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hall be operable when ice covered. Informational Note No. 1: The term raintight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 6, and 6P. The term rainproof is typically used in conjunction with Enclosure Types 3R and 3RX. The term watertight is typically used in conjun...

hall be operable when ice covered. Informational Note No. 1: The term raintight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 6, and 6P. The term rainproof is typically used in conjunction with Enclosure Types 3R and 3RX. The term watertight is typically used in conjunction with Enclosure Types 4, 4X, 6, and 6P. The term driptight is typically used in conjunction with Enclosure Types 2, 5, 12, 12K, and 13. The term dusttight is typically used in conjunction with Enclosure Types 3, 3S, 3SX, 3X, 4, 4X, 5, 6, 6P, 12, 12K, and 13. Informational Note No. 2: See ANSI/IEC 60529, Degrees of Protection Provided by Enclosures, for ingress protection (IP) ratings. Informational Note No. 3: See 502.10(A)(3), 502.10(B)(4), 503.10(A)(2), and 506.15(C)(9) for information on the use of dusttight enclosures in hazardous locations. Informational Note No. 4: Some enclosure types, such as 12, 12K, or 13 enclosures, may be marked with an ancillary “-XH” for corrosive and hosedown capable indoor enclosure. Informational Note No. 5: Some type 4X enclosures may be marked “indoor only.” Informational Note No. 6: See UL 508A, Standard for Industrial Control Panels, for information on determining applicable requirements for evaluating type 4, 4X, and 12 ventilated enclosures. Informational Note No. 7: See NEMA 250, Enclosures for Electrical Equipment (1000 Volts Maximum), for the description of the “Enclosure Type Rating: Ancillary - PW for Pressure Wash.” ENHANCED CONTENT Collapse Enclosures that comply with the requirements for more than one type of enclosure may be marked with multiple designations. Enclosures marked with a type may also be marked as follows: * Type 1 may be marked “Indoor Use Only.” * Type 3, 3S, 4, 4X, 6, or 6P may be marked “Raintight.” * Type 3R may be marked “Rainproof.” * Type 4, 4X, 6, or 6P may be marked “Watertight.” * Type 4X or 6P may be marked “Corrosion Resistant.” * Type 2, 5, 12, 12K, or 13 may be marked “Driptight.” * Type 3, 3S, 5, 12K, or 13 may be marked “Dusttight.” For equipment designated “raintight,” testing designed to simulate exposure to a beating rain will not result in entrance of water. For equipment designated “rainproof,” testing designed to simulate exposure to a beating rain will not interfere with the operation of the apparatus or result in wetting of live parts and wiring within the enclosure. “Watertight” equipment is constructed so that water does not enter the enclosure when subjected to a stream of water. “Corrosion-resistant” equipment is constructed so that it provides a degree of protection against exposure to corrosive agents such as salt spray. “Driptight” equipment is constructed so that falling moisture or dirt does not enter the enclosure. “Dusttight” equipment is constructed so that circulating or airborne dust does not enter the enclosure. Article 100 defines the term weatherproof as “constructed or protected so that exposure to the weather will not interfere with successful operation.” Rainproof, raintight, or watertight equipment can fulfill the requirements of this definition where varying weather conditions other than wetness, such as snow, ice, dust, or temperature extremes, are not a factor. 110.29 In Sight From (Within Sight From, Within Sight). Where this Code specifies that one equipment shall be “in sight from,” “within sight from,” or “within sight of” another equipment, the specified equipment shall be visible and not more than 15 m (50 ft) distant from the other. Part III. Over 1000 Volts, Nominal 110.30 General. Conductors and equipment used on circuits over 1000 volts, nominal, shall comply with Part I of this article and with 110.30 through 110.41, which supplement or modify Part I. In no case shall this part apply to equipment on the supply side of the service point. 110.31 Enclosure for Electrical Installations. Electrical installations in a vault, room, or closet or in an area surrounded by a wall, screen, or fence, access to which is controlled by a lock(s) or other approved means, shall be considered to be accessible to qualified persons only. The type of enclosure used in a given case shall be designed and constructed according to the nature and degree of the hazard(s) associated with the installation. For installations other than equipment as described in 110.31(D), a wall, screen, or fence shall be used to enclose an outdoor electrical installation to deter access by persons who are not qualified. A fence shall not be less than 2.1 m (7 ft) in height or a combination of 1.8 m (6 ft) or more of fence fabric and a 300 mm (1 ft) or more extension utilizing three or more strands of barbed wire or equivalent. The distance from the fence to live parts shall be not less than given in Table 110.31. Table 110.31 Minimum Distance from Fence to Live Parts Minimum Distance to Live Parts Nominal Voltage m ft 1001-13,799 3.05 10 13,800-230,000 4.57 15 Over 230,000 5.49 18 Informational Note: See ANSI/IEEE C2-2017, National Electrical Safety Code, for clearances of conductors for specific system voltages and typical BIL ratings. (A) Electrical Vaults. Where an electrical vault is required or specified for conductors and equipment 110.31(A)(1) to (A)?