Another reason to dislike tray cable [RE-wrenches]

Bob Maynard, Energy Outfitters bob at energyoutfitters.com
Mon Apr 21 15:58:51 PDT 2003


William,

I've been told by Sharp that cutting off the MC connector does not void
manufacturers warranty.  That was about 6 months ago, don't know if
anything's changed since.

Regards,
Bob

-----Original Message-----
From: Bill Brooks [mailto:billb at endecon.com]
Sent: Monday, April 21, 2003 3:05 PM
To: RE-wrenches at topica.com
Subject: RE: Another reason to dislike tray cable [RE-wrenches]


William,

Are you referring to two-conductor tray cable or USE-2 cable?

I don't know that you are violating the listing if you cut the MC connector
off as long as you use UL-listed parts to connect into a properly rated and
sized junction box. By the way, refer to THHN as THWN--a minor point, but
THHN is only allowed indoors.

Just to smack the hornet's nest--flexible non-metallic conduit still doesn't
have the proper ratings to connect directly to a junction box on a PV
module.

Bill.


-----Original Message-----
From: William Miller [mailto:wrmiller at slonet.org]
Sent: Monday, April 21, 2003 2:22 PM
To: RE-wrenches at topica.com
Subject: Another reason to dislike tray cable [RE-wrenches]


Friends:

I am bidding an off-gird installation.  The customer purchased his
equipment from a well known mail order outfit.  He has mounted his 8 Sharp
165 modules on two fixed, pole mount racks.  I need to connect the Sharp
modules to the Outback PV combiner.  Each module is a separate feed to the
combiner, since the system is 24 volt, nominal.  I can't just run the tray
cables to the combiner because 1, they aren't long enough and 2, there is
no hardware I know of to bring the tray cables into an enclosure.  The tray
cables with MC connectors are meant to connect to another MC connector. If
I cut the MC connector off to feed the lead into a J-box, I void the
warranty of the module.

Here's the only way I can see to connect these modules up:  I provide a
J-box on each pole with 8 tray leads hanging out of the bottom, each with
an MC connector.  To do this, I need to spend $192.80 and lots of time.

Below is an "ÄSCII" CAD drawing, if it doesn't get hacked up by line
wrapping:



-------------------------------------
Module plus -----> >----Gland nut-| box ---splice-------THHN--|----\
Module plus -----> >----Gland nut-| box ---splice-------THHN--|----\

              conduit-----combiner
Module neg  -----> >----Gland nut-| box ---splice-------THHN--|----/
Module neg  -----> >----Gland nut-| box ---splice-------THHN--|----/

-------------------------------------

For each mounting pole I need to provide a J-box.  In each J-box I need to
bring in 9 leads (4 modules with plus and minus and a ground).  I need 8
gland nuts (Arlington LPCG50, $1.10 each) on the bottom of each J box.  I
can't use a standard metallic Nema 3R box because by the time I find one
with 8 existing KOs or room to add enough KOs to total 8, it would be huge.
 So I need an 8X8X4 plastic J box (Carlon E898N, $24.00).  Then I need to
purchase 8 prefabricated tray cables with MC connectors ($14.00 each).  I
cut each one in two and install one end in each gland nut.  Once in the
J-box, I need to get my leads over to the combiner.  I run PVC conduit from
each J-box to the combiner.  If I put the combiner on one of the two poles,
the tray leads from the J-box on that pole might be long enough to reach
the combiner, but the leads from the other pole are not.  I need to splice
the tray leads (the ones in the gland nuts) to some THHN.  I could use wire
nuts, but I prefer a terminal strip ($24.00).
***snip***

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