Article 100 NEC Definitions (Letter T)

Tap Conductor

A tap conductor is a conductor, other than a service conductor, that has overcurrent protection ahead of its point of supply. The overcurrent protection exceeds the value permitted for similar conductors that are protected as described in section 240.4 of the NEC.
Reference: (240) (CMP—10)

Task Illumination

Task illumination refers to the minimum lighting provisions required to carry out necessary tasks in areas as described in section 517.34(A). This includes safe access to supplies, equipment, and exits.
Reference: [99:3.3.177] (517) (CMP—15)

Technical Power System

A technical power system is an electrical distribution system where the equipment grounding conductor is isolated from the premises’ grounded conductor and the premises’ equipment grounding conductor, except at a single grounded termination point.
Reference: (640) (CMP—12)

Temporary Equipment

Temporary equipment refers to portable wiring and equipment intended for use with events of a transient or temporary nature. All equipment is presumed to be removed at the conclusion of the event.
Reference: (640) (CMP—12)

Terminal (as applied to batteries)

The terminal is the part of a cell, container, or battery to which an external connection is made. It is commonly identified as a post, pillar, pole, or terminal post.
Reference: (CMP—13)

Thermal Protector (as applied to motors)

A thermal protector is a protective device used as an integral part of a motor or motor-compressor. It protects the motor from dangerous overheating due to overload or failure to start.
Reference: (CMP—11)
Informational Note: The thermal protector may include one or more sensing elements integral with the motor and an external control device.

Thermal Resistivity

Thermal resistivity refers to the heat transfer capability of a substance by conduction. It is the reciprocal of thermal conductivity and is designated as Rho (°C-cm/W).
Reference: (CMP—6)
Informational Note: Thermal resistivity is expressed in units of °C-cm/W.

Thermally Protected (as applied to motors)

A thermally protected motor or motor-compressor is one that is equipped with a thermal protector to prevent overheating.
Reference: (CMP—11)

Top Shield

A top shield is a grounded metal shield that covers under-carpet components of a flat conductor cable (Type FCC) system, providing protection against physical damage.
Reference: (324) (CMP—6)

Tower

A tower is a pole or other structure designed to support a wind turbine.
Reference: (694) (CMP—4)

Transfer Switch

A transfer switch is a device, either automatic or nonautomatic, used for transferring one or more load conductor connections from one power source to another.
Reference: (CMP—13)

Transfer Switch, Branch-Circuit Emergency Lighting

This transfer switch, located on the load side of a branch-circuit overcurrent protective device, transfers only emergency lighting loads to an emergency power source.
Reference: (700) (CMP—13)
Informational Note: Refer to ANSI/UL 1008 for more information on transfer switch equipment.

Transfer Switch, Bypass Isolation

A bypass isolation transfer switch is used in conjunction with a transfer switch to directly connect load conductors to a power source while isolating the transfer switch.
Reference: (CMP—13)

Transfer Switch, Meter-Mounted

This transfer switch is connected between the utility meter and the meter base and can plug directly into the meter base.
Reference: (CMP—13)
Informational Note: A transfer switch incorporating the meter base is not considered a meter-mounted transfer switch.

Transformer

A transformer is equipment that uses electromagnetic induction to convert current and voltage from a primary circuit to a secondary circuit.
Reference: (CMP—9)

Transition Assembly

A transition assembly facilitates the connection of flat conductor cables (Type FCC) to other wiring systems. It includes electrical interconnection means and a suitable box for electrical safety.
Reference: (324) (CMP—6)

Transport Refrigerated Unit (TRU)

A transport refrigerated unit (TRU) is a trailer or container with integrated cooling or heating to maintain the desired temperature for sensitive goods.
Reference: (626) (CMP—12)

Transportable

Transportable refers to X-ray equipment that can be installed in a vehicle or disassembled for transport in a vehicle.
Reference: (660) (CMP—12)

Truck

A truck is a motor vehicle designed for transporting goods, services, and equipment.
Reference: (626) (CMP—12)

Truck Coupler

A truck coupler is a flanged surface inlet and mating cord connector on a truck for providing electric energy and other services.
Reference: (626) (CMP—12)

Truck Flanged Surface Inlet

The truck flanged surface inlet is the device on the truck into which the connector is inserted to provide electric energy.
Reference: (626) (CMP—12)