(5) shall apply. (1) Walls and Roof. The walls and roof shall be constructed of materials that have adequate structural strength for the conditions, with a minimum fire rating of 3 hours. For the purpose of this section, studs and wallboard construction shall not be permitted. (2) Floors. The floors of vaults in contact with the earth shall be of concrete that is not less than 102 mm (4 in.) thick, but where the vault is constructed with a vacant space or other stories below it, the floor shall have adequate structural strength for the load imposed on it and a minimum fire resistance of 3 hours. (3) Doors. Each doorway leading into a vault from the building interior shall be provided with a tight-fitting door that has a minimum fire rating of 3 hours. The authority having jurisdiction shall be permitted to require such a door for an exterior wall opening where conditions warrant. Exception to (1), (2), and (3): Where the vault is protected with automatic sprinkler, water spray, carbon dioxide, or halon, construction with a 1-hour rating shall be permitted. (4) Locks. Doors shall be equipped with locks, and doors shall be kept locked, with access allowed only to qualified persons. Personnel doors shall open at least 90 degrees in the direction of egress and be equipped with listed panic hardware or listed fire exit hardware. Informational Note: See UL 305, Standard for Panic Hardware, for additional information, and UL10C, Standard for Safety for Positive Pressure Fire Tests of Door Assemblies. (5) Transformers. Where a transformer is installed in a vault as required by Part II of Article 450, the vault shall be constructed in accordance with Part III of Article 450. Informational Note No. 1: See ANSI/ASTM E119-2018a, Method for Fire Tests of Building Construction and Materials, for additional information, and see NFPA 80-2019, Standard for Fire Doors and Other Opening Protectives. Informational Note No. 2: A typical 3-hour construction is 150 mm (6 in.) thick reinforced concrete. (B) Indoor Installations. (1) In Places Accessible to Unqualified Persons. Indoor electrical installations that are accessible to unqualified persons shall be made with metal-enclosed equipment. Switchgear, transformers, pull boxes, connection boxes, and other similar associated equipment shall be marked with appropriate caution signs. Openings in ventilated dry-type transformers or similar openings in other equipment shall be designed so that foreign objects inserted through these openings are deflected from energized parts. (2) In Places Accessible to Qualified Persons Only. Indoor electrical installations considered accessible only to qualified persons in accordance with this section shall comply with 110.34, 110.36, and 495.24. (C) Outdoor Installations. (1) In Places Accessible to Unqualified Persons. Outdoor electrical installations that are open to unqualified persons shall comply with Part III of Article 225. (2) In Places Accessible to Qualified Persons Only. Outdoor electrical installations that have exposed live parts shall be accessible to qualified persons only in accordance with the first paragraph of this section and shall comply with 110.34, 110.36, and 495.24. (D) Enclosed Equipment Accessible to Unqualified Persons. Ventilating or similar openings in equipment shall be designed such that foreign objects inserted through these openings are deflected from energized parts. Where exposed to physical damage from vehicular traffic, suitable guards shall be provided. Equipment located outdoors and accessible to unqualified persons shall be designed such that exposed nuts or bolts cannot be readily removed, permitting access to live parts. Where equipment is accessible to unqualified persons and the bottom of the enclosure is less than 2.5 m (8 ft) above the floor or grade level, the enclosure door or hinged cover shall be kept locked. Doors and covers of enclosures used solely as pull boxes, splice boxes, or junction boxes shall be locked, bolted, or screwed on. Underground box covers that weigh over 45.4 kg (100 lb) shall be considered as meeting this requirement. 