have seen don't look
that
> robust to me.  Maybe I've been sent the wrong samples. They have grooves
on
> the outside of the jacket.  How does this seal in a gland connector?
>
> Routing of unprotected wire concerns me most of all, for example:  I am
> currently installing a roof-top system in which the modules are in racks
of
> 8, two rows of racks down the length of the roof, modules in strings of 4
> (48 volt system).  I have a combiner on the right end of each row of 16
> modules.  This means I have 10 leads to gather at the combiner (4
> negatives, 4 positives and two grounding wires).  Am I to understand that
I
> would run tray cable, unprotected by conduit, 40 feet from the left most
> module, across the backs of 16 modules, along with the other leads from
the
> modules at the far end of the row, all the way to the combiner?  Hey, I'm
> all for keeping costs down, but I've long ago established standards that
> don't allow wire flapping in the breeze.  Am I missing some hardware that
> is available to protect, support and make aesthetically pleasing these
tray
> cables?  Does anyone have any pictures I could look at of these tray cable
> installations, done well?
>
> If these concerns aren't addressed by the industry, I feel we should
> collectively condemn this wiring method.  Unprotected, unsupported  wire
is
> the same concept as "knob and tube" wiring.
>
> Still wondering........
>
> William Miller

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