Trunk Cable

A trunk cable is a portable extension cable with six or more branch circuits, a male multipole plug, and a female multipole receptacle.
Reference: (520) (CMP—15)

Tubing, Electrical Metallic (EMT)

Electrical metallic tubing (EMT) is a thin-walled, unthreaded raceway designed for protecting and routing electrical conductors and cables. It can also serve as an equipment grounding conductor when installed with appropriate fittings.
Reference: (CMP—8)

Tubing, Electrical Nonmetallic (ENT)

Electrical nonmetallic tubing (ENT) is a pliable, nonmetallic raceway with integral couplings, connectors, and fittings for electrical conductors. It is resistant to moisture and chemicals and is flame retardant.
Reference: (CMP—8)

Tubing, Flexible Metallic (FMT)

Flexible metallic tubing (FMT) is a flexible, liquid-tight metal raceway used for protecting electrical conductors without a nonmetallic jacket.
Reference: (CMP—8)

Two-Fer

A two-fer is an assembly containing one male plug and two female cord connectors, allowing two loads to be connected to one branch circuit.
Reference: (520) (CMP—15)

Type of Protection «n»

This protection type ensures that electrical equipment does not ignite a surrounding explosive gas atmosphere during normal operation, and a fault causing ignition is unlikely.
Reference: (CMP—14)
Informational Note: For more information, refer to ANSI/UL 60079-15.

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Summary Table

Term	Definition
Tap Conductor	A conductor with overcurrent protection exceeding permitted values, other than a service conductor. (240) (CMP—10)
Task Illumination	Provisions for minimum lighting required to carry out tasks in specified areas. (517) (CMP—15)
Technical Power System	A system where the equipment grounding conductor is isolated, except at one grounded termination point. (640) (CMP—12)
Temporary Equipment	Portable wiring and equipment for transient events. (640) (CMP—12)
Terminal (Battery)	Part of a cell or battery where an external connection is made. (CMP—13)
Thermal Protector	Protective device preventing motor overheating due to overload or failure to start. (CMP—11)
Thermal Resistivity	The heat transfer capability through a substance by conduction, reciprocal of thermal conductivity. (CMP—6)
Thermally Protected	A motor or motor-compressor protected with a thermal protector. (CMP—11)
Top Shield	Grounded metal shield protecting under-carpet components of flat conductor cables. (324) (CMP—6)
Tower	A structure supporting a wind turbine. (694) (CMP—4)
Transfer Switch	Device used to transfer load connections from one power source to another. (CMP—13)
Transfer Switch (Emergency Lighting)	Device transferring emergency lighting loads from normal to emergency power source. (700) (CMP—13)
Bypass Isolation Transfer Switch	A switch providing direct connection to the power source while isolating the transfer switch. (CMP—13)
Meter-Mounted Transfer Switch	A transfer switch connected between utility meter and meter base. (CMP—13)
Transformer	Equipment converting primary circuit current and voltage to secondary circuit. (CMP—9)
Transition Assembly	Assembly facilitating connection of flat conductor cables to other wiring systems. (324) (CMP—6)
Transport Refrigerated Unit (TRU)	A trailer or container maintaining temperature-sensitive goods. (626) (CMP—12)
Transportable	X-ray equipment designed for installation or transport in a vehicle. (660) (CMP—12)
Truck	Motor vehicle for transporting goods and services. (626) (CMP—12)
Truck Coupler	Device providing electric energy and services on a truck. (626) (CMP—12)
Truck Flanged Surface Inlet	Device receiving the connector to provide electric energy on a truck. (626) (CMP—12)
Trunk Cable	Portable extension cable with multiple branch circuits. (520) (CMP—15)
EMT (Electrical Metallic Tubing)	Thin-walled, unthreaded raceway for conductor protection and routing. (CMP—8)
ENT (Electrical Nonmetallic Tubing)	Pliable, nonmetallic raceway for conductor installation, resistant to moisture and chemicals. (CMP—8)
FMT (Flexible Metallic Tubing)	Flexible, liquid-tight metal raceway for conductor protection. (CMP—8)
Two-Fer	Assembly allowing two loads to connect to one branch circuit. (520) (CMP—15)
Type of Protection «n»	Protection ensuring electrical equipment does not ignite explosive gas atmospheres under normal operation. (CMP—14)