[RE-wrenches] Cable tray

[Bill Brooks]

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 conduit-particularly for long feeder runs-the
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.
 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130326/53e419eb/attachment-0003.html>