#cable-sizing
7 posts filed under this tag, newest first.
Cable size for large loads: when to run cables in parallel
Above 300 mm², a bigger cable size stops paying. When to run cables in parallel, the six rules for equal sharing, and the overload no breaker can see.
10 min read
Short-circuit withstand: the cable check everyone skips
A cable that passes current rating and volt drop can still fail under fault. The adiabatic check, the right k value, and why discrimination delays cost copper.
7 min read
Copper or aluminium: where aluminium stops being cheaper
Aluminium needs 1.6 times the cross-section for the same current — and still costs less per metre. The crossover, and the four places it goes wrong.
8 min read
How to read a cable datasheet without getting caught out
Reference conditions, two rating columns, mV/A/m versus ohms per km, one-second fault ratings and how to decode A2XFY — the fine print that decides the size.
7 min read
Cable derating factors: the complete table
Ambient, grouping and installation factors in one place, worked through — plus the four factors that are not in any table but still apply.
11 min read
Voltage drop limits: why lighting gets 3 % and power 5 %
What IS 732 actually permits, where the two limits come from, and why the same cable can pass for a motor and fail for a lighting board on the same site.
7 min read
How to size a cable correctly: the six-step sequence
Design current, derating, tabulated rating, breaker coordination, volt drop and short-circuit withstand — the full sequence, worked through for a 45 kW motor.
8 min read