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Protected Combination Motor Controller. A listed self-protected combination motor controller shall be permitted in lieu of the devices specified in Table 430.52(C)(1). Adjustable instantaneous-trip settings shall not exceed 1300 percent of the full-load motor current for other than Design B energy-e...

Protected Combination Motor Controller. A listed self-protected combination motor controller shall be permitted in lieu of the devices specified in Table 430.52(C)(1). Adjustable instantaneous-trip settings shall not exceed 1300 percent of the full-load motor current for other than Design B energy-efficient and Design B premium efficiency motors and not more than 1700 percent of the full-load motor current for Design B energy-efficient and Design B premium efficiency motors. Informational Note: Proper application of self-protected combination motor controllers on 3-phase systems, other than solidly grounded wye, particularly on corner grounded delta systems, considers the self-protected combination motor controllers’ individual pole-interrupting capability. ENHANCED CONTENT Collapse A self-protected combination controller combines the functions of short-circuit protection, disconnect, controller, and overload protection into a single unit. Below is an example of a combination controller. (Courtesy of Eaton Corporation) Motor Short-Circuit Protector. A motor short-circuit protector shall be permitted in lieu of devices listed in Table 430.52(C)(1) if the motor short-circuit protector is part of a listed combination motor controller having coordinated motor overload protection and short-circuit and ground-fault protection in each conductor and it will open the circuit at currents exceeding 1300 percent of the motor full-load current for other than Design B energy-efficient and Design B premium efficiency motors and 1700 percent of the motor full-load current for Design B energy-efficient and Design B premium efficiency motors. Informational Note: A motor short-circuit protector, as used in this section, is a fused device and is not an instantaneous-trip circuit breaker. (D) Torque Motors. Torque motor branch circuits shall be protected at the motor nameplate current rating in accordance with 240.4(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 conditions specified in 430.53(D) and in 430.53(A), (B), or (C). The branch-circuit protective device shall be fuses or inverse time circuit breakers. Not Over 1 Horsepower. Several motors, each not exceeding 1 hp in rating, shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes or a branch circuit of 1000 volts, nominal, or less, protected at not over 15 amperes, if all of the following conditions are met: The full-load rating of each motor does not exceed 6 amperes. The rating of the branch-circuit short-circuit and ground-fault protective device marked on any of the motor controllers is not exceeded. Individual overload protection conforms to 430.32. If Smallest Rated Motor Protected. Two or more motors or one or more motors and other loads shall be permitted to be connected to a branch circuit where all of the following conditions are met: The branch-circuit short-circuit and ground-fault protective device is selected not to exceed that allowed by 430.52 for the smallest rated motor supplied by the branch circuit. Each motor is provided with separate overload protection. It can be determined that the branch-circuit short-circuit and ground-fault protective device will not open under the most severe normal conditions of service that might be encountered. Other Group Installations. Two or more motors of any size or one or more motors and other loads, with each motor having individual overload protection, shall be permitted to be connected to a branch circuit where the motor controller(s) and overload device(s) comply with 430.53(C)(1) through (C)(5). Types of Assemblies. The assembly type shall meet one of the following conditions: A listed factory assembly, with the motor branch-circuit short-circuit and ground-fault protective device either provided as part of the assembly or specified by a marking on the assembly Field installation of the motor branch-circuit short-circuit and ground-fault protective device, motor controller(s), and overload device(s) as separate assemblies listed for such use and provided with manufacturers’ instructions for use with each other Motor Overload Devices. Each motor overload device shall meet one of the following conditions: Listed for group installation with a specified maximum rating of fuse, inverse time circuit breaker, or both Selected such that the ampere rating of the motor-branch short-circuit and ground-fault protective device does not exceed that permitted by 430.52 for that individual motor overload device and corresponding motor load Motor Controllers. Each motor controller shall meet one of the following conditions: Listed for group installation with a specified maximum rating of fuse, circuit breaker, or both Selected such that the ampere rating of the motor-branch short-circuit and ground-fault protective device does not exceed that permitted by 430.52 for that individual motor controller and corresponding motor load Short-Circuit & Ground-Fault Protection. The branch circuit shall be protected by fuses or listed inverse time circuit breakers having a rating not exceeding the sum of all of the