690.47 (was Enphase) [RE-wrenches]

Mark Frye markf at berkeleysolar.com
Fri Jun 13 10:14:03 PDT 2008


Drake,

Yes, it really is up in the air, and I am seeing it along different lines.

Most roofs are much more than 6 feet of an electrode.

The intent may have been that you take the most direct route from the array,
down along the side of the building to the ground and put your "additional
electrode" there.  If that is within six feet of the existing premise
electrode, then don't put in the additional electrode.

In any case, you have to run an additional GEC (separate from the DC system
GEC/EGC run as a single conductor from the inverter) from the array to this
new GE.
 
Mark Frye
Berkeley Solar Electric Systems
271 Vistamont Dr
Grass Valley CA 95945
(530) 401-8024
www.berkeleysolar.com 

-----Original Message-----
From: Drake Chamberlin [mailto:Drake.Chamberlin at redwoodalliance.org] 
Sent: Friday, June 13, 2008 12:05 PM
To: RE-wrenches at topica.com
Subject: RE: 690.47 (was Enphase) [RE-wrenches]


Mark,

I agree that here is ambiguity in this section.  In the quote below, it is
unclear as to me as to what is located within 6 ft of the premise wiring
electrode.

Quote:
"Exception No. 2:  Additional array grounding electrode(s) shall not be
required if located within 6 ft of the premises wiring electrode."

I had interpreted this to mean that if the rooftop array was within 6 feet
of the premise wiring electrode, the additional electrode would not be
required.  If the additional electrode was within 6 feet of the premises
wiring electrode, and therefore not be required, then it is there but not
required.  It would only not be required if it were 
there, and within 6 feet.   So it must mean within 6 feet of the 
array.  If that is the case, does this mean within 6 feet horizontally,
since most roofs are over 6 feet high?

On the issue of the other GEC, I also don't see how we get past the
requirements of 250.166 (a) , which is referenced in 690.47(c)(7).
Inspectors we have dealt with seem ok using wires down to the neutral
conductor size.

Drake


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