Mark,

Thank you for pointing me to 690.43 NEC 2008. 	I'm embarrassed to confess
I was unaware of the change there from 2005. 

This weekend, I've spent more time than I care to admit, trying to 
discover and understand the rationale for that change. In this, I will admit,
I was unsuccessful.

Failing to understand, one is left with the choice to either follow the code,
or continue with what seems to be a safer, and previously acceptable practice.
According to John Wiles, the code making panel for 2008 Article 690 was
disbanded
by the NFPA because it, "violated NEC code developement procedures and because 
of other issues." Doesn't leave one with much confidence in their work.

I lived in Western Washington 1977 to 1980 and actually missed the frequent
summer thunderstorms I'd grown up with in Pennsylvania. Unfortunately, 
they are often destructive, if not deadly. Here in VT /NH I have heard of phones 
blasted off the wall, large blue sparks leaping from wall receptacles 
and a Honda generator's remote starting unit. A woman reported her long hair 
stood on end as a storm approached her pole mount array. My son has burn marks
on 
the front of his television where he and a friend watched flames leap from it 
during a nearby strike. I have followed up on other installers work, where
inverters,
charge controllers and other equipment was damaged or destroyed. The internet is 
replete with spectacular accounts and photographs.

I do think arrays should have a low inpedance ground, local to the array and
exterior to 
to any structure, particularly a residence. It is frustrating to still be
debating
the best way to deal with this important issue.


Dick Ratico
Solarwind Electric
Bradford, VT 


--- You wrote:
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@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] On Behalf Of Richard L
Ratico
Sent: Friday, June 05, 2009 6:56 PM
To: re-wrenches@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
--- end of quote ---

