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500. 2 DefinitionsCombustible Dust. Dust particles that are 500 microns or smaller (material passing a U.S. No. 35 Standard Sieve as defined in ASTM E 11-09, Standard Specification for Wire Cloth and Sieves for Testing Purposes) and present a fire or explosion hazard when dispersed and ignited in air.Informational Note: See ASTM E 1226–12a, Standard Test Method for Explosibility of Dust Clouds, or ISO 6184-1, Explosion protection systems — Part 1: Determination of explosion indices of combustible dusts in air, for procedures for determining the explosibility of dusts.

Class 1 Locations501.10 Wiring Methods

(A) Class I, Division 1. (1) General. In Class I, Division 1

locations, the wiring methods in (a) through ( e) shall be permitted.

(e) Optical fiber cable Types OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, and OFC shall be permitted to be installed in raceways in accordance with 501.10(A). These optical fiber cables shall be sealed in accordance with 501.15.


(A) Class I, Division 1. (2) Flexible Connections. Where

necessary to employ flexible connections, as at motor terminals, the following shall be permitted:

(1) Flexible fittings listed for the location, or

(2) Flexible cord in accordance with the provisions of 501.140, terminated with cord connectors listed for the location, or


(A) Class I, Division 1. (2) Flexible Connections – (cont.) (3) In industrial establishments with

restricted public access, where the conditions of maintenance and supervision ensure that only qualified persons service the installation, for applications limited to 600 volts, nominal, or less, and where protected from damage by location or a suitable guard, listed Type TC-ER-HL cable with an overall jacket and a separate equipment grounding conductor(s) in accordance with 250.122 that is terminated with fittings listed for the location

Class 1 Locations501.15 Sealing and

Drainage (C) Class I, Divisions 1 and 2. (6) Conductor or Optical Fiber

Fill. The cross-sectional area of the conductors or optical fiber tubes (metallic or nonmetallic) permitted in a seal shall not exceed 25 percent of the cross-sectional area of a rigid metal conduit of the same trade size unless the seal is specifically identified for a higher percentage of fill.

Class 1 Locations 501.30 Grounding and Bonding,

Class I, Divisions 1 and 2Regardless of the voltage of the electrical system, wiring and equipment in Class I, Division 1 and 2 locations shall be grounded as specified in Article 250 and in accordance with the requirements of 501.30(A) and (B).

Class II Locations 502.10 Wiring Methods (A) Class II, Division 1. (1) General. In Class II, Division 1

locations, the wiring methods in (1) through (4) shall be permitted

(4) Optical fiber cables Types OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, and OFC shall be permitted to be installed in raceways in accordance with 502.10(A). Optical fiber cables shall be sealed in accordance with 502.15.d:

Class II Locations 502.30 Grounding and Bonding,

Class II, Divisions 1 and 2Regardless of the voltage of the electrical system, wiring and equipment in Class II, Division 1 and 2 locations shall be grounded as specified in Article 250 and in accordance with the requirements of 502.30(A) and (B).

Intrinsically Safe Systems

504.10 Equipment Installation (C) Enclosures. General-purpose

enclosures shall be permitted for intrinsically safe apparatus and associated apparatus unless otherwise specified in the manufacturer’s documentation.

Motor Fuel Dispensing Facilities

514.3 Classification of Locations (C) Motor Fuel Dispensing Stations in

Boatyards and Marinas. (1) General. Electrical wiring and

equipment located at or serving motor fuel dispensing locations shall be installed on the side of the wharf, pier, or dock opposite from the liquid piping system.

Informational Note: For additional information, see NFPA 303-2011, Fire Protection Standard for Marinas and Boatyards, and NFPA 30A-2012, Motor Fuel Dispensing Facilities and Repair Garages.


514.3 Classification of Locations (C) Motor Fuel Dispensing Stations in

Boatyards and Marinas – (cont.) (2) Classification of Class I, Division 1

and 2 Areas. The following criteria shall be used for the purposes of applying Table 514.3(B)(1) and Table 514.3(B)(2) to motor fuel dispensing equipment on floating or fixed piers, wharfs, or docks.


