Although a length of 1.5mm2 will carry 15A, if it was of any great length, it would overheat because of voltage drop.
Doubt that. According to the formulae of the European harmonised standards 1,5mm2 is good for around 12m on a 16A circuit regarding the voltage drop. Prior to the hrarmonised standards Germany used to disregard voltage drop at all and fused any length of 1,5mm2 with 16A... Austria was a lot more conservative on that. 1,5 always was max. 10, later 12A here (and still is if using fuses or older circuit breakers with H, L or U trip characteristics).
Welcome to the boards you're our first member from Italy!
