Article 100 NEC Definitions (Letter U-V-W-X-Y-Z)

Ungrounded
Not connected to ground or to a conductive body that extends the ground connection. (CMP—5)

Uninterruptible Power Supply (UPS)
A device or system that provides quality and continuity of AC power through the use of a stored-energy device as the backup power source for a period of time when the normal power supply is incapable of performing acceptably. (CMP—13)

Unit Equipment
A battery-equipped emergency luminaire that illuminates only as part of the emergency illumination system and is not illuminated when the normal supply is available. (CMP—13)

Utilization Equipment
Equipment that utilizes electric energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes. (CMP—1)

Valve Actuator Motor (VAM) Assemblies
A manufactured assembly, used to operate a valve, consisting of an actuator motor and other components such as motor controllers, torque switches, limit switches, and overload protection. (430) (CMP—11)
Informational Note: VAMs typically have short-time duty and high-torque characteristics.

Ventilated
Provided with a means to permit circulation of air sufficient to remove an excess of heat, fumes, or vapors. (CMP—14)

Vessel
A container such as a barrel, drum, or tank for holding fluids or other material. (CMP—17)

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. (CMP—14)

Voltage (of a circuit)
The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned. (CMP—1)
Informational Note: 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, High (High Voltage)
A potential difference of more than 1000 volts, nominal. (CMP—9)
Informational Note: Circuits and equipment rated at potential differences of more than 1000 volts and up to 52 kV are also commonly referred to as medium voltage.

Voltage, Low (Low Voltage)
An electromotive force rated 24 volts, nominal, or less. (551) (CMP—7)

Voltage, Nominal (Nominal Voltage)
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). (CMP—1)
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.
Informational Note No. 2: See ANSI C84.1-2011, 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. (CMP—1)

Watertight
Constructed so that moisture will not enter the enclosure under specified test conditions. (CMP—1)

Weatherproof
Constructed or protected so that exposure to the weather will not interfere with successful operation. (CMP—1)
Informational Note: 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.

Wharf
A structure at the shoreline that has a platform built along and parallel to a body of water with either an open deck or a superstructure. [307:3.3.28] (555) (CMP—7)

Wind Turbine
A mechanical device that converts wind energy to electrical energy. (CMP—4)

Wind Turbine Output Circuit (Turbine Output Circuit)
The circuit conductors between the internal components of a wind turbine (which might include an alternator, integrated rectifier, controller, and/or inverter) and other equipment. (694) (CMP—4)

Wire
A factory assembly of one or more insulated conductors without an overall covering. (805) (CMP—16)

Wireless Power Transfer (WPT)
The transfer of electrical energy from a power source to an electrical load via magnetic fields by a contactless means between a primary device and a secondary device. (625) (CMP—12)

Wireless Power Transfer Equipment (WPTE)
Equipment installed specifically for the purpose of transferring energy between the premises wiring and the electric vehicle without physical electrical contact. (625) (CMP—12)
Informational Note No. 1: The general form of WPTE consists of two physical packages: a control box and a primary pad.
Informational Note No. 2: Electric vehicle power export equipment and wireless power transfer equipment are sometimes contained in one set of equipment, sometimes referred to as a bidirectional WPTE.

Wire ways (Metal)
Sheet metal troughs with hinged or removable covers for housing and protecting electrical wires and cables and in which conductors are laid in place after the raceway has been installed as a complete system. (CMP—8)

Wireways, Nonmetallic (Nonmetallic Wireways)
Flame-retardant, nonmetallic troughs with removable covers for housing and protecting electrical wires and cables in which conductors are laid in place after the raceway has been installed as a complete system. (CMP—8)

Work Surface
A fixed, stationary, or portable surface typically intended for dry use and for tasks other than food preparation, personal lavation, or laundering that presents an incidental risk of spillage of smaller quantities of beverages and other liquids upon outlets mounted directly on or recessed in the surface. (CMP—2)
Informational Note No. 1: See UL 111, Outline of Investigation for Multioutlet Assemblies, and UL 962A, Furniture Power Distribution Units, which establish the performance evaluation criteria and construction criteria.
Informational Note No. 2: See 406.5(F), 406.5(G)(1), and 406.5(H) for information on receptacles for work surfaces distinguished from receptacles for counters and countertops.

Zone
A physically identifiable area (such as barriers or separation by distance) within an information technology equipment room, with dedicated power and cooling systems for the information technology equipment or systems. (645) (CMP—12)

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Summary Table

Term	Definition
Ungrounded	Not connected to ground or to a conductive body that extends the ground connection. (CMP—5)
Uninterruptible Power Supply (UPS)	A device or system that provides quality and continuity of AC power through the use of a stored-energy device as a backup power source when the normal power supply fails. (CMP—13)
Unit Equipment	A battery-equipped emergency luminaire for emergency illumination when the normal supply fails. (CMP—13)
Utilization Equipment	Equipment that uses electric energy for electronic, electromechanical, chemical, heating, lighting, or similar purposes. (CMP—1)
Valve Actuator Motor Assemblies	Assemblies used to operate a valve, including an actuator motor and components like motor controllers, torque switches, etc. (CMP—11)
Ventilated	Designed for air circulation to remove excess heat, fumes, or vapors. (CMP—14)
Vessel	A container such as a barrel, drum, or tank for holding fluids or other materials. (CMP—17)
Volatile Flammable Liquid	A flammable liquid with a flash point below 38°C (100°F) or a Class II combustible liquid. (CMP—14)
Voltage (of a circuit)	The greatest RMS difference of potential between conductors. (CMP—1)
Voltage, High	A potential difference of more than 1000 volts, nominal. (CMP—9)
Voltage, Low	An electromotive force rated 24 volts or less. (CMP—7)
Voltage, Nominal	A nominal value assigned to a system to designate its voltage class (e.g., 120/240 volts). (CMP—1)
Voltage to Ground	For grounded circuits, voltage between the conductor and the grounded point; for ungrounded circuits, voltage between conductors. (CMP—1)
Watertight	Constructed to prevent moisture entry under specified conditions. (CMP—1)
Weatherproof	Protected against exposure to weather to ensure successful operation. (CMP—1)
Wharf	A structure at the shoreline used for docking or shipping with a platform built along the water. (CMP—7)
Wind Turbine	A mechanical device converting wind energy to electrical energy. (CMP—4)
Wind Turbine Output Circuit	Conductors between the internal components of a wind turbine and other equipment. (CMP—4)
Wire	A factory assembly of one or more insulated conductors without an overall covering. (CMP—16)
Wireless Power Transfer (WPT)	Transfer of energy from a power source to an electrical load via magnetic fields without contact. (CMP—12)
Wireless Power Transfer Equipment (WPTE)	Equipment designed to transfer energy between the wiring and electric vehicle without physical contact. (CMP—12)
Wire ways (Metal)	Metal troughs with hinged covers for housing and protecting electrical wires. (CMP—8)
Wireways, Nonmetallic	Nonmetallic flame-retardant troughs for housing and protecting electrical cables. (CMP—8)
Work Surface	A fixed or portable surface intended for dry use and tasks other than food preparation or laundering. (CMP—2)
Zone	A dedicated area with power and cooling for IT equipment. (CMP—12)