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

(d) Tap Conductors. Tap conductors shall be permitted to be protected against overcurrent in accordance with Sections 210-19(c), 240-21, 364-11, 364-12, and 430-53(d). (e) Motor-Operated Appliance Circuit Conductors. Motor-operated appliance circuit conductors shall be permitted to be protected against overcurrent in accordance with Parts B and D of Article 422. (f) Motor and Motor-Control Circuit Conductors. Motor and motorcontrol circuit conductors shall be permitted to be protected against overcurrent in accordance with Parts C, D, E, and F of Article 430. (g) Phase Converter Supply Conductors. Phase converter supply conductors for motor loads and nonmotor loads shall be permitted to be protected against overcurrent in accordance with Section 455-7. (h) Air-Conditioning and Refrigeration Equipment Circuit Conductors. Air-conditioning and refrigeration equipment circuit conductors shall be permitted to be protected against overcurrent in accordance with Parts C and F of Article 440. (i) Transformer Secondary Conductors. Single-phase (other than 2-wire) and multiphase transformer secondary conductors are not considered to be protected by the primary overcurrent protection. Conductors supplied by the secondary side of a single-phase transformer having a 2-wire (single-voltage) secondary shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided this protection is in accordance with Section 450-3 and does not exceed the value determined by multiplying the secondary conductor ampacity by the secondary to primary transformer voltage ratio. (j) Capacitor Circuit Conductors. Capacitor circuit conductors shall be permitted to be protected against overcurrent in accordance with Sections 460-8(b) and 460-25(a) through (d). (k) Electric Welder Circuit Conductors. Welder circuit conductors shall be permitted to be protected against overcurrent in accordance with Sections 630-12, 630-22, and 630-32. (I) Remote-Control, Signaling, and Power-Limited Circuit Conductors. Remote-control, signaling, and power-limited circuit conductors shall be permitted to be protected against overcurrent in accordance with Sections 725-12, 725-13, 725-31, 725-35, and 725-36. ARTICLE 240 - OVERCURRENT PROTECTION 70-93 (m) Fire Protective Signaling System Circuit Conductors. Fire protective signaling system circuit conductors shall be permitted to be protected against overcurrent in accordance with Sections 760-12, 760-13, 760-21, 760-23, and 760-24. 240-4. Protection of Flexible Cords and Fixture Wires. Flexible cord, including tinsel cord and extension cords, shall be protected against overcurrent in accordance with their ampacities as specified in Tables 400-5(A) and 400-5(B). Fixture wire shall be protected against overcurrent in accordance with its ampacity as specified in Table 402-5. Supplementary overcurrent protection as in Section 240-10 shall be permitted to be an acceptable means for providing this protection. Exception No. 1: Where a flexible cord or a tinsel cord approved for and used with a specific listed appliance or portable lamps is connected to a branch circuit of Article 210 in accordance with the following: 20-ampere circuits, tinsel cord or No. 18 cord and larger. 30-ampere circuits, No. 16 cord and larger. 40-ampere circuits, cord of 20-ampere capacity and over. 50-ampere circuits, cord of 20-ampere capacity and over. Exception No. 2: Where fixture wire is connected to 120-volt or higher branch circuit of Article 210 in accordance with the following: 20-ampere circuits, No. 18 up to 50 feet (15.2 m) of run length. 20-ampere circuits, No. 16 up to 100 feet (30.5 m) of run length. 20-ampere circuits, No. 14 and larger. 30-ampere circuits, No. 14 and larger. 40-ampere circuits, No. 12 and larger. 50-ampere circuits, No. 12 and larger. Exception No. 3: Flexible cord used in listed extension cord sets having No. 16 or larger conductors shall be considered to be protected by 20-ampere branch-circuit overcurrent protection. 240-6. Standard Ampere Ratings. (a) Fuses and Fixed Trip Circuit Breakers. The standard ampere ratings for fuses and inverse time circuit breakers shall be considered 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amperes. Exception: Additional standard ratings for fuses shall be considered 1, 3, 6, 10, and 601. (b) Adjustable Trip Circuit Breakers. The rating of an adjustable trip circuit breaker having external means for adjusting the long-time pickup (ampere rating or overload) setting shall be the maximum setting possible. Exception: Circuit breakers that have removable and sealable covers over the adjusting means, or are located behind bolted equipment enclosure doors, or are located behind locked doors accessible only to qualified personnel, shall be permitted to have ampere ratings equal to the adjusted (set) long-time pickup settings. 