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he installation. ENHANCED CONTENT Collapse Table 110.26(A)(1) provides requirements for clearances from equipment to grounded or ungrounded objects and exposed live parts based on the circuit voltage to ground. The following exhibit illustrates the general working clearance requirements for each of...

he installation. ENHANCED CONTENT Collapse Table 110.26(A)(1) provides requirements for clearances from equipment to grounded or ungrounded objects and exposed live parts based on the circuit voltage to ground. The following exhibit illustrates the general working clearance requirements for each of the three conditions listed in Table 110.26(A)(1). Examples of common electrical supply systems covered in the 0 to 150 volts-to-ground group are 120/240-volt, single-phase, 3-wire and 208Y/120-volt, 3-phase, 4-wire systems. Examples of common electrical supply systems covered in the 151 to 1000 volts-to-ground group are 240-volt, 3-phase, 3-wire; 480Y/277-volt, 3-phase, 4-wire; and 480-volt, 3-phase, 3-wire (ungrounded and corner grounded) systems. Where an ungrounded system is used, the voltage to ground (by definition) is the greatest voltage between the given conductor and any other conductor of the circuit. For example, the voltage to ground for a 480-volt ungrounded delta system is 480 volts. For assemblies such as switchboards, switchgear, or motor-control centers that are accessible from the back and expose live parts, the working clearance dimensions are required at the rear of the equipment. For Condition 3, where enclosures are on opposite sides of the working space, the clearance for only one working space is required. Dead-Front Assemblies. In many cases, equipment of “dead-front” assemblies requires only front access. The workspace described in 110.26(A)(1) is required for any side of the equipment from which access to live parts or other maintenance is required. For equipment that requires rear access for nonelectrical maintenance, such as replacing a filter, a reduced working space of at least 30 inches must be provided. The exhibit below shows a reduced working space of 30 inches at the rear of equipment to allow work on nonelectrical parts, such as the replacement of an air filter. Existing Buildings. This section permits some relief for existing equipment being replaced if it is not practical to increase the existing work space. The following exhibit illustrates a permitted reduction from a Condition 3 to a Condition 2 clearance. Width of Working Space. The width of the working space in front of the electrical equipment shall be the width of the equipment or 762 mm (30 in.), whichever is greater. In all cases, the work space shall permit at least a 90-degree opening of equipment doors or hinged panels. ENHANCED CONTENT Collapse Regardless of the width of the electrical equipment, the working space cannot be less than 30 inches wide. This space allows an individual to have at least shoulder-width space in front of the equipment. The 30-inch measurement can be made from either the left or the right edge of the equipment and can overlap other electrical equipment, provided the equipment does not extend into the working space of the other equipment. If the equipment is wider than 30 inches, the space must be equal to the width of the equipment. The following exhibit illustrates the 30-inch width requirement. Sufficient depth in the working space is also required to allow a panel or a door to open at least 90 degrees. If doors or hinged panels are wider than 3 feet, more than a 3-foot- deep working space must be provided to allow a full 90-degree opening. as shown below. Doors are often part of bolted equipment covers. The 90-degree requirement applies only to the hinged door. It does not require that the bolted cover be capable of swinging 90 degrees. Height of Working Space. The work space shall be clear and extend from the grade, floor, or platform to a height of 2.0 m (61/2 ft) or the height of the equipment, whichever is greater. Within the height requirements of this section, other equipment or support structures, such as concrete pads, associated with the electrical installation and 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. Exception No. 1: On battery systems mounted on open racks, the top clearance shall comply with 480.10(D). Exception No. 2: In existing dwelling units, service equipment or enclosed panelboards that do not exceed 200 amperes shall be permitted in spaces where the height of the working space is less than 2.0 m (61/2 ft). Exception No. 3: Meters that are installed in meter sockets shall be permitted to extend beyond the other equipment. The meter socket shall be required to follow the rules of this section. ENHANCED CONTENT Collapse This requirement allows the placement of a 12-inch x 12-inch wireway on the wall directly above or below a 6-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. Freestanding, dry-type transformers are not permitted to be installed where they would extend into the work space for a wall- mounted panelboard, compromising clear access to the panelboard. Limited Access. Where equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized is required by installation instructions or function to be located in a space with limited access, all of the following shall apply: Where equipment is installed above a lay-in ceiling, there shall be an opening not smaller than 559 mm x 559 mm (22 in. x 22 in.), or in a crawl space, there shall be an accessible opening not smaller than 559 mm x 762 mm (22 in. x 30 in.). The width of the working space shall be the