following: The value specified in 430.52 for the highest rated motor connected to the branch circuit The sum of the full-load current ratings of all other motors The sum of the current ratings of other loads connected to the circuit Where this calculation results in a rating less than the ampacity of the branch-circuit conductors, it shall be permitted to increase the maximum rating of the fuses or circuit breaker to a value not exceeding that permitted by 240.4(B). Additionally, this rating shall not be larger than allowed by 430.40 for the overload relay protecting the smallest rated motor of the group. Overcurrent Protection. Loads other than motor loads shall be protected in accordance with Part I through Part VII of Article 240. Informational Note: See 110.10 for circuit impedance and other characteristics. ENHANCED CONTENT Collapse The ground-fault short-circuit protection for motors might be greater than is permitted for other loads in accordance with Article 240. Devices with the same ampere rating might have significantly different short-circuit current ratings. Prior to the 2011 edition of the NEC, all motor controllers and overload devices were required to be listed for group installation. A motor controller or overload device is not required to be marked for group motor installation if it is applied within a group installation in which the branch-circuit protection for the group is within the same size limit as what would be permitted for a single motor installation of that device. Single Motor Taps. For group installations described in 430.53(A), (B), or (C), 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 if they comply with 430.53(D)(1) or (D)(2). Conductors to the Motor. Conductors to the motor shall have an ampacity that is not less than the ampacity of the branch-circuit conductors unless all of the following conditions are met: The conductors from the point of the tap to the motor overload device shall not be longer than 7.5 m (25 ft). The conductor ampacity is not less than one-third the ampacity of the branch-circuit conductors. The minimum ampacity shall not be less than required in 430.22. The conductors from the point of the tap to the motor controller(s) shall be protected from physical damage by being enclosed in an approved raceway or other approved means. Tap Conductors Between the Branch Circuit and Listed Manual Motor Controllers. Conductors from the point of the tap from the branch circuit to a listed manual motor controller additionally marked “Suitable for Tap Conductor Protection in Group Installations,” or to a branch-circuit protective device, shall meet one of the following conditions: The length of the motor tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following: The ampacity of the tap conductors is not less than one-tenth of the rating or setting of the branch-circuit short-circuit ground-fault protective device. The conductors from the motor controller to the motor shall have an ampacity in accordance with 430.22. The conductors from the point of the tap to the motor controller(s) shall be suitably protected from physical damage and enclosed either by an enclosed motor controller or by a raceway. Exception to (1): Physical protection of the conductors from the point of the tap to the motor controllers shall not be required if the conductors have an ampacity not less than that of the branch-circuit conductors. The length of the motor tap conductors does not exceed 7.5 m (25 ft) and the tap conductors comply with all of the following: The ampacity of the tap conductors is not less than one-third of the branch-circuit conductor ampacity. The conductors from the motor controller to the motor shall have an ampacity in accordance with 430.22. The conductors from the point of the tap to the motor controller(s) shall be suitably protected from physical damage and enclosed either by an enclosed motor controller or by a raceway. Exception to (2): Physical protection of the conductors from the point of the tap to the motor controllers shall not be required if the conductors have an ampacity not less than that of the branch-circuit conductors. ENHANCED CONTENT Collapse The conditions for applying these tap rules are like those in 430.28 covering motor supply conductors tapped to a feeder. The short-circuit ground-fault device on the line side of the tap conductors protects more than one set of conductors that supply individual motors, which eliminates the need for an individual short-circuit ground-fault device for each set of conductors that supply a motor. Additional branch-circuit protective devices (such as fuses, inverse time circuit breakers, and listed self-protected combination motor controllers) can be used in the same location in the circuit of a group installation as a manual motor controller additionally marked “Suitable for Tap Conductor Protection in Group Installations.” This approach requires that the tap conductors meet certain size, physical protection, length, and termination conditions. The tap conductors must always meet the conductor size requirements of 430.22. The following exhibit illustrates main branch-circuit conductors supplying a motor that is part of a group installation. The tap conductors have an ampacity equal to the ampacity of the main branch-circuit conductors. Therefore, branch-circuit short-circuit and ground-fault protective devices, fuses, or circuit breakers for