[RE-wrenches] Mike Holt Solar Video - LIVE in your town, limited time only

Brian Mehalic brian at solarenergy.org
Mon Dec 9 13:21:26 PST 2013


I agree with Mike on this, as written this is a bad Section, and in reality
there is no need for it, so deleting it is better than trying to fix
something that is unnecessary.

The 2014 690.7(D) language has changed - the title is now "Additional
Auxiliary Electrodes.."; in 2008 the title to be "Additional
Electrodes...".  It can be confusing to keep the terminology straight, but:


   - "Additional Electrodes" from 2008 is seemingly undefined,
   - "Supplemental Electrodes" may be required as part of the grounding
   electrode system per 250.53(A)(2) and (3)
   - Auxiliary electrodes are defined in 250.54


It's the allowances for Auxiliary Electrodes which cause the problem.
 250.54, which must be followed per 690.47(D), states that auxiliary
electrodes do not have to be bonded to the grounded electrode system (as is
typically required of all present electrodes per 250.50), nor does it have
to follow the bonding jumper sizing requirements of 250.53(C).

This creates the problem Mike describes - two connections to ground that
can have dramatically different potential between them in the event of a
lightning incident.

I've always been a proponent of bonding residential pole and ground-mounted
PV structures back to the grounding system of the building they serve.
Large ground-mounted solar farms have lot of
auxiliary/supplemental/additional electrodes in the form of pilings, and
the systems I work on have these all bonded together and back to the
electrodes at the inverter pads - it's extra copper in the ground but it
helps alleviate the problem of different potentials.

The problem is for roof-mounted systems; the 2008 language, by not
explicitly calling it an auxiliary electrode, basically meant that
inspectors were requiring the additional electrode to be bonded to the
existing grounding electrode system on the building - which alleviates the
concerns of having two connections to the Earth.  Now 2014 calls it
"Auxiliary" and the language in 250 specifically says it doesn't have to be
bonded to the grounding electrode system - enter the safety concerns
described by Mike and Bill.

Not having to bond the 690.47(D) Auxiliary electrode to the grounding
electrode system alleviates some of the pain of having to put that rod in,
so I imagine that many installers will take this route if the AHJ allows
it.  Thus the need to do something about this, before it lingers for years
and years. So...go Bill!





Brian Mehalic
NABCEP Certified Solar PV Installation Professional™ R031508-59
IREC ISPQ Certified Affiliated Instructor/PV US-0132

PV Curriculum Developer and Instructor
Solar Energy International
http://www.solarenergy.org


On Mon, Dec 9, 2013 at 3:50 PM, Glenn Burt <glenn.burt at glbcc.com> wrote:

> The bad news from the 2014 codebook:
>
>
>
> *690.47 Grounding Electrode System.*
>
> *(D) Additional Auxiliary Electrodes for Array Grounding.*
>
> A grounding electrode shall be installed in accordance
>
> with 250.52 and 250.54 at the location of all ground- and
>
> pole-mounted PV arrays and as close as practicable to the
>
> location of roof-mounted PV arrays. The electrodes shall be
>
> connected directly to the array frame(s) or structure. The dc
>
> grounding electrode conductor shall be sized according to
>
> 250.166. Additional electrodes are not permitted to be used
>
> as a substitute for equipment bonding or equipment grounding
>
> conductor requirements. The structure of a ground- or
>
> pole-mounted PV array shall be permitted to be considered
>
> a grounding electrode if it meets the requirements of
>
> 250.52. Roof-mounted PV arrays shall be permitted to use
>
> the metal frame of a building or structure if the requirements
>
> of 250.52(A)(2) are met.
>
> *Exception No. 1: An array grounding electrode(s) shall*
>
> *not be required where the load served by the array is integral*
>
> *with the array.*
>
> *Exception No. 2: An additional array grounding electrode(*
>
> *s) shall not be required if located within 1.8 m (6 ft)*
>
> *of the premises wiring electrode.*
>
>
>
>
>
> -Glenn
>
>
>
> *From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
> re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Jason Szumlanski
> *Sent:* Monday, December 09, 2013 2:22 PM
> *To:* RE-wrenches
>
> *Subject:* Re: [RE-wrenches] Mike Holt Solar Video - LIVE in your town,
> limited time only
>
>
>
> I had to quit watching at noon, so I was disappointed to have missed the
> theatrics. I just installed a system on my home to NEC 2008 as is followed
> here. I have convinced a local plans reviewer that since it was removed in
> NEC 2011, the building official should waive the 690.47(D) requirement for
> rooftop systems. He specifically asked me if it would return in NEC 2014,
> and if I am reading this right, the answer is definitely "no."
>
>
>
> Since there was no aesthetically acceptable way to run the additional GEC
> in my case and make it "as close as practicable (which is ambiguous
> anyway), I cut it out immediately following inspection - something I would
> NEVER recommend a customer do, of course. Nonetheless, I feel this was a
> reasonable and acceptable move given that there are thousands of systems
> out there inspected under NEC 2011 that have not additional grounding
> electrode.
>
>
>
> I will continue to listen with great interest...
>
>
>
> Jason Szumlanski
>
> Fafco Solar
>
>
>
>
>
>
> On Mon, Dec 9, 2013 at 9:21 AM, Richard L Ratico <
> Richard.L.Ratico at valley.net> wrote:
>
>
> Mr. Holt explicitly stated his desire to create a groundswell of opinion to
> immediately eliminate this requirement of the code. Would it not be better
> to
> carefully think through and discuss the issue, in contrast to what was
> permitted
> on his "show"?
>
>
>
>
>
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