AS/NZS 3008.1.1 has a 2025 edition. AmpSize does not hold a copy of it. The tool cites the 2017 editions, and every number on this page comes from those. This page states which table each result reads, so a reader who holds the 2025 edition knows where to look.
The inputs
A three-phase submain on a cable ladder.
- Phases: 3, supply 400 V
- Design current: 100 A
- Run length: 40 m
- Installation method: unenclosed, cables touching
- Conductor: copper, XLPE, multicore
- Protective device: curve C, 100 A
- External impedance Ze: 0.1 Ω
- Ambient temperature: 30 °C, one circuit
The tables the tool reads
Cl 3.4 of AS/NZS 3000:2018 sets the selection rule. Current ratings come from Tables 4 to 21 of AS/NZS 3008.1.2:2017. Derating factors come from Tables 22 and 25 to 29 of the same document. Voltage drop uses Cl 4.5 with Tables 30 to 35. Maximum Zs comes from Table 8.1 of AS/NZS 3000:2018, and the earth conductor size from Table 5.1.
AS/NZS 3008.1.1 is the companion part used in Australia. The tool does not read it. Its 2025 edition is not held here, so this page quotes no value and no table number from it.
The steps
The route applies no derating. The ambient factor is 1 and the grouping factor is 1. The soil factor and the depth factor are also 1. The total derating factor is 1.
The required tabulated current is therefore 100 A. The tool tests each standard size against that figure and against every other check.
The smallest size that passes is 25 mm². The engine names its source as Table 13 of AS/NZS 3008.1.2:2017.
The result
- Conductor size: 25 mm²
- Derated capacity: 124 A
- Voltage drop: 1.51 %
- Device rating: 100 A
- Earth conductor: 6 mm²
- Earth fault loop impedance: 0.29 Ω
Capacity sets the size here. The 124 A capacity covers the 100 A device. The drop of 1.51 % sits inside the 5 % limit. Ze of 0.1 Ω is a site value, not a tool output. A higher Ze pushes Zs up and can force a larger conductor on the same load.
What a 2025 data set would change
Each line of a result names the table that produced it. That is the part a new edition moves. A 2025 data set replaces the tabulated ratings, and the tool reruns the same selection against the new numbers. The selected size can stay at 25 mm² or move.
This page does not say which way it moves. The 2025 edition is not held, so any direction of change stated here would be a guess. Treat every rating above as a 2017 value.
Two habits carry through the edition change. Record the edition beside the result in a cable schedule. A size on its own does not say which data produced it. Re-run the design when the tool cites a new edition, rather than carrying the old size forward.
A reader who holds the 2025 edition can compare it against the tables named above by hand. The result page lists a table reference on every step for that purpose.
This page is a design aid. Verify every value against the current edition of the standard.