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

85 85 90 140 Periodic Duty Rolls, ore- and coal-handling machines, etc. 85 90 95 140 Varying Duty 110 120 150 200 Any motor application shall be considered as continuous duty unless the nature of the apparatus it drives is such that the motor will not operate continuously with load under any condition of use. (b) Separate Terminal Enclosure. The conductors between a stationary motor rated 1 horsepower or less and the separate terminal enclosure permitted in Section 430-145(b) shall be permitted to be smaller than No. 14 but not smaller than No. 18, provided they have an ampacity as specified in (a) above. 430-23. Wound-Rotor Secondary. (a) Continuous Duty. For continuous duty, the conductors connecting the secondary of a wound-rotor alternating-current motor to its controller shall have an ampacity not less than 125 percent of the full-load secondary current of the motor. (b) Other than Continuous Duty. For other than continuous duty, these conductors shall have an ampacity, in percent of full-load secondary current, not less than that specified in Table 430-22(a), Exception. (c) Resistor Separate from Controller. Where the secondary resistor is separate from the controller, the ampacity of the conductors between controller and resistor shall not be less than that shown in Table 430-23(c). 70-398 NATIONAL ELECTRICAL CODE Table 430-23(c). Secondary Conductor Ampacity of Conductor in Percent of Full-Load Resistor Duty Classification Secondary Current Light starting duty 35 Heavy starting duty 45 Extra-heavy starting duty 55 Light intermittent duty 65 Medium intermittent duty 75 Heavy intermittent duty 85 Continuous duty 110 430-24. Several Motors or a Motor(s) and Other Load(s). Conductors supplying several motors, or a motor(s) and other load(s), shall have an ampacity at least equal to the sum of the full-load current rating of all the motors, plus 25 percent of the highest rated motor in the group, plus the ampere rating of other loads determined in accordance with Article 220 and other applicable sections. Exception No. 1: Where one or more of the motors of the group are used for short-time, intermittent, periodic, or varying duty, the ampere rating of such motors to be used in the summation shall be determined in accordance with Section 430-22(a), Exception No. 1. For the highest rated motor, the greater of either the ampere rating from 430-22(a), Exception No. 1 or the largest continuous duty motor full-load current multiplied by 1.25 shall be used in the summation. Exception No. 2: The ampacity of conductors supplying motor-operated fixed electric space heating equipment shall conform with Section 424-3(b). Exception No. 3: Where the circuitry is interlocked so as to prevent operation of selected motors or other loads at the same time, the conductor ampacity shall be permitted to be based on the summation of the currents of the motors and other loads to be operated at the same time that results in the highest total current. (FPN): See Chapter 9, Example No. 8. 430-25. Multimotor and Combination-Load Equipment. The ampacity of the conductors supplying multimotor and combination-load equipment shall be not less than the minimum circuit ampacity marked on the equipment in accordance with Section 430-7(d). Where the equipment is not factory-wired and the individual nameplates are visible in accordance with Section 430-7(d)(2), the conductor ampacity shall be determined in accordance with Section 430-24. 430-26. Feeder Demand Factor. Where reduced heating of the conductors results from motors operating on duty-cycle, intermittently, or from all motors not operating at one time, the authority having jurisdiction shall be permitted to grant permission for feeder conductors to have an ampacity less than specified in Section 430-24, provided the conductors have sufficient ampacity for the maximum load determined in accordance with the sizes and number of motors supplied and the character of their loads and duties. ARTICLE 430 - MOTOR CIRCUITS, CONTROLLERS 70-399 430-27. Capacitors with Motors. Where capacitors are installed in motor circuits, conductors shall comply with Sections 460-8 and 460-9. 430-28. Feeder Taps. Feeder tap conductors shall have an ampacity not less than that required by Part B, shall terminate in a branch-circuit protective device and, in addition, shall meet one of the following requirements: (1) be enclosed by either an enclosed controller or by a raceway, be not more than 10 feet (3.05 m) in length, and, for field installation, be protected by an overcurrent device on the line side of the tap conductor, the rating or setting of which shall not exceed 1000 percent of the tap conductor ampacity; or (2) have an ampacity of at least one-third that of the feeder conductors, be protected from physical damage and be not more than 25 feet (7.62 m) in length; or (3) have the same ampacity as the feeder conductors. Exception: Feeder Taps Over 25 Feet (7.62 m) Long. In high-bay manufacturing buildings [over 35 feet (10.67 m) high at walls] conductors tapped to a feeder shall be permitted to be not over 25 feet (7.62 m) long horizontally and not over 100 feet (30.5) total length where all of the following conditions are met: a. The ampacity of the tap conductors is not less than one-third that of the feeder conductors. b. The tap conductors terminate with a single circuit breaker or a single set of fuses conforming with (1) Part D if the tap is a branch circuit or (2) Part E if the tap is a feeder. c. The tap conductors are suitably protected from physical damage and are installed in raceways. d. The tap conductors are continuous from end-to-end and contain no splices. e. The tap conductors shall be No. 6 copper or No. 4 aluminum or I larger. f. The tap conductors shall not penetrate walls, floors, or ceilings. g. The tap shall not be made less than 30 feet (9.14 m) from the floor. 