Resolución 2535: adopta el Código Eléctrico Nacional, versión 1993. (Sustituye el Anejo A del Reglamento 4435)

Part B. Circuit and System Grounding. Part C. Location of System Grounding Connections. Part D. Enclosure Grounding. Part F. Methods of Grounding. Part G. Bonding. Part H. Grounding Electrode System. Part J. Grounding Conductors. 230-64. Working Space. Sufficient working space shall be provided in the vicinity of the service equipment to permit safe operation, inspection, and repairs. In no case shall this be less than that specified by Section 110-16. 230-65. Available Short-Circuit Current. Service equipment shall be suitable for the short-circuit current available at its supply terminals. 230-66. Marking. Service equipment shall be marked to identify it as being suitable for use as service equipment. F. Service Equipment - Disconnecting Means 230-70. General. Means shall be provided to disconnect all conductors in a building or other structure from the service-entrance conductors. (a) Location. The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure, or inside nearest the point of entrance of the service conductors. (b) Marking. Each service disconnecting means shall be permanently marked to identify it as a service disconnecting means. ARTICLE 230 - SERVICES 70-81 (c) Suitable For Use. Each service disconnecting means shall be suitable for the prevailing conditions. Service equipment installed in hazardous (classified) locations shall comply with the requirements of Articles 500 through 517. 230-71. Maximum Number of Disconnects. (a) General. The service disconnecting means for each service permitted by Section 230-2, or for each set of service-entrance conductors permitted by Section 230-40, Exception No. 1, shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be no more than six disconnects per service grouped in any one location. Exception: For the purpose of this section, disconnecting means used solely for the control circuit of the ground-fault protection system, installed as part of the listed equipment, shall not be considered a service disconnecting means. (b) Single-Pole Units. Two or three single-pole switches or breakers, capable of individual operation, shall be permitted on multiwire circuits, one pole for each ungrounded conductor, as one multipole disconnect, provided they are equipped with "handle ties" or a "master handle" to disconnect all conductors of the service with no more than six operations of the hand. (FPN): See Section 384-16(a) for service equipment in panelboards. 230-72. Grouping of Disconnects. (a) General. The two to six disconnects as permitted in Section 230-71 shall be grouped. Each disconnect shall be marked to indicate the load served. Exception: One of the two to six service disconnecting means permitted in Section 230-71, where used only for a water pump also intended to provide fire protection, shall be permitted to be located remote from the other disconnecting means. (b) Additional Service Disconnecting Means. The one or more additional service disconnecting means for fire pumps or for emergency, legally required standby, or optional standby services permitted by Section 230-2 shall be installed sufficiently remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply. (FPN): See Sections 700-12(d) and (e) for emergency system services. (c) Access to Occupants. In a multiple-occupancy building, each occupant shall have access to the occupant's service disconnecting means. Exception: In a multiple-occupancy building where electric service and electrical maintenance are provided by the building management and where these are under continuous building management supervision, the service disconnecting means supplying more than one occupancy shall be permitted to be accessible to authorized management personnel only. 70-82 NATIONAL ELECTRICAL CODE 230-74. Simultaneous Opening of Poles. Each service disconnecting means shall simultaneously disconnect all ungrounded service conductors from the premises wiring system. 230-75. Disconnection of Grounded Conductor. Where the service disconnecting means does not disconnect the grounded conductor from the premises wiring, other means shall be provided for this purpose in the service equipment. A terminal or bus to which all grounded conductors can be attached by means of pressure connectors shall be permitted for this purpose. In a multisection switchboard, disconnects for the grounded conductor shall be permitted to be in any section of the switchboard, provided any such switchboard section is marked. 230-76. Manually or Power Operable. The service disconnecting means for ungrounded service conductors shall consist of either (1) a manually operable switch or circuit breaker equipped with a handle or other suitable operating means, or (2) a power-operated switch or circuit breaker provided the switch or circuit breaker can be opened by hand in the event of a power supply failure. 230-77. Indicating. The service disconnecting means shall plainly indicate whether it is in the open or closed position. 230-78. Externally Operable. An enclosed service disconnecting means shall be externally operable without exposing the operator to contact with energized parts. Exception: A power-operated switch or circuit breaker shall not be required to be externally operable by hand to a closed position. 