LEGALLY REQUIRED STANDBY SYSTEMS

70-729 Exception No. 1: Where two or more single-throw switches are connected in parallel to control a single circuit, at least one of these switches shall be accessible only to authorized persons. Exception No. 2: Additional switches that act only to put emergency lights into operation but not disconnect them are permissible. Switches connected in series or 3- and 4-way switches shall not be used. 700-21. Switch Location. All manual switches for controlling emergency circuits shall be in locations convenient to authorized persons responsible for their actuation: In places of assembly, such as theaters, a switch for controlling emergency lighting systems shall be located in the lobby or at a place conveniently accessible thereto. In no case shall a control switch for emergency lighting in a theater, or motion-picture theater or place of assembly, be placed in a motion-picture projection booth or on a stage or platform. Exception: Where multiple switches are provided, one such switch shall be permitted in such locations where so arranged that it can energize the circuit only, but it cannot deenergize the circuit. 700-22. Exterior Lights. Those lights on the exterior of a building that are not required for illumination when there is sufficient daylight shall be permitted to be controlled by an automatic light-actuated device. F. Overcurrent Protection 700-25. Accessibility. The branch-circuit overcurrent devices in emergency circuits shall be accessible to authorized persons only. (FPN): Fuses and circuit breakers for emergency circuit overcurrent protection, where coordinated to ensure selective clearing of fault currents, increase overall reliability of the system. 700-26. Ground-Fault Protection of Equipment. The alternate source for emergency systems shall not be required to have ground-fault protection of equipment with automatic disconnecting means. Ground-fault indication of the emergency source shall be provided per Section 700-7(d). ARTICLE 701 -LEGALLY REQUIRED STANDBY SYSTEMS A. General 701-1. Scope. The provisions of this article apply to the electrical safety of the design, installation, operation, and maintenance of legally required standby systems consisting of circuits and equipment intended to supply, distribute, and control electricity to required facilities for illumination or power, or both, when the normal electrical supply or system is interrupted. The systems covered by this article consist only of those that are permanently installed in their entirety, including the power source. (FPN No. 1): For additional information, see Health Care Facilities, NFPA 99-1990 (ANSI). 70-730 NATIONAL ELECTRICAL CODE (FPN No. 2): For further information regarding performance of emergency and standby power systems, see Emergency and Standby Power Systems, NFPA 110- 1988 (ANSI). (FPN No. 3): For further information, see Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications, ANSI/IEEE 446-1987. 701-2. Legally Required Standby Systems. Legally required standby systems are those systems required and so classed as legally required standby by municipal, state, federal, or other codes or by any governmental agency having jurisdiction. These systems are intended to automatically supply power to selected loads (other than those classed as emergency systems) in the event of failure of the normal source. (FPN): Legally required standby systems are typically installed to serve loads, such as heating and refrigeration systems, communication systems, ventilation and smoke removal systems, sewerage disposal, lighting systems, and industrial processes, that, when stopped during any interruption of the normal electrical supply, could create hazards or hamper rescue or fire fighting operations. 701-3. Application of Other Articles. Except as modified by this article, all applicable articles of this Code shall apply. 701-4. Equipment Approval. All equipment shall be approved for the intended use. 701-5. Tests and Maintenance for Legally Required Standby Systems. (a) Conduct or Witness Test. The authority having jurisdiction shall conduct or witness a test on the complete system upon installation. (b) Tested Periodically. Systems shall be tested periodically on a schedule and in a manner acceptable to the authority having jurisdiction to assure their maintenance in proper operating condition. (c) Battery Systems Maintenance. Where batteries are used for control, starting, or ignition of prime movers, the authority having jurisdiction shall require periodic maintenance. (d) Written Record. A written record shall be kept on such tests and maintenance. (e) Testing under Load. Means for testing legally required standby systems under load shall be provided. 701-6. Capacity and Rating. A legally required standby system shall have adequate capacity and rating for the supply of all equipment intended to be operated at one time. Legally required standby system equipment shall be suitable for the maximum available fault current at its terminals. The alternate power source shall be permitted to supply legally required standby and optional standby system loads when automatic selective load pickup and load shedding is provided as needed to assure adequate power to the legally required standby circuits. 701-7. Transfer Equipment. Transfer equipment, including automatic transfer switches, shall be automatic and identified for standby use and approved by the authority having jurisdiction. Transfer equipment shall be ARTICLE 701 - LEGALLY REQUIRED STANDBY SYSTEMS 70-731 designed and installed to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment. See Section 230-83. Means to bypass and isolate the transfer switch equipment shall be permitted. Where bypass isolation switches are used, inadvertent parallel operation shall be avoided. 