Working learn pages
The ideas behind a real job: maximum demand, loop impedance and cable selection tables.
- 4 min readAS/NZS 3008.1.1:2025: what the AU part coversWhat AS/NZS 3008.1.1:2025 covers, a.c. to 0.6/1 kV and d.c. to 1500 V at 40 °C air and 25 °C soil, how its sections run, and where the d.c. tables are.
- 3 min readIB ≤ IN ≤ IZ: the overload rule on a 32 A circuitThe overload rule is IB ≤ IN ≤ IZ. A grouped 32 A circuit fails on 6 mm² and passes on 10 mm², with an IZ of 37.6 A. Why the order matters.
- 4 min readIEC 60364 and the Wiring RulesIEC 60364 is the international series that AS/NZS 3000 stays aligned with. See how its parts are numbered, what TN-C-S, TT and IT mean, and where MEN fits.
- 5 min readLoop 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.
- 4 min readMaximum 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.
- 5 min readRCD types and where they are requiredType AC, A, F and B, what each one detects, and the clauses that place them. The fault path behind them, worked on a 20 A circuit over 25 m.
- 4 min readShort-circuit withstand and the k factorThe adiabatic check in plain terms: prospective fault current, clearing time and k, worked on 25 mm² copper XLPE at 10 kA for 0.1 s.
Calculators these guides use
- Cable size calculatorFind the smallest cable size that passes each check.
- DC cable size calculatorSize a d.c. cable up to 1500 V for current and voltage drop.
- Cable fault rating calculatorCheck that a conductor can withstand the fault current.
- Earth fault loop impedance calculatorCheck earth fault loop impedance against the maximum Zs.
- Maximum demand calculatorEstimate maximum demand for domestic or non-domestic loads.
- Three phase power calculatorConvert between power, current, voltage and power factor.
- RCD selection calculatorCheck if an RCD is required and test the trip time.
- Transformer calculatorCalculate transformer full load current and impedance.