70-94 NATIONAL ELECTRICAL CODE (FPN): It is not the intent to prohibit the use of nonstandard ampere ratings for fuses and inverse time circuit breakers. 240-8. Fuses or Circuit Breakers in Parallel. Fuses, circuit breakers, or combinations thereof shall not be connected in parallel. Exception: Circuit breakers or fuses, factory-assembled in parallel, and listed as a unit. 240-9. Thermal Devices. Thermal relays and other devices not designed to open short circuits shall not be used for the protection of conductors against overcurrent due to short circuits or grounds, but the use of such devices shall be permitted to protect motor-branch-circuit conductors from overload if protected in accordance with Section 430-40. 240-10. Supplementary Overcurrent Protection. Where supplementary overcurrent protection is used for lighting fixtures, appliances, and other equipment or for internal circuits and components of equipment, it shall not be used as a substitute for branch-circuit overcurrent devices or in place of the branch-circuit protection specified in Article 210. Supplementary overcurrent devices shall not be required to be readily accessible. 240-11. Definition of Current-Limiting Overcurrent Protective Device. A current-limiting overcurrent protective device is a device that, when interrupting currents in its current-limiting range, will reduce the current flowing in the faulted circuit to a magnitude substantially less than that obtainable in the same circuit if the device were replaced with a solid conductor having comparable impedance. 240-12. Electrical System Coordination. Where an orderly shutdown is required to minimize hazard(s) to personnel and equipment, a system of coordination based on the following two conditions shall be permitted: (1) Coordinated short-circuit protection. (2) Overload indication based on monitoring systems or devices. (FPN): Coordination is defined as properly localizing a fault condition to restrict outages to the equipment affected, accomplished by choice of selective faultprotective devices. The monitoring system may cause the condition to go to alarm, allowing corrective action or an orderly shutdown, thereby minimizing personnel hazard and equipment damage. 240-13. Ground-Fault Protection of Equipment. Ground-fault protection of equipment shall be provided in accordance with the provisions of Section 230-95 for solidly grounded wye electrical systems of more than 150 volts to ground, but not exceeding 600 volts phase-to-phase for each building or structure main disconnecting means rated 1000 amperes or more. Exception No. 1: The provisions of this section shall not apply to a 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. Exception No. 3: The provisions of this section shall not apply if the disconnect is protected by the service ground-fault protection, and this ARTICLE 240 - OVERCURRENT PROTECTION 70-95 protection is not nullified by subsequent grounded circuit conductor connections to additional grounding electrodes, as may be permitted in Section 250-24. B. Location 240-20. Ungrounded Conductors. (a) Overcurrent Device Required. A fuse or an overcurrent trip unit of a circuit breaker shall be connected in series with each ungrounded conductor. A combination of a current transformer and overcurrent relay shall be considered equivalent to an overcurrent trip unit. (FPN): For motor circuits, see Parts C, D, F, and J of Article 430. (b) Circuit Breaker as Overcurrent Device. Circuit breakers shall open all ungrounded conductors of the circuit. Exception: In grounded systems, individual single-pole circuit breakers with handle ties shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads of the following: a. Single-phase circuits, b. 3- wire direct-current circuits, or C. Lighting or appliance branch circuits connected to 4-wire, 3-phase systems or 5-wire, 2-phase systems, provided such lighting or appliance circuits are supplied from a system having a grounded neutral and no conductor operates at a voltage greater than permitted in Section 210-6. (c) Closed-Loop Power Distribution Systems. Listed devices providing equivalent overcurrent protection in closed-loop power distribution systems shall be permitted as a substitute for fuses or circuit breakers. 240-21. Location in Circuit. An overcurrent device shall be connected in each ungrounded circuit conductor as follows: (a) Feeder and Branch-Circuit Conductors. Feeder and branch-circuit conductors shall be protected by overcurrent-protective devices connected at the point the conductors receive their supply, unless otherwise permitted in (b) through (m) below. (b) Feeder Taps Not Over 10 Feet (3.05 m) Long. