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

(d) Time Delay. The branch-circuit short-circuit and ground-fault protective device protecting a circuit to which a motor or motor-operated appliance is connected shall have sufficient time delay to permit the motor to start and accelerate its load. 430-43. Automatic Restarting. A motor overload device that can restart a motor automatically after overload tripping shall not be installed unless approved for use with the motor it protects. A motor that can restart automatically after shutdown shall not be installed if its automatic restarting can result in injury to persons. 430-44. Orderly Shutdown. If immediate automatic shutdown of a motor by a motor overload protective device(s) would introduce additional or increased hazard(s) to a person(s) and continued motor operation is necessary for safe shutdown of equipment or process, a motor overload sensing device(s) conforming with the provisions of Part C of this article shall be permitted to be connected to a supervised alarm instead of causing immediate interruption of the motor circuit, so that corrective action or an orderly shutdown can be initiated. D. Motor Branch-Circuit Short-Circuit and Ground-Fault Protection 430-51. General. Part D specifies devices intended to protect the motor branch-circuit conductors, the motor control apparatus, and the motors against overcurrent due to short circuits or grounds. They add to or amend the provisions of Article 240. The devices specified in Part D do not include the types of devices required by Sections 210-8, 230-95, and 305-6. 70-406 NATIONAL ELECTRICAL CODE The provisions of Part D do not apply to motor circuits rated over 600 volts, nominal. See Part J. (FPN): See Chapter 9, Example No. 8. 430-52. Rating or Setting for Individual Motor Circuit. The motor branchcircuit short-circuit and ground-fault protective device shall be capable of carrying the starting current of the motor. (a) General Motor Applications. Other than as specified for torque motors in (b) below, a protective device having a rating or setting not exceeding the value calculated according to the values given in Table 430-152 shall be used. Exception No. 1: Where the values for branch-circuit short-circuit and ground-fault protective devices determined by Table 430-152 do not correspond to the standard sizes or ratings of fuses, nonadjustable circuit breakers, thermal protective devices, or possible settings of adjustable circuit breakers, and the next lower standard size, rating, or possible setting is not adequate to carry the load, the next higher standard size, rating, or possible setting shall be permitted. Exception No. 2: Where the rating specified in Table 430-152 is not sufficient for the starting current of the motor: a. The rating of a nontime-delay fuse not exceeding 600 amperes shall be permitted to be increased but shall in no case exceed 400 percent of the full-load current. b. The rating of a time-delay (dual-element) fuse shall be permitted to be increased but shall in no case exceed 225 percent of the full-load current. c. The rating of an inverse time circuit breaker shall be permitted to be increased but shall in no case exceed (1) 400 percent for full-load currents of 100 amperes or less or (2) 300 percent for full-load currents greater than 100 amperes. d. The rating of a fuse of 601-6000 ampere classification shall be permitted to be increased but shall in no case exceed 300 percent of the fullload current. (FPN): See Section 240-6 for standard ratings of fuses and circuit breakers. An instantaneous trip circuit breaker shall be used only if adjustable, and if part of a listed combination controller having coordinated motor overload and short-circuit and ground-fault protection in each conductor, and if it will operate at not more than 1300 percent of full-load motor current. A motor short-circuit protector shall be permitted in lieu of devices listed in Table 430-152 if the motor short-circuit protector is part of a listed combination controller having coordinated motor overload protection and shortcircuit and ground-fault protection in each conductor and if it will operate at not more than 1300 percent of full-load motor current. (FPN): For the purpose of this article, instantaneous-trip circuit breakers may include a damping means to accomodate a transient motor inrush current without nuisance tripping of the circuit breaker. Exception: Where the setting specified in Table 430-152 is not sufficient for the starting current of the motor, the setting of an instantaneous trip circuit breaker shall be permitted to be increased but shall in no case ARTICLE 430 - MOTOR CIRCUITS, CONTROLLERS 70-407 exceed 1300 percent of the motor full-load current. Trip settings above 700 percent shall be permitted where the need has been demonstrated by engineering evaluation. In such cases, it shall not be necessary to first apply an instantaneous trip circuit breaker at 700 percent. For a multispeed motor, a single short-circuit and ground-fault protective device shall be permitted for two or more windings of the motor, provided the rating of the protective device does not exceed the above applicable percentage of the nameplate rating of the smallest winding protected. Exception: For a multispeed motor, a single short-circuit and groundfault protective device shall be permitted to be used and sized according to the full-load current of the highest current winding, provided that each winding is equipped with individual overload protection sized according to its full-load current and that the branch-circuit conductors feeding each winding are sized according to the full-load current of the highest full-load current winding. Where maximum branch-circuit short-circuit and ground-fault protective device ratings are shown in the manufacturer's overload relay table for use with a motor controller or are otherwise marked on the equipment, they shall not be exceeded even if higher values are allowed as shown above. (FPN): See Chapter 9, Example No. 8 and Diagram 430-1. Suitable fuses shall be permitted in lieu of devices listed in Table 430-152 for an adjustable speed drive system or a solid state motor controller system provided that the marking for replacement fuses is provided adjacent to the fuses. (b) Torque Motors. Torque motor branch circuits shall be protected at the motor nameplate current rating in accordance with Section 240-3(b). 