701-8. Signals. Audible and visual signal devices shall be provided, where practicable, for the following purposes: (a) Derangement. To indicate derangement of the standby source. (b) Carrying Load. To indicate that the standby source is carrying load. (c) Not Functioning. To indicate that the battery charger is not functioning. (FPN): For signals for generator sets, see Emergency and Standby Power Systems, NFPA 110-1988 (ANSI). 701-9. Signs. (a) Mandated Standby. A sign shall be placed at the service entrance I indicating type and location of on-site legally required standby power sources. (b) Grounding. Where the grounded circuit conductor connected to the emergency source is connected to a grounding electrode conductor at a location remote from the emergency source, there shall be a sign at the grounding location that shall identify all emergency and normal sources connected at that location. B. Circuit Wiring 701-10. Wiring Legally Required Standby Systems. The legally required standby system wiring shall be permitted to occupy the same raceways, cables, boxes, and cabinets with other general wiring. C. Sources of Power 701-11. Legally Required Standby Systems. Current supply shall be such that, in event of failure of the normal supply to, or within, the building or group of buildings concerned, legally required standby power will be available within the time required for the application but not to exceed 60 seconds. The supply system for legally required standby purposes, in addition to the normal services to the building, shall be permitted to comprise one or more of the types of systems described in (a) through (f) below. Unit equipment in accordance with Section 701-11(f) shall satisfy the applicable requirements of this article. In selecting a legally required standby source of power, consideration shall be given to the type of service to be rendered, whether of short-time duration or long duration. Consideration shall be given to the location or design, or both, of all equipment to minimize the hazards that might cause complete failure due to floods, fires, icing, and vandalism. 70-732 NATIONAL ELECTRICAL CODE (FPN): Assignment of degree of reliability of the recognized legally required standby supply system depends upon the careful evaluation of the variables at each particular installation. (a) Storage Battery. A storage battery of suitable rating and capacity to supply and maintain at not less than 87½ percent of system voltage the total load of the circuits supplying legally required standby power for a period of at least 1½ hours. Batteries, whether of the acid or alkali type, shall be designed and constructed to meet the service requirements of emergency service and shall be compatible with the charger for that particular installation. For a sealed battery, the container shall not be required to be transparent. However, for the lead acid battery which requires water additions, transparent or translucent jars shall be furnished. Automotive-type batteries shall not be used. An automatic battery charging means shall be provided. (b) Generator Set. (1) A generator set driven by a prime mover acceptable to the authority having jurisdiction and sized in accordance with Section 701-6. Means shall be provided for automatically starting the prime mover on failure of the normal service and for automatic transfer and operation of all required electrical circuits. A time-delay feature permitting a 15-minute setting shall be provided to avoid retransfer in case of short-time reestablishment of the normal source. (2) Where internal combustion engines are used as the prime mover, an on-site fuel supply shall be provided with an on-premise fuel supply sufficient for not less than 2 hours full-demand operation of the system. (3) Prime movers shall not be solely dependent upon a public utility gas system for their fuel supply or municipal water supply for their cooling systems. Means shall be provided for automatically transferring one fuel supply to another where dual fuel supplies are used. Exception: Where acceptable to the authority having jurisdiction, the use of other than on-site fuels shall be permitted where there is a low probability of a simultaneous failure of both the off-site fuel delivery system and power from the outside electrical utility company. (4) Where a storage battery is used for control or signal power, or as the means of starting the prime mover, it shall be suitable for the purpose and shall be equipped with an automatic charging means independent of the generator set. (c) Uninterruptible Power Supplies. Uninterruptible power supplies used to provide power for legally required standby systems shall comply with the applicable provisions of Sections 701-11(a) and (b). (d) Separate Service. Where acceptable to the authority having jurisdiction, a second service shall be permitted. This service shall be in accordance with Article 230, with separate service drop or lateral widely separated electrically and physically from the normal service to minimize the possibility of simultaneous interruption of supply. (e) Connection Ahead of Service Disconnecting Means. Where acceptable to the authority having jurisdiction, connections ahead of, but not within, the main service disconnecting means shall be permitted. The