Carflex revisited [RE-wrenches]

[Bill Brooks]

John,

690-7(a) tosses you into 110-27 on guarding of live parts which states "(4)
By elevation of 8 ft (2.44 m) or more above the floor or other working
surface" as a means of protection from live parts. Therefore, no
groundmounting of plug-connected systems a low levels where kiddies can get
to them--makes sense to me.

If USE-2 or tray cable is properly strain relieved, it should be fine in an
accessible ground mounted array. The trick is keeping it from becoming a
handle for kids to swing on--that is problem with conduit as well.

See my post to Joel about MC-connectors.

Bill.



-----Original Message-----
From: John Berdner [mailto:jberdner at sma-america.com]
Sent: Monday, May 28, 2001 5:53 PM
To: RE-wrenches at topica.com
Subject: RE: Carflex revisited [RE-wrenches]


Bill:

I am interested in your interpretation of 690-7(d) as it relates to
cable glands and USE-2 when used at > 150 and < 600 Vdc.
While the code says live parts I have been thinking all accessible
conductors is probably a good idea.
I have been recommending conduit for all exposed conductors unless they
are inaccessible.
I would consider a roof mounted array without too much space under it
inaccessible.
In contrast, a ground mounted array with structure less than 8' off the
ground is accessible.

Also, I don't want to create any hysteria but, with respect to quick
connects:

I know UL is looking at quick connects like the Multi-contact or Alden
connectors.
Neither of these are load break rated and this creates a problem.
The issue is 690-33(e)and carbon build up after a break under load
operation.
If the carbon gets wet then it could be conductive and that violates
690-33(e).
This is true at anything over 50 Vdc by the way!

690-32 says the connectors have to be listed for such use.
If you look carefully at the Listing for the MC or Alden I think you
will find that they are not "listed for such use".
For the 2005 code cycle it looks like UL is going to recommend changing
the requirement from latching or locking, as in 690-33(c)to locking
only.
This brings the NEC into harmony with Canada by the way.

The other requirement being discussed is a "tool" to unlock the
connector.
The UL definition of "tool" includes a penny, by the way.
IMHO, this is probably a good idea anyway to prevent unintentional
breaking under load situations.
The other choice is for someone to develop some load break rated
connectors that will meet 690-33(e).
I think the former is less costly to design than the latter - time will
tell.

Please let me know your thoughts.

Best regards,
John Berdner


-----Original Message-----
From: Bill Brooks [mailto:billbrooks7 at earthlink.net]
Sent: Monday, May 28, 2001 5:14 PM
To: RE-wrenches at topica.com
Subject: RE: Carflex revisited [RE-wrenches]


Joel,

Have a nice juicy slice of tomahto.

There may be many who object to exposed wire in the array, but it is
allowed
in the code. Even the Chicago inspectors, who require everything in
conduit
have been softening on their position about requiring conduit in arrays.

As I have pointed out on several occasions, not all PV modules are
conduit-ready. Meaning, you may be creating a much worse hazard by
connecting conduit since the junction box could pop off the back of the
module. Very few people check on the rating of the junction box before
connecting flex.

I believe USE-2 or Tray Cable is superior and can be used on any module
with
a junction box. If we don't get jurisdictions used to seeing this stuff,
it
is going to be difficult for Astropower, ASE, and others to deploy their
plug-in module products--an important part of lower cost PV systems.

Bill.

-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net]
Sent: Friday, May 25, 2001 5:39 PM
To: RE-wrenches at topica.com
Subject: Re: Carflex revisited [RE-wrenches]


We've wandered far afield (and into some swampy areas) since my original
question
about what is better,
faster, cheaper than gray flex for PV module interconnects and short
sub-panel whips.
You ask why use conduit? Commercial, industrial, institutional and
utility
customers
often require wire in conduit. Gray flex is fast and acceptable to
almost
all
inspectors. Many customers, inspectors and installers object to exposed
wire
even
when used with weatherseals and tiedowns. I say toe-may-toe and you say
toe-mah-toe...let's call the whole thing off.

David Blittersdorf wrote:

> On 25 May 01, at 14:13, Bill Brooks wrote:
> > All this emotion over flexible conduit. I still believe Tray Cable
or
USE-2 is
> > cheaper and better. Why is everyone so intent on using conduit in
the
> array?
>
> I agree with Bill that Tray Cable works great. It is fast to put
together
and can
> be installed with low cost weatherseals on the jct. boxes. Conduit
seems
> like an expensive (labor and material) way to go.
>
> Regards,
>
> David Blittersdorf
> NRG Systems, Inc.
> 110 Commerce Street
> Hinesburg, VT 05461 USA
> Tel: 802-482-2255
> Fax: 802-482-2272
> email: davidb at nrgsystems.com
> Web:http://www.nrgsystems.com
>
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