[RE-wrenches] Cable tray

Tue Mar 26 21:48:36 PDT 2013

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:
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>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.
>
>
>From: re-wrenches-bounces at lists.re-wrenches.org 
>[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of William Miller
>Sent: Monday, March 25, 2013 9:30 PM
>To: RE-wrenches
>Subject: Re: [RE-wrenches] Cable tray
>
>David:
>
>Of course, I understand that you are not saying we can willfully disregard 
>the Code in anticipation of future clarification.  I was just 
>extrapolating on your idea.
>
>If we want an exception based on a predicted update in the code, we are at 
>the mercy of the AHJ who may or may not be convinced.  I think most AHJs 
>are willing to diverge from the Code in a more strict interpretation, but 
>not the reverse. Right now, as I read it, unless the leads are 1/0 or 
>larger, we are forbade.
>
>I treat PV systems like rooftop AC units.  The voltages and currents are 
>similar, if not more severe.  I don't believe you could or should run 
>power to a rooftop AC unit in cable tray.  Conduit is a tried and true 
>practice and I recommend it.
>
>William Miller
>
>
>At 06:01 PM 3/25/2013, you wrote:
>
>Ouch. I promise I'm not advocating for anything like that. What I may be 
>missing is the Code reference that says "no cable tray on roofs" or similar.
>
>There is so much room for improvement in wire management practices, that 
>being able to use cable tray seems like a step forward. I understand some 
>jurisdictions do not allow it, but it appears as though Code changes were 
>made specifically to address this. It's boring stuff, but you can read the 
>explanation of the Code changes in the ROP and ROC documents.
>
>The Code changes a lot with regards to PV system, and Article 690 is more 
>fluid than other articles. Some of this is the Code trying to keep up with 
>technology. In other cases the Code evolves based on new applications for 
>existing products. Often it changes because some areas of the Code are 
>confusing for electricians and inspectors alike. If the new Code language 
>is more clear in its intent than previous versions, some inspectors are 
>willing to let installers build to the most current standard.
>
>That's all I'm advocating for: Trying to understand how the minimum 
>requirements outlined in Code evolve over time so that you can have a 
>friendly and informed conversation with your AHJ over a donut.
>
>
>
>
>On Mar 25, 2013, at 6:26 PM, William Miller wrote:
>
>
>David:
>
>This is great news.  Now, whenever I want to do something that is 
>prohibited by code, I can just say that the Code Making Panel is gonna 
>correct that pesky code section (insert your problem citation here) any 
>day now, so I might as well be allowed to do whatever it was I was fixin' 
>to do anyway.  Unless I am missing something...
>
>Thanks!
>
>William Miller
>
>PS:  Just kidding.  Hope no offense is taken.
>
>wm
>
>
>At 03:46 PM 3/25/2013, you wrote:
>
>
>So if you ever get called on 392.10(B)(2), I think you can point out that 
>the Code Making Panels have been busy clarifying that cable tray is okay 
>for source circuit conductors. Unless I'm missing something....
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