[RE-wrenches] Cable tray
Bill Loesch
solar1online at charter.net
Fri Mar 29 06:41:36 EDT 2013
Hi Chris,
Thanks for a glimpse of how our German brethren handle PV design &=20
installation. After all, who has more experience with design, execution,=20
and funding than the Germans? There remains an arrogance that the US has=20
a lock on how best to do any number of things. Hopefully, this=20
antiquated attitude will change, soon; hopefully, before we are all=20
reduced to asking the equivalent of, "Would you like to Supersize that=20
meal?"
Best wishes on your install. Please keep us informed of how others=20
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=20
> 60Hz for the grid, so we had to look to Europe for the inverters and=20
> work 1000V.
> I spent some time on the phone with SMA Germany to discuss the=20
> reqiurements in Germany and to understand the design methodology the=20
> inverters were designed for.
> First of all, the inverters are gorgeous. The first one we installed=20
> is a 3Ph 17KW with 6 sets string inputs, 2 x MPPT. They connect the=20
> strings directly to the inverters, no disconnects. The inverters have=20
> a Electronic Solar Switch on the bottom, pull it down and the strings=20
> are disconnected.
> We are using 26 module strings or that install, which massively=20
> reduces cabling and components.
> I showed the engineer a photo of our larger installs, he laughed at=20
> the use of "pipes" for the cables.
> We install massive AC disconnects, they use a little isolator about=20
> 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=20
> their approach to grounding is absolutely different.
> Since PV conductors are all isolated now, they don't even want you to=20
> ground the array structures, in fact they describe grounding as a=20
> shock hazard. Very different mentality.
> I might think that the US way is likely safer if we were comparing=20
> with China or the third world, but this is Germany. I think they know=20
> electricity.
>
> Chris
>
>
> On Wed, Mar 27, 2013 at 12:16 PM, John Berdner=20
> <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 =E2=80=93 Characterized by many, relatively smal=
l,
> 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=E2=80=99s 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:
>
> =E2=80=9CIt is only in the US where you need first to be a plumber be=
fore
> you can be an electrician=E2=80=9D
>
> 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=E2=80=99m =
not
> referring to =E2=80=9Cbasket tray=E2=80=9D, which is only app=
ropriate for
> small conductors. I=E2=80=99m talking about legitimate cable =
tray
> that can be up to 12=E2=80=9D wide and that has a top and run=
gs
> every 12=E2=80=9D. The main facilities that use it in the Uni=
ted
> States are large industrial facilities. Most electricians
> don=E2=80=99t 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=E2=80=99s all doable. My recommendation after se=
eing
> 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=3D"----=3D_NextPart_000_00E3_01CE29A6.37CC51=
10"
> 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=C2=ADparticularly for long
> feeder runs=C2=ADthe better.
>
> In Europe they don=E2=80=99t have problems with their rooftop
> wiring systems because everything is in tray.
>
> For those that don=E2=80=99t allow cable tray for anything le=
ss
> than 1/0, just remember that if it isn=E2=80=99t called cable
> tray, then 392 doesn=E2=80=99t 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=E2=80=99s w=
hy we
> try to fix it every three years.
>
> Bill.
>
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> --=20
> Chris Mason
> President, Comet Systems Ltd
> www.cometenergysystems.com <http://www.cometenergysystems.com>
> Cell: 264.235.5670
> Skype: netconcepts
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