RADIO AND TELEVISION EQUIPMENT

70-805 ARTICLE 810 - RADIO AND TELEVISION EQUIPMENT A. General 810-1. Scope. This article covers radio and television receiving equipment and amateur radio transmitting and receiving equipment, but not equipment and antennas used for coupling carrier current to power line conductors. 810-2. Other Articles. Wiring from the source of power to and between devices connected to the interior wiring system shall comply with Chapters 1 through 4 other than as modified by Sections 640-3, 640-4, and 640-5. Wiring for radio-frequency and audio-frequency equipment and loud speakers shall comply with Article 640. Where optical fiber is used Article 770 shall apply. Coaxial cable wiring for television receiving shall comply with Article 820. 810-3. Community Television Antenna. The antenna shall comply with this article. The distribution system shall comply with Article 820. 810-4. Radio Noise Suppressors. Radio interference eliminators, interference capacitors, or noise suppressors connected to power-supply leads shall be of a listed type. They shall not be exposed to physical damage. 810-5. Definitions. See Article 100. B. Receiving Equipment - Antenna Systems 810-11. Material. Antennas and lead-in conductors shall be of harddrawn copper, bronze, aluminum alloy, copper-clad steel, or other highstrength, corrosion-resistant material. Exception: Soft-drawn or medium-drawn copper shall be permitted for lead-in conductors where the maximum span between points of support is less than 35 feet (10.67 m). 810-12. Supports. Outdoor antennas and lead-in conductors shall be securely supported. The antennas shall not be attached to the electric service mast. They shall not be attached to poles or similar structures carrying open electric light or power wires or trolley wires of over 250 volts between conductors. Insulators supporting the antenna conductors shall have sufficient mechanical strength to safely support the conductors. Lead-in conductors shall be securely attached to the antennas. 810-13. Avoidance of Contacts with Conductors of Other Systems. Outdoor antennas and lead-in conductors from an antenna to a building shall not cross over open conductors of electric light or power circuits and shall be kept well away from all such circuits so as to avoid the possibility 70-806 NATIONAL ELECTRICAL CODE of accidental contact. Where proximity to open electric light or power service conductors of less than 250 volts between conductors cannot be avoided, the installation shall be such as to provide a clearance of at least 2 feet (610 mm). Where practicable, antenna conductors shall be so installed as not to cross under open electric light or power conductors. 810-14. Splices. Splices and joints in antenna spans shall be made mechanically secure with approved splicing devices or by such other means as will not appreciably weaken the conductors. 810-15. Grounding. Masts and metal structures supporting antennas shall be grounded in accordance with Section 810-21. 810-16. Size of Wire-Strung Antenna - Receiving Station. (a) Size of Antenna Conductors. Outdoor antenna conductors for receiving stations shall be of a size not less than given in Table 810-16(a). Table 810-16(a). Size of Receiving-Station Outdoor Antenna Conductors Minimum Size of Conductors When Maximum Open Span Length is Material Less than 35 feet to Over 35 feet 150 feet 150 feet Aluminum alloy, harddrawn copper 19 14 12 Copper-clad steel, bronze, or other high-strength material 20 17 14 For SI units: one foot = 0.3048 meter. (b) Self-Supporting Antennas. Outdoor antennas, such as vertical rods, dishes, or dipole structures, shall be of corrosion-resistant materials and of strength suitable to withstand ice and wind loading conditions, and shall be located well away from overhead conductors of electric light and power circuits of over 150 volts to ground, so as to avoid the possibility of the antenna or structure falling into or making accidental contact with such circuits. 810-17. Size of Lead-in - Receiving Station. Lead-in conductors from outside antennas for receiving stations shall, for various maximum open span lengths, be of such size as to have a tensile strength at least as great as that of the conductors for antennas as specified in Section 810-16. Where the lead-in consists of two or more conductors that are twisted together, are enclosed in the same covering, or are concentric, the conductor size shall, for various maximum open span lengths, be such that the tensile strength of the combination will be at least as great as that of the conductors for antennas as specified in Section 810-16. ARTICLE 810 - RADIO AND TELEVISION EQUIPMENT 70-807 810-18. Clearances - Receiving Stations. (a) Outside of Buildings. Lead-in conductors attached to buildings shall be so installed that they cannot swing closer than 2 feet (610 mm) to the conductors of