230-79. Rating of Disconnect. The service disconnecting means shall have a rating not less than the load to be carried, determined in accordance with Article 220. In no case shall the rating be lower than specified in (a), (b), (c), or (d) below. (a) One-Circuit Installation. For installations to supply only limited loads of a single branch circuit, the service disconnecting means shall have a rating of not less than 15 amperes. (b) Two-Circuit Installations. For installations consisting of not more than two 2-wire branch circuits, the service disconnecting means shall have a rating of not less than 30 amperes. (c) One-Family Dwelling. For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire under either of the following conditions: (1) where the initial computed load is 10 kVA or more, or (2) where the initial installation consists of six or more 2-wire branch circuits. (d) All Others. For all other installations, the service disconnecting means shall have a rating of not less than 60 amperes. ARTICLE 230 - SERVICES 70-83 230-80. Combined Rating of Disconnects. Where the service disconnecting means consists of more than one switch or circuit breaker, as permitted by Section 230-71, the combined ratings of all the switches or circuit breakers used shall not be less than the rating required for a single switch or circuit breaker. 230-81. Connection to Terminals. The service conductors shall be connected to the service disconnecting means by pressure connectors, clamps, or other approved means. Connections that depend upon solder shall not be used. 230-82. Equipment Connected to the Supply Side of Service Disconnect. Equipment shall not be connected to the supply side of the service disconnecting means. (FPN): It is not the intent of this section to require individual meter socket enclosures to be suitable for use as service equipment. Exception No. 1: Cable limiters or other current-limiting devices. Exception No. 2: Fuses and disconnecting means or circuit breakers suitable for use as service equipment, in meter pedestals or otherwise provided and connected in series with the ungrounded service conductors and located away from the building supplied. Exception No. 3: Meters nominally rated not in excess of 600 volts, provided all metal housings and service enclosures are grounded in accordance with Article 250. Exception No. 4: Instrument transformers (current and voltage), highimpedance shunts, surge-protective devices identified for use on the supply arresters. side of the service disconnect, load management devices, and surge Exception No. 5: Taps used only to supply load management devices, circuits for emergency systems, stand-by power systems, fire pump equipment, and fire and sprinkler alarms if provided with service equipment and installed in accordance with requirements for serviceentrance conductors. Exception No. 6: Solar photovoltaic systems or interconnected electric power production sources. See Articles 690 or 705 as applicable. Exception No. 7: Where the service disconnecting means is power operable, the control circuit shall be permitted to be connected ahead of the service disconnecting means if suitable overcurrent protection and disconnecting means are provided. Exception No. 8: Ground-fault protection systems where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided. 230-83. Transfer Equipment. Transfer equipment, including transfer switches, shall operate such that all ungrounded conductors of one source of supply are disconnected before any ungrounded conductors of the second source are connected. 70-84 NATIONAL ELECTRICAL CODE Exception No. 1: Where manual equipment identified for the purpose or suitable automatic equipment is utilized, two or more sources shall be permitted to be connected in parallel through transfer equipment. Exception No. 2: Where parallel operation is used and suitable automatic or manual control equipment is provided. G. Service Equipment - - Overcurrent Protection 230-90. Where Required. Each ungrounded service conductor shall have overload protection. (a) Ungrounded Conductor. Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor having a rating or setting not higher than the allowable ampacity of the conductor. Exception No. 1: For motor-starting currents, ratings in conformity with Sections 430-52, 430-62, and 430-63 shall be permitted. Exception No. 2: Fuses and circuit breakers with a rating or setting in conformity with Section 240-3(b) or (c) and Section 240-6. Exception No. 3: Not more than six circuit breakers or six sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load in accordance with Article 220 does not exceed the ampacity of the service conductors. Exception No. 4: Fire Pumps. Where the service to the fire pump room is judged to be outside of buildings, these provisions shall not apply. Overcurrent protection for fire pump services shall be selected or set to carry locked-rotor current of the motor(s) indefinitely. (FPN): See Centrifugal Fire Pumps, NFPA 20-1990 (ANSI). A set of fuses shall be considered all the fuses required to protect all the ungrounded conductors of a circuit. Single-pole circuit breakers, grouped in accordance with Section 230-71(b), shall be considered as one protective device. (b) Not in Grounded Conductor. No overcurrent device shall be inserted in a grounded service conductor except a circuit breaker that simultaneously opens all conductors of the circuit. 