430-53. Several Motors or Loads on One Branch Circuit. Two or more motors or one or more motors and other loads shall be permitted to be connected to the same branch circuit under the conditions specified in (a), (b), or (c) below. (a) Not Over 1 Horsepower. Several motors, each not exceeding 1 horsepower in rating, shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes or a branch circuit of 600 volts, nominal, or less, protected at not over 15 amperes, if all of the following conditions are met: (1) The full-load rating of each motor does not exceed 6 amperes. (2) The rating of the branch-circuit short-circuit and ground-fault protective device marked on any of the controllers is not exceeded. (3) Individual overload protection conforms to Section 430-32. (b) If Smallest Rated Motor Protected. If the branch-circuit short-circuit and ground-fault protective device is selected not to exceed that allowed by Section 430-52 for the smallest rated motor, two or more motors or one or more motors and other load(s), with each motor having individual overload protection, shall be permitted to be connected to a branch circuit where it can be determined that the branch-circuit short-circuit and 70-408 NATIONAL ELECTRICAL CODE ground-fault protective device will not open under the most severe normal conditions of service that might be encountered. (c) Other Group Installations. Two or more motors of any rating or one or more motors and other load(s), with each motor having individual overload protection, shall be permitted to be connected to one branch circuit where the motor controller(s) and overload device(s) are (1) installed as a listed factory assembly and the motor branch-circuit short-circuit and ground-fault protective device is either provided as part of the assembly or is specified by a marking on the assembly, or (2) the motor branch-circuit short-circuit and ground-fault protective device, the motor controller(s), and overload device(s) are field-installed as separate assemblies listed for such use and provided with manufacturers' instructions for use with each other, and (3) all of the following conditions are complied with: (1) Each motor overload device is listed for group installation with a specified maximum rating of fuse or inverse time circuit breaker, or both. (2) Each motor controller is listed for group installation with a specified maximum rating of fuse or circuit breaker, or both. (3) Each circuit breaker is one of the inverse time type and listed for group installation. (4) The branch circuit shall be protected by fuses or inverse time circuit breakers having a rating not exceeding that specified in Section 430-52 for the highest rated motor connected to the branch circuit plus an amount equal to the sum of the full-load current ratings of all other motors and the ratings of other loads connected to the circuit. Where this calculation results in a rating less than the ampacity of the supply conductors, it shall be permitted to increase the maximum rating of the fuses or circuit breaker to a value not exceeding that permitted by Section 240-3(b). (5) The branch-circuit fuses or inverse time circuit breakers are not larger than allowed by Section 430-40 for the overload relay protecting the smallest rated motor of the group. (FPN): See Section 110-10 for circuit impedance and other characteristics. (d) Single Motor Taps. For group installations described above, the conductors of any tap supplying a single motor shall not be required to have an individual branch-circuit short-circuit and ground-fault protective device, provided they comply with either of the following: (1) no conductor to the motor shall have an ampacity less than that of the branch-circuit conductors, or (2) no conductor to the motor shall have an ampacity less than one-third that of the branch-circuit conductors, with a minimum in accordance with Section 430-22; the conductors to the motor overload device being not more than 25 feet (7.62 m) long and being protected from physical damage. 430-54. Multimotor and Combination-Load Equipment. The rating of the branch-circuit short-circuit and ground-fault protective device for multimotor and combination-load equipment shall not exceed the rating marked on the equipment in accordance with Section 430-7(d). 430-55. Combined Overcurrent Protection. Motor branch-circuit shortcircuit and ground-fault protection and motor overload protection shall be ARTICLE 430 - MOTOR CIRCUITS, CONTROLLERS 70-409 permitted to be combined in a single protective device where the rating or setting of the device provides the overload protection specified in Section 430-32. 430-56. Branch-Circuit Protective Devices - In Which Conductor. Branchcircuit protective devices shall comply with the provisions of Section 240-20. 430-57. Size of Fuseholder. Where fuses are used for motor branchcircuit short-circuit and ground-fault protection, the fuseholders shall not be of a smaller size than required to accommodate the fuses specified by Table 430-152. Exception: Where fuses having time delay appropriate for the starting characteristics of the motor are used, fuseholders of smaller size than specified in Table 430-152 shall be permitted. 430-58. Rating of Circuit Breaker. A circuit breaker for motor branchcircuit short-circuit and ground-fault protection shall have a current rating in accordance with Sections 430-52 and 430-110. E. Motor Feeder Short-Circuit and Ground-Fault Protection 430-61. General. Part E specifies protective devices intended to protect feeder conductors supplying motors against overcurrents due to short circuits or grounds. (FPN): See Chapter 9, Example No. 8. 