[RE-wrenches] 690.47D (revisited)

[Mark Frye]

Kelly,

The question is, if the AJH had required you to run the new array DC GED
directly to an additional DC array GE, would that new DC GE system need to
be bonded with the exisitng AC GE system with a bonding wire other than the
new EGC running from the array to new DC GE?

Unfortunately, NEC 2008 is not clear about this with respect to the new DC
array GE.  That leaves us with only the general NEC requirement that all
premise GE's be bonded into a single system.

So the total effect of the new 690.47D, assuming that the "prcaticable"
location for the new DC array GE is not within 6 ft of the exisiting AC GE,
is this:

A new DC array GEC must run directly from the array to a new DC GE system
and and a new bonding jumper must be run from the new DC GE system to the
exisitng AC GE system.

It the new DC GE system can be the same as the existing AC GE by virtue of
it proximity (less than 6 ft) to the practiable location, then the ne DC
array GEC must still be run directly to exist GE system which is now the
AC/DC GE system.


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 Kelly
Keilwitz, Whidbey Sun & Wind
Sent: Friday, June 05, 2009 7:26 AM
To: RE Wrenches listserve
Subject: Re: [RE-wrenches] 690.47D (revisited)

Dick,
Thanks for your take on this.

The problem I see with using the existing AC/DC system GE for the PV GE is
that the EGC will run in parallel with it, separate, but connected at each
end (at the array and at the GE). This could set up a ground loop and still
leaves the electronic imperiled.

I think that, if the dedicated, PV GE is required it should NOT be bonded to
the other system GE's. If it is not required, the PV GEC should NOT be used.

What are you Wrenches being required to do? I"m wondering how other AHJ's
are seeing this. This is the first AHJ in our area to bring this up.

-Kelly

Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
WA Electrical Administrator #KEILWKM923RB
987 Wanamaker Rd.
Coupeville, WA, 98239
360.678.7131
sunwind at whidbeysunwind.com
WA Electrical Contractor #WHIDBSW920MS
WA General Contractor #WHIDBSW946M1





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