NEC 517-590 — Special Occupancies (Washington)

NEC 517-590 — Special Occupancies (Washington Journeyman)

Learning Objectives

1.1 Article 517 — Vocabulary, Categories, and Bed Locations

Patient care space [517.2]. Any space of a health care facility wherein patients are intended to be examined or treated; waiting rooms and dining rooms do not qualify unless patients are examined or treated there.

Patient bed location. The location of a patient sleeping bed, or the bed or procedure table of a Category 1 space — a subset of a patient care space, not a synonym.

Patient care vicinity. 1.8 m (6 ft) beyond the normal location of the bed, chair, table, treadmill, or other supporting device, and 2.3 m (7 ft 6 in.) above the floor.

Anesthetizing location. Any space designated for the administration of any flammable or nonflammable inhalation anesthetic agent during examination or treatment, including for relative analgesia.

Essential electrical system. Ensures continuity of power to designated areas and functions upon loss of an on-site or off-site source: Type 1 has three branches (life safety, critical, equipment), Type 2 two (life safety, equipment).

Risk categories [517.7]. Category 1 failure is likely to cause major injury or death, Category 2 failure minor injury.

Bed locations [517.18]. Two branch circuits per bed location, one critical and one from the normal system, normal-system circuits from the same panelboard, no multiwire branch circuits, distinctive marking of critical-branch receptacles [517.18(A)]; nonlocking receptacles listed "hospital grade" with an insulated copper equipment grounding conductor to the reference grounding point [517.18(B)(2)].

1.2 Redundant Grounding in Patient Care Spaces (517.13)

Two paths, always. Wiring serving patient care spaces must comply with both 517.13(A) and 517.13(B); either path alone is a wrong answer.

Path 1 [517.13(A)]. An effective ground-fault current path through a metal raceway system or a cable with a metallic armor or sheath assembly, including metallic boxes, fittings, and enclosures, qualifying as an equipment grounding conductor under 250.118 and 250.109(A); nonmetallic cable, nonmetallic raceway, and bonding to a metal water pipe fail.

Path 2 [517.13(B)]. An insulated copper equipment grounding conductor, identified green along its entire length and run with the branch-circuit conductors in the 517.13(A) wiring method, connected to the grounding terminals of all receptacles other than isolated ground receptacles, to metal boxes and enclosures, and to non-current-carrying surfaces of fixed equipment likely to become energized at over 100 volts.

Sizing. Table 250.122, indexed to the overcurrent device ahead of the circuit: 12 AWG copper at 20 amperes, 10 AWG at 60 amperes, 8 AWG at 100 amperes, 6 AWG at 200 amperes, 4 AWG at 300 amperes. Table 250.66 sizes grounding electrode conductors, Table 310.16 ampacity, and Article 547 does not relax the Table 250.122 minimum.

Single-path exception and bonding. Luminaires more than 2.3 m (71/2 ft) above the floor and switches outside the patient care vicinity may use either path, and bonding jumpers or the metal faceplate mounting screw may make the device and box connections [517.13(B)].

1.3 Isolated Grounds, Wet Locations, and GFCI (517.16 to 517.21)

Isolated ground receptacles [517.16]. Prohibited inside a patient care vicinity [517.16(A)]; outside it, 517.16(B)(1) requires an insulated equipment grounding conductor installed per 250.146(D) in a wiring method described in 517.13(A), identified green with one or more yellow stripes under 517.16(B)(2), while the 517.13(B) conductor is green with no yellow stripes and must not land on isolated ground receptacles.

Wet procedure locations [517.20]. Receptacles and fixed equipment need special protection against electric shock: an isolated power system designed and installed per 517.160, or GFCI protection for personnel.

GFCI in Category 1 and Category 2 spaces [517.21]. Receptacles are not required in bathrooms or toilet rooms, but where installed in Category 2 patient bathrooms or toilet rooms they need GFCI per 210.8(B)(1), and GFCI is not required in Category 2 or Category 1 spaces where a basin, sink, or similar fixture is installed in the patient bed location.

Patient equipment grounding point [517.19(D)]. Where supplied, an equipment bonding jumper not smaller than 10 AWG connects the grounding terminals of all grounding-type receptacles to it. Article 517 sets no 1.5 m (5 ft) receptacle height rule and no blanket GFCI rule for patient care space receptacles.

1.4 Type 1 Essential Electrical System (517.29 to 517.35)

Applicability [517.29]. The Type 1 rules run from 517.29 through 517.35. Category 1 spaces shall be served by a Type 1 EES and shall not be served by a Type 2 EES; Type 1 may also serve Category 2, Category 3, and Category 4 spaces through three separate branches.

