(Design Current): The maximum demand or expected load current of the circuit. INcap I sub cap N
A compliant installation must satisfy the largest cable size determined by three distinct checks:
Disclaimer: This guide is for educational purposes. Always consult the full text of AS/NZS 3000:2018 and verify calculations with a licensed electrician or engineer. as3000 current-carrying capacity table
This is the current the circuit is intended to carry. For single-phase: $$I_b = \frac\textPower (Watts)240 \text Volts$$
(Nominal Current): The rating of the protective device (e.g., circuit breaker or fuse). IZcap I sub cap Z (Design Current): The maximum demand or expected load
When selecting a cable size, ask yourself:
Current-carrying capacity (or ampacity) is the maximum current a conductor can carry continuously without its insulation exceeding its rated temperature. This is the current the circuit is intended to carry
| Table | Purpose | | :--- | :--- | | | Free air ratings (overhead lines, open wiring – higher capacity) | | Table 15 | Single-core cables enclosed in conduit (derated vs. clipped direct) | | Table 16 | Multi-core cables in conduit | | Table 20 | XLPE (90°C) insulation – higher ratings than PVC | | Table 26 | Aluminium conductors (typically 0.8× copper rating for same size) |
Always consult the current edition of AS/NZS 3000 directly. This review is for educational guidance – local supply authority requirements may impose additional constraints (e.g., Western Australia’s “WA Amendment”). When in doubt, consult a practicing electrical engineer or licensed electrician.