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Solar PV Earthing & Earth Conductor Size Calculator (AS/NZS)

Size the earth conductor and module-frame bonding for an Australian residential PV array per AS/NZS 5033:2021 and AS/NZS 3000 Table 5.1. Free copper / aluminium lookup.

Solar PV Earthing / EGC Size Calculator

Minimum earth conductor
6 mm²
Code reference: AS/NZS 3000 Tab. 5.1 + AS/NZS 5033
Terminal torque
2.3 N·m
Module frame bonding jumper: 6 mm²
Notes: AS/NZS 5033:2021 § 5.3 plus AS/NZS 3000 Table 5.1. Use listed earth lugs (e.g. WEEB-Lug-6.7) on every frame and continuous earth back to the main switchboard MEN bar.

How to use this calculator

Enter the active conductor cross-section of your PV DC string in mm², select copper or aluminium, and the calculator returns the minimum earth conductor size per AS/NZS 3000 Table 5.1 (referenced from AS/NZS 5033:2021 § 5.3). The same value applies to the bonding jumper between module frames and the rack-to-MEN earth conductor.

Inputs:

  1. Active conductor cross-section (mm²) — the DC string conductor area. A typical Australian 6.6 kW or 10 kW residential rooftop install uses 6 mm² PV1-F or H1Z2Z2-K solar cable. Larger 13 kW or 15 kW systems may step up to 10 mm² for VD on long roof-to-inverter runs.
  2. DC overcurrent protection (A) — the touch-safe DC fuse in the array isolator. Used for the lug torque guidance.
  3. Earth conductor material — copper for nearly every CEC-accredited install. Aluminium is permitted at 16 mm² and larger but rarely used due to corrosion concerns at outdoor terminations.
  4. Mechanically protected run — if the earth is in conduit or duct, minimum cross-section drops to 2.5 mm². Unprotected runs require 4 mm² minimum.

How the math works (AS/NZS 3000 Table 5.1)

Table 5.1 sizes the earth conductor from the active cross-section:

S (active) ≤ 16 mm²   → Earth = S (same as active)
16 < S     ≤ 35 mm²   → Earth = 16 mm²
S          > 35 mm²   → Earth = S / 2

Aluminium earth conductors are uprated by approximately 1.5× to match copper conductivity. CEC PV install guidelines add a 6 mm² minimum for arrays even when the table would allow smaller.

Worked example. A 6.6 kW Perth rooftop array has two strings of 10 modules at 11 A Imp each, into a single-MPPT 5 kW inverter. DC active conductors are 6 mm² H1Z2Z2-K (rated 70 A free air / 41 A in conduit). Table 5.1 gives Earth = 6 mm² copper. CEC minimum is also 6 mm². The 6 mm² green/yellow earth conductor runs alongside the DC pair through the roof, into the inverter, and on to the MEN bar at the main switchboard.

If the array uses 10 mm² actives for a long 30 m roof-to-inverter run (VD upsize), Table 5.1 still gives 10 mm² earth (because 10 ≤ 16 mm²). The continuity test from farthest module frame to MEN bar should read ≤ 1.0 Ω.

AS/NZS 5033:2021 earthing requirements

AS/NZS 5033:2021 is the PV-specific installation standard. The earthing clauses you actually use:

  • § 5.3.1 — every exposed conductive part of the PV system bonded via a protective earth conductor.
  • § 5.3.2 — earth conductor sized from AS/NZS 3000 Table 5.1 (active cross-section based).
  • § 5.3.3 — minimum 6 mm² copper from PV rack to main earthing terminal.
  • § 5.3.4 — no separate auxiliary earth electrode for the PV array.
  • § 5.4 — DC functional earthing rules (different from protective earthing — only applies to transformer-isolated inverters, which are now rare).

CEC accreditation audits specifically check § 5.3.3 (the 6 mm² minimum) and the < 1.0 Ω continuity test result. Failing either is grounds for STC rebate clawback under the CER’s PV inspection program.

Module-frame bonding hardware in Australia

CEC-accredited installers use one of three approaches:

  1. WEEB-Lug-6.7 or AS-Earthing-Pin (Wiley Electronics / Clenergy) — stainless toothed washers that bite through the anodising. Cheapest and most common at $0.50-$0.80 per module wholesale. Compatibility matrix on the rack manufacturer’s website (Clenergy, Sunlock, K2, Schletter).
  2. Integrated earthing rail — Clenergy PV-Earth-IRail, Schletter EcoFoot 2+ with FixZ pins, IronRidge XR1000 (imported via BayWa). The rail itself provides the UL 2703 / IEC 61730 listed grounding path.
  3. Discrete M6 stainless earth lugs and bare 6 mm² copper jumper — old-school but still acceptable for retrofits on legacy frames without listed bonding clips.

All three are acceptable under AS/NZS 5033. The CEC Approved Solar Retailer requirements add that the bonding hardware must be on the published compatibility list of the module manufacturer (Trina Vertex S, JinkoSolar Tiger Neo, REC Alpha Pure-R, Q-CELLS Q.PEAK DUO ML-G11 all publish compatibility tables).

