Electrical Connection Spring 2015

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www. e l e c t r i c a l c o nn e c t i o n . c om . a u 4 3
with Phil Kreveld
Cable ties, clips and other attachments
should be properly used so that cable
electrical properties are not compromised. A
PV installation is in the open, and movement
is something that installers have to factor
into cable management.
Installers use different ties to attach cables
to frames or other supporting features.
Cable ties are usually UV-stabilised and
available in a wide range of tensile strengths,
bundle diameters and styles. However, if
they are not UV-rated they will fall apart in
due course, as they can’t withstand 20-25
years of sun (plus rain and curious animals
with a penchant for plastic).
Note that the use of metal wire ties is
discouraged, as they can cut into cables.
In addition, AS/NZS 5033:2012 explicitly
states that plastic cable ties are not to be
used as a primary means of support.
Where landscape orientation of PV panels
is called for because of roof topography,
installers should look very carefully at the lead
lengths, as these are often relatively short and
designed for the usual portrait orientation.
This can lead to excessive time, as well
as materials, to splice in extra conductors.
To prevent kinking and compromising
conductor life, the minimum bend radius
of solar cables should be observed.
Over-bending of a conductor can cause
excessive heat at the bend and stress on
the connection. This also increases
conductor resistance.
The importance of good quality
connectors cannot be overstated,
particularly because cheap counterfeit
versions of the well-known MC4 connection
system are available. You indeed get what
you pay for.
MC4 connectors (named for the original
manufacturer, Multi-Contact USA) are single-
contact items designed for DC connections.
The MC4 system allows strings of panels
to be easily constructed by pushing the
connectors from adjacent panels together
by hand. However, a tool is required to
disconnect them to ensure they are not
accidentally disconnected when the cables
are pulled.
The MC4 system and compatible
products are common in the solar market
today, equipping almost all solar panels
produced since about 2011.
In short, the use of the correct protection
gear, conductors and conduit is essential
for solar PV rooftop installations capable of
withstanding the rigours of weather, sun,
vermin, dirt, etc.
Complete installation kits are available,
but installers are well advised to study the
requirements of intended installations.
Sketch plans should be done, with
indications for conductor length, connector
location and, where appropriate, junction
boxes and isolator switches.
The speed of opening contacts
is less critical in AC than in
DC circuits.
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