430-29. Constant Voltage DC Motors - Power Resistors. Conductors connecting the motor controller to separately mounted power accelerating and dynamic braking resistors in the armature circuit shall have an ampacity not less than the value calculated from Table 430-29 using motor fullload current. If an armature shunt resistor is used, the power accelerating resistor conductor ampacity shall be calculated using the total of motor full-load current and armature shunt resistor current. Armature shunt resistor conductors shall have an ampacity of not less than that calculated from Table 430-29 using rated shunt resistor current as full-load current. C. Motor and Branch-Circuit Overload Protection 430-31. General. Part C specifies overload devices intended to protect motors, motor-control apparatus, and motor branch-circuit conductors against excessive heating due to motor overloads and failure to start. 70-400 NATIONAL ELECTRICAL CODE Table 430-29. Conductor Rating Factors for Power Resistors Time in Seconds Ampacity of Conductor in Percent On Off of Full-Load Current 5 75 35 10 70 45 15 75 55 15 45 65 15 30 75 15 15 85 Continuous Duty 110 Overload in electrical apparatus is an operating overcurrent that, when it persists for a sufficient length of time, would cause damage or dangerous overheating of the apparatus. It does not include short circuits or ground faults. These provisions shall not be interpreted as requiring overload protection where it might introduce additional or increased hazards, as in the case of fire pumps. (FPN): See Installation of Centrifugal Fire Pumps, NFPA 20-1990 (ANSI). The provisions of Part C shall not apply to motor circuits rated over 600 volts, nominal. See Part J. (FPN): See Chapter 9, Example No. 8. 430-32. Continuous-Duty Motors. (a) More than 1 Horsepower. Each continuous-duty motor rated more than 1 horsepower shall be protected against overload by one of the following means: (1) A separate overload device that is responsive to motor current. This device shall be selected to trip or rated at no more than the following percent of the motor nameplate full-load current rating. Motors with a marked service factor not less than 1.15 125% Motors with a marked temperature rise not over 40° C 125% All other motors 115% Modification of this value shall be permitted as provided in Section 430-34. For a multispeed motor, each winding connection shall be considered separately. Where a separate motor overload device is so connected that it does not carry the total current designated on the motor nameplate, such as for wye-delta starting, the proper percentage of nameplate current applying to the selection or setting of the overload device shall be clearly designated on the equipment, or the manufacturer's selection table shall take this into account. ARTICLE 430 - MOTOR CIRCUITS, CONTROLLERS 70-401 (2) A thermal protector integral with the motor, approved for use with the motor it protects on the basis that it will prevent dangerous overheating of the motor due to overload and failure to start. The ultimate trip current of a thermally protected motor shall not exceed the following percentage of motor full-load current given in Tables 430-148, 430-149, and 430-150. Motor full-load current not exceeding 9 amperes 170% Motor full-load current 9.1 to and including 20 amperes 156% Motor full-load current greater than 20 amperes 140% If the motor current-interrupting device is separate from the motor and its control circuit is operated by a protective device integral with the motor, it shall be so arranged that the opening of the control circuit will result in interruption of current to the motor. (3) A protective device integral with a motor that will protect the motor against damage due to failure to start shall be permitted if the motor is part of an approved assembly that does not normally subject the motor to overloads. (4) For motors larger than 1500 horsepower, a protective device having embedded temperature detectors that cause current to the motor to be interrupted when the motor attains a temperature rise greater than marked on the nameplate in an ambient of 40°C. (b) One Horsepower or Less, Nonautomatically Started. (1) Each continuous-duty motor rated at 1 horsepower or less that is not permanently installed, is nonautomatically started, and is within sight from the controller location shall be permitted to be protected against overload by the branch-circuit short-circuit and ground-fault protective device. This branch-circuit protective device shall not be larger than that specified in Part D of Article 430. Exception: Any such motor shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes. (2) Any such motor that is not in sight from the controller location shall be protected as specified in Section 430-32(c). Any motor rated at 1 horsepower or less that is permanently installed shall be protected in accordance with Section 430-32(c). (c) One Horsepower or Less, Automatically Started. Any motor of 1 horsepower or less that is started automatically shall be protected against overload by one of the following means: (1) A separate overload device that is responsive to motor current. This device shall be selected to trip or rated at no more than the following percentage of the motor nameplate full-load current rating. Motors with a marked service factor not less than 1.15 125% Motors with a marked temperature rise not over 40°C. 125% All other motors 115% 70-402 NATIONAL ELECTRICAL CODE For a multispeed motor, each winding connection shall be considered separately. Modification of this value shall be permitted as provided in