Glossary of Terms

We’ve compiled this list of commonly used electrical terms for your quick reference.

Alternate corrosion protection

A coating, other than one consisting solely of zinc, which upon evaluation has demonstrated the ability to provide the level of corrosion resistance required on the exterior of the conduit. It is not prohibited that the coatings include zinc.


Acceptable to the authority having jurisdiction.

Authority having jurisdiction (AHJ)

The organization, office or individual with the authority to determine which code requirements apply, how they are to be interpreted and who gives final approval to the electrical installation. Some examples are the electrical inspector or other government entity and insurance underwriters.

NOTE: The “authority having jurisdiction” is most often the electrical inspector, but could be a project manager or other final approval authority.


A curvature of the conduit or tubing made so the raceway will fit a specific geometric location. This can be a factory elbow or can be a field bend of the raceway.

Circuit loading

Concentration of circuits in one raceway.

Conduit connection

Interface between conduit or tubing and other equipment.

Conduit joint

The coupling of two pieces of conduit or tubing, or coupling a length of conduit or tubing to a bend.

NOTE: One of the most important elements of an electrical installation.

Coupling, integral

A coupling meeting the requirements of UL-514B that is assembled to the conduit, tubing or elbow during manufacture and is not readily removable. The integral coupling of electrical metallic tubing is a “belled” end with set screws.

Coupling, standard conduit

As applied to intermediate metal conduit or rigid metal conduit, this is a threaded, straight-tapped means of joining two pieces of conduit. Such coupling meets the requirements of the applicable UL conduit standard.

Equipment grounding conductor

As defined in the NEC®. In addition, it is the path by which a fault is transmitted to the overcurrent protection device.

NOTE: Steel conduit and tubing are called equipment grounding conductors, as are copper or aluminum wire.


Using approved materials (generally detailed by building codes or specifications) that fill the opening (annular space) around the conduit to prevent the spread of fire and smoke and ensure the fire rating of the wall, floor or ceiling being penetrated is not reduced.

Fire-resistance-rated assemblies

Construction materials assembled together, then tested and rated for ability to inhibit the spread of fire for a specified period of time under specific test conditions. The rating is expressed in hours (e.g., one hour, two hours). Information can be found in various laboratory “listing” directories.

Fitting, threadless

A fitting intended to secure, without threading, rigid or intermediate metal conduit or electrical metallic tubing to another piece of equipment (connector) or to an adjacent length of conduit or tubing (coupling).


Protected from corrosion by a specified coating of zinc that may be applied by either the hot-dipped or electro-galvanized method.

Home run

The run of raceway between the panelboard / switchboard and the first distribution point.

Identified (for use)

As defined in the NEC.

NOTE: For the purposes of this standard, the product has been evaluated for a specific purpose, environment or application, and written documentation or labeling verifying this exists.

Penetration firestop system

A listed assemblage of specific materials or products that are designed, tested and fire-resistance rated in accordance with ASTM E814 to resist, for a prescribed period of time, the spread of fire through penetrations in fire-rated assemblies.

Primary coating

The corrosion protection coating evaluated by the listing authority and required by the applicable standard for listing.

Running threads

Continuous straight threads cut into a conduit and extended down its length — not permitted on conduit for connection at couplings.


As defined in the NEC, this term includes more than steel conduit. In this standard, it is steel rigid metal conduit, intermediate metal conduit or electrical metallic tubing, designed for enclosing and protecting electrical, communications, signaling and optical fiber wires and cables.

Supplementary coating

A coating other than the primary coating applied to listed conduit / tubing either at the factory or in the field, to provide additional corrosion protection where needed.

Contact us to learn more about steel conduit.