230-91. Location of Overcurrent Protection. (a) General. The service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto. (b) Access to Occupants. In a multiple-occupancy building, each occupant shall have access to the overcurrent protective devices. Exception: As permitted in Section 240-24(b), Exception. 230-92. Locked Service Overcurrent Devices. Where the service overcurrent devices are locked or sealed, or otherwise not readily accessible, ARTICLE 230 - SERVICES 70-85 branch-circuit overcurrent devices shall be installed on the load side, shall be mounted in a readily accessible location, and shall be of lower ampere rating than the service overcurrent device. 230-93. Protection of Specific Circuits. Where necessary to prevent tampering, an automatic overcurrent device protecting service conductors supplying only a specific load, such as a water heater, shall be permitted to be locked or sealed where located so as to be accessible. 230-94. Relative Location of Overcurrent Device and Other Service Equipment. The overcurrent device shall protect all circuits and devices. Exception No. 1: The service switch shall be permitted on the supply side. Exception No. 2: High-impedance shunt circuits, lightning arresters, surge protective capacitors, and instrument transformers (current and voltage) shall be permitted to be connected and installed on the supply side of the service disconnecting means as permitted in Section 230-82. Exception No. 3: Circuits for emergency supply and load management devices shall be permitted to be connected on the supply side of the service overcurrent device where separately provided with overcurrent protection. Exception No. 4: Circuits used only for the operation of fire alarm, other protective signaling systems, or the supply to fire pump equipment shall be permitted to be connected on the supply side of the service overcurrent device where separately provided with overcurrent protection. Exception No. 5: Meters nominally rated not in excess of 600 volts, provided all metal housings and service enclosures are grounded in accordance with Article 250. Exception No. 6: Where service equipment is power operable, the control circuit shall be permitted to be connected ahead of the service equipment if suitable overcurrent protection and disconnecting means are provided. 230-95. Ground-Fault Protection of Equipment. Ground-fault protection of equipment shall be provided for solidly grounded wye electrical services of more than 150 volts to ground, but not exceeding 600 volts phaseto-phase for each service disconnecting means rated 1000 amperes or more. Exception No. 1: The provisions of this section shall not apply to a service disconnecting means for a continuous industrial process where a nonorderly shutdown will introduce additional or increased hazards. Exception No. 2: The provisions of this section shall not apply to fire pumps. (a) Setting. The ground-fault protection system shall operate to cause the service disconnecting means to open all ungrounded conductors of the faulted circuit. The maximum setting of the ground-fault protection shall be 1200 amperes, and the maximum time delay shall be one second for ground-fault currents equal to or greater than 3000 amperes. 70-86 NATIONAL ELECTRICAL CODE (b) Fuses. If a switch and fuse combination is used, the fuses employed shall be capable of interrupting any current higher than the interrupting capacity of the switch during a time when the ground-fault protective system will not cause the switch to open. (FPN No. 1): As used in this section, the rating of the service disconnecting means is considered to be the rating of the largest fuse that can be installed or the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted. (FPN No. 2): It is recognized that ground-fault protection may be desirable for service disconnecting means rated less than 1000 amperes on solidly grounded wye systems having more than 150 volts to ground, not exceeding 600 volts phase-tophase. (FPN No. 3): As used in this section, solidly grounded means that the grounded conductor (neutral) is grounded without inserting any resistor or impedance device. (FPN No. 4): Ground-fault protection that functions to open the service disconnecting means will afford no protection from faults on the line side of the protective element. It serves only to limit damage to conductors and equipment on the load side in the event of an arcing ground fault on the load side of the protective element. (FPN No. 5): This added protective equipment at the service equipment will make it necessary to review the overall wiring system for proper selective overcurrent protection coordination. Additional installations of ground-fault protective equipment will be needed on feeders and branch circuits where maximum continuity of electrical service is necessary. (FPN No. 6): Where ground-fault protection is provided for the service disconnecting means and interconnection is made with another supply system by a transfer device, means or devices may be needed to assure proper ground-fault sensing by the ground-fault protection equipment. (c) Performance Testing. The ground-fault protection system shall be performance tested when first installed on site. The test shall be conducted in accordance with instructions which shall be provided with the equipment. A written record of this test shall be made and shall be available to the authority having jurisdiction. H. Services Exceeding 600 Volts, Nominal 230-200. General. Service conductors and equipment used on circuits exceeding 600 volts, nominal, shall comply with all applicable provisions of the preceding sections of this article and with the following sections, which supplement or modify the preceding sections. In no case shall the provisions of this article apply to equipment on the supply side of the service point. (FPN): For clearances of conductors of over 600 volts, nominal, see National Electrical Safety Code, ANSI C2-1990. 