Sorry for mis-statement as I was not trying to place blame on the designer or installer of the Target failure which I do not have any first hand knowledge.
My point was that regardless of who did what, the conduit did came loose at a fitting, most likely due to expansion and contraction in a long conduit run that either had improper expansion provision, or this expansion device failed, or was not installed properly, and the conduit came lose and dropped down enough to cut and short out a bundle of array strings to ground and to each other.
My question was more about what specific conduit "materials" and do's and don'ts for a very large roof array would reduce this risk of this type failure, and yes, this assumes it will be installed correctly. I know EMT is most likely the fisr choice, but are any of you using IPT on these really long runs exposed to lots of weather issues and expansion.
Somewhat related to this - it appears to me that the combiner box is properly fused to protect strings feeding other strings, but there still is no fused protection or emergency dis-connect between the array combiner box (s) and the long conduit run to the inverter (s), so a short to ground along this run (Target) will just keep welding and melting. As far as I can tell, there is no NEC requirement for this type combined string protection leaving the combiner box, but it seems like a good idea when dealing with 550 volts DC at over 125 amps in un-fused runs. Are any of you adding this protection on these larger systems?
Thanks for advice,
Jeff Yago
Netscape. Just the Net You Need.
_______________________________________________ List sponsored by Home Power magazine
List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
