REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 70-23

Table 110-16 (a). Working Clearances Voltage to Ground, Nominal Minimum Clear Distance (feet) Condition: 1 2 3 0-150 3 3 3 151-600 3 3½ 4 For SI units: one inch = 25.4 millimeters; one foot = 0.3048 meter. Where the "Conditions" are as follows: 1. Exposed live parts on one side and no live or grounded parts on the other side of the working space, or exposed live parts on both sides effectively guarded by suitable wood or other insulating materials. Insulated wire or insulated busbars operating at not over 300 volts shall not be considered live parts. 2. Exposed live parts on one side and grounded parts on the other side. 3. Exposed live parts on both sides of the work space (not guarded as provided in Condition 1) with the operator between. Exception No. 1: Working space shall not be required in back of assemblies such as dead-front switchboards, or motor control centers 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. Exception No. 2: By special permission, smaller spaces may be permitted (1) where it is judged that the particular arrangement of the installation will provide adequate accessibility or (2) where all uninsulated parts are at a voltage no greater than 30 volts RMS, 42 volts peak, or 60 volts dc. (b) 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. (c) Access and Entrance to Working Space. At least one entrance of sufficient area shall be provided to give access to the working space about electric equipment. For equipment rated 1200 amperes or more and over 6 ft (1.83 m) wide, containing overcurrent devices, switching devices, or control devices, there shall be one entrance not less than 24 inches (610 mm) wide and 6½ feet (1.98 m) high at each end. Exception No. 1: Where the location permits a continuous and unobstructed way of exit travel. Exception No. 2: Where the work space required by Section 110-16(a) is doubled, only one entrance to the working space is required. Working space with one entrance provided shall be so located that the edge of the entrance nearest the equipment is the minimum clear distance given in Table 110-16(a) away from such equipment. 70-24 NATIONAL ELECTRICAL CODE (d) Front Working Space. In all cases where there are live parts normally exposed on the front of switchboards or motor control centers, the working space in front of such equipment shall not be less than 3 feet (914 mm). (e) Illumination. Illumination shall be provided for all working spaces about service equipment, switchboards, panelboards, or motor control centers installed indoors. (FPN): Additional lighting fixtures are not intended where the workspace is illuminated by an adjacent light source. (f) Headroom. The minimum headroom of working spaces about service equipment, switchboards, panelboards, or motor control centers shall be 6½ feet (1.98 m). Exception: Service equipment or panelboards, in existing dwelling units, that do not exceed 200 amperes. (FPN No. 1): For higher voltages, see Article 710. (FPN No. 2): As used in this section, a motor control center is an assembly of one or more enclosed sections having a common power bus and principally containing motor control units. 110-17. Guarding of Live Parts (600 Volts, Nominal, or Less). (a) Live Parts Guarded Against Accidental Contact. Except as elsewhere required or permitted by this Code, live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by approved enclosures or by any of the following: (1) By location in a room, vault, or similar enclosure that is accessible only to qualified persons. (2) By suitable permanent, substantial partitions or screens so arranged that only qualified persons will have access to the space within reach of the live parts. Any openings in such partitions or screens shall be so sized and located 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 suitable balcony, gallery, or platform so elevated and arranged as to exclude unqualified persons. (4) By elevation of 8 feet (2.44 m) or more above the floor or other working surface. (b) Prevent Physical Damage. In locations where electric equipment would 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 containing exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter. (FPN): For motors, see Sections 430-132 and 430-133. For over 600 volts, see