40A wire size at 48V over 10 ft (copper)

Why this size

At 48V, voltage drop usually decides the conductor before ampacity does — the lower the voltage, the more the drop matters over distance. CircuitProof sizes to whichever constraint is stricter, then cites the code basis used. For this 10 ft run at 40A, the limiting factor is ampacity.

Aluminum runs about two AWG sizes larger than copper for the same load, and continuous loads add a 125% factor. Always confirm terminations and breaker ratings against the installed conductor.