[RE-wrenches] AUO ac moudles

[Dave Click]

As Abraham Lincoln famously said, "I'll give it my best shot, but I'm no
Bill Brooks."

A DC ground fault is not impossible on an AC module but it's not the 
issue that it is on large DC systems where numerous high-voltage 
parallel strings can feed an array fault. When the unit is listed it's 
tested to withstand the maximum DC current available from its power 
source- that 250W-ish module. I don't see any issue with the NEC 
"intent" relating to DC GFDI when 690.6(D) explicitly states that AC 
modules "shall be permitted to use a single detection device to detect 
only ac ground faults, and disable the array by removing ac power." (NEC 
2008)

That being said, I can't quite tell what's going on with the AC wire on 
that datasheet-- it seems that those wires would be dangling (even if 
installed end-to-end rather than side-by-side), so I'd recommend 
supporting those above the roof like you're used to doing.

On 2012/2/23 12:08, Bill Hoffer wrote:
> Todd
>
> I have been researching micro inverters and AC modules for another
> client and have been wondering about GFDI requirements on the DC
> side, according to the NEC code an AC module may be permitted to have
> GFDI on the AC side only, apparently because it has been tested as a
> " complete , environmentally protected unit ".  This is a no brainer
> with units like the Exceltech AC module which is integrated into the
> junction box of the module, but the AUO brand seems to be also listed
> as an AC module which has normal MC4 connectors between the module
> and inverter (kinda jerry rigged in my opinion).  This makes me think
> that there is a potential for a DC ground fault, but because of the
> AC Module listing on this unit , as far as I can tell, does not have
> an integrated GFDI.  My main concern is safety and liability, but
> there seems to be a real gaggle of wiring under the module w/o a good
> way to protect it from damage on the roof.  There could be a
> situation of a DC ground fault causing a fire on a residence that
> would result in some legal finger pointing, which I would not like to
> have pointed back to me as an installer!
>
> As far as how well this AC module performs, I have no field
> experience. There seems to be a real disconnect between UL 1741
> requirements and what the testing authorities are calling AC modules
> and the the intent of the NEC GFDI requirements on the DC side.  I am
> concerned that the final interpretation will fall on the local
> inspector and cause a lot of grief for us installers.  IMHO
> installers need to beware of this hassle potential and at a minimum
> insure that their local inspector accepts it before installing and
> make sure your insurance is up to date!
>
> It would be interesting to hear from Bill Brooks on this one!
>
> Bill
>
> Bill Hoffer PE NABCEP Certified Solar PV Installer™ Sunergy
> Engineering Services PLLC 2504 Columbia Ave NW East Wenatchee WA
> 98802-3941 SunEngSer at gmail.com <mailto:SunEngSer at gmail.com>
> Cell:(509)679-6165
>
>
>
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