The IET Wiring Regulations (BS 7671) categorize ratings based on how the cable is "clipped" or "buried." Here is how a 4mm² cable performs under different conditions:
However, if you run that same cable 100 meters, the drop becomes significant, and you may need to upgrade to a 6mm cable to compensate. 4mm cable amp rating 240v
(less common at this size): roughly 0.65–0.75× copper rating → ~16–24 A. The IET Wiring Regulations (BS 7671) categorize ratings
Your circuit breaker (MCB) must be rated lower than the cable's capacity to ensure the fuse blows before the cable melts. Typically, a 32A breaker is paired with 4mm² cable. the drop becomes significant