width of the equipment enclosure or a minimum of 762 mm (30 in.), whichever is greater. All enclosure doors or hinged panels shall be capable of opening a minimum of 90 degrees. The space in front of the enclosure shall comply with the depth requirements of Table 110.26(A)(1) and shall be unobstructed to the floor by fixed cabinets, walls, or partitions. Space reductions in accordance with 110.26(A)(1)(b) shall be permitted. The maximum height of the working space shall be the height necessary to install the equipment in the limited space. A horizontal ceiling structural member or access panel shall be permitted in this space provided the location of weight-bearing structural members does not result in a side reach of more than 150 mm (6 in.) to work within the enclosure. ENHANCED CONTENT Collapse This requirement was located in 424.66 prior to the 2017 edition. A typical application of this requirement is the installation of duct heaters and other ventilation equipment located above suspended ceilings. The workspace is usually limited, and workers are usually performing maintenance from ladders. Separation from High-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 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. Grade, Floor, or Working Platform. 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 required depth and width of the working space. Clear Spaces. 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 Prohibited storage includes portable equipment on rollers. Below is an example of an equipment location that is free of storage, allowing the equipment to be worked on safely. This section and the rest of 110.26 do not prohibit the placement of panelboards in corridors or passageways. When the covers of corridor-mounted panelboards are removed for authorized energized work, access to the area around the panelboard should be guarded or limited to prevent injury to unqualified persons using the corridor in accordance with Article 130 of NFPA 70E, Standard for Electrical Safety in the Workplace. Entrance to and Egress from Working Space. Minimum Required. At least one entrance of sufficient area shall be provided to give access to and egress from working space about electrical equipment. ENHANCED CONTENT Collapse The requirements in this section provide access to and egress from electrical equipment. However, the primary intent is to provide egress from the area so that workers can escape if an arc-flash incident occurs. Large Equipment. For large equipment that contains overcurrent devices, switching devices, or control devices, there shall be one entrance to and egress from the required working space not less than 610 mm (24 in.) wide and 2.0 m (61/2 ft) high at each end of the working space. This requirement shall apply to either of the following conditions: For equipment rated 1200 amperes or more and over 1.8 m (6 ft) wide For service disconnecting means installed in accordance with 230.71(B) where the combined ampere rating is 1200 amperes or more and where the combined width is over 1.8 m (6 ft) A single entrance to and egress from the required working space shall be permitted where either of the conditions in 110.26(C)(2)(a) or (C)(2)(b) is met. Unobstructed Egress. Where the location permits a continuous and unobstructed way of egress travel, a single entrance to the working space shall be permitted. Extra Working Space. Where the depth of the working space is twice that required by 110.26(A)(1), a single entrance shall be permitted. It shall be located such that the distance from the equipment to the nearest edge of the entrance is not less than the minimum clear distance specified in Table 110.26(A)(1) for equipment operating at that voltage and in that condition. ENHANCED CONTENT Collapse Open equipment doors must not impede access to or egress from the work space. This requirement is intended to prevent workers from being entrapped between equipment doors and walls or other equipment facing the installation. The following exhibits illustrate access and entrance requirements for working spaces. For large equipment, one entrance not less than 24 inches wide and 61/2 feet high is required at each end, as shown in the example below. The next exhibit shows an unacceptable and hazardous work space arrangement. The following two exhibits provide representations of the single egress requirements for large equipment. Below is an example of an equipment location that allows a continuous and unobstructed way of exit travel. Next is a working space with one entrance, which is permitted if the working space required by 110.26(A) is doubled [see Table 110.26(A)(1) for permitted dimensions of X]. Large equipment is equipment rated 1200 amperes or more and over 6 feet wide. Equipment consisting of multiple disconnecting means, in accordance with 230.71, where the combined rating is 1200 amperes or more and over 6 feet wide, is also considered large equipment. (3) Personnel Doors. Where equipment rated 800 amperes or more that contains overcurrent devices, switching devices, or control devices is installed and there is a personnel door(s) 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 door(s) 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 on panic hardware, and see UL 10C, Standard for Safety for Positive Pressure Fire Tests of Door Assemblies, for additional information. ENHANCED CONTENT Collapse The requirements in this section are based on equipment rated 800 amperes or more and not on the width of the equipment. The 25-foot measurement for the personnel door(s) is made from the nearest edge of the working space. It applies to the personnel