514.3 Classification of Locations (D) Closed Construction. Where the

construction of floating docks, piers, or wharfs is closed so that there is no space between the bottom of the dock, pier, or wharf and the water, as in the case of concrete-enclosed expanded foam or similar construction, and the construction includes integral service boxes with supply chases, the following shall apply:


514.3 Classification of Locations (1) The space above the surface of the

floating dock, pier, or wharf shall be a Class I, Division 2 location with distances as specified in Table 514.3(B)(1)(1) for dispenser and outdoor locations.

(2) Spaces below the surface of the floating dock, pier, or wharf that have areas or enclosures, such as tubs, voids, pits, vaults, boxes, depressions, fuel piping chases, or similar spaces, where flammable liquid or vapor can accumulate shall be a Class I, Division 1 location.


514.3 Classification of Locations Exception No. 1: Dock, pier, or wharf sections

that do not support fuel dispensers and abut, but are located 6.0 m (20 ft) or more from, dock sections that support a fuel dispenser(s) shall be permitted to be Class I, Division 2 locations where documented air space is provided between dock sections to allow flammable liquids or vapors to dissipate without traveling to such dock sections. The documentation shall comply with 500.4(A).

Exception No. 2: Dock, pier, or wharf sections that do not support fuel dispensers and do not directly abut sections that support fuel dispensers shall be permitted to be unclassified where documented air space is provided and where flammable liquids or vapors cannot travel to such dock sections. The documentation shall comply with 500.4(A).


514.3 Classification of Locations (E) Open Construction. Where the

construction of piers, wharfs, or docks is open, as in the case of decks built on stringers supported by pilings, floats, pontoons, or similar construct ion, the following shall apply:

(1) The area 450 mm (18 in.) above the surface of the dock, pier, or wharf and extending 6.0 m (20 ft) horizontally in all directions from the outside edge of the dispenser and down to the water level shall be a Class 1, Division 2 location.

(2) Enclosures such as tubs, voids, pits, vaults, boxes, depressions, piping chases, or similar spaces where flammable liquids or vapors can accumulate within 6.0 m (20 ft) of the dispenser shall be a Class I, Division 1 location.

ARTICLE 516 Spray Application, Dipping, Coating, and Printing Processes Using Flammable or

Combustible Materials 516.2 Definitions Flash-Off Area. An open or enclosed area after

a spray application process where vapors are released due to exposure to ambient air or a heated atmosphere. [33:3.3.1.1]

Limited Finishing Workstation. An apparatus that is capable of confining the vapors, mists, residues, dusts, or deposits that are generated by a spray application process and that meets the requirements of Section 14.3 of NFPA 33, Standard for Spray Application Using Flammable or Combustible Materials, but does not meet the requirements of a spray booth or spray room, as herein defined. [33:3.3.15.1]


Combustible Materials 516.2 Definitions – (cont.) Resin Application Area. Any area in which

polyester resins or gelcoats are spray applied. [33:3.3.1.2]

Spray Area. Any fully enclosed, partly enclosed, or unenclosed area in which ignitible quantities of flammable or combustible vapors, mists, residues, dusts, or deposits are present due to the operation of spray processes, including (1) any area in the direct path of a spray application process; (2) the interior of a spray booth or spray room or limited finishing workstation, as herein defined; (3) the interior of any exhaust plenum, eliminator section, or scrubber section; (4) the interior of any exhaust duct or exhaust stack leading from a spray application process;


Combustible Materials 516.2 Definitions – (cont.) (5) the interior of any air recirculation

filter house or enclosure, including secondary recirculation particulate filters; (6) any solvent concentrator (pollution abatement) unit or solvent recovery (distillation) unit. The following are not considered to be a part of the spray area: (1) fresh air make-up units; (2) air supply ducts and air supply plenums; (3) recirculation air supply ducts downstream of secondary filters; (4) exhaust ducts from solvent concentrateur (pollution abattement) units. [33:3.3.2.3]


