Jacuzzi Premium, Sundance , Vita, Keys Backyard and many more tubs only use 3 wires. In the case of a 3 wire system you would not use the White Neutral wire you would put a wire nut or electrical tape on that wire to keep it from shorting to power or ground. Some codes will require you to use a GFCI breaker even though the Neutral part of the breaker will not be used. I don't understand why they require that because the GFCI will not act any different than a regular breaker in the case of a short. These 3 wire systems are call dedicated 240V systems meaning all of the components in the system are 240V including the board transformer and all pumps or blowers. Installing a 120V component in this system is a no no because you have no safety system to keep Voltage out of the water in case something goes wrong. An Example would be you replaced the Circulation pump with a 120V version and wired the neutral side to the ground bar. The pump will run and run correctly although if there was a short to ground inside of the Circulation pump it would put 120 Volts in the water and not trip the breaker unless it was pulling 50 Amps. These pumps only pull 1 amp so in this scenario you could create a Dangerous Situation so never put 120V components in a 3 wire system!! Thanks for your time!! The Spa Guy