When voltage drop forces an earth upsize

AS/NZS 3000 keeps domestic VD ≤ 3% on lighting and 5% on power circuits. CEC PV practice limits DC VD to 1% from string to inverter and AC VD to 2% from inverter to main switchboard. On a long 30+ m roof-to-inverter run, the actives often jump from 6 mm² to 10 mm² for VD. Under Table 5.1 the earth conductor follows — 6 mm² becomes 10 mm² to stay at full active cross-section.

Use the solar panel voltage calculator to check VD before sizing the earth.

Common Australian inspection findings

The five most-common earthing faults flagged by CEC accreditation audits and CER PV inspection program reports:

  1. Earth conductor under-sized (4 mm² used instead of 6 mm² minimum per AS/NZS 5033 § 5.3.3).
  2. Module-frame bonding hardware not listed for the specific frame profile.
  3. No bonding between separate rail sections joined by sliding joints.
  4. M6 earth lug installed without a toothed washer biting the anodising — passes a visual but fails continuity test at > 5 Ω.
  5. Earth conductor terminated under a non-UV-rated grommet — degrades within 5 years of summer roof temperatures.

A pre-energisation continuity test from the farthest module frame to the MEN bar catches all five — should read ≤ 1.0 Ω before energising the AC isolator.

Stand-alone (off-grid) and battery-coupled systems

Battery-coupled and stand-alone systems add AS/NZS 4509 and AS/NZS 5139 requirements on top of AS/NZS 5033:

  • DC bus earthing must be functional (not protective) — typically a single midpoint reference to earth via a 100 mA-class fuse.
  • Battery enclosure bonded to PV earth via the same earth conductor.
  • Lithium battery installations under AS/NZS 5139 require an emergency-stop button on the AC side that also disconnects the DC bus.

The 6 mm² minimum and < 1.0 Ω continuity rules still apply. The bonded chain extends from module frame → rack → DC combiner → inverter → battery enclosure → AC switchboard → MEN bar.

Sources

Frequently asked questions

What size earth conductor do I need for an Australian rooftop solar PV install?
Per AS/NZS 5033:2021 Section 5.3 plus AS/NZS 3000:2018 Table 5.1, the protective earth conductor is sized from the active conductor cross-section. For a typical Australian 6.6 kW or 10 kW rooftop string with 6 mm² active conductors the earth conductor is also 6 mm² copper. For 10 mm² actives the earth is 10 mm². Above 16 mm² active, the earth drops to 16 mm²; above 35 mm², it's half the active. Clean Energy Council (CEC) accredited installers also impose a 6 mm² minimum for any PV array regardless of the table result.
Does the earth conductor need to be upsized for long cable runs?
AS/NZS 5033 doesn't impose a voltage-drop upsize on the earth conductor. If you uprate the active conductor for VD (typical on long roof-to-inverter runs above 25 m), the adiabatic equation in AS/NZS 3000 clause 5.3.3.1.2 still has to be satisfied — running the earth at the upsized active cross-section is the practical answer. CEC's installation guidelines recommend matching earth to active cross-section to avoid the calculation altogether.
How do I bond solar panel frames in Australia?
AS/NZS 5033:2021 requires every module frame and rack to be bonded back to the main earthing terminal of the building via a continuous earth conductor. Use WEEB-Lug-6.7 stainless toothed washers (or equivalent listed for the specific frame profile), Clenergy AS-Earthing-Pin integrated rail clips, or M6 stainless earth lugs with toothed washers and a bare 6 mm² copper jumper. Continuity test must read ≤ 1.0 Ω from the farthest module frame to the main switchboard MEN bar.
Do I need a separate earth electrode at the PV array?
Not on a typical roof-mounted residential array under MEN earthing. AS/NZS 5033:2021 clause 5.3.4 explicitly states no separate auxiliary earth electrode is required for the PV array — the earth conductor runs back to the existing main earthing terminal at the switchboard. Ground-mount arrays on detached structures more than 50 m from the main switchboard may require a sub-board with its own earth electrode under AS/NZS 3000 § 5.5.
What torque should I use on solar earthing lugs in Australia?
Follow the value stamped on the lug or in the manufacturer's instructions. Typical figures for residential PV: WEEB-Lug-6.7 is 5 N·m on the 6 mm² slot, Clenergy AS-EAR-LUG is 6 N·m, ILSCO GBL-4DBT (imported but commonly used) is 5.6 N·m. Use a calibrated torque screwdriver — finger-tight will fail the < 1 Ω continuity test within 12 months due to anodising creep.
What's the difference between earthing and bonding in an Australian PV install?
Earthing connects exposed conductive parts (module frames, inverter chassis, racks, metallic conduit) to the MEN bar at the main switchboard so a fault drives enough current through the protective device to disconnect. Bonding is supplementary equipotential connection between separately-earthed metalwork (e.g. PV rack to a nearby steel chimney flue) under AS/NZS 3000 § 5.6 to maintain equal potential during a lightning strike or earth fault. CEC compliance and the AS/NZS 5033 audit both check the earth path; bonding is a designer judgement call for arrays mounted near other metallic services.

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