Sources and connection [517.30, 517.32(A)]. Two or more independent sources or sets of sources and sets of feeders, at least one on-site and sized to supply the entire EES; the life safety and critical branches must automatically restore all their specified functions within 10 seconds after interruption of power — not 24 hours, and with no generator-size threshold.

Life safety branch [517.33]. Limited to circuits essential to life safety, with no functions other than 517.33(A)(1) through 517.33(A)(7), which cover the illumination of means of egress, exit signs, alarm and alerting systems, and communications systems used for emergency instructions.

Critical branch [517.34]. Task illumination, fixed equipment, select receptacles, and select power circuits for patient care functions, including Category 1 spaces where deep sedation or general anesthesia is administered. General-use receptacles in patient care areas are not automatically on the EES.

Equipment branch [517.35]. Equipment in 517.35(A) is automatically restored at appropriate time-lag intervals after the life safety and critical branches are energized, and the arrangement must also provide for the 517.35(B) equipment; for an EES under 150 kVA, deletion of the time-lag intervals feature is permitted.

Delayed-automatic list [517.35(A)]. Central suction and compressed air systems serving medical and surgical functions; sump pumps and other equipment required for the safety of major apparatus, including controls and alarms; smoke control and stair pressurization systems; kitchen hood supply or exhaust systems required to operate during a fire in or under the hood; and supply, return, and exhaust ventilating systems for airborne infectious/isolation rooms, protective environment rooms, exhaust fans for laboratory fume hoods, nuclear medicine areas, ethylene oxide evacuation, and anesthetic evacuation, which may instead be placed on the critical branch where delayed-automatic connection is not appropriate [517.35(A)(6)].

Delayed-automatic or manual list [517.35(B)]. Heating equipment for operating, delivery, labor, recovery, intensive care, and coronary care spaces, nurseries, infection/isolation rooms, and emergency treatment rooms; automatically restored equipment includes the elevators selected to serve patient, surgical, obstetrical, and ground floors, surgical and obstetrical suite ventilation, hyperbaric and hypobaric facilities, and autoclaving equipment.

1.5 Type 2 Essential Electrical System (517.40 to 517.45)

Applicability [517.40(A)]. The requirements of 517.40(C) through 517.44 apply to Type 2 EESs, and a Type 2 system is permitted to serve Category 2, Category 3, and Category 4 spaces; it never serves a Category 1 space.

Freestanding nursing home exception [517.40(A)]. Those requirements shall not apply to freestanding buildings used as nursing homes and limited care facilities where admitting and discharge policies preclude the provision of care for any patient or resident who might need to be sustained by electrical life-support equipment; generator rating, Category 2 space count, and transfer-switch count are not the conditions.

Life-support patients [517.40(B), (C)]. Facilities that do admit such patients must comply with 517.29 through 517.35, the Type 1 rules, while facilities contiguous with, or on the same site as, a hospital may have their EESs supplied by the hospital.

Sources and branches [517.41 to 517.44]. Independent sources with one on-site source sized for the entire EES; one transfer switch may serve one or more branches where the continuous EES load is 150 kVA (120 kW) or less; the life safety branch is restored automatically within 10 seconds and limited to 517.43(A)(1) through 517.43(A)(7); equipment in 517.44(A) is restored at appropriate time-lag intervals after the life safety branch, and 517.44(C) equipment may be arranged for delayed-automatic or manual connection. Other health care facilities are covered by 517.45.

Memory aid. The informational note to 517.40 states that a Type 2 EES is comprised of the life safety branch and the equipment branch; there is no critical branch, emergency branch, or fire pump branch.

1.6 Assembly Occupancies and Theaters (518, 520)

Assembly threshold [518.1]. Except for occupancies covered by 520.1, Article 518 covers buildings or portions of buildings designed for the gathering together of 100 or more persons for purposes such as deliberation, worship, entertainment, eating, drinking, amusement, or awaiting transportation; the scope lists purposes, so any named activity must still clear the 100-person threshold.

Mixed buildings [518.4]. The article applies only to the assembly portion of a building containing other occupancies, and assembly use of a room or space by less than 100 persons in a building of other occupancy, incidental to it, is classified as part of the other occupancy; theatrical areas — projection booth or stage area, associated audience seating, and portable equipment and wiring that will not connect to permanently installed wiring — comply with Article 520, and ENT and rigid nonmetallic conduit are permitted in spaces with a finish rating [518.4(D)].

Strip lights [520.42]. Foot, border, proscenium, or portable strip lights and connector strips need insulation not less than 125°C (257°F), and the ampacity of those 125°C (257°F) conductors is treated as that of 60°C (140°F) conductors; drops from connector strips are 90°C (194°F) wire sized to the ampacity of 60°C (140°F) cords, with no more than 150 mm (6 in.) of conductor in the strip.