the conductors in the tap are not required at the point of connection of the tap conductors to the main conductors, provided that the motor controller and motor overload protective device are listed for group installation with the size of the main branch-circuit short-circuit and ground-fault protective device used. The exhibit below also illustrates main branch-circuit conductors supplying a motor that is part of a group installation. Here, the tap conductors have an ampacity at least one-third the ampacity of the main branch-circuit conductors, are not more than 25 feet in length, and are suitably protected from physical damage. The motor controller and motor overload protective device must be listed for group installation with the size of the main branch-circuit short-circuit and ground-fault protective device used. The next exhibit illustrates the requirements of 430.53(D)(3). Here the tap conductors from the point of the tap to the controller have an ampacity not less than one-tenth the rating or setting of the branch-circuit short-circuit and ground-fault protective device. These tap conductors cannot be more than 10 feet in length and must be suitably protected from physical damage. This does not apply to the conductors from the controller to the motor, which must have an ampacity in accordance with 430.22. The following exhibit illustrates the requirements of 430.53(D)(4). This requirement is similar to 430.53(D)(2)(1) but increases the maximum length to 25 feet and requires the tap conductors to be at least one-third the ampacity of the branch-circuit conductors. This requirement differs from the 25 feet tap requirement in 430.53(D)(1)(2), which requires the conductors to the motor connection to have an ampacity not less than one-third that of the branch-circuit conductors. In these examples, the main branch-circuit fuses or circuit breakers would operate in the event of a short circuit, and the overload protective device would operate to protect the motor and tap conductors under overload conditions. The tap conductors should never be of a smaller size and ampacity than the branch-circuit conductors required by 430.22. That is, a tap conductor (25 feet or less) may be one-third the ampacity of the main branch-circuit conductor to which it is connected; however, this ampacity must be equal to or larger than 125 percent of the motor’s full-load current rating (see 430.22). 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 430.7(D). 430.55 Combined Overcurrent Protection. Motor branch-circuit short-circuit and ground-fault protection and motor overload protection shall be permitted to be combined in a single protective device where the rating or setting of the device provides the overload protection specified in 430.32. ENHANCED CONTENT Collapse Either a circuit breaker with inverse time characteristics or a dual-element (time-delay) fuse is permitted to serve both as motor overload protection and as the branch-circuit short-circuit and ground-fault protection if the requirements of 430.32 are met. These devices are not permitted to be sized as overload protection according to the values of 430.32(C). Rather, fuses are permitted to be sized as overload protection only, according to the values found in 430.32(A)(1), 430.32(B)(1), and 430.32(D)(1). One-time, time-delay dual-element and Type S dual-element fuses and adapters are available with up to a 30-ampere rating. Type S fuses are designed to prevent oversize fusing. See 240.50 through 240.54 for more information about these fuses and adapters. The exhibit below shows examples of time-delay, cartridge-type dual-element fuses that can withstand the normal motor starting current if sized at or near the motor full-load rating but that open when subjected to prolonged overload or open quickly during a short circuit or ground fault. The dual element characteristics are the thermal cutout element, which permits harmless high-inrush currents to flow for short periods (but which would open the circuit during a prolonged period), and the fuse link element, which has current-limiting ability for short-circuit currents. Dual-element fuses may be used in larger sizes to provide only short-circuit and ground-fault protection. (Courtesy of Eaton, Bussman Division) 430.56 Branch-Circuit Protective Devices — In Which Conductor. Branch-circuit protective devices shall comply with 240.15. 430.57 Size of Fuseholder. Where fuses are used for motor branch-circuit short-circuit and ground-fault protection, the fuseholders shall not be of a smaller size than required to accommodate the fuses specified by Table 430.52(C)(1). Exception: Where fuses having time delay appropriate for the starting characteristics of the motor are used, it shall be permitted to use fuseholders sized to fit the fuses that are used. ENHANCED CONTENT Collapse The use of dual-element (time-delay) fuses makes it possible to use smaller fuses, thereby providing better protection because of the smaller fuses’ lower ratings. They also allow for easier arrangement of equipment where space is at a premium. 430.58 Rating of Circuit Breaker. A circuit breaker for motor branch-circuit short-circuit and ground-fault protection shall have a current rating in accordance with 430.52 and 430.110. Part V. Motor Feeder Short-Circuit and Ground-Fault Protection 430.61 General. Part V specifies protective devices intended to protect feeder conductors supplying motors against overcurrents due to short circuits or ground-faults. Informational Note: See Informative Annex D, Example D8, for an example of motor feeder circuit short-circuit and ground-fault protection rating and setting. 