Bill - What is your take in conductor insulation degradation over time when exposed to UV? Regardless of the "sunlight resistant" labeling, USE-2 (and I assume PV wire though I haven't seen it yet) does show wear after years of exposure to direct sunlight. Maybe best practice would be to use cable trays where conductors are shaded and [properly installed] conduit when exposed to direct UV?
- Andrew Truitt Sent from my iPad On Mar 26, 2013, at 11:55 PM, "Bill Brooks" <billbroo...@yahoo.com> wrote: > William, > > I have all the respect in the world for you, but I’m not referring to “basket > tray”, which is only appropriate for small conductors. I’m talking about > legitimate cable tray that can be up to 12” wide and that has a top and rungs > every 12”. The main facilities that use it in the United States are large > industrial facilities. Most electricians don’t get to work with it. It is > clearly superior to EMT and is at least as good as IMC without all the hassle > of threaded fittings and setting up expansion joints and worrying about 20 > years of conductors thermal cycling. Even the best electricians have problems > with this stuff. > > I am talking about projects with 800 foot long feeder runs. We can bring them > in the building and build a rack for the conduit or run covered tray outside. > As the 2014 NEC will require, you will have to use contactor combiners or > some other means to shut down the conductors inside a building. It’s all > doable. My recommendation after seeing the aftermath of rooftop conduit by > good electricians is to put cable tray on roofs and use conduit if you bring > the feeders indoors. It will become common practice soon. Hopefully sooner > than later. > > Bill. > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller > Sent: Tuesday, March 26, 2013 9:49 PM > To: RE-wrenches > Subject: Re: [RE-wrenches] Cable tray > > Bill: > > I have to disagree with you on this one. We can not abandoned a tried and > true practice just because some practitioners don't do it right. I don't > know how one can justify saying that encapsulating high voltage conductors in > a conduit is less safe than exposed in a flimsy basket. Consider snow and > ice and falling objects. > > Too many installers entered the PV field without first acquiring the > necessary skills as journeymen or women electricians. I don't see the > benefit of rewriting the code to accommodate a lack of skills in the industry. > > Respectfully, > > William Miller > > PS: The temperature adders always encourage us to enter the building > envelope at the first appropriate location to avoid adding them. Thoughtful > installers will do the same. > > Wm > > > At 10:15 PM 3/25/2013, you wrote: > > Content-Type: multipart/alternative; > boundary="----=_NextPart_000_00E3_01CE29A6.37CC5110" > Content-Language: en-us > > William, > > I would strongly disagree that conduit is tried and true on rooftops. I have > rarely seen good conduit runs on rooftops. Most electricians have no clue how > to work with expansion joints. Conduit on rooftops is a bad idea in general. > Most conduit runs in big buildings are all done indoors for good reason. We > are the crazy people doing things on the roof. > > The sooner we get away from conduitparticularly for long feeder runsthe > better. > > In Europe they don’t have problems with their rooftop wiring systems because > everything is in tray. > > For those that don’t allow cable tray for anything less than 1/0, just > remember that if it isn’t called cable tray, then 392 doesn’t apply. The NEC > would allow us to use treated lumber in place of cable tray. This makes no > sense. > > We did some research on the origin of the 1/0 requirement, and it is ancient > and no longer relevant. Just because it is in the code, does not mean it is > correct. That’s why we try to fix it every three years. > > Bill. > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & 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 >
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