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How this is calculated#

The tool checks a cord or flexible cable on a construction site. It uses the length limit in AS/NZS 3012:2019 Table 1. The limit depends on the rated current, the conductor area, the use and the phases.

1. Length entered. You enter the length of the cord run. You can add the length of the PSOA supply lead, under Cl 2.6.10(b).
2. Length checked. The tool adds the two. It checks that total against Table 1.
3. Rated current and area. It reads the Table 1 row for your rated current and conductor area.
4. Use and phases. It picks the column: general or specific use, single or three phase.
5. Maximum length. It gives the Table 1 length. The inside-the-limit answer passes when the length checked is at or under it.
6. Total drop. The Table 1 length is based on a 5 % drop. The tool adds the drop already used upstream and gives the total at the equipment.

Worked example#

A 10 A single‑phase cord of 1.5 mm², 50 m long, for general use. The maximum length is 35 m. The 50 m run fails. A 2.5 mm² cord at 40 m passes, with a maximum of 60 m.

Limits#

• The 5 % drop is in addition to the drop the fixed installation already used. Enter the real upstream drop.
• A zero upstream drop is the default. Treat it as optimistic.
• The figures suit ordinary site power tools.
• The smallest flexible cord conductor is 1 mm². Every cord carries its own earth conductor.
• Cord extension sets use heavy duty sheathed cable (Cl 2.6.3).
• Do not use double adaptors or piggyback plug adaptors (Cl 2.6.6).

See also: Construction site supplies, AS/NZS 3012, Builder's pole house build supply, RCDs and cord lengths and the site supply tool.