Spas or hot tubs are large outdoor water-containing installations that are not drained after use. Wiring a hot tub is a challenging task even for someone well acquainted with home wiring, as these installations are hard-wired separately and cannot share supply with other objects or appliances. The blog presents a look into the types of cables used for these installations.

Copper vs. Aluminum in Hot Tubs

Hot tubes used copper stranded wire at all times. Aluminum is not recommended for hot tubes because it can corrode in hot tub water. Of course, not all types of water in hot tub are created equal, and using filtered water with an adequate Ph may help prevent corrosion. Still, using copper wire is an optimal long-term strategy. The wires should always be stranded as it is a suitable solution for pulling and installations.

Outdoor Spa Wiring and the National Electric Code

Wiring for the hot tube is regulated by article 680 of NEC, together with wiring for swimming pools, fountains, and other types of outdoor installations. According to it:

• The cord cannot exceed 3 ft in length, so all the distancing has to be planned accordingly.
• All water installations should not be placed within 10 ft of communication cables.
• Underground wiring should be placed in rigid metal conduit, intermediate metal conduit, or PVC conduit.
• The Hot tub has to be protected with ground protection.

Common Types Of Cables Used in Hot Tubs

THHN/THWN Wire

THHN/THWN is, by far, the most popular choice of cables for wiring a 220V hot tub. THHN/THWN wires for hot tube wiring are placed in conduit as the conduit is a requirement for most outdoor installations in the United States, and THHN is not a direct burial cable. Due to the specifications of the outdoor installations, you should always use the cable with the double THHN/THWN rating, as it is required due to the environmental challenges of outdoor applications. THHN/THWN wires are optimal because outdoor hot tun requires green insulated ground according to the National Electrical Code. Nylon insulation also performs well in specific hot tub conditions.

SWA Steel Wire Armored Cables

SWA cables are a common recommendation for hot tubs and spas. This is the option that requires no conduit, as steel armor provides the necessary protection for outdoor and underground applications. The cable is rated for direct burial.

UF-B Wire, Romex Are Not Used

While UF-B might sound like a possible choice for hot tubs because it is a popular cable for outdoor installations, it should not be used. Direct burial cable for outdoor water constructions is prohibited by most jurisdictions within the United States. UF-B cable does not have an insulated ground, and its bare copper ground is actually dangerous to use in these conditions.

Nm-B Romex is only used for part of the run of the hot tub wiring because it is not permitted for outdoor conduit as a strictly indoor cable. The only way in which NM-B Romex can be used for hot tub wiring is by using it indoors only, combined with THHN/THWN outdoors.

Sizing of Hot Tub Wiring

The size of the wires for your hot tub depends on the circuit, length of the run, manufacturer of the jacuzzi, and other characteristics. In all cases, the sizes for jacuzzi wiring is between 6 AWG and 12 AWG. Anything smaller than 12 AWG is too small for the hot tub wiring, and spa control box terminals do not allow gauges heavier than 6 AWG, which explains this bracket.

Sizing down, a common practice for many electrical installations to save money is not safe for hot tub wiring. Never size down hot tub wiring due to the risk of injury, electrocution, or electrical fire. Always use the correct wire size. 

The amperage range for hot tubs is anywhere between 30 to 60 Amps, but 50 Amps is the most common one, followed by 60 Amps. 

• 50 Amps Hot Tubs use 6 or 8 AWG wires
• 60 Amp Hot Tubs use 6 AWG wires
• 30 Amp Hot Tubs use 10 AWG or 12 AWG wires
• 40 Amp Hot Tubs use 10 AWG or 8 AWG wires

NNC sells high-quality THHN/THWN wire for hot tubs at excellent prices.