Switchgear. An assembly completely enclosed on all sides and top with sheet metal (except for ventilating openings and inspection windows) and containing primary power circuit switching, interrupting devices, or both, with buses and connections. The assembly may include control and auxiliary devices. Access to the interior of the enclosure is provided by doors, removable covers, or both.
This definition was revised for the 2014 Code . It formerly appeared as metal-enclosed power switchgear . The revised definition is inclusive of all types of switchgear governed by the NEC .
The generic term can be used in most Code text where the term switchboard is already mentioned, and where the use of the term switchgear is appropriate. According to ANSI C37.20,
Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear , the term switchgear includes “metal-enclosed low-voltage power circuit-breaker switchgear,” “metal-clad switchgear,” and “metal-enclosed interrupter switchgear.”
Informational Note: All switchgear subject to NEC requirements is metal enclosed. Switchgear rated below 1000 V or less may be identified as “low-voltage power circuit breaker switchgear.”
Switchgear rated over 1000 V may be identified as “metal-enclosed switchgear” or “metal-clad switchgear.” Switchgear is available in non–arc-resistant or arc-resistant constructions.
Thermal Protector (as applied to motors). A protective device for assembly as an integral part of a motor or motor-compressor that, when properly applied, protects the motor against dangerous overheating due to overload and failure to start.
FPN: The thermal protector may consist of one or more sensing elements integral with the motor or motor-compressor and an external control device.
Thermally Protected (as applied to motors). The words Thermally Protected appearing on the nameplate of a motor or motor-compressor indicate that the motor is provided with a thermal protector.
Ungrounded. Not connected to ground or to a conductive body that extends the ground connection.
Uninterruptible Power Supply. A power supply used to alternating current power to a load for some period of time in the event of a power failure.
Utility-Interactive Inverter. An inverter intended for use in parallel with an electric utility to supply common loads that may deliver power to the utility.
Utilization Equipment . Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes.
Ventilated. Provided with a means to permit circulation of air sufficient to remove an excess of heat, fumes, or vapors.
Volatile Flammable Liquid . A flammable liquid having a flash point below 38°C

(100°F), or a flammable liquid whose temperature is above its flash point, or a Class II combustible liquid that has a vapor pressure not exceeding 276 kPa (40 psia) at 38°C
(100°F) and whose temperature is above its flash point.
The flash point of a liquid is defined as the minimum temperature at which it gives off sufficient vapor to form an ignitible mixture, with the air near the surface of the liquid or within the vessel used to contain the liquid. An ignitible mixture is defined as a mixture within the explosive or flammable range (between upper and lower limits) that is capable of the propagation of flame away from the source of ignition when ignited. Some emission of vapors takes place below the flash point but not in sufficient quantities to form an ignitible mixture.
Voltage (of a circuit). The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned.
Common 3-phase, 4-wire wye systems are 480/277 volts and 208/120 volts. The voltage of the circuit is the higher voltage between any two conductors (i.e., 480 volts or 208 volts). The voltage of the circuit of a 2-wire feeder or branch circuit (single phase and the grounded conductor) derived from these systems would be the lower voltage between two conductors (i.e., 277 volts or 120 volts). The same applies to dc or single-phase, 3-wire systems where there are two voltages.
FPN: Some systems, such as 3-phase 4-wire, single-phase 3-wire, and 3-wire direct current, may have various circuits of various voltages.
Voltage, Nominal. A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts).
Informational Note No. 1: The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.
See 220.5(A) for a list of nominal voltages used in computing branch-circuit and feeder loads.
Informational Note No. 2: FPN: See ANSI C84.1-2006, Voltage Ratings for Electric Power
Systems and Equipment (60 Hz).
Voltage to Ground . For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit.
The voltage to ground of a 277/480-volt wye system would be 277 volts; of a 120/208- volt wye system, 120 volts; and of a 3-phase, 3-wire ungrounded 480-volt system, 480 volts.
For a 3-phase, 4-wire delta system with the center of one leg grounded, there are two

voltages to ground. For example, on a 240-volt system, two legs would each have 120 volts to ground, and the third, or “high,” leg would have 208 volts to ground. See 110.15,
230.56, and 408.3(E) for special marking and arrangements on such circuit conductors.
Watertight. Constructed so that moisture will not enter the enclosure under specified test conditions.
Unless an enclosure is hermetically sealed, it is possible for moisture to enter the enclosure. See the commentary following the definition of enclosure and following Table
110.20.
Weatherproof . Constructed or protected so that exposure to the weather will not interfere with successful operation.
FPN: Rainproof, raintight, or watertight equipment can fulfill the requirements for weatherproof where varying weather conditions other than wetness, such as snow, ice, dust, or temperature extremes, are not a factor.