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Cables &
Wiring
To make efficient use of the precious electricity
made by either wind generators or solar modules and stored in batteries,
it is most important to choose cables and fittings carefully. The right
cables of the correct cross-section should be used to ensure safety,
reliability and to minimise voltage drop and energy losses.
Larger wire sizes are required in lower voltage DC
systems than in standard AC systems.
See Sizing Cables
Cables consist of conducting wires with a protective,
insulating covering which must be resistant to moisture, sunlight, heat,
chemicals and abrasion. For better protection underground, outside or in
harsh conditions conduit or armoured cable must be used. For outside
applications, cables and other exposed external plastic fittings must be
weatherproof and resistant to deterioration in sunlight.
All cables should be adequately supported using
conduit, cable cleats, cable clips or cable ties etc.
Flexible multi-stranded wire should be used instead
of single stranded wire to ensure good connections and reliability.
Standard 230Vac household ‘twin & earth’ type wiring
uses PVC insulation which is somewhat resistant to sunlight (it should
last about 5 years), and this is the cheapest choice for internal wiring
such as DC and AC load circuits. Common single insulated wires are not
sunlight resistant.
The production, use and disposal of PVC results in
the creation and release of large amounts of persistent toxic &
carcinogenic chemicals, including dioxin - a hormone disrupter, one of
the most toxic substances known.
By using polyethylene or rubber insulated cables
(described as halogen-free cables) in place of PVC this environmental
contamination can be avoided.
PV ARRAY WIRING
 For battery based PV systems, with average mechanical
stresses and use in the open the following flexible 2 core cables are
very suitable. Their H07RN-F rating means they are sunlight UV, ozone,
temperature and weather resistant. Rubber insulation, black outer,
blue/brown cores.
For higher voltage DC systems (such as grid connect
PV arrays) double insulated single core cable should be used. Black
rubber double insulation - suitable for use with MultiContact polarised
weatherproof DC connectors.
See
Multi-contact Cables
PV Array Junction Boxes
 
These are used to allow the parallel connection of
several strings of PV modules or to enable large or armoured cables to
be connected from the PV array to charge controller or inverter location
so minimising voltage & power losses. Since the PV array cannot be
switched off these junction boxes must be labelled as ‘PV Array Junction
Box - Danger, contains live parts during daylight’.
These boxes can also contain string fuses which
provide a means to isolate the PV strings. String fuses must be provided
for all arrays formed of four or more strings.
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