Combustible Materials 516.2 Definitions – (cont.) Spray Area – (cont.)(5) the interior of any air recirculation filter house or enclosure, including secondary recirculation particulate filters; (6) any solvent concentrator (pollution abatement) unit or solvent recovery (distillation) unit. The following are not considered to be a part of the spray area: (1) fresh air make-up units; (2) air supply ducts and air supply plenums; (3) recirculation air supply ducts downstream of secondary filters; (4) exhaust ducts from solvent concentrator (pollution abatement) units. [33:3.3.2.3]


Combustible Materials 516.2 Definitions Spray Booth. A power-ventilated

enclosure for a spray application operation or process that confines and limits the escape of the material being sprayed, including vapors, mists, dusts, and residues that are produced by the spraying operation and conducts or directs these materials to an exhaust system. [33:3.3.14]


Combustible Materials 516.2 Definitions Spray Room. A power-ventilated fully

enclosed room used exclusively for open spraying of flammable or combustible materials. A spray room is a purposefully enclosed room built for spray/coating/dipping applications provided with dedicated ventilation supply and exhaust. Normally the room is configured to house the item to be painted, providing reasonable access around the item/process. Depending on the size of the item being painted, such rooms may actually be the entire building or the major portion thereof. [33:3.3.15]


Combustible Materials 516.2 Definitions Unenclosed Spray Area. Any spray

area that is not confined by a limited finishing workstation, spray booth, or spray room, as herein defined. [33:3.3.2.3.2]

516. 3 Classification of Locations (A) Zone Classification of Locations.

(1) For the purposes of this article, the zone system of electrical area classification shall be applied as follows:a. The inside of open or closed containers or vessels shall be considered a Class I, Zone 0 location.b. A Class I, Division 1 location shall be permitted to be alternatively classified as a Class I, Zone 1 location. c. A Class I, Division 2 location shall be permitted to be alternatively classified as a Class I, Zone 2 location.d. A Class II, Division 1 location shall be permitted to be alternatively classified as a Zone 21 location.e. A Class II, Division 2 location shall be permitted to be alternatively classified as a Zone 22 location. [33:6.2.2]

516. 3 Classification of Locations

(cont.)(2) For the purposes of electrical area classification, the division system and the zone system shall not be intermixed for any given source of release. [33:6.2.3](3) In instances of areas within the same facility classified separately, Class I, Zone 2 locations shall be permitted to abut, but not overlap, Class I, Division 2 locations. Class I, Zone 0 or Zone 1 locations shall not abut Class I, Division 1 or Division 2 locations. [33:6.2.4]


(cont.)(4) Open flames, spark-producing equipment or processes, and equipment whose exposed surfaces exceed the autoignition temperature of the material being sprayed shall not be located in a spray area or in any surrounding area that is classified as Division 2, Zone 2, or Zone 22.Exception: This requirement shall not apply to drying, curing, or fusing apparatus. [33:6.2.5]


(cont.)(5) Any utilization equipment or apparatus that is capable of producing sparks or particles of hot metal and that is located above or adjacent to either the spray area or the surrounding Division 2, Zone 2, or Zone 22 areas shall be of the totally enclosed type or shall be constructed to prevent the escape of sparks or particles of hot metal. [33:6.2.6]

Health Care Facilities517.2 Definitions

Life Safety Branch. A system of feeders and branch circuits supplying power for lighting, receptacles, and equipment essential for life safety that is automatically connected to alternate power sources by one or more transfer switches during interruption of the normal power source. [99:3.3.94]

Health Care Facilities517.2 Definitions –

(cont.) Patient Care Space. Space within a health care

facility wherein patients are intended to be examined or treated.

Basic Care Space. Space in which failure of equipment or a system is not likely t o cause injury to the patients or caregivers but may cause patient discomfort.

General Care Space. Space in which failure of equipment or a system is likely to cause minor injury to patients or caregivers.

Critical Care Space. Space in which failure of equipment or a system is likely to cause major injury or death to patients or caregivers.