230-202. Service-Entrance Conductors. Service-entrance conductors to buildings or enclosures shall be installed to conform to the following: ARTICLE 230 - SERVICES 70-87 (a) Conductor Size. Service-entrance conductors shall not be smaller than No. 6 unless in cable. Conductors in cable shall not be smaller than No. 8. (b) Wiring Methods. Service-entrance conductors shall be installed by means of one of the following wiring methods: (1) in rigid metal conduit; (2) in intermediate metal conduit; (3) in rigid nonmetallic conduit; (4) as multiconductor cable identified as service cable; (5) as open conductors where supported on insulators and where either accessible only to qualified persons or where effectively guarded against accidental contact; (6) in cablebus; or (7) in busways. Underground service-entrance conductors shall conform to Section 710-4(b). Cable tray systems shall be permitted to support cables identified as service-entrance conductors. See Article 318. (FPN): See Section 310-6 for shielding of solid dielectric insulated conductors. (c) Open Work. Open wire services shall be installed in accordance with the provisions of Article 710, Part D. (d) Supports. Service-entrance conductors and their supports, including insulators, shall have strength and stability sufficient to ensure maintenance of adequate clearance with abnormal currents in case of short circuits. (e) Guarding. Open wires shall be guarded to make them accessible only to qualified persons. (f) Service Cable. Where cable conductors emerge from a metal sheath or raceway, the insulation of the conductors shall be protected from moisture and physical damage by a pothead or other approved means. (g) Draining Raceways. Unless conductors identified for use in wet locations are used, raceways embedded in masonry or exposed to the weather shall be arranged to drain. (h) Over 15,000 Volts. Where the voltage exceeds 15,000 volts between conductors, they shall enter either metal-enclosed switchgear or a transformer vault conforming to the requirements of Sections 450-41 through 450-48. 230-203. Warning Signs. Signs with the words "Danger High Voltage- Keep Out" shall be posted in plain view where unauthorized persons might come in contact with energized parts. 230-204. Isolating Switches. (a) Where Required. Where oil switches or air, oil, vacuum, or sulfur hexafluoride circuit breakers constitute the service disconnecting means, an air-break isolating switch shall be installed on the supply side of the disconnecting means and all associated service equipment. Exception: Where such equipment is mounted on removable truck panels or metal-enclosed switchgear units, which cannot be opened unless the 70-88 NATIONAL ELECTRICAL CODE circuit is disconnected, and which, when removed from the normal operating position, automatically disconnect the circuit breaker or switch from all energized parts. (b) Fuses as Isolating Switch. Where fuses are of the type that can be operated as a disconnecting switch, a set of such fuses shall be permitted as the isolating switch where: (1) the oil disconnecting means is a nonautomatic switch, and (2) the set of fuses disconnect the oil switch and all associated service equipment from the service conductors. (c) Accessible to Qualified Persons Only. The isolating switch shall be accessible to qualified persons only. (d) Grounding Connection. Isolating switches shall be provided with a means for readily connecting the load side conductors to ground when disconnected from the source of supply. A means for grounding the load side conductors shall not be required for any duplicate isolating switch installed and maintained by the electric supply company. 230-205. Disconnecting Means. (a) Location. The service disconnecting means shall be located in accordance with Section 230-70 or Section 230-208(b). Exception: Where under single management, the service disconnecting means shall be permitted to be located in a separate building or structure on the same premises. In such case, the service disconnecting means shall be capable of being electrically opened by a readily accessible control device located as near as practicable to where the feeder conductors enter the building served. The control device shall be permanently marked to identify its function and shall provide visual indication of the "on" or "off" status of the remote service disconnect. (b) Type. The service disconnecting means shall simultaneously disconnect all ungrounded conductors and shall have a fault-closing rating not less than the maximum short-circuit current available at its supply terminals. Where fused switches or separately mounted fuses are installed, the fuse characteristics shall be permitted to contribute to the fault-closing rating of the disconnecting means. 