This limit shall apply to any single unit in an installation of

capacitors. (b) Accidental Contact. Capacitors shall be enclosed, located, or guarded so that persons cannot come into accidental contact or bring conducting materials into accidental contact with exposed energized parts, terminals, or buses associated with them. Exception: No additional guarding is required for enclosures accessible only to authorized and qualified persons. A. 600 Volts, Nominal, and Under 460-6. Discharge of Stored Energy. Capacitors shall be provided with a means of discharging stored energy. (a) Time of Discharge. The residual voltage of a capacitor shall be reduced to 50 volts, nominal, or less, within 1 minute after the capacitor is disconnected from the source of supply. (b) Means of Discharge. The discharge circuit shall be either permanently connected to the terminals of the capacitor or capacitor bank, or provided with automatic means of connecting it to the terminals of the capacitor bank on removal of voltage from the line. Manual means of switching or connecting the discharge circuit shall not be used. 460-8. Conductors. (a) Ampacity. The ampacity of capacitor circuit conductors shall not be less than 135 percent of the rated current of the capacitor. The ampacity of conductors that connect a capacitor to the terminals of a motor or to motor circuit conductors shall not be less than one third the ampacity of the motor circuit conductors and in no case less than 135 percent of the rated current of the capacitor. (b) Overcurrent Protection. (1) An overcurrent device shall be provided in each ungrounded conductor for each capacitor bank. Exception: A separate overcurrent device shall not be required for a capacitor connected on the load side of a motor overload protective device. (2) The rating or setting of the overcurrent device shall be as low as practicable. (c) Disconnecting Means. (1) A disconnecting means shall be provided in each ungrounded conductor for each capacitor bank. Exception: Where a capacitor is connected on the load side of a motor overload protective device. 70-460 NATIONAL ELECTRICAL CODE (2) The disconnecting means shall open all ungrounded conductors simultaneously. (3) The disconnecting means shall be permitted to disconnect the capacitor from the line as a regular operating procedure. (4) The rating of the disconnecting means shall not be less than 135 percent of the rated current of the capacitor. 460-9. Rating or Setting of Motor Overload Device. Where a motor installation includes a capacitor connected on the load side of the motor overload device, the rating or setting of the motor overload device shall be based on the improved power factor of the motor circuit. The effect of the capacitor shall be disregarded in determining the motor circuit conductor rating in accordance with Section 430-22. 460-10. Grounding. Capacitor cases shall be grounded in accordance with Article 250. Exception: Where the capacitor units are supported on a structure that is designed to operate at other than ground potential. 460-12. Marking. Each capacitor shall be provided with a nameplate giving the name of the manufacturer, rated voltage, frequency, kilovar or amperes, number of phases, and, if filled with a combustible liquid, the amount of liquid in gallons. Where filled with a nonflammable liquid, the nameplate shall so state. The nameplate shall also indicate if a capacitor has a discharge device inside the case. B. Over 600 Volts, Nominal 460-24. Switching. (a) Load Current. Group-operated switches shall be used for capacitor switching and shall be capable of (1) carrying continuously not less than 135 percent of the rated current of the capacitor installation; (2) interrupting the maximum continuous load current of each capacitor, capacitor bank, or capacitor installation that will be switched as a unit; (3) withstanding the maximum inrush current, including contributions from adjacent capacitor installations; (4) carrying currents due to faults on capacitor side of switch. (b) Isolation. (1) A means shall be installed to isolate from all sources of voltage each capacitor, capacitor bank, or capacitor installation that will be removed from service as a unit. (2) The isolating means shall provide a visible gap in the electrical circuit adequate for the operating voltage. (3) Isolating or disconnecting switches (with no interrupting rating) shall be interlocked with the load-interrupting device or shall be provided with prominently displayed caution signs in accordance with Section 710-22 to prevent switching load current. ARTICLE 460 - CAPACITORS 70-461 (c) Additional Requirements for Series Capacitors. The proper switching sequence shall be assured by use of one of the following: (1) mechanically sequenced isolating and bypass switches; (2) interlocks; or (3) switching procedure prominently displayed at the switching location. 460-25. Overcurrent Protection. (a) Provided to Detect and Interrupt Fault Current. A means shall be provided to detect and interrupt fault current likely to cause dangerous pressure within an individual capacitor. (b) Single-Phase or Multiphase Devices. Single-phase or multiphase devices shall be permitted for this purpose. (c) Protected Individually or in Groups. Capacitors shall be permitted to be protected individually or in groups. (d) Protective Devices Rated or Adjusted. Protective devices for capacitors or capacitor equipment shall be rated or adjusted to operate within the limits of the safe zone for individual capacitors. Exception: If the protective devices are rated or adjusted to operate within the limits for Zone 1 or Zone 2, the capacitors shall be enclosed or isolated. In no event shall the rating or adjustment of the protective devices exceed the maximum limit of Zone 2. (FPN): For definitions of the Safe Zone, Zone 1, and Zone 2, see Shunt Power Capacitors, ANSI/IEEE 18-1980. 460-26. Identification. Each capacitor shall be provided with a permanent nameplate giving the maker's name, rated voltage, frequency, kilovar or amperes, number of phases, and the amount of liquid in gallons identified as flammable, if such is the case. 460-27. Grounding. Capacitor neutrals and cases, if grounded, shall be grounded in accordance with Article 250. Exception: Where the capacitor units are supported on a structure that is designed to operate at other than ground potential. 460-28. Means for Discharge. (a) Means to Reduce the Residual Voltage. A means shall be provided to reduce the residual voltage of a capacitor to 50 volts or less within 5 minutes after the capacitor is disconnected from the source of supply. (b) Connection to Terminals. A discharge circuit shall be either permanently connected to the terminals of the capacitor or provided with automatic means of connecting it to the terminals of the capacitor bank after disconnection of the capacitor from the source of supply. The windings of motors, or transformers, or of other equipment directly connected to capacitors without a switch or overcurrent device interposed shall meet the requirements of (a) above. 70-462 NATIONAL ELECTRICAL CODE