690.47(C) applies to almost all our solar work (anything with an
inverter). The whole point is: where does the equipment grounding
conductor EGC become the grounded electrode conductor GEC? At that
point and down, 250.166 applies as well. IMHO, once the separate
modules are bonded to a center grounding point at or very near the
array framing, then the conductor to the required supplementary
electrode is the GEC. (which can be the framing, if 250.52 is followed.)
A separate EGC sized by 250.122 connects this center array grounding
point back along with the power conductors to the AC ground buss ,
which is bonded to the house's GEC to a separate electrode.
These electrodes are connected through the EGC, and therefore satisfy
250.54 and ultimately 250.4.
They should not be connected by a 2nd pathway, as this creates a
ground loop.
Connecting the various electrodes through EGC system alone satisfies
both the requirements of the NEC, and good lightning protection
practice of a single connection point grounding system with no loops.
Lightning strikes are conducted directly to earth at multiple points
in the system by their separate large GECs while decoupling parts of
the system somewhat from surges (via the reduced size EGC), but still
bonded, insuring that no potential exists in different parts of the
ground system normally.
Ok I'm going home
R. Walters
Solarray.com
NABCEP # 04170442
On Jun 19, 2009, at 12:22 PM, Peter Parrish wrote:
Thanks. One last thing: 690.47(C) has its own set of grounding
requirements (C)(1)-(8). So we need to follow those as apposed to
250-166?
- Peter
<image002.gif>Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parr...@calsolareng.com
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-
boun...@lists.re-wrenches.org] On Behalf Of R. Walters
Sent: Friday, June 19, 2009 10:50 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] What is a "direct-current system"?
I just sort of hit this in a previous post:
check 690.47C(3). Your system falls under (C) AC & DC grounding
requirements.....
This just shouldn't be that hard with the inspectors....
R. Walters
Solarray.com
NABCEP # 04170442
On Jun 19, 2009, at 10:55 AM, Peter Parrish wrote:
I have a LA Dept. of B&S inspector cite Article 690.47(B) “Direct-
Current Systems” and its consequent grounding requirements (250.166
(A)(B)) in connection with a very straightforward grid tied PV
system (i.e. no batteries, just PV and a Xantrex GT inverter).
He said that since there is a DC circuit as well as an AC circuit,
690.47(B) applies. I countered that all PV systems have a DC
circuit, so to separately call out a “Direct-Current System” must
apply to something other than the DC PV circuit inherent in all PV
systems.
Am I missing something here? Is “Direct-Current System” defined in
Article 690? We are working off NEC 2008.
Thanks in advance for your help.
- Peter
<image003.gif>Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parr...@calsolareng.com
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
<image003.gif>
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & 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
<image002.gif>
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & 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
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & 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