door(s) that provide access to and egress from the room containing the working space. Not every electrical installation is in an equipment room. Where electrical installations are in a room, personnel doors that are up to 25 feet from the working space are required to have listed panic hardware or listed fire exit hardware, and they must open in the direction of egress from the area. The requirement for listed panic hardware is independent of the need for two exits from the working space. Below is an equipment room showing an exit with panic hardware. Door-opening hardware must not require the turning of a doorknob or similar action that could preclude quick exit from the area in the event of an emergency. This requirement allows an injured worker to exit from the equipment room without having to turn knobs or pull doors open. The exhibit below illustrates egress doors in relation to the working space around equipment with listed panic hardware that open in the direction of egress. Illumination. Illumination shall be provided for all working spaces about service equipment, switchboards, switchgear, enclosed panelboards, or motor control centers installed indoors. Control by automatic means shall not be permitted to control all illumination within the working space. Additional lighting outlets shall not be required where the work space is illuminated by an adjacent light source or as permitted by 210.70(A)(1), Exception No. 1, for switched receptacles. ENHANCED CONTENT Collapse Automatic lighting control through devices such as timers, occupancy sensors, and similar devices is not prohibited, but a manual means to bypass the automatic control is required. Dedicated Equipment Space. All service equipment, switchboards, switchgear, panelboards, and motor control centers shall be located in dedicated spaces and protected from damage. Exception: Control equipment that by its very nature or because of other rules of the Code must be adjacent to or within sight of its operating machinery shall be permitted in those locations. Indoor. Indoor installations shall comply with 110.26(E)(1)(a) through (E)(1)(d). Dedicated Electrical Space. The space equal to the width and depth of the equipment and extending from the floor to a height of 1.8 m (6 ft) above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation shall be located in this zone. Exception: Suspended ceilings with removable panels shall be permitted within the 1.8 m (6 ft) zone. Foreign Systems. The area above the dedicated space required by 110.26(E)(1)(a) shall be permitted to contain foreign systems, provided protection is installed to avoid damage to the electrical equipment from condensation, leaks, or breaks in such foreign systems. Sprinkler Protection. Sprinkler protection shall be permitted for the dedicated space where the piping complies with this section. Suspended Ceilings. A dropped, suspended, or similar ceiling that does not add strength to the building structure shall not be considered a structural ceiling. ENHANCED CONTENT Collapse This requirement applies only to switchboards, panelboards, switchgear, or motor control centers. The dedicated electrical space extends the footprint of the equipment from the floor to a height of 6 feet above the height of the equipment or to the structural ceiling (whichever is lower). The dedicated space is required to be clear of piping, ducts, leak protection apparatus, or equipment foreign to the electrical installation. Plumbing, heating, ventilation, and air-conditioning piping, ducts, and equipment must be installed outside this space. Busways, conduits, raceways, and cables are permitted to enter equipment through this zone. Foreign systems installed directly above the dedicated space reserved for electrical equipment are required to include protective equipment that ensures that occurrences such as leaks, condensation, and even breaks do not damage the electrical equipment located below. Sprinkler protection is permitted for the dedicated space. The sprinkler or other suppression system piping must comply with 110.26(E)(1). A dropped, suspended, or similar ceiling is permitted to be located directly in the dedicated space, because they are not considered structural ceilings. Building structural members are also permitted in this space. The three exhibits that follow illustrate the two distinct indoor installation spaces required by 110.26(A) and 110.26(E) - the working space and the dedicated electrical space. The dedicated electrical space is reserved for the installation of electrical equipment and for the installation of conduits, cable trays, and so forth, entering or exiting that equipment. The outlined area in front of the electrical equipment in the exhibit below is the working space required by 110.26(A). Note that sprinkler protection is afforded the entire dedicated electrical space and working space without actually entering either space. Also note that the exhaust duct is not located in the dedicated electrical space. The next exhibit illustrates the working space required in front of the panelboard by 110.26(A). No equipment, electrical or otherwise, is allowed in the working space. The exhibit below illustrates the dedicated electrical space above and below the panelboard required by 110.26(E)(1). This space is for the cables, raceways, and so on, that run to and from the panelboard. Outdoor. Outdoor installations shall comply with 110.26(E)(2)(a) through (E)(2)(c). Installation Requirements. Outdoor electrical equipment shall be the following: o (1) Installed in identified enclosures o (2) Protected from accidental contact by unauthorized personnel