AZ ROC R-11 Electrical key terms

The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Ampacity depends on conductor size, material, insulation type, and how the conductor is installed.

A multiplier applied to a conductor's ampacity when the surrounding air temperature differs from the 30 degrees C (86 degrees F) value on which the code tables are based. Hotter surroundings require a lower correction factor.

A reduction in conductor ampacity required when more than three current-carrying conductors are installed together in a raceway or cable, because heat cannot dissipate as freely as it can from a single conductor.

The loss of voltage along circuit conductors caused by their impedance. The NEC recommends keeping drop to about 3 percent on branch circuits and 5 percent overall so equipment operates efficiently.

A load whose maximum current is expected to continue for three hours or more. Conductors and overcurrent devices serving continuous loads are typically sized at 125 percent of the load.

The circuit conductors between the final overcurrent device protecting the circuit and the outlets or equipment it supplies. Branch circuits are the last level of wiring before the load.

All circuit conductors between the service equipment, the source of a separately derived system, or another supply source and the final branch-circuit overcurrent device.

The point where the serving utility's conductors connect to the premises wiring, typically at the service drop or lateral terminations. It marks where the National Electrical Code begins to govern the installation.

The conductors that carry power from the service point to the service equipment. They are normally service-rated conductors installed overhead or underground and sized for the calculated load.

A single panel or group of panel units with buses, automatic overcurrent devices, and switches, designed for installation in a cabinet and used to distribute power to branch circuits or feeders.

Any current greater than the rated current of equipment or the ampacity of a conductor. It may result from an overload, a short circuit, or a ground fault.

A fuse or circuit breaker that automatically opens a circuit when current exceeds a set value, protecting conductors and equipment from overheating and damage.

An unintentional, electrically conducting connection between a normally current-carrying conductor and the earth or grounded metal. It can shock people, damage equipment, and start fires.

A device that detects small ground-fault currents, typically 4 to 6 milliamperes, and quickly opens the circuit. It is required in bathrooms, kitchens, outdoors, and other wet or damp locations.

A device that monitors a branch circuit for current and voltage patterns characteristic of dangerous arcing and then de-energizes the circuit. It is required in dwelling-unit bedrooms and other specified rooms.

The conductive path that connects normally non-current-carrying metal parts of equipment to the system grounded conductor or grounding electrode, allowing fault current to return and trip the overcurrent device.

A rod, pipe, plate, ring, or other conductive object in direct contact with the earth that provides a connection to ground. Common types include ground rods and metal water pipe.

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

A reliable conductor that ensures electrical continuity between metal parts required to be electrically connected. Bonding jumpers carry fault current and keep metal parts at the same potential.

Premises wiring whose power comes from a source with no direct electrical connection to the supply conductors except through magnetic coupling, such as a transformer or generator. It must be grounded and bonded as its own system.

An enclosed channel designed expressly for holding wires, cables, or busbars. Examples include rigid conduit, electrical metallic tubing, and wireways.

The maximum number and size of conductors permitted inside a raceway, limited by the total conductor cross-sectional area, which for three or more conductors may not exceed about 40 percent of the raceway's interior area.

The required cubic-inch volume of an outlet, device, or junction box based on the number and size of conductors, devices, and fittings it contains. Correct box fill prevents overheating and insulation damage.

A factory assembly of two or more insulated conductors with a bare or insulated ground, enclosed in a moisture-resistant, flame-retardant nonmetallic jacket. It is used mainly in dry interior locations such as wood-frame dwellings.

A factory assembly of insulated conductors enclosed in a flexible metallic armor. Depending on its listing, it can be used in many locations where nonmetallic-sheathed cable is not permitted.

A device or group of devices that can disconnect all ungrounded conductors of a circuit or piece of equipment from their source of supply. It must be readily accessible and clearly marked.

A device that protects a motor from sustained excess current caused by overload or overheating, usually set to the motor nameplate current or service factor. It operates separately from short-circuit protection.

A fuse or circuit breaker that clears short circuits and ground faults on a motor branch circuit. It is sized from the code tables based on motor horsepower and may be larger than the conductor ampacity.

A device or assembly that starts and stops a motor and may also protect against overload, regulate speed, or control direction. Common examples are manual starters and magnetic motor starters.

The required clear space in front of electrical equipment, measured from the floor to a height of about 2 meters, that allows safe examination and maintenance work while the equipment is energized.

The organization, office, or individual responsible for enforcing the code and approving equipment, materials, and installations. In Arizona this is usually a city or county building department.

The state agency that licenses and regulates contractors, including electrical contractors, and investigates complaints about workmanship. Holding an ROC license is generally required to contract for electrical work in Arizona.

Official authorization from the local building department to install or alter electrical work. It triggers the required inspections and must be obtained before the work begins.

A safety procedure in which an energy source is shut off, locked, and tagged so it cannot be re-energized while workers service equipment. Only the person who applied the lock removes it.

A sudden release of energy caused by an arcing fault, producing intense heat, light, pressure, and molten metal. It can cause severe burns and is a major reason for de-energized work and protective equipment.

A method of adding up connected loads and applying the demand factors the code allows to determine the minimum size of service, feeder, and branch-circuit conductors and their overcurrent devices.

A written modification to the construction contract that changes scope, price, or schedule before or during the work. It must be properly authorized by the owner to be valid and enforceable.

An itemized breakdown of the contract price by work item, used to determine progress payments. The items should add up to the total contract amount and be supported by the estimate.