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder or transformer secondary where all the following conditions are met: (1) The length of the tap conductors does not exceed 10 feet (3.05 m). (2) The ampacity of the tap conductors is: a. Not less than the combined computed loads on the circuits supplied by the tap conductors, and b. Not less than the rating of the device supplied by the tap conductors, or not less than the rating of the overcurrent-protective device at the termination of the tap conductors. 70-96 NATIONAL ELECTRICAL CODE (3) The tap conductors do not extend beyond the switchboard, panelboard, or control devices they supply. (4) Except at the point of connection to the feeder, the tap conductors are enclosed in a raceway, which shall extend from the tap to the enclosure of an enclosed switchboard, panelboard, or control devices, or to the back of an open switchboard. (5) For field installations where the tap conductors leave the enclosure or vault in which the tap is made, the rating of the overcurrent device on the line side of the tap conductors shall not exceed 1000 percent of the tap conductor's ampacity. (FPN): See Sections 384-16(a) and (d) for lighting and appliance branch-circuit panelboards. (c) Feeder Taps Not Over 25 Feet (7.62 m) Long. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder where all the following conditions are met: (1) The length of the tap conductors does not exceed 25 feet (7.62 m). (2) The ampacity of the tap conductors is not less than ½ of the rating of the overcurrent device protecting the feeder conductors. (3) The tap conductors terminate in a single circuit breaker or a single set of fuses that will limit the load to the ampacity of the tap conductors. This device shall be permitted to supply any number of additional overcurrent devices on its load side. (4) The tap conductors are suitably protected from physical damage or are enclosed in a raceway. (d) Transformer Feeder Taps With Primary Plus Secondary Not Over 25 Feet (7.62 m) Long. Conductors supplying a transformer shall be permitted to be tapped, without overcurrent protection at the tap, from a feeder where all the following conditions are met: (1) The conductors supplying the primary of a transformer have an ampacity at least ½ of the rating of the overcurrent device protecting the feeder conductors. (2) The conductors supplied by the secondary of the transformer shall have an ampacity that, when multiplied by the ratio of the secondary-toprimary voltage, is at least ½ of the rating of the overcurrent device protecting the feeder conductors. (3) The total length of one primary plus one secondary conductor, excluding any portion of the primary conductor that is protected at its ampacity, is not over 25 feet (7.62 m). (4) The primary and secondary conductors are suitably protected from physical damage. (5) The secondary conductors terminate in a single circuit breaker or set of fuses that will limit the load to that allowed in Section 310-15. (e) Feeder Taps Over 25 Feet (7.62 m) Long. Conductors over 25 feet (7.62 m) long shall be permitted to be tapped from feeders in high bay ARTICLE 240 - OVERCURRENT PROTECTION 70-97 manufacturing buildings over 35 feet (10.67 m) high at walls, where conditions of maintenance and supervision ensure that only qualified persons will service the systems. Conductors tapped, without overcurrent protection at the tap, to a feeder shall be permitted to be not over 25 feet (7.62 m) long horizontally and not over 100 feet (30.5 m) total length where all the following conditions are met: (1) The ampacity of the tap conductors is not less than ½ of the rating of the overcurrent device protecting the feeder conductors. (2) The tap conductors terminate at a single circuit breaker or a single set of fuses that will limit the load to the ampacity of the tap conductors. This single overcurrent device shall be permitted to supply any number of additional overcurrent devices on its load side. (3) The tap conductors are suitably protected from physical damage or are enclosed in a raceway. (4) The tap conductors are continuous from end-to-end and contain no splices. (5) The tap conductors are sized No. 6 copper or No. 4 aluminum or larger. (6) The tap conductors do not penetrate walls, floors, or ceilings. (7) The tap is made no less than 30 feet (9.14 m) from the floor. (f) Branch-Circuit Taps. Taps to individual outlets and circuit conductors supplying a single electric household range shall be permitted to be protected by the branch-circuit overcurrent devices where in accordance with the requirements of Sections 210-19, 210-20, and 210-24. (g) Busway Taps. Busways and busway taps shall be permitted to be protected against overcurrent in accordance with Sections 364-10 through 364-14. (h) Motor Circuit Taps. Motor-branch-circuit conductors shall be permitted to be protected