or by vehicular traffic o (3) Protected from accidental spillage or leakage from piping systems Work Space. The working clearance space shall include the zone described in 110.26(A). No architectural appurtenance or other equipment shall be located in this zone. Dedicated Equipment Space. The space equal to the width and depth of the equipment, and extending from grade to a height of 1.8 m (6 ft) above the equipment, shall be dedicated to the electrical installation. No piping or other equipment foreign to the electrical installation shall be located in this zone. Exception: Structural overhangs or roof extensions shall be permitted in this zone. ENHANCED CONTENT Collapse If protection of the outdoor installation is requested, consideration should be taken for any underground wiring before any excavation or driving any steel into the ground for the placement of fencing, vehicle stops, or bollards. Locked Electrical Equipment Rooms or Enclosures. Electrical equipment rooms or enclosures housing electrical apparatus that are controlled by a lock(s) shall be considered accessible to qualified persons. 110.27 Guarding of Live Parts. (A) Live Parts Guarded Against Accidental Contact. Except as elsewhere required or permitted by this Code, live parts of electrical equipment operating at 50 to 1000 volts, nominal shall be guarded against accidental contact by approved enclosures or by any of the following means: * (1) By location in a room, vault, or similar enclosure that is accessible only to qualified persons. * (2) By permanent, substantial partitions or screens arranged so that only qualified persons have access to the space within reach of the live parts. Any openings in such partitions or screens shall be sized and located so that persons are not likely to come into accidental contact with the live parts or to bring conducting objects into contact with them. * (3) By location on a balcony, gallery, or platform elevated and arranged so as to exclude unqualified persons. * (4) By elevation above the floor or other working surface as follows: o a. A minimum of 2.5 m (8 ft) for 50 volts to 300 volts between ungrounded conductors o b. A minimum of 2.6 m (8 ft 6 in.) for 301 volts to 600 volts between ungrounded conductors o c. A minimum of 2.62 m (8 ft 7 in.) for 601 volts to 1000 volts between ungrounded conductors ENHANCED CONTENT Collapse Live parts of electrical equipment should be covered, shielded, enclosed, or otherwise protected by covers, barriers, or platforms to prevent contact by persons or objects. Contact conductors used for traveling cranes are permitted by 610.13(B) and 610.21(A) to be bare because they are protected from contact by elevation. Although contact conductors obviously must be bare for contact shoes on the moving member to make contact with the conductor, guards can be placed near the conductor to prevent accidental contact with persons and still have slots or spaces through which the moving contacts can operate. The NEC also recognizes the guarding of live parts by elevation. The elevation levels correlate with requirements in ANSI/ IEEE C2, National Electrical Safety Code(r) (NESC(r)). (B) Prevent Physical Damage. In locations where electrical equipment is likely to be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage. (C) Warning Signs. Entrances to rooms and other guarded locations that contain exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter. The marking shall meet the requirements in 110.21(B). 110.28 Enclosure Types. Enclosures (other than surrounding fences or walls covered in 110.31) of switchboards, switchgear, enclosed panelboards, industrial control panels, motor control centers, meter sockets, enclosed switches, transfer switches, power outlets, circuit breakers, adjustable-speed drive systems, pullout switches, portable power distribution equipment, termination boxes, general-purpose transformers, fire pump controllers, fire pump motors, and motor controllers, rated not over 1000 volts nominal and intended for such locations, shall be marked with an enclosure-type number as shown in Table 110.28. Table 110.28 shall be used for selecting these enclosures for use in specific locations other than hazardous (classified) locations. The enclosures are not intended to protect against conditions such as condensation, icing, corrosion, or contamination that may occur within the enclosure or enter via the raceway or unsealed openings. Table 110.28 Enclosure Selection Provides a Degree of Protection Against the Following Environmental Conditions For Outdoor Use Enclosure Type Number 3 3R 3S 3X 3RX 3SX 4 4X 6 6P Incidental contact with the enclosed equipment X X X X X X X X X X Rain, snow, and sleet X X X X X X X X X X Sleet* - - X - - X - - - - Windblown dust X - X X - X X X X X Hosedown - - - - - - X X X X Corrosive agents - - - X X X - X - X Temporary submersion - - - - - - - - X X Prolonged submersion - - - - - - - - - X Provides a Degree of Protection Against the Following Environmental Conditions For Indoor Use Enclosure Type Number 1 2 4 4X 5 6 6P 12 12K 13 Incidental contact with the enclosed equipment X X X X X X X X X X Falling dirt X X X X X X X X X X Falling liquids and light splashing - X X X X X X X X X Circulating dust, lint, fibers, and flyings - - X X - X X X X X Settling airborne dust, lint, fibers, and flyings - - X X X X X X X X Hosedown and splashing water - - X X - X X - - - Oil and coolant seepage - - - - - - - X X X Oil or coolant spraying and splashing - - - - - - - - - X Corrosive agents - - - X - - X - - - Temporary submersion - - - - - X X - - - Prolonged submersion - - - - - - X - - - *The mechanism s