110.32 Work Space About Equipment. Sufficient space shall be provided and maintained about electrical equipment to permit ready and safe operation and maintenance of such equipment. Where energized parts are exposed, the minimum clear work space shall be not less than 2.0 m (61/2 ft) high (measured vertically from the floor or platform) and the width of the equipment or 914 mm (3 ft) wide (measured parallel to the equipment), whichever is greater. The depth shall be as required in 110.34(A). In all cases, the work space shall permit at least a 90-degree opening of doors or hinged panels. Within the height requirements of this section, other equipment that is associated with the electrical installation and is located above or below the electrical equipment shall be permitted to extend not more than 150 mm (6 in.) beyond the front of the electrical equipment. Working space required by this section shall not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or general open space, shall be suitably guarded. ENHANCED CONTENT Collapse This requirement allows the placement of an 18-inch x 18-inch wireway on the wall directly above or below a 12-inch-deep panelboard without encroaching on the working space. The allowable 6-inch extension into working space also applies to support structures or housekeeping pads that the equipment may be affixed to. The requirement prohibits large differences in depth of equipment below or above other equipment that specifically requires working space. 110.33 Entrance to Enclosures and Access to Working Space. (A) Entrance. At least one entrance to enclosures for electrical installations as described in 110.31 not less than 610 mm (24 in.) wide and 2.0 m (61/2 ft) high shall be provided to give access to the working space about electrical equipment. Open equipment doors shall not impede access to and egress from the working space. Access or egress is impeded if one or more simultaneously opened equipment doors restrict working space access to be less than 610 mm (24 in.) wide and 2.0 m (61/2 ft) high. (1) Large Equipment. On switchgear and control panels exceeding 1.8 m (6 ft) in width, there shall be one entrance at each end of the equipment. A single entrance to the required working space shall be permitted where either of the conditions in 110.33(A)(1)(a) or (A)(1)(b) is met. * (a) Unobstructed Exit. Where the location permits a continuous and unobstructed way of exit travel, a single entrance to the working space shall be permitted. * (b) Extra Working Space. Where the depth of the working space is twice that required by 110.34(A), a single entrance shall be permitted. It shall be located so that the distance from the equipment to the nearest edge of the entrance is not less than the minimum clear distance specified in Table 110.34(A) for equipment operating at that voltage and in that condition. (2) Guarding. Where bare energized parts at any voltage or insulated energized parts above 1000 volts, nominal, are located adjacent to such entrance, they shall be suitably guarded. (3) Personnel Doors. Where there are personnel doors intended for entrance to and egress from the working space less than 7.6 m (25 ft) from the nearest edge of the working space, the doors shall open at least 90 degrees in the direction of egress and be equipped with listed panic hardware or listed fire exit hardware. Informational Note: See UL 305, Standard for Panic Hardware, for additional information, and UL 10C, Standard for Safety for Positive Pressure Fire Tests of Door Assemblies. ENHANCED CONTENT Collapse Not every electrical installation is in an equipment room. This section also does not mandate that the installation be enclosed in a room. If there are personnel doors within 25 feet from the working space, they must have listed panic hardware or listed fire exit hardware and they must open in the direction of egress from the area. (B) Access. Permanent ladders or stairways shall be provided to give safe access to the working space around electrical equipment installed on platforms, balconies, or mezzanine floors or in attic or roof rooms or spaces. 110.34 Work Space and Guarding. (A) Working Space. Except as elsewhere required or permitted in this Code, equipment likely to require examination, adjustment, servicing, or maintenance while energized shall have clear working space in the direction of access to live parts of the electrical equipment and shall be not less than specified in Table 110.34(A). Distances shall be measured from the live parts, if such are exposed, or from the enclosure front or opening if such are enclosed. The grade, floor, or platform in the required working space shall be kept clear, and the floor, grade, or platform in the working space shall be as level and flat as practical for the entire depth and width of the working space. Exception: Working space shall not be required in back of equipment such as switchgear or control assemblies where there are