REQUIREMENTS FOR ELECTRICAL INSTALLATIONS 70-21

110-13. Mounting and Cooling of Equipment. (a) Mounting. Electric equipment shall be firmly secured to the surface on which it is mounted. Wooden plugs driven into holes in masonry, concrete, plaster, or similar materials shall not be used. (b) Cooling. Electrical equipment that depends upon the natural circulation of air and convection principles for cooling of exposed surfaces shall be installed so that room airflow over such surfaces is not prevented by walls or by adjacent installed equipment. For equipment designed for floor mounting, clearance between top surfaces and adjacent surfaces shall be provided to dissipate rising warm air. Electrical equipment provided with ventilating openings shall be installed so that walls or other obstructions do not prevent the free circulation of air through the equipment. 110-14. Electrical Connections. Because of different characteristics of copper and aluminum, devices such as pressure terminal or pressure splicing connectors and soldering lugs shall be identified for the material of the conductor and shall be properly installed and used. Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors (such as copper and aluminum, copper and copper-clad aluminum, or aluminum and copperclad aluminum), unless the device is identified for the purpose and conditions of use. Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment. (FPN): Many terminations and equipment are marked with a tightening torque. (a) Terminals. Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Exception: Connection by means of wire binding screws or studs and nuts having upturned lugs or equivalent shall be permitted for No. 10 or smaller conductors. Terminals for more than one conductor and terminals used to connect aluminum shall be so identified. (b) Splices. Conductors shall be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices shall first be so spliced or joined as to be mechanically and electrically secure without solder and then soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an insulating device identified for the purpose. (c) Temperature Limitations. The temperature rating associated with the ampacity of a conductor shall be so selected and coordinated as to not exceed the lowest temperature rating of any connected termination, conductor, or device. 70-22 NATIONAL ELECTRICAL CODE (1) Termination provisions of equipment for circuits rated 100 amperes or less, or marked for Nos. 14 through 1 conductors, shall be used only for conductors rated 60°C (140°F). Exception No. 1: Conductors with higher temperature ratings shall be permitted to be used, provided the ampacity of such conductors is determined based on the 60°C (140°F) ampacity of the conductor size used. Exception No. 2: Equipment termination provisions shall be permitted to be used with higher rated conductors at the ampacity of the higher rated conductors, provided the equipment is listed and identified for use with the higher rated conductors. (2) Termination provisions of equipment for circuits rated over 100 amperes, or marked for conductors larger than No. 1, shall be used only with conductors rated 75°C (167°F). Exception No. 1: Conductors with higher temperature ratings shall be permitted to be used, provided the ampacity of such conductors is determined based on the 75°C (167°F) ampacity of the conductor size used. Exception No. 2: Equipment termination provisions shall be permitted to be used with the higher rated conductors at the ampacity of the higher rated conductors, provided the equipment is listed and identified for use with the higher rated conductors. (3) Separately installed pressure connectors shall be used with conductors at the ampacities not exceeding the ampacity at the listed and identified temperature rating of the connector. (FPN): With respect to Sections 110-14(c)(1), (2), and (3), equipment markings or listing information may additionally restrict the sizing and temperature ratings of connected conductors. 110-16. Working Space About Electric Equipment (600 Volts, Nominal, or Less). Sufficient access and working space shall be provided and maintained about all electric equipment to permit ready and safe operation and maintenance of such equipment. (a) Working Clearances. Except as elsewhere required or permitted in this Code, the dimension of the working space in the direction of access to live parts operating at 600 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized shall not be less than indicated in Table 110-16(a). Distances shall be measured from the live parts if such are exposed or from the enclosure front or opening if such are enclosed. Concrete, brick, or tile walls shall be considered as grounded. In addition to the dimensions shown in Table 110-16(a), the work space shall not be less than 30 inches (762 mm) wide in front of the electric equipment. The work space shall be clear and extend from the floor or platform to the height required by this section. In all cases, the work space shall permit at least a 90-degree opening of equipment doors or hinged panels.