[RE-wrenches] Secure/support PV wire requirements?

[William Miller]

Rebekah:



What you desire to do is not impossible.  Most module manufacturers specify
supports approximately 20% form each short side.  For a 66 inch module this
is 13.2 inches.  If you attach the factory PV leads to the rail, you are
close to the 12 inch requirement.  If you reduce the offset to an actual
12” you are at 18% of the module width. Either way, I suggest it is close
enough.



How to secure the leads?  Well there are “UV resistant” wire ties, but the
lack of longevity of these is starting to be realized.  There are other
clips or metal reinforced ties that may be adequate.   Clips we tried are
loose and/or flimsy.



We have been experimenting with various procedures for over a decade.  Our
best method so far is to slot PVC pipe and ley the leads inside.  We do
this on the table saw using dual blades.  The cut is sharp and needs to be
deburred.  Once we lay the leads in we secure them with a clip made form a
short section of the same slotted pie.  We cut short lengths of the same
slotted pipe (3”), expand the slot using PVC cutters and it clips securely
over the long sections of PVC.  See attached.



William





[image: Gradient Cap_mini]
Lic 773985
millersolar.com <http://www.millersolar.com/>
805-438-5600



*From:* RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org
<re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of *Rebekah Hren
*Sent:* Wednesday, December 09, 2015 6:06 AM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Secure/support PV wire requirements?



Hi,

Wondering if anyone has insight into Code requirements for
securing/supporting PV wire behind the modules?



I am aware that USE-2 sends you to Section 334.30 requirements for Type NM
(12" from box, every 4.5 ').



However, I think this is totally bogus, for 2 reasons.

1) Section 338.10(B)(4)(b) that refers the NM article is titled "Branch
circuits or Feeders."  These are PV source and output circuits, not branch
circuits or feeders.



2) it is nearly IMPOSSIBLE to secure the PV wire within 12" of the module
junction box for many modules, especially in landscape wiring, without
causing more harm than good, too tight a bending radius, stress on
conductors.


334.40(B) maybe leaves a little wiggle room for concealed spaces in
structures where it is impracticable to support.



My big problem here is that both requirements of 334.30 are useless or
harmful to PV systems. 12" to the box is often impossible, and 4.5" feet is
too long to go without any support behind the array!!! I just noticed there
was a proposal in 2017 to Codify the 334.40 requirements for PV cables and
so I guess I only have myself to blame for not writing a better proposal at
this point.



Rebekah

-- 

Tel: 336.266.8800
NABCEP Certified Solar PV Installation Professional™ 091209-85
NC Licensed Electrical Contractor
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