Swimming Pool Wiring Methods

Jeffrey Sargent

Since the 1962 edition, the NEC®  has contained requirements aimed at making an electrically safe environment in swimming pools, an area where the users are highly vulnerable to electric shock because they are wet and not well insulated. Ensuring that swimming pool circuits, and particularly the all important equipment grounding conductors, remain uninterrupted and undamaged is the objective of the more stringent wiring method requirements in the 2008 NEC’s Article 680. The rules of this article have the singular purpose of establishing and maintaining a shock-free environment for swimmers immersed in the pool water. The shock hazard may not necessarily be at an electrocution level, but lower levels of current experienced by swimmers have led to loss of muscular control and accidental drowning.

Special Equipment

In looking at the wiring method requirements for swimming pools, let’s first start with the arrangement of the NEC as stated in 90.3. That section specifies the requirements of Chapters 1 through 4 apply generally, and that Chapters 5, 6, and 7 address occupancies, equipment, and conditions that necessitate special requirements to address electrical hazards unique to that occupancy, equipment, or condition. The rules for safe electrical installations in and around swimming pools are found in Chapter 6 (specifically Article 680), where  the special equipment includes the circulating pump motors, underwater luminaires, electrically operated pool covers, and luminaires and receptacles in the pool area. The pool itself is also subject to special requirements for equipotential bonding.  

Swimming pools and the other bodies of water covered by Article 680 present a challenge because of  the enhanced level of electric shock exposure inherent in a wet environment, particularly where users are immersed in a body of water in which electrical equipment is intentionally installed. The requirements of Article 680 apply to swimming pools at all occupancies, including those installed at a one-family dwellings, municipal facilities, institutional facilities, health clubs, and health care facilities.

The requirements of Article 680 provide for enhanced electric shock protection in this wet environment, through one or more of the following means:

• GFCI protection and low-voltage equipment
• Double-insulated equipment
• Insulation and isolation
• Equipotenial bonding
• Physical separation and restricted locations for equipment
• Robust physical protection requirements for circuit conductors

This discussion will concentrate on the wiring methods required for circuits supplying equipment associated with permanently installed swimming pools, probably the most common application of the Article 680 requirements and the focus of the original Article 680 in the 1962 NEC. Article 680 has evolved since then, and requirements covering other bodies of water including spas and hot tubs, fountains, storable swimming pools, therapeutic pools, and hydromassage bathtubs have been added. Also, Article 682, covering other “natural and manmade bodies of water” that are not encompassed by the scope of Article 680, was first included in the 2005 NEC. Article 682 contains requirements that embrace the safety concepts of GFCI protection, equipment grounding and bonding, equipotential bonding, and equipment location relative to the datum plane, (a concept found in Article 680 and also Article 555, Marinas and Boatyards).  

Permanently Installed Swimming Pools

Because Article 680 covers more than just swimming pools, it is important to understand what is encompassed by the NEC definition of “permanently installed swimming pool.” Section 680.2 in the 2008 NEC contains definitions unique to this article.

There are clear distinctions made in these definitions between “permanently installed” and “storable” pools. One of the most important distinguishing features is the difference implied by the titles of the terms. A permanently installed pool is located in or on one site and is not manufactured or built as a structure that can be easily relocated. A storable pool, as implied by its name, is specifically manufactured to facilitate relocation and/or storage. The water depth of 42 inches (established based on swimming pool industry standards) is also a defining benchmark, however this depth is not applicable in the case of inflatable pools or aboveground pools that are constructed with nonmetallic molded polymeric walls.  Regardless of depth, these “on or above the ground” swimming pools are considered to be “storable swimming, wading, or immersion” pools.

One other term that bears discussion is the inclusion of “immersion” in the titles and within the text of these definitions. The rationale for this change in the 2008 NEC explained that bodies of water used for religious ceremony were not clearly covered by the definitions in previous editions, since these bodies of water were not used for swimming or wading yet the users were immersed and exposed to similar hazards as swimmers and waders. Code-Making Panel 17 agreed with the proposal’s substantiation and extended the coverage of Article 680 requirements to those swimming pools used in conjunction with religious or other ceremonies in which users are immersed in the pool.

Once the body of water has been clearly defined as a permanently installed swimming pool, the requirements of Parts I (General) and II (Permanently Installed Pools) are applicable to the installation. Let’s look at several of the sets of rules on wiring methods for specific equipment and circuits.

