AS/NZS 3008 Table 13: Current Carrying Capacity

Table 13 of AS/NZS 3008.1.1:2017 provides the current-carrying capacity (in amperes) for multicore cables with thermoplastic and thermosetting insulation. It is the primary table used for sizing multicore cables in Australian and New Zealand electrical installations.

The table covers:

• Conductor materials: Copper and aluminium
• Insulation types: V-75 (75°C PVC), V-90 (90°C PVC), and X-90 (90°C XLPE)
• Cable sizes: 1 mm² through 630 mm²
• Installation methods: 29 configurations from Table 3, each mapped to a specific column in Table 13

All values are based on the AS/NZS 3008 reference conditions: 40°C ambient air temperature (higher than the 30°C used by BS 7671 and IEC 60364), single circuit, no contact with thermal insulation, and conductor loaded to its maximum operating temperature.

For single-core cables, use Table 14 instead. For flat thermoplastic sheathed cables (TPS), use Table 15.

Table 13 has multiple columns, each corresponding to specific installation methods from Table 3. Selecting the correct column is the critical first step:

The following table shows current-carrying capacity for copper conductors with V-90 (90°C PVC) insulation in multicore configuration. Values are at the 40°C reference ambient:

Note: These values are for the 40°C reference ambient. At 30°C ambient (common in many countries), a derating factor greater than 1.0 applies — see Table 22 — effectively increasing the cable’s usable capacity.

AS/NZS 3008 covers three main insulation types, each with different maximum conductor operating temperatures and therefore different current ratings:

While V-90 and X-90 both have a 90°C maximum temperature, XLPE has superior short-circuit withstand performance and better ageing characteristics. In practice, V-90 is the most common insulation type for general commercial and industrial installations in Australia, while X-90 (XLPE) is preferred for power distribution cables and heavy industrial applications.

V-75 cables are less common in new installations but are still encountered in older existing work. When assessing existing cables, always check the insulation type marking to use the correct column in Table 13.

AS/NZS 3008 provides three main current rating tables, each for a different cable configuration:

Single-core cables (Table 14) generally have higher current ratings than equivalent-sized multicore cables (Table 13) because single-core cables have less mutual heating between conductors. However, single-core cables require careful installation to avoid circulating currents in metallic enclosures.

Table 15 applies specifically to the flat thermoplastic sheathed (TPS) cables commonly used in Australian domestic wiring. These cables have unique flat construction and are typically clipped directly to timber framing inside walls and ceilings.

A worked example demonstrates how Table 13 is used in practice:

Design brief:
  Three-phase motor circuit, 45 A full-load current
  Multicore V-90 copper cable in perforated tray
  Ambient temperature: 45°C
  3 other circuits on the same tray

Step 1: Installation method → Table 3 = Column 13 (perforated tray)

Step 2: Derating factors
  Temperature: Table 22, 45°C for V-90 → Ct = 0.89
  Grouping: Table 25, 4 circuits on perf tray → Cg = 0.77
  Overall: 0.89 × 0.77 = 0.685

Step 3: Required tabulated rating
  It = 45 / 0.685 = 65.7 A

Step 4: Table 13, Column 13, V-90 copper
  6 mm² = 45 A  (too low)
  10 mm² = 62 A  (too low)
  16 mm² = 83 A  (65.7 ≤ 83 √)

Step 5: Verify voltage drop using Tables 30–42

Selected cable: 16 mm² 4-core V-90 copper