Electrical Terms and Definitions

National Electrical Code (NEC) is a set of minimum standards and regulations that governs planning, construction, and installation of electrical conductors and equipment. The NEC is the basis for all electrical codes used in the United States.

Plenum refers to an air chamber in a heating, ventilation, and air conditioning (HVAC) system or to the space above the ceiling or below the floor used for air circulation. In many buildings, the plenum space is often used to route conductors and cables.

Variable frequency drive is a type of electronic variable speed drive used with AC motors. The AC frequency is modulated to increase or decrease the speed of the motor.

A variable speed drive (VSD) is a control system used to modulate the speed of a motor or actuator.

A unit of electrical potential. One watt is equal to one volt-amp, or one amp of current at one volt of potential.

A watt is a unit of power, frequently used to define electrical power consumption. It is also used as a unit of heating power. One watt is approximately 3.41 BTU/hr. It’s important to note that a BTU is a unit of energy, while a Watt is a unit of power.

A watt-hour is a unit of energy. The amount of power consumed over a set time period – in this case, a power of one watt consumed for one hour. A Kilowatt-hour is 1,000 watts of power exerted on a system for one hour and is commonly used as the basic unit of energy sold on the power grid.

A kilowatt is a unit of power. It may be used to describe mechanical, electrical, or heating power. One Kilowatt is equal to 1,000 watts.

Power factor is a ratio of real power to apparent power. Real power, typically measured in Kilowatts (kW), is the amount of power needed to operate a piece of equipment. Apparent power, measured in kilovolt-amps (kVA), is the amout of power present in the circuit to keep it energized. These may diverge when used to power inductive loads, such as refrigeration compressors or other large electrical motors. Poor power factor can waste significant amounts of energy and overburden electrical infrastructure.

An arc-fault circuit interrupter (AFCI) is a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.