Branch Circuits to Circulating Pump Motors

The general rule of 680.21(A)(1) is that the branch-circuit conductors be installed from the branch-circuit overcurrent protective device to the motor using one of the following wiring methods:

• Rigid metal conduit (RMC)
• Intermediate metal conduit (IMC)
• Rigid polyvinyl chloride conduit (PVC)
• Reinforced thermosetting resin conduit (RTRC)
• Type MC Cable listed for the location (MC listed for the location implies that it be identified for specific environmental conditions inherent to swimming pool installations such as wet location or direct burial. It is not required to be specifically listed for swimming pool locations.)

This section also specifies that an insulated wire-type copper equipment grounding conductor be installed with the circuit conductors and that the equipment grounding conductor is not to be smaller than 12 AWG. This requirement of Article 680 modifies the general requirement from 250.122(A) that permits the equipment grounding conductor to not be sized larger than the circuit conductors. For swimming pools, the ungrounded and grounded circuit conductors may be 14 AWG, however the equipment grounding conductor cannot be smaller than a 12 AWG copper conductor. This provision has been part of Article 680 since its inception (originally applied just to underwater luminaire circuits) and recognizes that the environment in the vicinity of a swimming pool can be extremely corrosive and that the minimum 12 AWG copper conductor requirement provides for a larger, more resilient grounding conductor.

Section 680.21(A) also contains limited provisions allowing for wiring methods other than the five identified above. These limited provisions are as follows:

• Electrical metallic tubing (EMT): On or within a building or structure
• Liquidtight flexible metal conduit (LFMC) and liguidtight flexible nonmetallic conduit (LFNMC): For flexible connections adjacent to circulating pump motors
• Flexible Cord: The cord must be used as part of a cord-and plug-connected motor. Section 680.7 also applies to this type of installation and the cord must not be longer than 3 feet and the equipment grounding conductor shall be not less than 12 AWG copper. The cord also has to be suitable for the environmental conditions associated with the motor location (i.e. wet location and sunlight exposure).
• One-family dwellings and associated accessory buildings: Within the interior of these structures any wiring method of Chapter 3 that is permitted to be used in these structures can be employed. The equipment grounding conductor is required to be a wire-type and not smaller than 12 AWG copper. However, it is not required to be insulated. This limited provision allows for an uninsulated equipment grounding conductor that is contained within a sheathed or jacketed cable. Once the wiring method leaves the interior of the structure, the general requirement of 680.21(A)(1) applies.
• Double-insulated circulating pump motors: Where this type of listed swimming pool pump motor is used, 680.21(B) permits the wiring method for the entire branch to be anyChapter 3 wiring method that is identified for the location. This would allow, for example, Type UF cable to be the wiring method installed underground to the outdoor pump motor location. It should be noted, though, that if the double insulated motor is replaced at some point with a standard pump motor (not listed as double insulated), the UF cable no longer complies with the general wiring method requirements. In addition, this provision is amended to the general wiring method requirement of 680.21(A)(1) if the sole bonding connection between the 680.26 equipotential bonding grid and the electrical grounding system occurs at the pump motor branch circuit.

Branch Circuits to Underwater Luminaires

Underwater luminaires for permanently installed swimming pools come in four different construction types. As defined in 680.2, they are: Dry-Niche Luminaire, No-Niche Luminair,. Through-Wall Lighting Assembly, and Wet-Niche Luminaire. (The Section 680.2 definitions can be found at the end of this article.)

Of these four construction types, the wet-niche luminaire is the most commonly installed. Section 680.23 provides general requirements for underwater luminaires and requirements specific to the four different types. for the general wiring methods permitted from the branch-circuit overcurrent protective device to the field wiring enclosure of a dry-niche luminaire or from the junction box or transformer enclosure connected to the forming shell of a wet-niche luminaire or housing of a no-niche luminaire are  the following:

• Rigid metal conduit (RMC)
• Intermediate metal conduit (IMC)
• Liquidtight flexible nonmetallic conduit (LFMC)
• Rigid polyvinyl chloride conduit (PVC)
• Reinforced thermosetting resin conduit (RTRC)

As is the case for swimming pool pump motors, the requirement on equipment grounding conductors for underwater luminaires specifies that an insulated wire-type copper equipment grounding conductor be installed with the circuit conductors, and that the equipment grounding conductor is not to be smaller than 12 AWG regardless of the size of the ungrounded and grounded circuit conductors. Of course, 250.122 also applies to circuits larger than 20 amperes.