circuits of 250 volts or less between conductors, or 10 feet (3.05 m) to the conductors of circuits of over 250 volts between conductors, except that in the case of circuits not over 150 volts between conductors, where all conductors involved are supported so as to ensure permanent separation, the clearance shall be permitted to be reduced but shall not be less than 4 inches (102 mm). The clearance between lead-in conductors and any conductor forming a part of a lightning-rod system shall not be less than 6 feet (1.83 m) unless the bonding referred to in Section 250-86 is accomplished. Underground conductors shall be separated at least 12 inches (305 mm) from conductors of any light or power circuits, or Class 1 circuits. Exception: Where the electric light or power conductors, Class 1 conductors, or lead-in conductors are installed in raceways or metal cable armor. (b) Antennas and Lead-ins - Indoors. Indoor antennas and indoor lead-ins shall not be run nearer than 2 inches (50.8 mm) to conductors of other wiring systems in the premises. Exception No. 1: Where such other conductors are in metal raceways or cable armor. Exception No. 2: Where permanently separated from such other conductors by a continuous and firmly fixed nonconductor, such as porcelain tubes or flexible tubing. (c) In Boxes or Other Enclosures. Indoor antennas and indoor lead-ins shall be permitted to occupy the same box or enclosure with conductors of other wiring systems where separated from such other conductors by an effective permanently installed barrier. 810-19. Electric Supply Circuits Used in Lieu of Antenna - Receiving Stations. Where an electric supply circuit is used in lieu of an antenna, the device by which the radio receiving set is connected to the supply circuit shall be listed. 810-20. Antenna Discharge Units - Receiving Stations. (a) Where Required. Each conductor of a lead-in from an outdoor antenna shall be provided with a listed antenna discharge unit. Exception: Where the lead-in conductors are enclosed in a continuous metallic shield that is either permanently and effectively grounded, or is protected by an antenna discharge unit. (b) Location. Antenna discharge units shall be located outside the building or inside the building between the point of entrance of the lead-in and the radio set or transformers, and as near as practicable to the entrance of the conductors to the building. The antenna discharge unit shall not be located near combustible material nor in a hazardous (classified) location as defined in Article 500. (c) Grounding. The antenna discharge unit shall be grounded in accordance with Section 810-21. 70-808 NATIONAL ELECTRICAL CODE 810-21. Grounding Conductors - Receiving Stations. Grounding conductors shall comply with (a) through (j) below. (a) Material. The grounding conductor shall be of copper, aluminum, copper-clad steel, bronze, or similar corrosion-resistant material. (b) Insulation. Insulation on grounding conductors shall not be required. (c) Supports. The grounding conductors shall be securely fastened in place and shall be permitted to be directly attached to the surface wired over without the use of insulating supports. Exception: Where proper support cannot be provided, the size of the grounding conductors shall be increased proportionately. (d) Mechanical Protection. The grounding conductor shall be protected where exposed to physical damage, or the size of the grounding conductors shall be increased proportionately to compensate for the lack of protection. (e) Run in Straight Line. The grounding conductor for an antenna mast or antenna discharge unit shall be run in as straight a line as practicable from the mast or discharge unit to the grounding electrode. (f) Electrode. The grounding conductor shall be connected as follows: (1) To the nearest accessible location on (1) the building or structure grounding electrode system as covered in Section 250-81, (2) the grounded interior metal water piping system as covered in Section 250-80(a), (3) the power service accessible means external to enclosures as covered in Section 250-71(b), (4) the metallic power service raceway, (5) the service equipment enclosure, or (6) the grounding electrode conductor or the grounding electrode conductor metal enclosures; or (2) If the building or structure served has no grounding means, as described in (f)(1), to any one of the individual electrodes described in Section 250-81; or (3) If the building or structure served has no grounding means, as described in (f)(1) or (f)(2), to (1) an effectively grounded metal structure or (2) to any of the individual electrodes described in Section 250-83. (g) Inside or Outside Building. The grounding conductor shall be permitted to be run either inside or outside the building. (h) Size. The grounding conductor shall not be smaller than No. 10 cop- I per or No. 8 aluminum or No. 