[RE-wrenches] Ground Mount Screening

Fri Oct 22 08:26:54 PDT 2010

Mark,

I certainly was not implying that you were in any way unintelligent. I was
merely suggesting that fences or only one means of compliance. You have a
different opinion, and you are entitled to it. However, if all jurisdictions
viewed prevention of ready access to mean fences, that would not be good for
the PV industry as a whole. 

Both crawl spaces and unfinished basements can have numerous hazards so
these locations are generally not seen as habitable and should not be
readily accessible locations. However, a garage does require that NM be
above 8' or protected--usually by sheetrock--below 8 feet. Under a PV array
that is lower than 8' would be like a crawl space only if access to the
underside were protected as crawl spaces should be. We tried to get specific
language in the NEC on types of guards that were permitted, but the Code
Making Panel rejected the proposal stating that it was well-understood in
the electrical industry how to prevent ready access--maybe not so much.

The much bigger problem is that installers put not protection around their
wiring systems so that children can use the "black vines" to play Tarzan on
them. I think you would agree that is not good--but we see it all the time
in rural areas. 

Animals are another big problem in certain places. While this thread is
about ground mount systems, roof mounting in wooded areas populated by
squirrels is a serious problem--as discussed many times in this forum. The
code currently does not address this problem, but perimeter screening may be
a requirement in the future to prevent both squirrels and debris from
creating a fire hazard under a PV array. Just yesterday I was talking to a
contractor that had just come back from an installation with a fully eaten
6-foot section of USE-2 where they had to remove the array to repair the
wiring. Fortunately, the ground fault protection activated and prevented a
fire.

Bill.

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mark Frye
Sent: Thursday, October 21, 2010 5:51 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Ground Mount Screening

Bill,

I don't really want to call you out, but I also don't like you lording your
expertise over me, implying that I am stupid and I am going to get myself
killed someday, or worse yet kill someone else:

1 - 2008 NEC 334.15 NM Cable...Exposed Work....(C) in unfinished basements.
What exactly changed in 1990 to prevent the scenario I mentioned?
2 - Which code are you referring to that includes wood lattice as part of a
minimum standard for guarding exposed electrical work?
3 - I think I understand the definition of readily accessible fairly well
and think there is a basis to argue that placing wood lattice around a
ground mount rack does not mean that the exposed wiring on the rack is no
longer in a readily accessible location. The use of the term "remove
obstacles" in the definition of readily accessible refers to obstacles that
prevent personnel from approaching the workspace around equipment. In this
sense the lattice may serve as a guard to the otherwise exposed wiring, but
it does not change the fact that wiring is in a readily accessible location
and must therefore, according to Code, be run in a raceway. Only placing a
fence around the entire rack (such that the workspace around the equipment
therein can no longer be reached quickly) eliminates the requirement that
the PV circuit conductor be run in raceway.

The Code is in place and we will all learn how to work with it. But I think
this issue points out the continuing growing pains of the industry when we
are still talking about on one hand the detailed requirements of a UL1741
inverter and on the other the use of garden supply material as requirements
for ensuring the safety of the system we build.

Mark Frye
Berkeley Solar Electric Systems
303 Redbud Way
Nevada City,  CA 95959
(530) 401-8024
www.berkeleysolar.com 

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bill Brooks
Sent: Thursday, October 21, 2010 3:55 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Ground Mount Screening

Mark,

The fact is you can't legally walk up and touch NM cable anymore. Whenever
your house was built, that may have been code compliant, but not since the
early 1990s has that been allowed. You may think a wooden lattice work is
insufficient protection, but the code disagrees with you as a minimum
standard. You can build all the chain link fences you want around your PV
systems. Not me. It is a waste of money. The code is addressing the issue of
"readily accessible." Darwin awards are plentiful for people who want to get
themselves into trouble. We just have to make it a little more difficult for
unsuspecting kids using the underside of a PV array for a play fort. You
obviously haven't been to one of my code trainings in a long time. Maybe
it's time for a refresher.

The 30V limit has to do with the voltage at which serious shock can occur in
wet environments. Most people are familiar with the 50V limit by OSHA, but
that is for dry environments. In the UL standards for shock hazard, the
voltage limit is 30V. Now you know.

Bill.

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Mark Frye
Sent: Thursday, October 21, 2010 3:37 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Ground Mount Screening

You know, I can go down into my unfinished basement, through an unlocked
full height door.  The wiring in this space is fully Code compliant. And
yet, I can walk over and put my bare hand right onto a piece NM cable that
has 200A of 240 VAC running on it.

But God forbid I should be able to walk over to a PV array and put my hand
on a piece of double insulated PV wire with 10A of 30VDC running on it.

I don't get it.

Mark Frye
Berkeley Solar Electric Systems
303 Redbud Way
Nevada City,  CA 95959
(530) 401-8024
www.berkeleysolar.com 

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jason
Szumlanski
Sent: Thursday, October 21, 2010 3:26 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Ground Mount Screening

Maybe they should require that extension cords be in conduit. :) where do
you draw the line? If lattice is good enough, is fiberglass screen okay? How
about bird netting or orange construction fence?

Seriously though, we have never been required to use a lattice or fenced
enclosure for a ground rack around here to pass inspection. It would be nice
if a rack manufacturer came up with a slick and cost effective (cheap)
method to cover the back of the panels /racks without losing air flow and
meeting code requirements. I would install that regardless of lax local
interpretation. 

Jason Szumlanski
Fafco Solar

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