[RE-wrenches] 690.47D (revisited)

[Mark Frye]

Dick,

Kudos for the contributions to the magazine.  I do hope as John W.
speculates that this will all be sorted out in NEC 2011.

In the meantime, while I can see the validity of your method, I don't think
it is well supported by NEC 2008. Specifally at 690.43 (which would overide
the more general allowances of 250) that requires the EGC for the PV array
to be contained within the same raceway as the PV circuit conductors when
they leave the vicinity of the array.

Unfortunately, the ambiguity of the Code is causing everyone to come up with
their own creative solutions, so long as they can sell them to the AJH, if
any.

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 Richard L
Ratico
Sent: Friday, June 05, 2009 6:56 PM
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] 690.47D (revisited)

Kelly, 

I always install a grounding electrode at the array. I always run a
continuous (not spliced), properly sized, or oversize (usually #4), bare,
copper conductor from the array modules and frame, to that electrode, then
continue it, direct buried, to all of the other grounding electrodes in the
system. 

I DO NOT run a separate equipment grounding conductor (EGC) with the array
circuit conductors, for the reason you mention. I don't want to create a
ground loop. I also want to keep any energy from lightning away from the
circuit conductors. 
Here in Vermont, we get our share of lightning and I've seen way too much
equipment that's been fried.

The NEC, in article 250 permits the EGC, IN DC CIRCUITS ONLY, to be run
SEPARATELY from the DC circuit conductors. In the method above, the direct
buried, bare conductor serves as BOTH the EGC and the GEC for the array.

In the premier issue of Solar Pro Magazine,
<http://solarprofessional.com/article/?file=SP1_1_pg28_3Phase>
Bill Brooks, John Wiles and I took turns trying to make sense of 690.47.
I'm not sure we succeeded. :-)

There are no residential inspections in VT. 
Hope this helps.

Dick