Minimum earth conductor size (AS/NZS 3000 Table 5.1)
The minimum protective earthing conductor for a given active conductor size under AS/NZS 3000:2018 Table 5.1, from 1 mm² to 630 mm² copper.
AS/NZS 3000:2018 Table 5.1
Copper, per AS/NZS 3000 Table 5.1.
Minimum protective earth
AS/NZS 3000:2018 · Table 5.1
For an active of 16 mm². A larger earth is always acceptable.
How this is worked out
- Straight lookup of AS/NZS 3000:2018 Table 5.1 (minimum copper earthing conductor size) by active conductor size.
- Copper conductors only. The table gives a minimum: a larger earth is always acceptable, and a design may call for one.
- Table 5.1 sizes the protective earthing conductor; main earthing conductor and equipotential bonding sizes have their own clauses and are not covered.
Common questions
Why is the earth smaller than the active above 6 mm²?+
The earth only carries fault current for the time it takes the protective device to operate, so it can be smaller than the active once the active exceeds 6 mm². Below that, Table 5.1 keeps earth and active the same size.
Does this cover the earth in a twin & earth cable?+
Compare the earth size printed on the cable sheath (or measured) with the result here. Table 5.1 is the minimum regardless of how the cable was manufactured, so a flat cable whose earth is below the figure for its active is undersized for that circuit.
What if the earth I find is undersized?+
Record it as found. The circuit fails the earthing check and the report should say so with the Table 5.1 minimum beside the measured size.
Related guide
AS/NZS 3000 verification: the tests every installation needsThe mandatory verification tests AS/NZS 3000 requires before a new installation is energised — in order, dead before live — and what goes on the report.
Recording this test?
Field Efficient derives the Table 5.1 minimum from the active size you record on the board schedule and flags an undersized earth as you capture it.
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Indicative only. Verify against the current edition of the standard before relying on a result for design, certification or a compliance decision. This tool is not a substitute for the standard or for a licensed electrician's judgement.