against overcurrent in accordance with Sections 430-28 and 430-53. (i) Conductors From Generator Terminals. Conductors from generator terminals shall be permitted to be protected against overcurrent in accordance with Section 445-5. (j) Transformer Secondary Conductors of Separately Derived Systems for Industrial Installations. Conductors connected to a transformer secondary of a separately derived system for industrial installations shall be considered to be protected against overcurrent where all the following conditions are met: (1) The length of the secondary conductors does not exceed 25 feet (7.62 m). (2) The ampacity of the secondary conductors is not less than the secondary current rating of the transformer, and the sum of the ratings of the overcurrent devices does not exceed the ampacity of the secondary conductors. (3) All overcurrent devices are grouped. 70-98 NATIONAL ELECTRICAL CODE (4) The tap conductors are suitably protected from physical damage. (m) Outside Feeder Taps. Outside conductors tapped to a feeder or connected to a transformer secondary shall be permitted to be protected by complying with all of the following conditions: (1) The conductors are suitably protected from physical damage. (2) The conductors terminate at a single circuit breaker or a single set of fuses that will limit the load to the ampacity of the conductors. This single overcurrent device shall be permitted to supply any number of additional overcurrent devices on its load side. (3) The overcurrent device for the conductors is an integral part of a disconnecting means or shall be located immediately adjacent thereto. (4) The disconnecting means for the conductors are installed at a readily accessible location either outside of a building or structure, or inside nearest the point of entrance of the conductors. (n) Service Conductors. Service-entrance conductors shall be permitted to be protected by overcurrent devices in accordance with Section 230-91. 240-22. Grounded Conductors. No overcurrent device shall be connected in series with any conductor that is intentionally grounded. Exception No. 1: Where the overcurrent device opens all conductors of the circuit, including the grounded conductor, and is so designed that no pole can operate independently. Exception No. 2: Where required by Sections 430-36 and 430-37 for motor overload protection. 240-23. Change in Size of Grounded Conductor. Where a change occurs in the size of the ungrounded conductor, a similar change shall be permitted to be made in the size of the grounded conductor. 240-24. Location in or on Premises. (a) Readily Accessible. Overcurrent devices shall be readily accessible. Exception No. 1: For busways as provided in Section 364-12. Exception No. 2: For supplementary overcurrent protection as described in Section 240-10. Exception No. 3: For service overcurrent devices as described in Section 230-92. (b) Occupant to Have Ready Access. Each occupant shall have ready access to all overcurrent devices protecting the conductors supplying that occupancy. Exception: In a multiple-occupancy building where electric service and electrical maintenance are provided by the building management and ARTICLE 240 - OVERCURRENT PROTECTION 70-99 where these are under continuous building management supervision, the service overcurrent devices and feeder overcurrent devices supplying more than one occupancy shall be permitted to be accessible to authorized management personnel only. (c) Not Exposed to Physical Damage. Overcurrent devices shall be located where they will not be exposed to physical damage. (FPN): See Section 110-11, Deteriorating Agents. (d) Not in Vicinity of Easily Ignitible Material. Overcurrent devices shall not be located in the vicinity of easily ignitible material such as in clothes closets. (e) Not Located in Bathrooms. In dwelling units and guest rooms of hotels and motels, branch-circuit overcurrent devices shall not be located in bathrooms as defined in Section 210-8. C. Enclosures 240-30. General. Overcurrent devices shall be enclosed in cabinets or cutout boxes. Exception No. 1: Where a part of an assembly that provides equivalent protection. Exception No. 2: Where mounted on open-type switchboards, panelboards, or control boards that are in rooms or enclosures free from dampness and easily ignitible material and accessible only to qualified personnel. Exception No. 3: The operating handle of a circuit breaker shall be permitted to be accessible without opening a door or cover. 240-32. Damp or Wet Locations. Enclosures for overcurrent devices in damp or wet locations shall comply with Section 373-2(a). 240-33. Vertical Position. Enclosures for overcurrent devices shall be mounted in a vertical position. Exception: Where this is shown to be impracticable and complies with