Earthing and Bonding
Size earthing, main earth and bonding conductors.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the earthing tool do?
The tool reads the protective earthing conductor size for the largest active conductor, and the main earthing conductor size for the consumer mains. It applies the 4 mm² minimum and the 120 mm² maximum, reports the bonding size, and can check the size by calculation.
Which table gives the earthing conductor size?
AS/NZS 3000:2018 Table 5.1. The tool reads the copper active column or the aluminium active column. The main earthing conductor rule comes from Clause 5.3.3.2. The bonding sizes come from Clause 5.6.3.2.
How does the calculation option work?
It applies Equation 5.1 of Clause 5.3.3.1.3. The area is the square root of the fault current squared multiplied by the disconnection time, divided by K. The result is rounded up to the next standard size. The equation applies from 0.1 s to 5 s.
Which K value should I use?
Clause 5.3.3.1.3 gives 136 for PVC insulated copper that is not laid up with other conductors, and 170 for bare copper. Where the earthing conductor is laid up with other conductors, use the k factor from AS/NZS 3008.1.2 Table 52 instead.
What size is the MEN connection?
The tool sizes the main earthing conductor from the consumer mains active size. A copper main earthing conductor is not less than 4 mm² and need not be greater than 120 mm². Aluminium active conductors below 16 mm² are not tabulated.