17 copper-clad steel or bronze. (i) Common Ground. A single grounding conductor shall be permitted for both protective and operating purposes. (j) Bonding of Electrodes. A bonding jumper not smaller than No. 6 copper or equivalent shall be connected between the radio and television equipment grounding electrode and the power grounding electrode system at the building or structure served where separate electrodes are used. C. Amateur Transmitting and Receiving Stations - Antenna Systems 810-51. Other Sections. In addition to complying with Part C, antenna systems for amateur transmitting and receiving stations shall also comply with Sections 810-11 through 810-15. ARTICLE 810 - RADIO AND TELEVISION EQUIPMENT 70-809 810-52. Size of Antenna. Antenna conductors for transmitting and receiving stations shall be of a size not less than given in Table 810-52. Table 810-52. Size of Amateur Station Outdoor Antenna Conductors Minimum Size of Conductors Where Maximum Open Span Length is Material Less than Over 150 feet 150 feet Hard-drawn copper 14 10 Copper-clad steel, bronze, or other high-strength material 14 12 For SI units: one foot = 0.3048 meter. 810-53. Size of Lead-in Conductors. Lead-in conductors for transmitting stations shall, for various maximum span lengths, be of a size at least as great as that of conductors for antennas as specified in Section 810-52. 810-54. Clearance on Building. Antenna conductors for transmitting stations, attached to buildings, shall be firmly mounted at least 3 inches (76 mm) clear of the surface of the building on nonabsorbent insulating supports, such as treated pins or brackets equipped with insulators having not less than 3-inch (76-mm) creepage and airgap distances. Lead-in conductors attached to buildings shall also comply with these requirements. Exception: Where the lead-in conductors are enclosed in a continuous metallic shield that is permanently and effectively grounded, they shall not be required to comply with these requirements. Where grounded, the metallic shield shall also be permitted to be used as a conductor. 810-55. Entrance to Building. Except where protected with a continuous metallic shield that is permanently and effectively grounded, lead-in conductors for transmitting stations shall enter buildings by one of the following methods: (1) through a rigid, noncombustible, nonabsorbent insulating tube or bushing; (2) through an opening provided for the purpose in which the entrance conductors are firmly secured so as to provide a clearance of at least 2 inches (50.8 mm); or (3) through a drilled window pane. 810-56. Protection Against Accidental Contact. Lead-in conductors to radio transmitters shall be so located or installed as to make accidental contact with them difficult. 810-57. Antenna Discharge Units - Transmitting Stations. Each conductor of a lead-in for outdoor antennas shall be provided with an antenna discharge unit or other suitable means that will drain static charges from the antenna system. 70-810 NATIONAL ELECTRICAL CODE Exception No. 1: Where protected by a continuous metallic shield that is permanently and effectively grounded. grounded. Exception No. 2: Where the antenna is permanently and effectively 810-58. Grounding Conductors - Amateur Transmitting and Receiving Stations. Grounding conductors shall comply with (a) through (c) below. (a) Other Sections. All grounding conductors for amateur transmitting and receiving stations shall comply with Sections 810-21(a) through (j). (b) Size of Protective Grounding Conductor. The protective grounding conductor for transmitting stations shall be as large as the lead-in, but not smaller than No. 10 copper, bronze, or copper-clad steel. (c) Size of Operating Grounding Conductor. The operating grounding conductor for transmitting stations shall not be less than No. 14 copper or its equivalent. D. Interior Installation - Transmitting Stations 810-70. Clearance from Other Conductors. All conductors inside the building shall be separated at least 4 inches (102 mm) from the conductors of any electric light, power, or signaling circuit. Exception No. 1: As provided in Article 640. Exception No. 2: Where separated from other conductors by raceway or some firmly fixed nonconductor, such as porcelain tubes or flexible tubing. 810-71. General. Transmitters shall comply with (a) through (c) below. (a) Enclosing. The transmitter shall be enclosed in a metal frame or grille, or separated from the operating space by a barrier or other equivalent means, all metallic parts of which are effectively connected to ground. (b) Grounding of Controls. All external metal handles and controls accessible to the operating personnel shall be effectively grounded. (c) Interlocks on Doors. All access doors shall be provided with interlocks that will disconnect all voltages of over 350 volts between conductors when any access door is opened.