Stage cables [Table 520.44(C)(2)(1)]. For listed extra-hard usage cords and cables the 90°C (194°F) ampacity and the maximum OCPD rating are 28 amperes and 15 amperes at 14 AWG, 35 amperes and 20 amperes at 12 AWG, 47 amperes and 25 amperes at 10 AWG, and 65 amperes and 35 amperes at 8 AWG; ampacity and OCPD rating are different columns.

Load diversity [Table 520.44(C)(2)(2)]. Below 50 percent load diversity, more than three current-carrying conductors use 80 percent (4 to 6 conductors), 70 percent (7 to 24), 60 percent (25 to 42), or 50 percent (43 and above) of the table value, so ten current-carrying conductors take 70 percent.

1.7 Carnivals, Circuses, Fairs, and Similar Events (525)

Article 525 covers portable wiring and equipment for carnivals, circuses, fairs, and similar functions, including wiring in or on all structures, and governs wherever it differs from other articles [525.4(A)].

Generators and multiple sources [525.11, 525.12]. Portable, vehicle-mounted, and trailer-mounted generators comply with 250.34, and portable generators rated less than 15 kW comply with 445.20; where multiple services or separately derived systems supply portable structures separated by less than 3.7 m (12 ft), the equipment grounding conductors of all sources must be bonded together at the structures with a copper bonding conductor sized per Table 250.122 on the largest OCPD supplying them, but not smaller than 6 AWG.

Cord and cable rules [525.20]. Extra-hard usage listing, or hard usage where not subject to physical damage, and outdoors also listed for wet locations and sunlight resistant [525.20(A)]; single-conductor cable only in 2 AWG or larger [525.20(B)]; open conductors prohibited except as part of listed assemblies or festoon lighting [525.20(C)]; cords and cables continuous without splices or taps [525.20(D)]; no connectors in audience traffic paths or public areas unless guarded, and cord connectors not laid on the ground unless listed for wet locations [525.20(E)]; audience-accessible cords arranged to minimize tripping, optionally covered with nonconductive matting secured to the walkway [525.20(G)].

Rides, boxes, grounding [525.21, 525.23, 525.31]. Moving rides need a disconnecting means within sight of and within 1.8 m (6 ft) of the operator's station, readily accessible and lockable where accessible to unqualified persons; outdoor portable distribution boxes must be weatherproof with the bottom not less than 150 mm (6 in.) above the ground [525.23(A)], busbars rated not less than the OCPD supplying the box [525.23(B)], and receptacle overcurrent protection not exceeding the receptacle rating [525.23(C)]; the equipment grounding conductor connects to the grounded conductor at the service disconnecting means or the first disconnecting means supplied by the generator, which does not apply to portable generators used under the 445.20(A) Exception [525.31].

GFCI [525.24]. In addition to 210.8(B): all 125-volt, single-phase, 15- and 20-ampere non-locking-type receptacles used for disassembly and reassembly or readily accessible to the general public, and equipment readily accessible to the public on a 125-volt, single-phase, 15- or 20-ampere branch circuit; GFCI may be integral to the attachment plug or in the cord within 300 mm (12 in.) of it, and a 30-ampere receptacle is protected under the location rules of 210.8(B).

1.8 Motion Picture and Television Studios (530)

Supervision and generators [530.5, 530.43]. Portable distribution systems, generators, battery systems, and other portable power sources must be deployed, energized, and maintained under the supervision of qualified persons [530.5]; portable and vehicle-mounted generators must be located away from flammable materials with exhaust vented away from structures and areas where people congregate, and must not run without natural or provided ventilation [530.43].

Feeder protection [530.23]. Portable stage cables follow 240.5 [530.23(A)]; portable feeder cables in production areas using single-pole separable connectors must be protected by OCPDs set at not more than 400 percent of the cable ampacity listed in Table 400.5(A)(2), and the load on a single conductor must not exceed that ampacity [530.23(B)]; direct-current plugging boxes are limited to copper conductors and are not permitted on alternating-current systems [530.23(C)], and alternating-current distribution boxes must contain polarized, grounding-type receptacles and be listed [530.23(D)].

GFCI [530.44]. In addition to 210.8(B): 125-volt, single-phase, 15- and 20-ampere receptacles readily accessible to unqualified personnel and used for other than production equipment [530.44(A)(1)], and equipment other than production equipment readily accessible to unqualified personnel on such a branch circuit [530.44(A)(2)]; egress lighting shall not be protected by a GFCI [530.44(B)].

1.9 Agricultural Buildings (547)

Scope [547.1]. Article 547 covers installations in agricultural buildings — buildings used for the storage, confinement, or production of livestock or poultry, or for the storage or processing of agricultural products that produce dust or corrosive atmospheres [547.1(A)]. Installations comply with Chapters 1 through 4 as modified by Article 547 [547.5].

