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

F. Motor-Compressor and Branch-Circuit Overload Protection 440-51. General. The provisions of Part F specify devices intended to protect the motor-compressor, the motor-control apparatus, and the ARTICLE 440 - AIR CONDITIONING EQUIPMENT 70-439 branch-circuit conductors against excessive heating due to motor overload and failure to start. See Sections 240-3(e) through (h). (FPN): Note: Overload in electrically driven apparatus is an operating overcurrent that, when it persists for a sufficient length of time, would cause damage or dangerous overheating. It does not include short circuits or ground faults. 440-52. Application and Selection. (a) Protection of Motor-Compressor. Each motor-compressor shall be protected against overload and failure to start by one of the following means: (1) A separate overload relay that is responsive to motor-compressor current. This device shall be selected to trip at not more than 140 percent of the motor-compressor rated-load current. (2) A thermal protector integral with the motor-compressor, approved for use with the motor-compressor that it protects on the basis that it will prevent dangerous overheating of the motor-compressor due to overload and failure to start. If the current-interrupting device is separate from the motor-compressor and its control circuit is operated by a protective device integral with the motor-compressor, it shall be so arranged that the opening of the control circuit will result in interruption of current to the motorcompressor. (3) A fuse or inverse time circuit breaker responsive to motor current, which shall also be permitted to serve as the branch-circuit short-circuit and ground-fault protective device. This device shall be rated at not more than 125 percent of the motor-compressor rated-load current. It shall have sufficient time delay to permit the motor-compressor to start and accelerate its load. The equipment or the motor-compressor shall be marked with this maximum branch-circuit fuse or inverse time circuit breaker rating. (4) A protective system, furnished or specified and approved for use with the motor-compressor that it protects on the basis that it will prevent dangerous overheating of the motor-compressor due to overload and failure to start. If the current interrupting device is separate from the motorcompressor and its control circuit is operated by a protective device that is not integral with the current-interrupting device, it shall be so arranged that the opening of the control circuit will result in interruption of current to the motor-compressor. (b) Protection of Motor-Compressor Control Apparatus and Branch- Circuit Conductors. The motor-compressor controller(s), the disconnecting means, and branch-circuit conductors shall be protected against overcurrent due to motor overload and failure to start by one of the following means, which shall be permitted to be the same device or system protecting the motor-compressor in accordance with Section 440-52(a). Exception: For motor-compressors and equipment on 15- or 20-ampere single-phase branch circuits as provided in Sections 440-54 and 440-55. (1) An overload relay selected in accordance with Section 440-52(a)(1). (2) A thermal protector applied in accordance with Section 440-52(a)(2) and that will not permit a continuous current in excess of 156 percent of the marked rated-load current or branch-circuit selection current. 70-440 NATIONAL ELECTRICAL CODE (3) A fuse or inverse time circuit breaker selected in accordance with