[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

 

 

 

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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