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How to Wire a Hot Tub Disconnect and Feeder

How-to Guide ServiceDelivery Updated Oct 28, 2026 ยท Electrical

Why this matters

A hot tub puts people in water next to a 240 V heater, a pump motor and a control board. Every rule that governs its circuit exists because of that combination. The usual failures on this job are not exotic: a disconnect mounted on the deck post two feet from the tub so the owner can reach it from the water, an EGC that is bare where the code wants it insulated, a GFCI breaker landed without its neutral so the tub's 120 V controls trip it, or conductors sized from a sales sheet instead of the tub's own nameplate. This card is the circuit from the panel to the tub: sizing, the spa disconnect, the raceway and the finish test. The equipotential bonding around the tub is 'Pool + Spa Electrical (NEC Article 680)'.

Safety first

De-energize, lock out and prove dead before any termination, at the panel and at the spa disconnect: CAT III or better meter, live-dead-live (proved on a known live source before and after, per NFPA 70E Article 120, 120.5 in the 2021 edition and renumbered in 2024; work practices at 29 CFR 1910.333(b)(2), and 29 CFR 1926.417 where the job is construction). Nobody is in the tub or touching its water while you work, and the tub is not energized with its cover off and people near it until the GFCI has been proved in the finish test.

Do not energize an empty tub. The heater element can burn out in seconds without water around it. Fill to the level the tub's instructions require before the first power-up.

The layout and where the disconnect goes

 PANEL        SPA DISCONNECT              TUB
 50A 2P       50A 2P GFCI breaker         equip bay
 L1 --------> line L1    load L1 -------> L1
 L2 --------> line L2    load L2 -------> L2
 N  --------> N bar <-- GFCI pigtail
                         load N --------> N
 EGC -------> EGC bar ------------------> EGC
   PVC, 65 ft             PVC + LFNC, 12 ft
              |<-- 6 ft horiz -->| inside wall
              disconnect within sight of tub

The disconnect rule. NEC 680.13 (2023 edition, as adopted by your jurisdiction) requires in substance a means to disconnect all ungrounded conductors to the tub's equipment that is readily accessible, within sight of the tub's equipment, and at least 5 ft horizontally from the inside wall of the tub unless a permanent barrier makes the reach path 5 ft or more. Measure the horizontal distance from the inside wall, not from the outside of the cabinet. The point is that someone in the water cannot reach it. Within sight means visible and not more than 50 ft away, per the NEC definition in Article 100.

GFCI. NEC 680.44 as adopted requires GFCI protection for the outlet supplying a spa or hot tub, with an exception for a listed self-contained unit with integral protection. The usual way is a spa disconnect enclosure with a two-pole GFCI breaker in it, which does both jobs in one box. GFCI here means the 5 mA personnel type.

Sizing from the nameplate

The tub's data plate and installation instructions decide the circuit. Size from them, not from the sales literature or the last tub you wired. A typical 240 V tub plate gives the voltage, phase, maximum load in amps, the required branch-circuit or GFCI breaker size, and whether the tub needs a neutral. A tub with 120 V controls or a 120 V pump needs the 4-wire circuit: L1, L2, neutral and an EGC. Reading MCA and MOCP off a plate in general is 'Reading an Appliance Nameplate for Circuit Sizing'.

The worked job. A six-person outdoor tub on a patio slab. Data plate: 240/120 V, 1 phase, 40 A maximum load, requires a 50 A GFCI circuit, 4-wire. The panel is in the attached garage.

  • Breaker: 50 A two-pole at the panel and a 50 A two-pole GFCI breaker in the spa disconnect, both as the plate requires. The 40 A load at 125 percent is 50 A, so the maker's 50 A circuit is consistent with treating the heater as a continuous load (see related: 'Continuous Load and the 125 Percent Rule').
  • Conductors: 8 AWG copper THWN, 50 A in the 75 C column of NEC Table 310.16, with every termination along the run rated 75 C (see related: 'The Termination Temperature Rule (110.14(C))'). 8 AWG NM would not work: NM is held to the 60 C column, where 8 AWG copper is 40 A.
  • EGC: NEC Table 250.122 at 50 A gives 10 AWG copper. Article 680 also sets a 12 AWG floor for the EGC on these circuits; 10 AWG is the larger and governs.
  • Voltage drop: 65 ft to the disconnect plus 12 ft to the tub is 77 ft one way. 8 AWG copper is about 0.778 ohm per 1,000 ft (Chapter 9 Table 8, stranded). At the plate's 40 A: 2 x 77 ft x 40 A x 0.778 / 1,000 = 4.8 V, which is 2.0 percent of 240 V. Acceptable; at three times the distance it would be worth upsizing to 6 AWG.
  • Raceway fill: three 8 AWG THWN at about 0.0366 sq in each plus one 10 AWG THWN at about 0.0211 sq in is 0.131 sq in (Chapter 9 Table 5). That sits well inside the 40 percent fill allowance for 3/4 in PVC in Chapter 9 Table 4, Schedule 40 or 80.

