NE Journeyman Electrician key terms

The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. It depends on conductor size, insulation type, ambient temperature, and how many current-carrying conductors share a raceway.

A multiplier applied to a conductor's table ampacity when the surrounding air is hotter or colder than the 30 degrees C (86 degrees F) baseline used in the ampacity tables. Hotter surroundings reduce the allowable current.

A percentage reduction applied to conductor ampacity when more than three current-carrying conductors are installed together in a raceway or cable without maintaining spacing. The more bundled conductors, the lower the permitted ampacity.

The temperature limit of the terminals to which a conductor connects. The conductor's usable ampacity is capped by the lowest-rated termination in the circuit, such as a 75 degrees C breaker terminal on a 90 degrees C conductor.

The loss of voltage along a circuit caused by conductor resistance and reactance as current flows. Long runs or undersized conductors cause excessive drop, which can make equipment operate poorly even though the circuit is otherwise code-compliant.

The relationship stating that voltage equals current multiplied by resistance (E = I x R). It is the basis for finding current draw, voltage, or resistance in a circuit when the other two values are known.

The ratio of real power, in watts, to apparent power, in volt-amperes, in an alternating-current circuit. A low power factor means more current is needed to deliver the same useful work, affecting load calculations.

The ratio of the maximum demand on a system to the total connected load. It allows a service or feeder to be sized smaller than the sum of all loads because not every load operates at once.

The sum of the nameplate ratings of all equipment that could be operated at the same time on a service or feeder. It is the starting point before demand factors are applied.

The conductors that run from the utility's service point to the service equipment disconnecting means. Their size is based on calculated load and must be protected against overload and short circuits.

All circuit conductors between the service equipment, source of a separately derived system, or other power supply and the final branch-circuit overcurrent device. Feeders supply panelboards rather than individual outlets.

The circuit conductors between the final overcurrent device protecting the circuit and the outlets or equipment it serves. Branch circuits are classified by rating, such as 15, 20, or 30 amperes.

A breaker or fuse designed to open a circuit automatically when current exceeds a safe level. It protects conductors and equipment from overloads and short circuits and must be coordinated with conductor ampacity.

The maximum prospective fault current a device or assembly can safely withstand without failing. Equipment must have a rating at least equal to the available fault current at its point of installation.

The calculated or measured current that would flow at a point in the system during a bolted short circuit. It depends on transformer impedance and conductor impedance between the source and the point.

A tested combination in which a downstream circuit breaker is protected by a specific upstream current-limiting device, allowing the downstream breaker to have a lower interrupting rating than the available fault current.

The conductive path that connects normally non-current-carrying metal parts of equipment to the system grounding point. It provides a low-impedance fault path so overcurrent devices trip during a ground fault.

The conductor that connects the system grounded conductor or equipment to the grounding electrode, such as a ground rod or metal water pipe. It carries fault and lightning current to earth.

The set of electrodes and their bonding connections that establish a connection to earth. It typically includes metal underground water pipe, a concrete-encased electrode, ground rods, and metal building framing.

A reliable conductor that ensures electrical continuity between metal parts that must be electrically connected. It equalizes potential so metallic paths cannot carry unwanted current or create a shock hazard.

The percentage of a raceway's cross-sectional area occupied by conductors. Limits keep conductors from jamming during installation and from overheating because they cannot dissipate heat.

The required internal volume of an outlet, device, or junction box based on the number and size of conductors, devices, clamps, and grounding conductors it contains. Undersized boxes risk damaged insulation and overheating.

An enclosure where conductors are spliced or where raceways and cables meet. It must be accessible and sized for the conductors and splices it contains so connections can be inspected and serviced.

The field practice of shaping raceway to route it around obstacles and into boxes. It includes stub-ups, offsets, and saddles, and must preserve the raceway's internal diameter so conductors can be pulled without damage.

The current a motor draws at rated load and rated voltage, taken from the code's motor tables rather than the nameplate for conductor and protection sizing. It is the basis for branch-circuit and feeder calculations.

A device, such as a thermal overload relay, that protects the motor from sustained excess current that would overheat it. It is separate from branch-circuit short-circuit and ground-fault protection.

A switch or disconnecting means located within sight of and readily accessible from the motor that isolates it from all ungrounded conductors for servicing. It must be sized to the motor's rated current.

The circuit that carries the signals controlling a motor starter or contactor, such as start and stop pushbuttons and holding contacts. It is separate from the power circuit that carries motor current.

A motor compressor assembly enclosed in a sealed housing with the refrigerant, so the motor is cooled by the refrigerant rather than air. Its nameplate current is used differently than standard motor tables.

The percent voltage drop inside a transformer when it delivers full-load current, caused by winding resistance and reactance. It determines the available fault current on the transformer's secondary.

The breakers or fuses on the primary and secondary sides of a transformer that protect it from overload and fault current. Ratings are set by code rules based on transformer size and voltage.

The system that classifies areas by the presence of flammable gases, dusts, or fibers, and by how often those materials are present. It determines which wiring methods and equipment are permitted.

Enclosures and devices designed to contain an internal explosion and prevent ignition of surrounding flammable atmosphere. They are required in certain classified locations and must be installed with listed seals and fittings.

A circuit designed so that any spark or thermal effect produced is incapable of igniting a flammable atmosphere under normal or fault conditions. It limits energy through barriers and is common in classified areas.

The state body that licenses electricians and adopts rules governing electrical work in Nebraska. It administers exams, issues licenses, and handles complaints and disciplinary actions under state statute.

A credential issued by Nebraska that authorizes a person to perform electrical work under the rules adopted by the state electrical board. It requires passing an exam and meeting experience and education requirements.

The number of approved instruction hours a licensed electrician must complete before renewing a license. Nebraska rules specify the hours and the topics that qualify, and records must be kept for audit.

The local or state authorization required before electrical work begins, followed by official inspection of the completed work. Permits create a record and inspections verify that installations meet adopted code.