Equipotential planes [547.40, 547.44]. A distribution point is required where each building is served, and equipotential planes are installed as in 547.44(A) and bonded together per 547.44(C); the plane covers the area where livestock stands while accessing metal equipment that might become energized and is bonded to the electrical system with solid copper not smaller than 8 AWG, and "livestock" does not include poultry [547.44(B)].

1.10 Marinas, Boatyards, and Floating Buildings (555)

Transformers and bonding [555.7, 555.13]. Dry-type transformers of more than 1121/2 kVA cannot be installed in the marina area, and a transformer enclosure or metal barrier is required where a transformer is installed outdoors or where accessible to unqualified persons [555.7]; all metal parts of the electrical system and non-current-carrying metal parts of boats, hoists, and equipment must be bonded together and to the grounding electrode system, and a bonding conductor is not required to be larger than 8 AWG copper where it is not part of a circuit conductor [555.13].

Service equipment [555.15]. A service disconnecting means must be located within 762 mm (30 in.) of the point of entry and must be suitable for use as service equipment.

Ground-fault and GFCI protection [555.35]. Ground-fault protection of equipment, set to open at not more than 100 milliamperes (mA), is required on feeders and branch circuits [555.35(A)]; shore-power receptacles not exceeding 50 amperes need an automatic device opening at not more than 30 mA [555.35(C)(1)], personnel GFCI is required at other receptacles within the limits of 555.35(C)(2).

1.11 Temporary Installations (590)

General [590.4]. Temporary installations must comply with all applicable requirements of Chapters 1 through 4; receptacles must be of the grounding type [590.4(B)]; cords and cables must be supported at intervals not exceeding 3.0 m (10 ft) [590.4(E)].

Duration and removal [590.5]. Decorative lighting for public, community, or seasonal events is limited to 90 days [590.5(B)], removal is required immediately upon completion of the purpose [590.5(D)], and Article 590 sets no general 90-day removal limit and no maximum wiring length.

GFCI and ground-fault protection [590.6, 590.7, 590.8]. All 125-volt, single-phase, 15-, 20-, and 30-ampere receptacle outlets used by personnel must have GFCI protection, and 15- and 20-ampere outlets on portable generators rated up to 15 kW must be protected by GFCI integral to the generator or by a listed GFCI receptacle [590.7(A)]; an assured equipment grounding conductor program is an alternative where permitted [590.7(B)], and ground-fault protection is required for temporary feeder or branch circuits over 150 volts to ground [590.8].

Code Navigation

Numbering note: older keys in this chapter still cite numbers the 2026 edition has moved. The separate equipment grounding conductor rule of _547.9_ now sits in 547.27, the equipotential plane rule of _547.10_ now sits in 547.44, the time-of-installation rule of _590.3_ now sits in 590.5, and the ground-fault rule of 590.6 now sits in 590.7. The marina ground-fault rule older keys cite as _555.3_ is now split between 555.35(A), 555.35(C)(1), 555.35(C)(2), and 555.35(D).

Common Exam Traps

Practical Field Points

Chapter Summary

Special occupancies are ordinary wiring with added layers, and the layers are what the exam tests. Article 517 sets the vocabulary — patient care spaces, patient care vicinities measured 1.8 m (6 ft) out and 2.3 m (7 ft 6 in.) up, and patient bed locations that each need two branch circuits, one critical and one normal — then devotes 517.13 to its most tested rule: a metal raceway or metallic cable path plus a separate insulated copper equipment grounding conductor sized from Table 250.122, with isolated ground receptacles barred from the patient care vicinity by 517.16 and the protections of 517.20 and 517.21 reserved for wet procedure locations and Category 2 bathrooms.

Power continuity is sorted by system type. A Type 1 essential electrical system serves Category 1 spaces with three branches: life safety restored within 10 seconds under 517.32(A), critical under 517.34, and equipment under 517.35 with its delayed-automatic lists and its under-150 kVA exception. A Type 2 system serves Categories 2, 3, and 4 only, keeps the life safety and equipment branches, and disappears entirely for freestanding nursing homes that never admit residents who might need electrical life-support equipment.

The remaining articles reduce to thresholds and single values: Article 518 begins at 100 or more persons, 520.42 holds strip-light insulation at 125°C (257°F) while treating ampacity as 60°C (140°F), 525.12 bonds structures less than 3.7 m (12 ft) apart with not less than 6 AWG copper, 530.23 caps single-pole separable connector protection at 400 percent of Table 400.5(A)(2) ampacity, 547.44 bonds equipotential planes with solid copper not smaller than 8 AWG, 555.35 requires 100 milliamperes (mA) of ground-fault protection on marina feeders and branch circuits and 30 mA at shore-power receptacles, and Article 590 makes permanent-wiring rules, a 90-day holiday limit, and GFCI protection apply to wiring that is by definition temporary.