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 dont have problems with their rooftop wiring systems
because everything is in tray.
For those that dont allow cable tray for anything less than 1/0, just
remember that if it isnt called cable tray, then 392 doesnt 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. Thats why we try to fix it every three years.
Bill.
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@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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