REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 70-27

be as required in Section 110-34(a). In all cases, the work space shall be adequate to permit at least a 90-degree opening of doors or hinged panels. 110-33. Entrance and Access to Work Space. (a) Entrance. At least one entrance not less than 24 inches (610 mm) wide and 6½ feet (1.98 m) high shall be provided to give access to the working space about electric equipment. On switchboard and control panels exceeding 6 feet (1.83 m) in width, there shall be one entrance at each end of such board. Exception No. 1: Where the switchboards and control panels location permits a continuous and unobstructed way of exit travel. Exception No. 2: Where the work space required in Section 110-34(a) is doubled. Working space with one entrance provided shall be so located that the edge of the entrance nearest the switchboards and control panels is the I minimum clear distance given in Table 110-34(a) away from such equipment. Where bare energized parts at any voltage or insulated energized parts above 600 volts, nominal, to ground are located adjacent to such entrance, they shall be suitably guarded. (b) Access. Permanent ladders or stairways shall be provided to give safe access to the working space around electric equipment installed on platforms, balconies, mezzanine floors, or in attic or roof rooms or spaces. 110-34. Work Space and Guarding. (a) Working Space. The minimum clear working space in front of electric equipment such as switchboards, control panels, switches, circuit breakers, motor controllers, relays, and similar equipment shall not be less than specified in Table 110-34(a) unless otherwise specified in this Code. Distances shall be measured from the live parts, if such are exposed, or from the enclosure front or opening if such are enclosed. Table 110-34(a). Minimum Depth of Clear Working Space in Front of Electric Equipment Nominal Conditions Voltage to Ground 1 2 3 (Feet) (Feet) (Feet) 601-2500 3 4 5 2501-9000 4 5 6 9001-25,000 5 6 9 25,001-75 kV 6 8 10 Above 75 kV 8 10 12 For SI units: one foot = 0.3048 meter. 70-28 NATIONAL ELECTRICAL CODE 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. Concrete, brick, or tile walls will be considered as grounded surfaces. 3. Exposed live parts on both sides of the work space (not guarded as provided in Condition 1) with the operator between. Exception: Working space is not required in back of equipment such as dead-front switchboards 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 deenergized parts on the back of enclosed equipment, a minimum working space of 30 inches (762 mm) horizontally shall be provided. (b) Separation from Low-Voltage Equipment. Where switches, cutouts, or other equipment operating at 600 volts, nominal, or less, are installed in a room or enclosure where there are exposed live parts or exposed wiring operating at over 600 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 600 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 enclosure, room, or vault if accessible to qualified persons only. (c) Locked Rooms or Enclosures. The entrances to all buildings, rooms, or enclosures containing exposed live parts or exposed conductors operating at over 600 volts, nominal, shall be kept locked. Exception: Where such entrances are under the observation of a qualified person at all times. Where the voltage exceeds 600 volts, nominal, permanent and conspicuous warning signs shall be provided, reading substantially as follows: "Danger-High Voltage-Keep Out." (d) Illumination. Adequate illumination shall be provided for all working spaces about electrical equipment. The lighting outlets shall be so arranged that persons changing lamps or making repairs on the lighting system will not be endangered by live parts or other equipment. The points of control shall be so located 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).