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

70-364 NATIONAL ELECTRICAL CODE (b) Resistance Elements. Resistance-type heating elements in electric space heating equipment shall be protected at not more than 60 amperes. Equipment rated more than 48 amperes and employing such elements shall have the heating elements subdivided, and each subdivided load shall not exceed 48 amperes. Where a subdivided load is less than 48 amperes, the rating of the supplementary overcurrent protective device shall comply with Section 424-3(b). Exception: As provided in Section 424-72(a). (c) Overcurrent Protective Devices. The supplementary overcurrent protective devices for the subdivided loads specified in (b) above shall be (1) factory-installed within or on the heater enclosure or supplied for use with the heater as a separate assembly by the heater manufacturer; (2) accessible, but shall not be required to be readily accessible; and (3) suitable for branch-circuit protection. (FPN): See Section 240-10. Where cartridge fuses are used to provide this overcurrent protection, a single disconnecting means shall be permitted to be used for the several subdivided loads. (FPN No. 1): For supplementary overcurrent protection, see Section 240-10. (FPN No. 2): For disconnecting means for cartridge fuses in circuits of any voltage, see Section 240-40. (d) Branch-Circuit Conductors. The conductors supplying the supplementary overcurrent protective devices shall be considered branch-circuit conductors. Exception: For heaters rated 50 kW or more, the conductors supplying the supplementary overcurrent protective devices specified in (c) above shall be permitted to be sized at not less than 100 percent of the nameplate rating of the heater, provided all of the following conditions are met: a. The heater is marked with a minimum conductor size; and b. The conductors are not smaller than the marked minimum size; and c. A temperature-actuated device controls the cyclic operation of the equipment. (e) Conductors for Subdivided Loads. Field-wired conductors between the heater and the supplementary overcurrent protective devices shall be sized at not less than 125 percent of the load served. The supplementary overcurrent protective devices specified in (c) shall protect these conductors in accordance with Section 240-3. Exception: For heaters rated 50 kW or more, the ampacity of field-wired conductors between the heater and the supplementary overcurrent protective devices shall be permitted to be not less than 100 percent of the load of their respective subdivided circuits, provided all of the following conditions are met: a. The heater is marked with a minimum conductor size; and b. The conductors are not smaller than the marked minimum size; and c. A temperature-activated device controls the cyclic operation of the equipment.