no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations other than the back. Where rear access is required to work on nonelectrical parts on the back of enclosed equipment, a minimum working space of 762 mm (30 in.) horizontally shall be provided. Table 110.34(A) Minimum Depth of Clear Working Space at Electrical Equipment Nominal Voltage to Ground Minimum Clear Distance Condition 1 Condition 2 Condition 3 1001-2500 V 900 mm (3 ft) 1.2 m (4 ft) 1.5 m (5 ft) 2501-9000 V 1.2 m (4 ft) 1.5 m (5 ft) 1.8 m (6 ft) 9001-25,000 V 1.5 m (5 ft) 1.8 m (6 ft) 2.8 m (9 ft) 25,001 V-75 kV 1.8 m (6 ft) 2.5 m (8 ft) 3.0 m (10 ft) Above 75 kV 2.5 m (8 ft) 3.0 m (10 ft) 3.7 m (12 ft) Note: Where the conditions are as follows: Condition 1 - Exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or exposed live parts on both sides of the working space that are effectively guarded by insulating materials. Condition 2 - Exposed live parts on one side of the working space and grounded parts on the other side of the working space. Concrete, brick, or tile walls shall be considered as grounded. Condition 3 - Exposed live parts on both sides of the working space. (B) Separation from Low-Voltage Equipment. Where switches, cutouts, or other equipment operating at 1000 volts, nominal, or less are installed in a vault, room, or enclosure where there are exposed live parts or exposed wiring operating at over 1000 volts, nominal, the high-voltage equipment shall be effectively separated from the space occupied by the low-voltage equipment by a suitable partition, fence, or screen. Exception: Switches or other equipment operating at 1000 volts, nominal, or less and serving only equipment within the high-voltage vault, room, or enclosure shall be permitted to be installed in the high-voltage vault, room, or enclosure without a partition, fence, or screen if accessible to qualified persons only. (C) Locked Rooms or Enclosures. The entrance to all buildings, vaults, rooms, or enclosures containing exposed live parts or exposed conductors operating at over 1000 volts, nominal, shall be kept locked unless such entrances are under the observation of a qualified person at all times. Permanent and conspicuous danger signs shall be provided. The danger sign shall meet the requirements in 110.21(B) and shall read as follows: DANGER - HIGH VOLTAGE - KEEP OUT (D) Illumination. Illumination shall be provided for all working spaces about electrical equipment. Control by automatic means only shall not be permitted. The lighting outlets shall be arranged so that persons changing lamps or making repairs on the lighting system are not endangered by live parts or other equipment. The points of control shall be located so that persons are not likely to come in contact with any live part or moving part of the equipment while turning on the lights. (E) Elevation of Unguarded Live Parts. Unguarded live parts above working space shall be maintained at elevations not less than required by Table 110.34(E). Table 110.34(E) Elevation of Unguarded Live Parts Above Working Space Nominal Voltage Between Phases Elevation m ft 1001-7500 V 2.7 9 7501-35,000 V 2.9 9 ft 6 in. Over 35 kV Add 9.5 mm per kV above 35 kV Add 0.37 in. per kV above 35 kV (F) Protection of Service Equipment, Switchgear, and Industrial Control Assemblies. Pipes or ducts foreign to the electrical installation and requiring periodic maintenance or whose malfunction would endanger the operation of the electrical system shall not be located in the vicinity of the service equipment, switchgear, or industrial control assemblies. Protection shall be provided where necessary to avoid damage from condensation leaks and breaks in such foreign systems. Piping and other facilities shall not be considered foreign if provided for fire protection of the electrical installation. 110.36 Circuit Conductors. Circuit conductors shall be permitted to be installed in raceways; in cable trays; as metal-clad cable Type MC; as bare wire, cable, and busbars; or as Type MV cables or conductors as provided in 305.3, 305.9, 305.10, and 305.15. Bare live conductors shall comply with 495.24. Insulators, together with their mounting and conductor attachments, where used as supports for wires, single-conductor cables, or busbars, shall be capable of safely withstanding the maximum magnetic forces that would prevail if two or more conductors of a circuit were subjected to short-circuit current. Exposed runs of insulated wires and cables that have a bare lead sheath or a braided outer covering shall be supported in a manner designed to prevent physical damage to the braid or sheath. Supports for lead-covered cables shall be designed to prevent electrolysis of the sheath. 110.40 Temperature Limitations at Terminations. Conductors shall be permitted to be terminated based on the 90øC (194øF) temperature rating and ampacity as given in Table 315.60(C)(1) through Table 315.60(C)(20), unless otherwise identified. 