AS/NZS Earthing
Australia uses a Multiple Earthed Neutral system rather than a purely separate earth conductor scheme. Here is what that means for solar and general installations.
Australia and New Zealand use what's called a Multiple Earthed Neutral (MEN) system — functionally equivalent to what IEC terminology calls TN-C-S. Understanding this system is the foundation for getting earthing right under AS/NZS 3000.
The supply neutral is earthed at the distribution transformer, at points along the distribution line, and again at the customer's main switchboard — the MEN link. This means the neutral and earth conductors share a common reference in the upstream network, but remain electrically separate once inside the customer's own installation past that link.
| Component | Earthing requirement |
|---|---|
| Every metal enclosure, chassis, and exposed conductive part | Bonded to the main earth bar via a dedicated protective earth conductor |
| Solar panel frames | Bonded to the mounting rail, which is itself bonded to structure earth |
| Inverter chassis | Earthed independently of the DC circuit's own internal reference |
Most residential inverters are transformerless, meaning the DC and AC sides share an internal reference through the inverter's own circuitry, monitored by the inverter's built-in ground fault detection. Adding an external earth bond on the DC positive or negative conductor — something well-intentioned installers sometimes do thinking it adds safety — actually defeats that internal ground fault detection and can create an earth loop that lets fault current flow through panel frames instead of being cleanly detected and cleared.
Like PEC and the NEC, AS/NZS specifies minimum earth conductor sizes via a lookup table keyed to the active conductor's size — not a flat percentage or ratio. Smaller active conductors need a proportionally larger earth conductor relative to their own size than very large active conductors do.
Look up the correct minimum size for your active conductor in the AS/NZS Earthing calculator.