Gridtie, breaking grounded conductor [RE-wrenches]

[John Berdner]

Wrenches:
 
Robert correctly raises a good point to which I would like to add some
clarification.
In the overall scope of an installation it is important to understand
the ranking of what trumps what.
Since we are talking about code compliant systems I will assume we are
talking about Listed devices. 
 
- In a Listed device the manufacturers instructions take precidence.
If you do not follow the manufacturers instructions then you may not be
using the device in accordance with the Listing.
This could invalidate the Listing and, since Listing is a requirement
for Code compliance, it could also create a code violation.
One example would be the grounding of the PV array via anythign other
than the GFDI.
- Second comes the Listing mark on the product tested by the NRTL.
The NRTL's mark means they have tested the product and certified that
it is safe within "the intended use and purpose"
Essentially a Listing says the NRTL has tested what is inside the box
and, frankly speaking, what is inside is none of the inpsectors business
because the inspector is not qualified to over rule the NRTL.
- Next come any local codes (if any) and last comes the NEC which is
normally a minimum set of requirements in most juristictions.
The Code is limited to the installation of the Listed products "in
accordance with the terms of the Listing and manufacturers
instructions".
 
All of that being said the AHJ (the inspector) still has the last word
and can red tag a perfectly code compliant installation.
When this happens you have to start the delicate dance of education and
if that does not work possibly move on to an appeals process.
Before that happens I suggest you call the equipent manufacturer.
We (manufactures) can try and help with a low pressure,
non-confrontational, education approach.
Sometimes this works but obviously we have a bias and the AHJ's know
this.
When that does not work J. Wiles at NMSU is a great resource. 
John does know his PV Code inside and out.
Sometimes you might also learn a thing or two that you were not
planning on.
This reminds me of something one of my old professors used to say:
"Students are the only group of people who complain when they get more
than they pay for"
 
Best Regards,
 
John Berdner
 

>>> robertwarren at mail.com 2/24/2004 11:00:40 PM >>>
If the PV system was one with amorphous modules instead of crystaline,

that capacitive charge that John B. and Bill Brooks speak of is not
such 
a small shock: it can pack quite a wallop! Apparently the nature of 
amorphous cells is conducive to building up and holding a huge
capactive 
charge. Sure, it will zero out through your DVM, but it it happens to 
zero out through your fingers, it can knock you on your butt, as friend

or mine in Scotland found out while testing a 12 kW Unisolar amorphous

system while standing on a metal roof.
The lesson here is to always treat all wires as live. I don't think 
this means that we need a disconnect on the roof, though. 
As for the location of the connection of the negative to ground (or the

suggestion that it be possible to break it), doesn't the recommended 
practice of a UL listed device such as the Sunnyboy inverters 
automatically supercede any new and fuzzy installation concept that 
inspectors might come up with? I remember a clause in the NEC code 
saying something to the effect that the manufacturer recommendations
may 
superceed the NEC code in terms of being more safe than Code. Let the 
GFI do its job.
Robert Warren 




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