MN Journeyman Electrician key terms

The maximum continuous current a conductor can carry under the conditions of use without exceeding its temperature rating. Ampacity depends on conductor size, insulation type, ambient temperature, and number of current-carrying conductors bundled together.

The required reduction of a conductor's base ampacity when more than three current-carrying conductors share a raceway or cable without maintaining spacing, because trapped heat reduces the conductor's ability to dissipate heat.

A multiplier applied to a conductor's table ampacity when the surrounding air or earth temperature differs from the temperature basis of the ampacity table, accounting for reduced heat dissipation in hotter locations.

A load expected to operate at maximum current for three hours or more. Continuous loads require overcurrent devices and conductors sized at 125 percent of the load unless the code permits otherwise.

A load that operates at maximum current for less than three hours at a time. Unlike continuous loads, it does not require the 125 percent sizing adder for conductors and overcurrent protection.

A ratio applied to the total connected load to account for the fact that not all loads operate simultaneously at full capacity. It allows service and feeder conductors to be smaller than total connected load would require.

The sum of the nameplate ratings of all equipment and devices supplied by a system, before any demand factors are applied. It represents the maximum possible draw if everything ran at once.

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

The circuit conductors between the final overcurrent device protecting the circuit and the outlet or outlets. Branch circuits supply the actual utilization equipment such as receptacles, lighting, and appliances.

A branch circuit consisting of two or more ungrounded conductors with a voltage between them and a grounded conductor with equal voltage to each ungrounded conductor. It requires a means to simultaneously disconnect all ungrounded conductors.

The conductors from the service point to the service disconnecting means. Overhead and underground service conductors have specific sizing, clearance, and installation requirements distinct from feeders and branch circuits.

The point of connection between the serving utility's facilities and the premises wiring system. It marks where the utility's responsibility ends and the premises electrical system begins.

The necessary equipment, usually a switchboard or panelboard with a main switch and overcurrent protection, connected to the load end of service conductors to control and cut off the supply to a building.

The main switch or breaker that disconnects all service conductors from the premises wiring. It must be located at a readily accessible point nearest the point of entry of the service conductors.

A fuse or circuit breaker designed to open a circuit automatically when current exceeds a predetermined value, protecting conductors and equipment from overheating and short circuits.

Operation of equipment in excess of its normal full-load rating, or a conductor carrying current beyond its ampacity, that if sustained would cause damage or dangerous overheating.

An abnormal connection of relatively low impedance between two points of different potential in an electrical circuit, causing excessive current flow that overcurrent devices must interrupt quickly.

An unintentional electrical connection between a normally current-carrying conductor and the equipment grounding conductor, grounding electrode, or earth. Ground-fault protection reduces fire and shock hazards.

A device that detects small ground-fault currents, typically in the 4 to 6 milliampere range, and opens the circuit to protect people from electric shock. Required in bathrooms, kitchens, outdoors, and other specified locations.

A device that detects and interrupts dangerous electrical arcs that could ignite surrounding materials. It is required for many branch circuits serving outlets in dwelling units, such as bedrooms and living areas.

The conductive path installed to connect normally non-current-carrying metal parts of equipment to the system grounded conductor or grounding electrode, providing a low-impedance path for fault current.

A system or circuit conductor intentionally connected to earth, commonly the neutral conductor. It carries normal return current and is white or gray in color.

A conductive object such as a ground rod, metal water pipe, or concrete-encased electrode that establishes a direct electrical connection to earth for the grounding system.

The conductor that connects the grounding electrode system to the grounded conductor or equipment grounding conductor at the service or at a separately derived system.

A reliable conductor that ensures electrical continuity between metal parts required to be electrically connected, such as around a water meter or between sections of metal raceway.

A point on the wiring system at which current is taken to supply utilization equipment. Receptacles, luminaires, and appliance connection points are all examples of outlets.

A contact device installed at an outlet for the connection of an attachment plug to supply current to utilization equipment. Standard and specialty types have specific ratings and installation requirements.

The current a motor draws at its rated load and voltage, taken from code tables rather than nameplate for sizing conductors and overcurrent devices. It forms the basis for motor circuit calculations.

A device or protective scheme that senses and interrupts excessive motor current caused by overload, such as a thermal relay, sized according to the motor's service factor and temperature rise.

The fuse or circuit breaker protecting the motor branch circuit against short circuits and ground faults, sized as a percentage of full-load current and permitted to be increased to allow motor starting.

A device that transfers electrical energy between circuits through electromagnetic induction, changing voltage and current levels. Transformers require overcurrent protection and grounding rules for separately derived systems.

A premises wiring system whose power comes from a source other than a service, such as a transformer or generator, and that has no direct electrical connection to supply conductors originating in another system.

An enclosed channel designed expressly for holding wires, cables, or busbars. Common types include conduit, electrical metallic tubing, and surface metal raceway, each with its own installation rules.

The required minimum volume of an outlet, junction, or device box based on the number and size of conductors, devices, clamps, and connectors it contains, preventing overheating and crowded connections.

A means of connecting the handles of two or more circuit breakers so they operate simultaneously, required on the two ungrounded conductors of a multi-wire branch circuit for safe servicing.

A state-specific modification adopted by Minnesota that adds to, deletes, or changes a provision of the national electrical code as it applies to electrical work performed within the state.

The organization, office, or individual responsible for approving equipment, installations, and procedures. In Minnesota this is typically the state electrical inspector or local municipal inspector enforcing the code.

A required Minnesota credential authorizing a person or business to contract for electrical work. It requires a licensed master electrician or administrator, bonding, and compliance with state licensing rules.

A Minnesota credential allowing an individual to perform electrical work under supervision of a master electrician, obtained by meeting experience and education requirements and passing a licensing examination.

Required periodic training that Minnesota licensed electricians complete to renew their licenses, covering code updates, safety, and technical topics approved by the state licensing board.