Things You'll Need
Ground-fault circuit interrupters, or GFCI, are special outlets with circuit breakers in them installed at the point of use instead of in a breaker panel. These GFCI breakers monitor the amount of electricity flowing out of the outlet and returning to the outlet. If the GFCI detects a difference, the breaker trips and disconnects power to the outlet. This helps prevent shocks by quickly cutting the power in the event of a short circuit or other malfunction. It is essential to connect hot tubs to GFCI circuits because they have both water and electricity present. In the event of a wiring problem with the hot tub, the breaker interrupts the flow of electricity, helping to prevent injury or death.
Disconnect power to the hot tub circuit at the main breaker panel.
Remove the cover from the GFCI box by raising the lid, squeezing the sides of the box and pulling the lid straight out from the front of the box. Mount the box in a location that is protected from the weather and convenient to the hot tub. Use the included hardware to mount the panel to a wall or wooden post near the hot tub.
Remove two of the knockouts from the bottom of the GFCI box with a flat-head screwdriver. Feed the wire powering the hot tub through one of the knockout holes, into the GFCI box. Cut the wire to length, leaving enough slack to reach the terminals inside the box. Remove the outer insulation jacket from the wire. Use wire strippers to bare 1/2 an inch of each conductor.
Slide the end of the bare or green ground wire into an empty terminal on the grounding bar. Slide the white wire into a space on the neutral bar. Connect the red wire to the left terminal on the "Line in" side of the GFCI. Connect the black wire to the right terminal on the "Line in" side of the GFCI. Tighten the terminal screws securely.
Feed the wire from the hot tub control box through the knockout hole, into the GFCI box. Cut it to length, leaving slack for wiring the terminals. Strip the ends of the conductors.
Connect the green or bare wire to the grounding bar. Connect the white wire to the center terminal on the bottom of the GFCI. Slide the red wire into the bottom left terminal and the black wire into the bottom right terminal of the GFCI. Tighten the terminal screws.
Push the cover back into the front of the box and swing it down to close it. Turn on power to the hot tub at the main breaker panel.
For three-wire hot tubs, leave the bottom-center terminal on the GFCI empty.
Water and electricity are a lethal combination. If you're not comfortable working on electrical equipment, consider hiring a licensed electrician to perform the wiring.