Remember target had two fires. one caused by the conduit cutting insulation and the other by the ground current passing through small module ground leads. Had the grounded conductor not been grounded this other fire would not have happened. We need to move to ungrounded systems. Darryl
--- On Sat, 12/5/09, Keith Cronin <[email protected]> wrote: > From: Keith Cronin <[email protected]> > Subject: Re: [RE-wrenches] large array conduit runs > To: [email protected], "RE-wrenches" <[email protected]> > Date: Saturday, December 5, 2009, 12:24 PM > Jeff > EMT is fine on the roof. Rigid will add weight > to the roof, as well as increase your labor costs to install > it. > My take away from the Target project after > reading the report was they did not use the correct > fittings. Coupled with long conduit runs and perhaps not > using junction boxes and providing loops in the box to > address expansion and contraction contributed to the > incident. It is like a plane crash- it is usually not one > thing that makes the plane crash, but a series of events > that leads to the demise of a situation. It seems the same > goes for the Target project. > If any of you have ever driven over a bridge and > have sat in traffic, sometimes you get visually exposed to > the conduit runs, and the expansion > fittings. You will also see junction boxes, with generous > loops of wire to address the expansion and contraction that > occurs. > Also, the temp derate on 310-15-B-2-C has a > table for exposed conduits on the roof; 310-16 & 310-17 > should be reviewed. > Keith > > From: > Jeff Yago <[email protected]> > To: > RE-wrenches <[email protected]> > Sent: Sat, > December 5, 2009 8:03:04 AM > Subject: Re: > [RE-wrenches] large array conduit runs > > > We are starting to get much > larger grid tie systems above 100 kW and I still remember > very clearly that Target melt down related to conduit that > shorted out a bundle of string runs between the array and > inverters due to improper allowance for expansion and > contraction in the long above roof conduit runs. With > this in mind I wanted to specify a conduit between multiple > array rows back to the inverters and we get rain, snow, high > temps, low temps that make me want to go with extra > protection and cable support and have budget to do it > right. > > What type of metal conduit are you using on these > larger roof array commercial systems - - - EMT, > Intermediate, pipe, other? > > Thanks, > > Jeff Yago > > Netscape. Just the Net You Need. > > > > > > -----Inline Attachment Follows----- > > _______________________________________________ > 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 > > _______________________________________________ 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
