Flexible Cables: Important Safety Issue [RE-wrenches]

Matt Tritt solarone at charter.net
Wed Aug 25 15:45:51 PDT 2004


 

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  Bob-O,

  Sheesh, maybe you're on to something here. Push the price up enough and no
one will buy it?

  Why is PV so reasonable in Germany? Because their rules allow for
reasonably priced systems!

  But I've got an even more irritating story about ridiculous rules and
reg's, this one from Sonoma County (that's in California for you
non-Californians)

  One of my wind dealers sells a WT to a client. He gets all the miles of
engineering data on the tower, the soils and foundation , does the required
Earthen Hue paint job on turbine and tower, gets the permits and goes ahead
with the install. We even provided him with a very nice monopole tower 45'
hub height - which is the limit in that county(!)

  Low and behold, last week the county tells him that he has to excavate
next to the tower foundation and take core samples of the concrete clear
down at the bottom of the pour. Then, because they have screwed up the
foundation, he has to fill the excavation with cement. Then they tell him
that he has to provide a "certificate of construction" from the tower
manufacturer because "for all we know, you might have built this thing
yourself". It's do it or you don't get an occupancy permit for the house.
(The tower is located 150' from the house).

  I consider this type of official harrasment to be even worse and more
damaging to our business than all the others; it drives up costs to the
installer (who hasn't figured this surprise into his bid margin) and
discourages others from buying a similar system.

  In my opinion, every possible incentive and benefeit of the doubt needs to
be offered and given to every single RE installation, be it on or off grid,
regardless of it's size. Everything possible simply MUST be done that can be
done to offset CO2 emmissions or were' all going to eat it big time sooner
than we would prefer.

  Where did THAT come from?

  Matt T


  ----- Original Message ----- 
  From: "Bob-O Schultze, Electron Connection" <econnect at snowcrest.net>
  To: <RE-wrenches at topica.com>
  Sent: Wednesday, August 25, 2004 8:28 AM
  Subject: Re: Flexible Cables: Important Safety Issue [RE-wrenches]




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  Well, that's old JW all over isn't it? Find a situation that could be
  a problem or that is very, very rarely a problem and make Mt Everest
  out of a molehill. Since day one of his inputs to the RE industry
  everything he suggests or opines that UL/NEC requires raises the cost
  of a PV system. EVERYTHING! Ever notice that? This man comes to us
  from the nuke industry. I find it damn hard not to question his
  motives. He's kind of a Swift Boat PV Opinionater for Arcane Stuff,
  ain't he?
  Jesus H. Christ!


