Richard,
I agree. I caught part of the streaming as well.
Thanks for sharing.
Bringing lightning protection into the discussion is a whole other can of worms.
He made a variety of assumptions.
1. That the auxiliary rods were not bonded. For instance, I was trained in the exact opposite manner for ground mounts and off grid. Installing a rod at each pole mount, inverter and generator. But then bonding all of these rods together, with the intention of keeping all metal, modules, etc in the entire system at the same potential. This approach seems to really be echoing his own comments of keeping everything underground bonded. The important part seems to be having the DC electrical bonding, GFI etc and the AC neutral bond in only one location.
2. Ground lightning strikes will create differences in potential on all conductors. The insulation on most conductors buried in conduit is only good to 600 to 1000 volts at best. If there is a strike creating 100,000's of volts then all conductors will surely see current and voltage spikes. This is why we always install Surge Arrestors.
3. While I can appreciate the physics of lightning protection, I have it on my house, I am not so sure about its impact on a large PV array. I have a hard time accepting that a 1-2 foot spike of metal on the roof connected directly to ground will handle anything near a direct strike like he showed in the picture. Unfortunately, in that regard you get hit, or you don't. In fact, some lightning folks will admit that lightning protection can encourage the passage of some strikes. But the question here seems to be ---1. Is 1000 ft2 of aluminum rectangles, racking and wire, less conductive than a 2 foot metal spike. And is the extra 20-100 feet that the grounds pass to the rod, really enough to resist current in a strike. 2. If logic holds that a lightning protection system has merit, then wouldn't bringing every rail to ground at multiple points and then bonding them all together do the same thing.
I am not saying that this is the way it should be done, but making the point that it is essentially the same thing.
So, I respect Mike and what he is trying to do for many people, which is provide clear and accurate training materials.
However, I agree with Richard that I would like to hear from all the voices in the industry that have their minds around this as well.
Doug Wells
The Solar Specialists
Morrisville, VT 05661
(p) 802-223-7014
(c) 802-498-5856
www.thesolarspecialists.com
On Dec 9, 2013, at 9:21 AM, Richard L Ratico wrote:
I watched most of the streaming video of Mike Holt and six PV industry
professionals this weekend. The most interesting aspect of it was Mr. Holt's
very dramatic build up to the Sunday discussion of Article 690.47(D) which
brings back the requirement for an auxiliary grounding electrode for PV arrays.
He used everything short of drum rolls to build anticipation for this part of
the presentation.
Having personally contributed a short piece on this subject for SolarPro
magazine along with Bill Brooks and John Wiles in 2008, I looked forward to this
discussion. Finally, midday Sunday, instead of a discussion of an important and
controversial part of the 2014 code, we received a rant by Mr. Holt demanding an
immediate and unprecedented withdrawal of the article.
Prior to his remarks, in contrast to the preceding article discussions, Mr. Holt
asked that the guest panel not make any comments that would explain how the
requirement came to return to the code after being eliminated in the 2011
edition, or any comment that might "confuse" the issue. To my very great
surprise and disappointment, they complied, uttering not a single word, nodding
their heads and moving on to the next article.
After all the buildup by Mr. Holt, the "discussion" amounted to his monolog,
which if parsed, though stated to be for safety concerns, seemed primarily an
exercise designed to sell his books, videos and consulting services on
grounding. This was of course expected. The weekend live streaming was
generously offered free of charge, a rare opportunity to hear current PV expert
opinion on the NEC. My concern is that Mr. Holt's control of the process here
inhibited the dialog that should have taken place.
There are significant implications of allowing his opinion to go unchallenged.
Is there, or is there not, any merit in 690.47(D)? Could the language be better?
Could the requirement be modified to make it better rather than simply
discarding it? Does accepting his argument mean all those systems installed
according to the 2008 code are unsafe?
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"?
Dick Ratico
Solarwind Electric
--- You wrote:
Dear Wrenches,
Several of your co-wrenches are helping Mike Holt with the video
companion to his PV & the NEC 2014 book. So since you spend all your
weekdays thinking about the NEC, what better way to spend this weekend
than to watch NEC nerds discuss the meanings of shalls and shall-nots,
the unwelcome return of 690.47(D), and the continued flights of our
favorite sections to 705, right? Before you answer that, know that you
can also ask questions during the video in case something is unclear or
if we're wrong about something.
Broadcasting (free) from:
www.MikeHolt.com/live
Times:
~9a-4p ET Sat 12/7
~9a-5p ET Sun 12/8
Video from this weekend will be what's edited into the official DVD that
Mike puts out in the next few weeks.
Because Bill Brooks has a great joke about separate direct-current
grounding electrode systems bonded to the alternating current grounding
electrode systems that you don't want to miss,
Dave
PS If this post violates list etiquette, my apologies in advance,
Michael. We don't get a commission, if that helps...
_______________________________________
--- end of quote ---
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches at lists.re-wrenches.org
Change email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
