[RE-wrenches] Cable tray
Bill Loesch
solar1online at charter.net
Fri Mar 29 03:41:36 PDT 2013
Hi Chris,
Thanks for a glimpse of how our German brethren handle PV design &
installation. After all, who has more experience with design, execution,
and funding than the Germans? There remains an arrogance that the US has
a lock on how best to do any number of things. Hopefully, this
antiquated attitude will change, soon; hopefully, before we are all
reduced to asking the equivalent of, "Would you like to Supersize that
meal?"
Best wishes on your install. Please keep us informed of how others
around the world better handle these items.
Bill Loesch
Solar 1 - Saint Louis Solar
On 28-Mar-13 1:03 PM, Chris Mason wrote:
> I am working on a large installation in a country that uses 230/400V
> 60Hz for the grid, so we had to look to Europe for the inverters and
> work 1000V.
> I spent some time on the phone with SMA Germany to discuss the
> reqiurements in Germany and to understand the design methodology the
> inverters were designed for.
> First of all, the inverters are gorgeous. The first one we installed
> is a 3Ph 17KW with 6 sets string inputs, 2 x MPPT. They connect the
> strings directly to the inverters, no disconnects. The inverters have
> a Electronic Solar Switch on the bottom, pull it down and the strings
> are disconnected.
> We are using 26 module strings or that install, which massively
> reduces cabling and components.
> I showed the engineer a photo of our larger installs, he laughed at
> the use of "pipes" for the cables.
> We install massive AC disconnects, they use a little isolator about
> the size of a Coke can.
> Everything is a multi-core cable.
>
> I also read a guide to the British Standards on PV installation, and
> their approach to grounding is absolutely different.
> Since PV conductors are all isolated now, they don't even want you to
> ground the array structures, in fact they describe grounding as a
> shock hazard. Very different mentality.
> I might think that the US way is likely safer if we were comparing
> with China or the third world, but this is Germany. I think they know
> electricity.
>
> Chris
>
>
> On Wed, Mar 27, 2013 at 12:16 PM, John Berdner
> <John.Berdner at solaredge.com <mailto:John.Berdner at solaredge.com>> wrote:
>
> Exposed single conductor sunlight resistant cable in cable trays
> are widely used in PV systems outside the US.
>
> There is a very large installed base of systems with good long
> term performance data using this type of construction.
>
> We should not discount the advantages of wire cable trays just
> because we are unfamiliar with it.
>
> Look at data cabling – Characterized by many, relatively small,
> cables over long distances with periodic drops.
>
> Sounds a lot like PV source circuits (other than voltage and
> current in the wires of course).
>
> There are lots of videos out there showing how to pull 10’s of
> pairs of wires simultaneously in cable trays.
>
> IMHO, we need to look at ideas like this to reduce installation
> cost and time.
>
> Installation costs are becoming the tall pole in the tent and new
> thinking is needed.
>
> As systems are falling to sub $3.00 /Watt all-in, running wire in
> conduit will simply not be cost effective.
>
> Running wire in conduit is one of the reasons PV installation
> costs in the US are double (or more) of those in Europe.
>
> As one of my former German colleagues noted:
>
> “It is only in the US where you need first to be a plumber before
> you can be an electrician”
>
> Best Regards,
>
> John Berdner
>
> General Manager, North America
>
> SolarEdge Technologies, Inc.
>
> 3347 Gateway Boulevard, Fremont CA 94538 USA */(*Please note of
> our new address.)/*
> T: 510.498.3200, X 747 <tel:510.498.3200%2C%20X%20747>
>
> M: 530.277.4894 <tel:530.277.4894>
>
> *From:*re-wrenches-bounces at lists.re-wrenches.org
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>
> [mailto:re-wrenches-bounces at lists.re-wrenches.org
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of
> *Allan Sindelar
> *Sent:* Wednesday, March 27, 2013 8:51 AM
>
>
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] Cable tray
>
> Andrew,
> We have used #10 USE-2 for about 16 years, and our high-elevation
> New Mexico sun is quite intense. I have yet to see any degradation
> exceeding fading discoloration on any conductors from that far
> back, even when directly exposed to sunlight. No cracking,
> peeling, delaminating, or hardening.
> Allan
>
> *Allan Sindelar*
> Allan at positiveenergysolar.com <mailto:Allan at positiveenergysolar.com>
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> Founder and Chief Technology Officer
> *Positive Energy, Inc.*
> 3209 Richards Lane (note new address)
> Santa Fe, New Mexico 87507
> *505 424-1112 <tel:505%20424-1112>*
> www.positiveenergysolar.com <http://www.positiveenergysolar.com/>
>
> On 3/27/2013 8:41 AM, Andrew Truitt wrote:
>
> 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 <mailto: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>
> [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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> --
> Chris Mason
> President, Comet Systems Ltd
> www.cometenergysystems.com <http://www.cometenergysystems.com>
> Cell: 264.235.5670
> Skype: netconcepts
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