  >  Oh my God.
  >
  >   This isn't April 1st is it?
  >
  >   So now all those inverters that we've been putting in with "fine
stranded
  >wire" for the past 20 years are going to have to have their cables
removed
  >and exchanged because "there have been problems"? What, fires?
Explosions?
  >Electrocutions? Befuddled inspectors?
  >
  >   I have to say that in all the years I've been working on battery-based
  >inverters, the ONLY connection problems I have observed  have ONLY been
  >those that had stiffy wire for inverter cables! There is so much
potential
  >for tension-caused breakage with this method, so many (virtually)
impossible
  >wire bends and seeming non-compatablity with all the commonly used, tried
  >and true connection components, I just can't bel;ieve that this can be
for
  >real.
  >
  >   If this such a huge problem, why not simply tin the wire ends?! UL
indeed.
  >
  >   Matt T
  >   ----- Original Message -----
  >   From: "Allan Sindelar" <allan at positiveenergysolar.com>
  >   To: "New wrenches posting" <RE-wrenches at topica.com>
  >   Sent: Tuesday, August 24, 2004 3:35 PM
  >   Subject: Fw: Flexible Cables: Important Safety Issue [RE-wrenches]
  >  Wrenches,
  >   Forwarded to this list at the request of John Wiles
  >
  >   ----- Original Message -----
  >   From: "John Wiles" <jwiles at nmsu.edu>
  >   Sent: Tuesday, August 24, 2004 3:50 PM
  >   Subject: Flexible Cables
  >
  >
  >   Flexible, Fine-Stranded Cables: Incompatibilities with Set-Screw
  >Mechanical
  >   Terminals and Lugs
  >
  >   Reports have been received over the last several years about
field-made
  >   connections that have failed when flexible, fine-stranded cables have
been
  >   used with mechanical terminals or lugs that use a set screw to hold
the
  >wire
  >   in the terminal.
  >
  >   These terminals are found on nearly all circuit breakers (except those
  >with
  >   stud-type terminals), fuse holders, disconnects, PV inverters, charge
  >   controllers, power distribution blocks, some PV modules, and many
other
  >   types of electrical equipment.
  >
  >   Fine-stranded conductors and cables are considered as those cables
having
  >   stranding more numerous than Class B or C stranding. Class B stranding
  >(the
  >   most common) will normally have 7 strands of wire per conductor in
sizes
  >   18-2 AWG, 19 strands in sizes 1-4/0 AWG, and 37 strands in sizes
250-500
  >   kcmil. Conductors having more strands than these are widely available
and
  >   are in different classes such as K and M used for portable power cords
and
  >   welding cables. Commonly used building-wire cables such as USE, THW,
RHW,
  >   THHN and the like are most commonly available with Class B stranding,
but
  >   are also readily available with higher stranding. Fine-stranded cables
are
  >   frequently used by PV installers to ease installation and are used in
PV
  >   systems for battery cables, power conductors to large
utility-interactive
  >   inverters and elsewhere.
  >
  >   Some modules are supplied with fine-stranded interconnecting cables
with
  >   attached connectors. While these crimped-on connectors listed with the
  >   module are suitable for use with the fine-stranded conductors, an
  >   end-of-string conductor with mating connector may also be supplied
with
  >the
  >   fine-stranded conductor ,and the unterminated end of that conductor
will
  >not
  >   be compatible with mechanical terminals.
  >
  >   According to UL Standard 486 A-B, a terminal/lug/connector must be
listed
  >   and marked for use with conductors stranded in other than Class B and
C.
  >   With no marking or factory literature/instructions to the contrary,
the
  >   terminal may only be used with conductors with the most common Class B
and
  >C
  >   stranded conductors. They are not suitable and should not be used with
  >   fine-stranded cables. UL engineers have said that few (if any) of the
  >normal
  >   screw-type mechanical terminals that the PV industry commonly uses
have
  >been
  >   listed for use with fine stranded wires. The terminal must be marked
or
  >   labeled specifically for use with fine-stranded conductors.
  >
  >   UL suggests two problems, both of which have been experienced in PV
  >systems.
  >   First, the turning screw tends to break the fine wire strands,
reducing
  >the
  >   amount of copper available to meet the listed ampacity. Secondly, the
  >   initial torque setting does not hold and the fine strands continue to
  >   compress after the initial tightening. Even after subsequent
retorquing,
  >the
  >   connection may still loosen. The loosening connection creates a
  >   higher-than-normal resistance connection that heats and may eventually
  >fail.
  >   Recent examples of failed mechanical terminals from a large PV system
have
  >   been found. The terminal had been torqued properly less than three
months
  >   before the failure.
  >
  >   Solutions
  >
  >   All electrical equipment listed to UL Standards has:
  >
  >   . Terminals rated for the required current and sized to accept the
proper
  >   conductors
  >
  >   . Sufficient wire bending space to accommodate the Class B stranded
  >   conductors in a manner that meets the wire bending requirements of the
NEC
  >
  >   . Provisions to accept the appropriate conduit size for these
conductors
  >   where conduit is required.
  >
  >   It is therefore unnecessary to use the fine-stranded cables except
  >possibly
  >   when dealing with conductors 4/0 AWG and larger.
  >
  >   In those cases where a fine-stranded cable must be used, a few
  >manufacturers
  >   make a limited number of crimp-on compression lugs in various sizes
that
  >are
  >   suitable for use with fine-stranded cables.
  >
  >   Factory-supplied markings and literature indicate which lugs are
suitable.
  >   An example is the ILSCO FE series of lugs in sizes 2/0 AWG and larger.
  >   Burndy makes a YA series of lugs in sizes 14 AWG and up. In both cases
the
  >   lugs are solid copper. It should be emphasized: Most crimp-on lugs are
not
  >   listed for use with fine-stranded wire. Where the crimp-on compression
  >lugs
  >   can be used, they must be installed using the tools recommended by the
  >   manufacturer and, of course, they must be attached to a stud with a
nut
  >and
  >   washer.
  >
  >   Burndy and others make pin adapters (a.k.a. pigtail adapters) that can
be
  >   crimped on fine-stranded cables. These pin adapters provide a
protruding
  >pin
  >   that can be inserted into a standard screw-type mechanical connector.
  >Again,
  >   not all pin adapters/pigtail adapters are listed for use with
  >fine-stranded
  >   conductors; some are intended for use with aluminum wire and others
  >provide
  >   only a conversion to a smaller AWG size for B Class conductor.
  >
  >   It is suggested that the use of fine-stranded conductors be avoided
  >wherever
  >   possible. Where such cables must be used, they should only be
terminated
  >   with the appropriate connectors/lugs. Previously installed systems
should
  >be
  >   revisited and the cables replaced where possible or terminated
properly.
  >
  >   John Wiles SWTDI/NMSU jwiles at nmsu.edu 505-646-6105
  >
  >   > If I can provide further information, please do not hesitate to
call,
  >   > e-mail or fax me.
  >   >
  >   > John
  >   >
  >   > John C. Wiles,  Program Manager
  >   > Southwest Technology Development Institute, New Mexico State
University
  >   > 505-646-6105      505-646-3841 (FAX)   http://www.NMSU.Edu/~tdi
  >   > SWTDI/NMSU
  >   > Corner Research Drive and Sam Steel Way
  >   > Box 30001/MSC 3 SOLAR
  >   > Las Cruces, NM 88003-8001
  >

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