[RE-wrenches] Cable tray

[Andrew Truitt]

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" <billbrooks7 at 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-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at 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.
>  
>  
> 
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