The steps

1. Set the disconnect location first. On this patio, the disconnect goes on the house wall 6 ft horizontally from the tub's nearest inside wall, facing it. That clears 5 ft with margin for the tub moving an inch at delivery, and stays in sight. Do it before conduit is cut, because every other measurement starts here. Skipped, the disconnect ends up wherever the conduit happened to come up.

2. Run the raceway with an insulated copper EGC. Article 680 (680.21 for the wiring methods carried into spas by 680.42, as adopted) wants the outdoor portion in a raceway such as PVC with an insulated copper EGC. Pull a green-insulated 10 AWG, never a bare one, and never count on the PVC for a ground path. Inside the house, 680.42(C) in substance permits ordinary Chapter 3 wiring methods if the EGC is copper, insulated or within the outer sheath, and not smaller than 12 AWG. On this job the whole run is THWN in conduit. Where it goes underground, the depth for PVC on a 240 V circuit comes from 'Underground Wiring Burial Depth Card'; the reduced 12 in residential column does not apply because that column is for 120 V circuits of 20 A or less.

3. Make up the panel end. L1 and L2 on the 50 A two-pole, the neutral on the neutral bar, the EGC on the ground bar (in a service panel these are bonded; in a subpanel they are separate, and the EGC never goes on the neutral bar).

4. Make up the spa disconnect. Incoming L1 and L2 to the GFCI breaker's line terminals. Incoming neutral to the disconnect's isolated neutral bar. The GFCI breaker's coiled neutral pigtail to that same bar. The tub's L1, L2 and neutral leave from the GFCI breaker's load terminals, so the tub's neutral current passes through the breaker's sensor. The EGC in and the EGC out both go on the enclosure's bonded EGC bar. The two failures to catch here are a tub neutral landed on the neutral bar instead of the breaker's load neutral, which makes the breaker see current leave and not return and trip as soon as a 120 V load runs, and a pigtail left coiled and unconnected, which leaves the GFCI's electronics without the reference many models need.

5. Run to the tub. Continue in PVC to near the tub, then the last few feet in liquidtight flexible nonmetallic conduit into the equipment bay, as 680.42(A) permits and the tub's instructions show. Land on the tub's terminal block per its diagram.

6. Torque every termination. Panel breaker, both sides of the GFCI breaker, the bars and the tub's block, to the values marked on each with a calibrated tool (NEC 110.14(D)).

7. Bonding. The tub's bonding lug and the equipotential bonding around it are a separate scope with their own rules; see 'Pool + Spa Electrical (NEC Article 680)'.

The finish test

The tub is filled, the covers on the disconnect and the tub's equipment bay are back on, and nobody is in the water.

  1. Restore. Stand to the side of the panel and of the disconnect as each breaker closes. The tub's controller should boot.
  2. Supply and neutral, without opening anything. The controller's display reads supply voltage: 242 V on this job. The neutral is proved by the tub's 120 V loads working: on this tub the light and the low-speed pump both run from 120 V, and both run. If either is dead with the 240 V heater working, suspect the neutral at the GFCI's load terminal first, with the circuit locked out again.
  3. The GFCI. Start the pump, press the GFCI breaker's test button. The breaker trips and the pump stops. Reset. A GFCI that does not trip on its own test button is replaced, not reset again.
  4. The heater. Call for heat and clamp each leg. In most spa disconnects the conductors sit behind the dead front, so clamping there is energized diagnostic work: CAT III or better clamp meter, the PPE your shop's NFPA 70E assessment calls for, only the jaw near the conductor. If the tub's controller reports current, read it there instead: the heater plus pump should read no more than the plate's 40 A. On this job, 34 A with the heater and the low-speed pump running.
  5. Tell the owner. The GFCI is tested monthly with its test button, and the disconnect is where the tub is shut off for service, not the panel.

What changes the answer

  • A 120 V plug-in tub. Some smaller tubs come with a cord and a GFCI on it, for a dedicated 20 A receptacle. Article 680 limits the cord length and the receptacle location; the 240 V layout above does not apply.
  • Not a single-family dwelling. A tub at a hotel, gym or multifamily common area also needs an emergency shutoff under NEC 680.41 as adopted, which the dwelling layout above does not show.

References

  • NFPA 70, National Electrical Code, 2023 edition (2020 where numbering moved) as adopted, local amendments checked: 110.14, 250.122, 310.16, 680.13, 680.21, 680.41, 680.42, 680.44, Chapter 9 Tables 4, 5 and 8
  • NFPA 70E, current edition, Article 120; 29 CFR 1910.333(b)(2); 29 CFR 1926.417 for construction work
  • See related: Pool + Spa Electrical (NEC Article 680)
  • See related: Reading an Appliance Nameplate for Circuit Sizing
  • Spa manufacturer's data plate and installation instructions

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