Learn
One idea per page, in plain words, with the clause numbers that carry it. Each page names the calculators that apply the idea. For worked examples with numbers, read the guides.
Foundation
3- FoundationCurrent-carrying capacity and deratingWhy one cable size has many ratings. Install method, ambient, grouping, soil and depth, with a 25 A circuit that needs 10 mm² once the factors apply.Cable Size
- FoundationThe MEN system: earth and neutral at the boardWhy the neutral and the earth are joined at the main switchboard in New Zealand, what the MEN link, the main earthing conductor and the electrode each do.Loop ImpedanceCable SizeFault Rating
- FoundationVoltage drop basicsOhm's law on a cable, the mV/A·m shortcut, the percent limit and the maximum length, worked on a 25 A run over 35 m of 4 mm² copper.Voltage DropVoltage RiseCable Size
Working
3- WorkingIB, IN and IZ: matching a breaker to a cableThe three currents that decide whether a circuit breaker protects its cable, why the order matters, and a worked 32 A circuit that shows the rule being applied.Cable SizeFault RatingLoop Impedance
- WorkingLoop impedance and disconnection timeZe, R1+R2, Zs and Ia, and the two disconnection times, worked on a 32 A curve C circuit over 30 m that returns 0.79 Ω against a 0.96 Ω limit.Loop ImpedanceCable Size
- WorkingMaximum demand and diversityWhy consumer mains are smaller than the sum of the loads. The four methods of Cl 2.2.2, the Table C1 groups, and a house that lands on 70.18 A.Maximum DemandThree Phase Power