230-206. Overcurrent Devices as Disconnecting Means. Where the circuit breaker or alternative for it specified in Section 230-208 for service overcurrent devices meets the requirements specified in Section 230-205, they shall constitute the service disconnecting means. 230-207. Equipment in Secondaries. Where the primary service equipment supplies one or more transformers whose secondary windings connect to a common bus of bars or wires, and the primary load-interrupter switch or circuit breaker is capable of being opened and closed from a point outside the transformer vault, the disconnecting means and overcurrent protection shall not be required in the secondary circuit if the primary fuse or circuit breaker is rated or set to protect the secondary circuit. ARTICLE 230 - SERVICES 70-89 230-208. Overcurrent Protection Requirements. Service-entrance conductors shall have a short-circuit protective device in each ungrounded conductor on the load side of, or as an integral part of, the service-entrance switch. The protective device shall be capable of detecting and interrupting all values of current in excess of its trip setting or melting point, that can occur at its location. A fuse rated in continuous amperes not to exceed three times the ampacity of the conductor, or a circuit breaker with a trip setting of not more than six times the ampacity of the conductors, shall be considered as providing the required short-circuit protection. (FPN): See Tables 310-69 through 310-84 for ampacities of conductors rated 2001 volts and above. Overcurrent devices shall conform to the following: (a) In Vault or Consisting of Metal-Enclosed Switchgear. Where the service equipment is installed in a transformer vault meeting the provisions of Sections 450-41 through 450-48, or consists of metal-enclosed switchgear, the overcurrent protection and disconnecting means shall be one of the following: (1) A nonautomatic oil switch, oil fuse cutout, or air load-interrupter switch shall be permitted with fuses. The interrupting rating of this switch shall equal or exceed the continuous current rating of the fuse. (2) An automatic trip circuit breaker of suitable current-carrying and interrupting capacity. (3) A switch capable of interrupting the no-load current of the transformer supplied through the switch and suitable fuses shall be permitted provided the switch is interlocked with a single switch or circuit breaker on the secondary circuit of the transformer so that the primary switch cannot be opened when the secondary circuit is closed. (b) Not in Vault or Not Consisting of Metal-Enclosed Switchgear. Where the service equipment is not in a vault or metal-enclosed switchgear, the overcurrent protection and disconnecting means shall be either of the following: (1) An air load-interrupter switch or other switch capable of interrupting the rated circuit load shall be permitted with fuses on a pole or elevated structure outside the building, provided the switch is operable by persons using the building. (2) An automatic-trip circuit breaker of suitable ampacity and interrupting capacity. The circuit breaker shall be located outside the building as near as practicable to where the feeder conductors enter the building. The location shall be permitted on a pole, roof, foundation, or other structure. (c) Fuses. Fuses shall have an interrupting rating no less than the maximum available short-circuit current in the circuit at their supply terminals. (d) Circuit Breakers. Circuit breakers shall be free to open in case. the circuit is closed on an overload. This can be accomplished by means such as trip-free circuit breakers. A service circuit breaker shall indicate clearly whether it is open or closed, and shall have an interrupting rating no less than the maximum available short-circuit current at its supply terminals. 70-90 NATIONAL ELECTRICAL CODE Overcurrent relays shall be furnished in connection with current transformers in one of the following combinations: (1) Three overcurrent relays operated from current transformers in each phase. (2) Two overcurrent relays operated by current from current transformers in any two phases and one overcurrent relay sensitive to groundfault current that is operated by the sum of the currents from current transformers in each phase. (3) Two overcurrent relays operated by current from current transformers in any two phases and one overcurrent relay sensitive to groundfault current that is operated from a current transformer that links all three phase conductors and the grounded circuit conductor (neutral), if provided. (e) Enclosed Overcurrent Devices. The restriction to 80 percent of rating for an enclosed overcurrent device on continuous loads shall not apply to overcurrent devices installed in services operating at over 600 volts. 230-209. Surge Arresters (Lightning Arresters). Surge arresters installed in accordance with the requirements of Article 280 shall be permitted on each ungrounded overhead service conductor. 230-210. Service Equipment-General Provisions. Service equipment including instrument transformers shall conform to Article 710, Part B. 230-211. Metal-Enclosed Switchgear. Metal-enclosed switchgear shall consist of a substantial metal structure and a sheet metal enclosure. Where installed over a combustible floor, suitable protection thereto shall be provided.