110.41 Inspections and Tests. (A) Pre-energization and Operating Tests. Where required elsewhere in this Code, the complete electrical system design, including settings for protective, switching, and control circuits, shall be prepared in advance and made available on request to the authority having jurisdiction and shall be tested when first installed on-site. (B) Test Report. A test report covering the results of the tests required in 110.41(A) shall be available to the authority having jurisdiction prior to energization and made available to those authorized to install, operate, test, and maintain the system. Part IV. Tunnel Installations over 1000 Volts, Nominal 110.51 General. (A) Covered. This part shall apply to the installation and use of high-voltage power distribution and utilization equipment that is portable, mobile, or both, such as substations, trailers, cars, mobile shovels, draglines, hoists, drills, dredges, compressors, pumps, conveyors, underground excavators, and the like. (B) Protection Against Physical Damage. Conductors and cables in tunnels shall be located above the tunnel floor and so placed or guarded to protect them from physical damage. 110.52 Overcurrent Protection. Motor-operated equipment shall be protected from overcurrent in accordance with Parts III, IV, and V of Article 430. Transformers shall be protected from overcurrent in accordance with 450.3. 110.53 Conductors. High-voltage conductors in tunnels shall be installed in metal raceway, Type MC cable, or other approved multiconductor cable. Multiconductor portable cable shall be permitted to supply mobile equipment. 110.54 Bonding and Equipment Grounding Conductors. (A) Grounded and Bonded. All non-current-carrying metal parts of electrical equipment and all metal raceways and cable sheaths shall be solidly grounded and bonded to all metal pipes and rails at the portal and at intervals not exceeding 300 m (1000 ft) throughout the tunnel. (B) Equipment Grounding Conductors. An equipment grounding conductor shall be run with circuit conductors inside the metal raceway or inside the multiconductor cable jacket. The equipment grounding conductor shall be permitted to be insulated or bare. 110.55 Transformers, Switches, and Electrical Equipment. All transformers, switches, motor controllers, motors, rectifiers, and other equipment installed belowground shall be protected from physical damage by location or guarding. 110.56 Energized Parts. Bare terminals of transformers, switches, motor controllers, and other equipment shall be enclosed to prevent accidental contact with energized parts. 110.57 Ventilation System Controls. Electrical controls for the ventilation system shall be arranged so that the airflow can be reversed. 110.58 Disconnecting Means. A switch or circuit breaker that simultaneously opens all ungrounded conductors of the circuit shall be installed within sight of each transformer or motor location for disconnecting the transformer or motor. The switch or circuit breaker for a transformer shall have an ampere rating not less than the ampacity of the transformer supply conductors. The switch or circuit breaker for a motor shall comply with the applicable requirements of Part IX of Article 430. 110.59 Enclosures. Enclosures for use in tunnels shall be dripproof, weatherproof, or submersible as required by the environmental conditions. Switch or contactor enclosures shall not be used as junction boxes or as raceways for conductors feeding through or tapping off to other switches, unless the enclosures comply with 312.8. Part V. Manholes and Other Electrical Enclosures Intended for Personnel Entry 110.70 General. Electrical enclosures intended for personnel entry and specifically fabricated for this purpose shall be of sufficient size to provide safe work space about electrical equipment with live parts that is likely to require examination, adjustment, servicing, or maintenance while energized. Such enclosures shall have sufficient size to permit ready installation or withdrawal of the conductors employed without damage to the conductors or to their insulation. They shall comply with this part. Exception: Where electrical enclosures covered by Part V of this article are part of an industrial wiring system operating under conditions of maintenance and supervision that ensure that only qualified persons monitor and supervise the system, they shall be permitted to be designed and installed in accordance with appropriate engineering practice. If required by the authority having jurisdiction, design documentation shall be provided. 110.71 Strength. Manholes, vaults, and their means of access shall be designed under qualified engineering supervision and shall withstand all loads likely to be imposed on the structures. I