430-62. Rating or Setting - Motor Load. (a) Specific Load. A feeder supplying a specific fixed motor load(s) and consisting of conductor sizes based on Section 430-24 shall be provided with a protective device having a rating or setting not greater than the largest rating or setting of the branch-circuit short-circuit and ground-fault protective device for any motor of the group (based on the maximum permitted value for the specific type of a protective device shown in Table 430- 152, or Section 440-22(a) for hermetic refrigerant motor-compressors), plus the sum of the full-load currents of the other motors of the group. Where the same rating or setting of the branch-circuit short-circuit and ground-fault protective device is used on two or more of the branch circuits of the group, one of the protective devices shall be considered the largest for the above calculations. Exception: Where one or more instantaneous trip circuit breakers or motor short-circuit protectors are used for motor branch-circuit shortcircuit and ground-fault protection as permitted in Section 430-52(a), the procedure provided above for determining the maximum rating of the feeder protective device shall apply with the following provision. For the purpose of the calculation, each instantaneous trip circuit breaker or motor short-circuit protector shall be assumed to have a rating not exceeding the maximum percentage of motor full-load current permitted by Table 430-152 for the type of feeder protective device employed. (FPN): See Chapter 9, Example No. 8. 70-410 NATIONAL ELECTRICAL CODE (b) Future Additions. For large-capacity installations, where heavycapacity feeders are installed to provide for future additions or changes, the rating or setting of the feeder protective devices shall be permitted to be based on the ampacity of the feeder conductors. 430-63. Rating or Setting - Power and Light Loads. Where a feeder supplies a motor load and, in addition, a lighting or a lighting and appliance load, the feeder protective device shall be permitted to have a rating or setting sufficient to carry the lighting or the lighting and appliance load as determined in accordance with Articles 210 and 220 plus, for a single motor, the rating permitted by Section 430-52, and, for two or more motors, the rating permitted by Section 430-62. F. Motor Control Circuits 430-71. General. Part F contains modifications of the general requirements and applies to the particular conditions of motor control circuits. (FPN): See Section 430-9(b) for equipment device terminal requirements. Definition of Motor Control Circuit: The circuit of a control apparatus or system that carries the electric signals directing the performance of the controller, but does not carry the main power current. 430-72. Overcurrent Protection. (a) General. A motor control circuit tapped from the load side of a motor branch-circuit short-circuit and ground-fault protective device(s) and functioning to control the motor(s) connected to that branch circuit shall be protected against overcurrent in accordance with Section 430-72. Such a tapped control circuit shall not be considered to be a branch circuit and shall be permitted to be protected by either a supplementary or branchcircuit overcurrent protective device(s). A motor control circuit other than such a tapped control circuit shall be protected against overcurrent in accordance with Section 725-12 or 725-35, as applicable. (b) Conductor Protection. The overcurrent protection for conductors shall not exceed the values specified in Column A of Table 430-72(b). Exception No. 1: Conductors that do not extend beyond the motor control equipment enclosure shall require only short-circuit and ground-fault protection and shall be permitted to be protected by the motor branchcircuit short-circuit and ground-fault protective device(s) where the rating of the protective device(s) is not over the value specified in Column B of Table 430-72(b). Exception No. 2: Conductors that extend beyond the motor control equipment enclosure shall require only short-circuit and ground-fault protection and shall be permitted to be protected by the motor branch-circuit short-circuit and ground-fault protective device(s) where the rating of the protective device(s) is not over the value specified in Column C of Table 430-72(b). Exception No. 3: Conductors supplied by the secondary side of a singlephase transformer having only a two-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 does not ARTICLE 430 - MOTOR CIRCUITS, CONTROLLERS 70-411 exceed the value determined by multiplying the appropriate maximum rating of the overcurrent device for the secondary conductor from Table 430- 72(b) by the secondary-to-primary voltage ratio. Transformer secondary conductors (other than two-wire) are not considered to be protected by the primary overcurrent protection. Exception No. 4: Conductors of control circuits shall require only shortcircuit and ground-fault protection and shall be permitted to be protected by the motor branch-circuit short-circuit and ground-fault protective device(s) where the opening of the control circuit would create a hazard as, for example, the control circuit of a fire pump motor, and the like. Table 430-72(b). Maximum Rating of Overcurrent Protective Device-Amperes Column A Column B Column C Basic Rule Exception No. 1 Exception No. 2 Control Circuit Alum. or Alum. or Alum. or Conductor Copper-Clad Copper-Clad Copper-Clad Size, AWG Copper Alum. Copper Alum. Copper Alum. 18 7 - 25 - 7 - 16 10 - 40 - 10 - 14 Note 1 - 100 - 45 - 12 Note 1 Note 1 120 100 60 45 10 Note 1 Note 1 160 140 90 75 larger than 10 Note 1 Note 1 Note 2 Note 2 Note 3 Note 3 Note 1: Value specified in Section 310-15 as applicable. Note 2: 400 percent of value specified in Table 310-17 for 60°C conductors. Note 3: 300 percent of value specified in Table 310-16 for 60°C conductors. (c) Control Circuit Transformer. Where a motor control circuit transformer is provided, the transformer shall be protected in accordance with