NEC

Standards

• Automatic Transfer Switches

  Automatic transfer switches rated 1000 V and below, listed to UL 1008, that move a load between a normal source and an alternate source without operator action. Covers the switching mechanism, transition type, bypass-isolation construction, neutral treatment, the controller and its sensing, time delays, exerciser, load management and communications provisions, ratings including withstand and closing and short-time ratings, service-entrance construction, enclosures, identification, factory and field testing, installation, warranty, and spare parts, for switches serving emergency, legally required standby, optional standby, critical operations, and health care essential electrical system loads.

• Conductors and Cables

  Building wire and cable for power, lighting, branch circuit, and feeder applications rated 600V and below in commercial, institutional, and industrial buildings. Covers single conductors installed in raceways and cable tray, Type MC metal-clad cable, and Type AC armored cable; conductor materials (copper and aluminum); insulation types (THHN/THWN-2, XHHW-2, RHW-2, USE-2); ampacity selection and derating; voltage drop; color coding and conductor identification; splicing, connectors, and terminations; pulling and installation; insulation resistance testing; and field acceptance.

• Electrical Equipment Labels

  The labels, nameplates, directories and signs applied in the field to the enclosures of electrical equipment rated 1000 V and below, and of the medium-voltage equipment on the same project: switchgear, switchboards, panelboards, motor control centers, transformers, transfer switches, generators, drives, disconnects, starters, busway, meter enclosures and control enclosures. Covers the equipment identification nameplate with its designation and source, the nameplates on each device and compartment, the circuit directory, the warning and danger signs NFPA 70 requires on equipment for voltage, multiple sources, disconnect location, back-fed devices, series ratings and ungrounded systems, the arc-flash warning label as a product and its installation, the available fault current marking, service equipment signs, the marking of emergency and standby system equipment, nameplate material, colors, character heights and attachment, the ANSI Z535.4 format of safety signs, installation, warranty and spare stock.

• Electrical Rooms

  The dedicated indoor electrical room and the electrical closet as a space: the room that houses service equipment, switchgear, switchboards, panelboards, motor control centers, dry-type transformers, transfer switches, drives, UPS modules, control-power batteries and the open or paralleling generator sets installed indoors. Covers the working space and the dedicated electrical space the adopted electrical code requires about the equipment, headroom, the number of entrances, door swing, clear opening and panic hardware, locking and free egress, the fire-resistance rating of the enclosing construction where a code sets one, the exclusion of piping and ductwork foreign to the electrical installation, water protection at the door and on the floor, the heat-release basis and the ventilation or cooling performance the room has to deliver, the temperature and humidity limits taken from the equipment ratings, illumination and emergency illumination of the working space, the convenience receptacle, housekeeping pad provision, floor finish, the room ground bar, the signs on the room door, the coordination drawing that proves every clearance before the room is framed, and the field verification before the room is closed in and before equipment is set.

• Emergency and Standby Power Systems

  System-level standard establishing the classification, source selection, load assignment, transfer scheme, overcurrent coordination, and acceptance testing for a building's emergency and standby power system, in accordance with NFPA 70 Articles 700 (Emergency Systems), 701 (Legally Required Standby), 702 (Optional Standby), and 708 (Critical Operations Power Systems), and NFPA 110 and NFPA 111. Use this standard to define what the system must do as a whole — which loads are emergency vs. standby, what alternate source serves them, how fast they transfer, and how they are commissioned and maintained. Component-level requirements are deferred to the equipment standards for the engine-generator set (see Generators), the automatic transfer switches (see Automatic Transfer Switches), and the stored-energy sources (see Battery Energy Storage Systems).

• Protective Device Coordination Study

  The time-current coordination study for a project's electrical power distribution system, from the utility's protective device at the point of delivery through every overcurrent protective device within the extent the datasheet selects, on AC systems rated 1000 V and below through 38 kV with utility, generator, inverter-based, and paralleled sources. Covers who performs the study and when it is delivered, the degree of coordination applied to normal distribution and the circuits on which NFPA 70 620.62, 645.27, 700.32, 701.32, 708.54, and 517.31(G) require selective coordination, the coordination time intervals and band separations, the curves of the utility device, transformers, motors, conductors, generators, and inverter-based sources that bound every setting, the coordination of ground-fault protection including the two levels NFPA 70 517.17 requires, the recommended setting of every trip unit, relay, fuse, and overload relay, the trade-off between selectivity and incident energy, the coordination deficiencies and who accepts them, the settings record handed to the field, the report, and the events that call for a re-study.

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