(cont.) Support Space. Space in which failure of

equipment or a system is not likely to have a physical impact on patients or caregivers.

Informational Note No. 1: The governing body of the facility designates patient care space in accordance with the type of patient care anticipated and with the definitions of the area classification. Business offices, corridors, lounges, day rooms, dining rooms, or similar areas typically are not classified as patient care space.Informational Note No. 2: Basic care space is typically a location where basic medical or dental care, treatment, or examinations are performed. Examples include, but are not limited to, examination or treatment rooms in clinics, medical and dental offices, nursing homes, and limited care facilities.


(cont.) Informational Note No. 3: General care space includes areas such as patient bedrooms, examining rooms, treatment rooms, clinics, and similar areas where the patient may come into contact with electromedical devices or ordinary appliances such as a nurse call system, electric beds, examining lamps, telephones, and entertainment devices.

Informational Note No. 4: Critical care space includes special care units, intensive care units, coronary care units, angiography laboratories, cardiac catheterization laboratories, delivery rooms, operating rooms, and similar areas in which are patients are intended to be subjected to invasive procedures and are connected to line-operated, electromedical devices.

Informational Note No. 5: Spaces where a procedure is performed that subjects patients or staff to wet conditions are considered as wet procedure areas. Wet conditions include standing fluids on the floor or drenching of the work area. Routine housekeeping procedures and incidental spillage of liquids do not define wet procedure areas. It is the responsibility of the governing body of the health care facility to designate the wet procedure areas.


(cont.) Patient Care Vicinity. A space,

within a location intended for the examination and treatment of patients, extending 1.8 m (6 ft) beyond the normal location of the patient bed, chair, table, treadmill, or other device that supports the patient during examination and treatment and extending vertically to 2.3 m (7 ft 6 in.) above the floor. [99:3.3.139]


(cont.) Wet Procedure Location. The area in a

patient care space where a procedure is performed that is normally subject to wet conditions while patients are present, including standing fluids on the floor or drenching of the work area, where either such condition is intimate to the patient or staff.

Informational Note: Routine housekeeping procedures and incidental spillage of liquids do not define a wet procedure location.

Further Information Wet procedure locations may also include

such areas as hydrotherapy areas, dialysis laboratories, and certain wet laboratories at the discretion of the governing body of the facility. The definition excludes areas such as lavatories or bathrooms within a health care facility. For infection control purposes, many patient and treatment areas have a sink for hand washing, which also is not a wet procedure location.

Health Care Facilities517.19(C) Operating Room

Receptacles (1) Minimum Number and Supply.

Each operating room shall be provided with a minimum of 36 receptacles, at least 12 of which shall be connected to eit her of the following:

(1) The normal system branch circuit required in 517.19(A)

(2) A critical branch circuit supplied by a different transfer switch than the other receptacles at the same location

Health Care Facilities517.19(C) Operating Room

Receptacles

(2) Receptacle Requirements. The receptacles required in (517.19)(C)(1) shall be permitted to be of the single or duplex types or a combination of both. All receptacles shall be listed hospital grade and so identified. The grounding terminal of each receptacle shall be connected to the reference grounding point by means of an insulated copper equipment grounding conductor.

ARTICLE 520Theaters, Audience Areas of Motion Picture and Television Studios, Performance Areas, and Similar Locations

520.2 Definitions Stage Equipment. Equipment at any

location on the premises integral to the stage production including, but not limited to, equipment for lighting, audio, special effects, rigging, motion control, projection, or video.

520.2 Definitions – (cont.)

Stage Lighting Hoist. A motorized lifting

device that contains a mounting position for one or more luminaires, with wiring devices for connection of luminaires to branchcircuits, and integral flexible cablesto allow the luminairesto travel over thelifting range of thehoist while energized.

520.2 Definitions – (cont.)

Stage Switchboard. A switchboard, panelboard, or rack containing dimmers or relays with associated overcurrent protective devices, or overcurrent protective devices alone, used primarily to feed stage equipment.

