What Cable Suits PV Arrays? A Trade Guide

A cable that looks right in the carton can still be wrong for the circuit. When a supervisor asks, “what cable suits PV arrays”, the answer is not simply 4 mm² or 6 mm². The cable must suit the array voltage, string current, route length, rooftop temperature, mechanical exposure and the connector terminals fitted on site. Get those details right before the modules go up, and the DC side is easier to terminate, test and hand over.

For most Australian rooftop array wiring, purpose-made solar DC cable with tinned copper conductors and double insulation is the starting point. But the final cable size and rating need to follow the system design and applicable Australian requirements, not a rule of thumb carried over from the last job.

What cable suits PV arrays in Australia?

PV array cable needs to be designed for photovoltaic DC circuits. This is different from ordinary building wire. An array can operate at high DC voltage for long periods, sit in direct sun, run across hot roofs and remain exposed to moisture, ozone and UV for years.

Specify solar DC cable with the voltage rating required by the installation. Many current commercial and larger rooftop designs use 1,500 V DC equipment, while older and smaller systems may operate at lower maximum DC voltages. The cable rating must cover the maximum system voltage, including the low-temperature open-circuit voltage calculation, rather than only the nominal inverter input voltage.

The cable should also be suitable for outdoor solar use, with insulation and sheath materials built to tolerate UV and elevated temperature. Tinned, fine-stranded copper conductors are commonly used because they are flexible for rooftop routing and offer better resistance to corrosion than bare copper in demanding environments. Cable marked to recognised PV cable standards, such as IEC 62930 or EN 50618 H1Z2Z2-K where relevant to the specification, is commonly selected for this duty.

The installation still needs to comply with the applicable Australian and New Zealand standards, project documentation, manufacturer instructions and electrical rules. Cable markings and a data sheet are useful procurement checks, but they do not replace the designer’s cable calculation.

Start with the circuit, not the cable reel

Array cable selection is a circuit-design task. First confirm whether the cable is a short module-to-module string link, a string run to a rooftop isolator or combiner, or a longer DC homerun to the inverter. These runs can have very different current, voltage-drop and containment requirements.

String current is based on the module electrical data and the design method required for the system. Use the module short-circuit current and the relevant design factors, then allow for the actual installation conditions. Parallel strings increase the current in shared conductors. A cable adequate for one 13 A string may be undersized once three or four strings are combined ahead of an inverter or combiner enclosure.

Voltage drop matters as well. On a short residential string run, the difference between 4 mm² and 6 mm² may be modest. On a commercial roof with long routes back to centralised equipment, conductor size can materially affect energy yield and system performance. A larger cable costs more per metre, but can be the better commercial outcome when it reduces losses and avoids rework.

As a practical guide, 4 mm² and 6 mm² solar cable are common for individual module strings. Larger sizes are often required for combined string circuits and longer DC runs. That is a purchasing guide, not a design approval. Check the calculated current-carrying capacity, voltage drop and terminal acceptance for every circuit.

Heat, containment and installation route change the result

A cable’s published current rating is not a universal site rating. Rooftop temperatures, grouping, conduit, trunking, insulation and restricted airflow all affect heat dissipation. Black cable on a dark metal roof in Queensland can face very different conditions from a ventilated cable run in Tasmania.

Direct sunlight is only one part of the exposure question. Consider where the cable leaves the module area, passes beneath modules, enters conduit, crosses roof penetrations and runs down to isolators or inverters. Sharp edges, unsupported spans, ponding areas and locations accessible to vermin or birds all need attention.

Use a cable management method suited to the roof type and cable route. Solar-rated clips, appropriate ties and properly supported conduit help prevent sagging and abrasion. Avoid leaving cable loops on the roof where water, debris and heat can accumulate. A neat route is not only better for presentation - it reduces the chance of insulation damage over the operating life of the array.

Where cable enters metal enclosures, conduit or roof penetrations, use correctly sized fittings and edge protection. A quality DC cable will not compensate for a poorly protected entry point.

Match the cable to genuine connector terminals

The connector and cable must be treated as one system. MC4-style connectors may look interchangeable, but connector body dimensions, contact design, cable sealing range and approved mating arrangements vary between manufacturers and product families.

Before ordering, check the connector’s accepted conductor cross-section and outside cable diameter range. A 6 mm² conductor may fit the contact barrel, yet the overall cable diameter may not seal correctly in a particular gland. Conversely, forcing an oversized cable into a connector can damage the seal or strain the termination.

Use the specified crimping tool and die set for the connector system. A poor crimp creates resistance, heat and a future fault location, regardless of how good the cable is. The same applies to mixing non-genuine or incompatible connector components. On a large array, the cost saving is small beside the cost of fault-finding, replacement labour and lost generation.

For crews using genuine MC4 or MC4-EVO 2 products, confirm the manufacturer’s approved cable sizes, stripping dimensions, crimp profile and mating requirements before the first termination. Keep connector caps in place until final assembly and protect terminated leads from contamination during installation.

Do not use general-purpose cable as a substitute

General-purpose building cable, automotive cable and ordinary flexible cable are not substitutes for solar DC cable on an exposed PV array. They may lack the required UV resistance, temperature performance, DC voltage rating or double insulation. Even if they appear acceptable on day one, premature sheath deterioration and insulation failure can turn a low-cost substitution into a warranty and compliance problem.

Likewise, do not select cable by conductor size alone. Two cables both labelled 6 mm² can differ in voltage rating, insulation material, external diameter, temperature rating, flexibility and suitability for connector glands. Read the full specification, especially when replacing an existing cable or matching a nominated design.

A practical ordering check for solar crews

Before placing the cable order, confirm the maximum DC system voltage, calculated circuit current, route length, installation method and required voltage-drop outcome. Then check the cable’s solar rating, conductor size, outer diameter and connector compatibility. Finally, allow for realistic wastage, polarity identification, spare length at equipment and the pack or reel quantity that best suits the job schedule.

For repeat work, standardising on proven cable sizes and genuine compatible connectors can reduce procurement errors and speed up vehicle replenishment. It also makes it easier for crews to carry the correct clips, glands, conduit fittings and crimp tooling for the work they actually install.

Solar Products Supply customers buying for multiple jobs should weigh reel size and carton quantities against site demand, freight and stockholding. A lower per-metre price only helps if the cable is the correct specification and will be used within the normal workflow.

The right PV cable is the one that remains correctly rated from module lead to inverter termination, not the one that simply gets the array connected on the day. Confirm the design, match every component, and the cable run becomes one less item to revisit after commissioning.