Foundation learn pages
The ideas a reader needs before the first calculation: current, volt drop and the MEN system.
- 4 min readConduit fill and installation methodsHow the conduit space factor works, what the fill percent means against the 40 percent limit, and how the install method names on site map to the 3008 columns.
- 5 min readCurrent-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.
- 3 min readMEN system: multiple earthed neutral explainedMEN means multiple earthed neutral. In NZ, earth and neutral join at the main switchboard. A fault on a 32 A C curve circuit then draws 343.8 A and clears.
- 4 min readVoltage 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.
Calculators these guides use
- Conduit fill calculatorCheck that a cable bundle fits in a conduit.
- Cable size calculatorFind the smallest cable size that passes each check.
- Earth fault loop impedance calculatorCheck earth fault loop impedance against the maximum Zs.
- Cable fault rating calculatorCheck that a conductor can withstand the fault current.
- Voltage drop calculatorCalculate voltage drop on a cable run and check the limit.
- Voltage rise calculatorCalculate voltage rise for embedded generation or PV.