II. Fixed Stage Switchboards

520.21 General Fixed stage switchboards shall comply with

520.21(1) through (4): (1) Fixed stage switchboards shall be listed. (2) Fixed stage switchboards shall be readily

accessible but shall not be required to be located on or adjacent to the stage. Multiple fixed stage switchboards shall be permitted at different locations.

(3) A fixed stage switchboard shall contain overcurrent protective devices for all branch circuits supplied by that switchboard.

(4) A fixed stage switchboard shall be permitted to supply both stage and non-stage equipment.

III. Fixed Stage Equipment Other Than

Switchboards 520.40 Stage Lighting HoistsWhere a stage lighting hoist is listed as a complete assembly and contains an integral cable-handling system and cable to connect a moving wiring device to a fixed junction box for connection to permanent wiring, the extra-hard usage requirement of 520.44(C)(1) shall not apply.

ARTICLE 640Audio Signal Processing,

Amplification, and Reproduction

Equipment

640.1 Scope (B) Not Covered. This article does not

cover the installation and wiring of fire and burglary alarm signaling devices.

680.22 Lighting, Receptacles, and Equipment

(B) Luminaires, Lighting Outlets, and Ceiling-Suspended (Paddle)

Fans. (6) Low-Voltage Luminaires. Listed low-voltage luminaires not requiring grounding, not exceeding the low-voltage contact limit, and supplied by listed transformers or power supplies that comply with 680.23(A)(2) shall be permitted to be located less than 1.5 m (5 ft) from the inside walls of the pool.

680.26 Equipotential Bonding

(C) Pool Water. Where none of the bonded parts is in direct connection with the pool water, the pool water shall be in direct contact with an approved corrosion-resistant conductive surface that exposes not less than 5800 mm2 (9 in.2) of surface area to the pool water at all times. The conductive surface shall be located where it is not exposed to physical damage or dislodgement during usual pool activities, and it shall be bonded in accordance with 680.26(B).

Solar Photovoltaic (PV ) Systems

690.2 Definitions DC-to-DC Converter. A device installed

in the PV source circuit or PV output circuit that can provide an output dc voltage and current at a higher or lower value than the input dc voltage and current.


690.2 Definitions Direct-Current

(dc) Combiner. A device used in the PV source and PV output circuits to combine two or more dc circuit inputs and provide one dc circuit output.


690.2 Definitions Multimode

Inverter. Equipment having the capabilities of both the utility-interactive inverter and the stand-alone inverter.

IV. Wiring Methods690.31 Methods

Permitted (B) Identification and Grouping. PV

source circuits and PV output circuits shall not be contained in the same raceway, cable tray, cable, outlet box, junction box, or similar fitting as conductors, feeders, branch circuits of other non-PV systems, or inverter output circuits, unless the conductors of the different systems are separated by a partition. PV system conductors shall be identified and grouped as required by 690.31(B)(1) through (4). The means of identification shall be permitted by separate color coding, marking tape, tagging, or other approved means.


Permitted (B) Identification and Grouping

(cont.)

(1) PV Source Circuits. PV source circuits shall be identified at all points of termination, connection, and splices.

(2) PV Output and Inverter Circuits. The conductors of PV output circuits and inverter input and output circuits shall be identified at all points of termination, connection, and splices.



(cont.) (3) Conductors of Multiple Systems.

Where the conductors of more than one PV system occupy the same junction box, raceway, or equipment, the conductors of each system shall be identified at all termination, connection, and splice points.

Exception: Where the identification of the conductors is evident by spacing or arrangement, further identification shall not be required.



(cont.) (4) Grouping. Where the conductors of

more than one PV system occupy the same junction box or raceway with a removable cover(s), the ac and dc conductors of each system shall be grouped separately by cable ties or similar means at least once and shall then be grouped at intervals not to exceed 1.8 m (6 ft).

Exception: The requirement for grouping shall not apply if the circuit enters from a cable or raceway unique to the circuit that makes the grouping obvious.

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Engineering

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