430.62 Rating or Setting — Motor Load. Specific Load. A feeder supplying a specific fixed motor load(s) and consisting of conductor sizes in accordance with 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 supplied by the feeder [based on the maximum permitted value for the specific type of protective device in accordance with 430.52, or 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 supplied by the feeder, one of the protective devices shall be considered the largest for the above calculations. Exception No. 1: Where one or more instantaneous-trip circuit breakers or motor short-circuit protectors are used for motor branch-circuit short-circuit and ground-fault protection as permitted in 430.52(C), the maximum rating of 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 430.52(C)(1) for the type of feeder protective device employed. Exception No. 2: Where the feeder overcurrent protective device also provides overcurrent protection for a motor control center, the provisions of 430.94 shall apply. Informational Note: See Informative Annex D, Example D8, for an example of motor feeder circuit short-circuit and ground-fault protection rating and setting. ENHANCED CONTENT Collapse The rating of a motor feeder short-circuit ground-fault protective device is determined by adding the rating of the largest branch-circuit short-circuit and ground-fault protective device for any motor supplied by the feeder to the sum of the full-load currents of all the other motors supplied by that feeder. The largest branch-circuit short-circuit and ground-fault protective device is based on 430.52(A) and Table 430.52(C)(1). The largest rating can be based on either 430.52(C)(1)(a) or (C)(1)(b). For the purposes of sizing the feeder protective device, it is assumed that the same type of protective device is being used for the feeder and the branch circuits. This assumption is necessary if the feeder protective device and the largest branch-circuit protective device are different types; for example, one is a fuse and the other is a circuit breaker. Exception No. 2 to 430.62(A) correlates the requirement of 430.62(B) for determining feeder short-circuit ground-fault protection with the requirements of 430.94 covering overcurrent protection for motor control centers. Where the motor feeder short-circuit ground-fault protective device is also the overcurrent protective device (OCPD) for a motor control center, its rating cannot exceed that allowed for protecting the common power bus of the motor control center. Other Installations. Where feeder conductors have an ampacity greater than required by 430.24, the rating or setting of the feeder overcurrent protective device shall be permitted to be based on the ampacity of the feeder conductors. 430.63 Rating or Setting — Motor Load and Other Load(s). Where a feeder supplies a motor load and other load(s), the feeder protective device shall have a rating not less than that required for the sum of the other load(s) plus the following: For a single motor, the rating permitted by 430.52 For a single hermetic refrigerant motor-compressor, the rating permitted by 440.22 For two or more motors, the rating permitted by 430.62 Exception: Where the feeder overcurrent device provides the overcurrent protection for a motor control center, the provisions of 430.94 shall apply. Part VI. Motor Control Circuits 430.71 General. Part VI contains modifications of the general requirements and applies to the particular conditions of motor control circuits. 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 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 branch-circuit overcurrent protective device(s). A motor control circuit other than such a tapped control circuit shall be protected against overcurrent in accordance with 724.43 or the notes to Table 11(A) and Table 11(B) in Chapter 9, as applicable. Conductor Protection. The overcurrent protection for conductors shall be provided as specified in 430.72(B)(1) or (B)(2). Exception No. 1: 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, conductors of control circuits 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). Exception No. 2: Conductors supplied by the secondary side of a single-phase 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 exceed the value determined by multiplying the appropriate maximum rating of the overcurrent device for the secondary conductor from Table 430.72(B)(2) by the secondary-to-primary voltage ratio. Transformer secondary conductors (other than two-wire) shall not be considered to be protected by the primary overcurrent protection. (1) Separate Overcurrent Protection. Where the motor branch-circuit short-circuit and ground-fault protective device does not provide protection in accordance with 430.72(B)(2), separate overcurrent protection shall be provided. The overcurrent protection shall not exceed the values specified in Column A of Table 430.72(B)(2). Branch-Circuit Overcurrent Protective Device. Conductors shall be permitted to be protected by the motor branch-circuit short-circuit and ground-fault protective device and shall require only short-circuit and ground-fault protection. Where