Section 680.23(F) also contains limited provisions allowing for wiring methods other than the five identified above. These limited provisions are as follows:

• Electrical metallic tubing (EMT): On or within a building or structure
• Type MC cable (MC), electrical nonmetallic tubing (ENT), or Type AC cable (AC): Within a building or structure
• Liquidtight flexible metal conduit (LFMC) or liquidtight flexible nonmetallic conduit (LFNMC): Permitted for connection to enclosures of transformers supplying underwater luminaires. For other than liquidtight flexible nonmetallic conduit, Type B (LFNMC-B) the length must not exceed 6 feet for any one length or exceed 10 feet in total length used.

For wet-niche luminaires, a junction box or a listed enclosure for a ground-fault circuit interrupter or underwater luminaire transformer must be installed between the point at which the branch circuit originates and the forming shell. This junction box or enclosure is required to be listed for swimming pool application and has to be installed and incorporate the construction features specified in 680.24. Section 680.23(B)(2) specifies that the wiring method between the junction box or enclosure and the forming shell be either rigid nonmetallic conduit, liquidtight flexible nonmetallic conduit, rigid metal conduit, or intermediate metal conduit.

Metal conduits used in this location are required to be constructed of brass or other corrosion-resistant metal. It is assumed that these conduits will contain the chlorinated water of the swimming pool, thus the enhanced requirement for resistance to corrosion.

Where the wiring method between the junction box or enclosure and the forming shell is rigid nonmetallic or flexible nonmetallic, an insulated copper equipment bonding jumper is required to be installed. This equipment bonding jumper is permitted to be solid or stranded. At the forming shell end of this conductor, encapsulation of the termination to the shell in a listed potting compound is required.

Unlike the case for the swimming pool pump motor, there are no provisions for these installations allowing an uninsulated equipment grounding conductor for underwater luminaires or the use of a nonmetallic sheathed cable such as Type NM or Type UF. Also, per 680.23(F)(3), conductors supplying an underwater luminaire and protected by a ground-fault circuit interrupter or connected to the secondary of an underwater luminaire transformer are not permitted to occupy the same raceway or enclosure with conductors not similarly protected.  There are limited provisions allowing for unprotected conductor to supply a feed-through type GFCI or for conductors mixed with unprotected conductors in a panelboard enclosure.

Meeting the Expectation

The old adage thatwater and electricity do not mix is certainly one to adhere to. However, there are, as in the case of swimming pools, applications where the operation of equipment requires an interface between water and electricity. Using the requirements of Article 680 has proven to be an approach that makes the swimmers’ safety the paramount concern, and the enhanced requirements for the wiring methods containing the circuit and grounding conductors for pool equipment is one important piece of the overall equation allowing water and electricity to be safely mixed. Most people do not think twice about diving into a pool containing one or more underwater electric luminaires, because their expectation is that the installation is electrically safe. Employing the requirements of Article 680 in designing, installing, and inspecting electrical installations associated with swimming pools goes a long way toward fulfilling that expectation.

Section 680.2 Definitions

Pool. Manufactured or field-constructed equipment designed to contain water on a permanent or semipermanent basis and used for swimming, wading, immersion, or therapeutic purposes.

Permanently Installed Swimming, Wading, Immersion, and Therapeutic Pools. Those that are constructed in the ground or partially in the ground, and all others capable of holding water in a depth greater than 1.0 m (42 in.), and all pools installed inside of a building, regardless of water depth, whether or not served by electrical circuits of any nature.

Storable Swimming, Wading, or Immersion Pool. Those that are constructed on or above the ground and are capable of holding water to a maximum depth of 1.0 m (42 in.), or a pool with nonmetallic, molded polymeric walls or inflatable fabric walls regardless of dimension.

Dry-Niche Luminaire. A luminaire intended for installation in the wall of a pool or fountain in a niche that is sealed against the entry of pool water.

No-Niche Luminaire. A luminaire intended for installation above or below the water without a niche.

Through-Wall Lighting Assembly. A lighting assembly intended for installation above grade, on or through the wall of a pool, consisting of two interconnected groups of components separated by the pool wall.

Wet-Niche Luminaire. A luminaire intended for installation in a forming shell mounted in a pool or fountain structure where the luminaire will be completely surrounded by water.

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