What Size Wire for a Hot Tub?

A hot tub typically uses a 50A / 240V circuit, which calls for #6 copper (or #4 aluminum) conductors and a #10 copper equipment ground per NEC Table 250.122. That is the 60C column, the NEC default for NM-B cable and terminations 100A and under; on 75C-rated terminals in conduit you may use #8 copper. Portable spas and hot tubs are commonly on a 50A GFCI circuit, but the nameplate rules: some are 40A and some 60A. NEC Article 680 requires GFCI protection and a disconnect within sight and at least 5 feet from the tub.

A 50A double-pole breaker. The #6 copper conductors are matched to that 50A rating, and it must be a GFCI breaker (or GFCI protection ahead of the appliance). Always confirm against the appliance nameplate, which lists the exact minimum circuit and maximum breaker.

Yes. Current NEC requires GFCI protection for this appliance (NEC 680.44 and 210.8). Use a GFCI breaker or a GFCI device ahead of it. For a hot tub or spa, a disconnect within sight and at least 5 feet away is also required (NEC 680).

Yes. For the 50A circuit, aluminum needs #4 (versus #6 copper) at the 75C column. Aluminum is common on larger circuits and services to save cost; apply antioxidant to the terminations, torque to the listed spec, and remember aluminum drops slightly more voltage on long runs.