[RE-wrenches] wiring methods between arrays

[William Miller]

August:



I know conduit and boxes seem way too hard for the new generation of
plug-and-play installers.  Because of this we’ve seen a trend to cheapen
how we run DC circuits.  We can’t let this dissuade us from doing our jobs
safely and correctly.



If this question were asked about any other kind of power circuit,
Journeymen and women would shake their heads wondering why the fuss about a
little bit of EMT work.  Power circuits, DC or AC, deserve to be protected
in conduit, cable tray or other approved methods, and those methods have
long been established.  I don’t imagine you could install rooftop air
conditioner feeders by cable-tying them along strut or conduit.  Why is it
that PV installers figure this is OK for 600 volt DC circuits?



I think it is bad enough that high voltage DC circuits are allowed to be
unprotected under arrays, but once the circuit leaves the perimeter of the
array there is no excuse to leave the conductors vulnerable to damage and
to hurt people.



The problem is that, although you are ethical enough to weigh the long term
implications of various solutions, many installers and inspectors are not.
Many then get away with or approve of tying high voltage cables to whatever
is handy. You and I cannot therefore do a safe job and provide bids that
are competitive in price.



Sorry if I appear to have a strong opinion on this subject, but poor
electrical practices do kill people, and I take that seriously.



Sincerely,



William Miller







[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] *On
Behalf Of *August Goers
*Sent:* Tuesday, August 11, 2015 3:20 PM
*To:* RE-wrenches
*Subject:* [RE-wrenches] wiring methods between arrays



Hi Wrenches,



I have another best practices questions: what are you doing to run your PV
wire between arrays on a rooftops? This question has come up on this list
in the past but I’m still on the hunt for a robust and faster lower cost
method. We mostly install outdoor boxes on each sub array and then run EMT
between these boxes. We use strain reliefs to enter the boxes and then
either keep PV wire or transition to THWN-2 in the EMT depending on the
layout.  This method takes time and the outdoor boxes aren’t cheap.
Alternatively, we can run open-ended EMT with ground bushings on the ends
to bond the conduit. Since ground bushings are designed to be used in boxes
we switch out the aluminum lug with a tin-coated outdoor rated lug and
stainless hardware. This technically violates the listing but at least the
materials hold up. The EMT needs to be carefully bent down at the ends so
rain doesn’t enter. Lastly, we sometimes run our PV wires along strut or
angle aluminum (this is the fastest method) which also needs to be bonded
with a lay-in lug.



Does anyone have other methods?



Best,



August

Luminalt
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