Module grounding analysis-600V residential [RE-wrenches]

[William Miller]

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I am resending the post below because Topica apparently ate my first attempt:



Friends:

I read the article, suggested on this forum, analyzing grounding 
problems.  The article was written by Thomas Bowes.  Here is a more 
manageable link to the article:

http://tinyurl.com/yo3ckx

I found the article to be very germane to safety issues emerging as 
industry installation practices evolve.  The most important point made, in 
my opinion, is the point that installation of 600 volt systems in 
residential settings is a very new concept.  This idea has implications 
beyond just the grounding issues.

I have some very strong safety concerns prompted by this knowledge.  What 
causes me dismay is that the industry is hell-bent on cheapening and 
speeding up installation techniques.  I believe the motivation is partly to 
make Utility-interconnected PV systems more accessible to the masses, which 
is a good motivation.  The other motivation is to obtain an advantage over 
competing vendors of systems, a bad thing.

It is, in my opinion, not a matter of if, but when we kill our first human 
(if it has no happened already) with our shoddy installation 
procedures.  My scariest scenario is of the child who throws a Frisbee or 
ball onto a roof to have it become stuck under a PV array.  A USE cable has 
been rubbing against abrasive roofing material, exposing the 
conductor.  The child finds a length of metallic pipe in the garage and 
uses it to dislodge the toy.  You imagine the rest of the story...

The trend in reducing wire protection is driven also in part by practices 
in Europe.  It is my understanding that the "quick-connect" is ubiquitous 
there and that leads from the roof to the inverter and from the inverter to 
the AC distribution are all USE or similar cable, not protected by 
conduit.  Does anyone have experience with these European standards or 
practices?

Lastly, the point made in the article is very correct in that if a module 
in a "top-down" installation has a short circuit, how does one remove the 
module without getting electrocuted?  This is particularly risky when one 
can not verify the short circuited module until one removes it from the 
ground connection and undergoes a very real risk of becoming the ground 
path, with possible fatal consequences.

I'd like to hear from those that share my concerns about these 
practices.  I would hope we could, as a group, put aside our pursuit of 
paying contracts long enough to convene an installer based group to examine 
some of these concerns.


William Miller


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