| Ampere Interrupt Capacity (AIC)
| Also “Interrupting Rating.” A rating of the amount of current that a protective device, such as a fuse or circuit breaker, can safely interrupt. |
| Ampere Rating
| A rating of the amount of current a protective device will carry continuously without deteriorating or exceeding temperature rise limits. |
| Blank Space
| A space on a panel of a switchboard that will never be used for expansion. It is covered with a blank panel and no bus runs behind it. |
| Branch Circuit
| A circuit that supplies power to the electrical loads in a building and is terminated at the panelboard or switchboard. |
| Bus Bar
| A component of a panelboard that serves as an extension of the main service conductors. Simplifies the connection of circuit protective devices to the main service conductors. |
| Bus
| Components of a switchboard that serves as an extension of the main service conductors. Simplifies the connection of circuit protective devices to the main service conductors. Utilized to move power between two or more components or circuits. |
| Can
| Also “Box.” Component of a panelboard used to contain the other components. It is designed to provide component and personnel protection. |
| Circuit Breaker
| A reusable overcurrent protection device. After tripping to break the circuit, it can be reset to protect the circuit again. |
| Current Rating
| A rating of the level of fault current a piece of equipment can withstand without sustaining damage. |
| Disconnect Device
| A blanket term used to describe a number of circuit protection devices, such as fuses and circuit breakers. |
| Distribution Equipment
| Also “Distribution/ Power Only Panelboard”. A panelboard or switchboard used to feed lighting and appliance panelboards and three-phase motor loads. Also can power small transformers to provide other voltage levels. |
| Flush-Mounted
| Recessed into a hole in the wall. |
| Front and Rear Alignment
| A type of switchboard arrangement where the front and the rear faces of the switchboard sections are aligned. |
| Full Rating Method
| A method of selecting circuit protection devices where all device ratings are equal to or greater than the available fault current. |
| Fuse
| A non-reusable overcurrent protection device. After tripping to break the circuit, it must be replaced to restore power to the circuit. |
| Ground
| A conducting connection (intentional or accidental) between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth. |
| Ground Fault
| An electrical fault where contact is accidentally made between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth. |
| Horizontal Bus
| Distributes power to each section of a switchboard. |
| Interrupting Rating
| Also “Ampere Interrupting Capacity (AIC).” A rating of the amount of current that a protective device, such as a fuse or circuit breaker, can safely interrupt. |
| Knockouts
| Circular perforations in the top and bottom panels of a panelboard that can be removed to provide entrances and exits for feeder wires enclosed in conduit. |
| Lighting and Appliance Panelboard
| A panelboard that supplies electrical power to branch circuits that use a constant amount of power. |
| Loadcenter
| A device that delivers electricity from a supply source to loads in light commercial or residential applications. |
| Main Breaker
| Also “Main Circuit Breaker.” A reusable overcurrent protection device designed to protect an entire panelboard or switchboard. Power from the mains is fed through a main breaker to the bus bars. |
| Main Disconnect Device
| A blanket term used to describe a number of panel protection devices, such as a main circuit breaker or main switch. |
| Main Lug Only (MLO)
| A panelboard where power from the mains is fed directly to the bus bars. |
| Neutral Bars
| Provides the termination point for the neutral wires from both the incoming service and the load circuits in a panelboard. |
| Neutral Bus
| Provides the termination point for the neutral wires from both the incoming service and the load circuits in a switchboard. |
| Overcurrent Protective Device
| A device such as a circuit breaker or fuse. In the event of an overload or short circuit, this device will quickly terminate power to the circuit. |
| Panelboard
| A wall-mounted electrical power distribution device for use in commercial and industrial applications. It provides circuit control and overcurrent protection for light, heat or power circuits.NEC defines it as a single panel or group of panel units designed for assembly in the form of a single panel; including buses, automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall or partition and accessible only from the front. |
| Pole
| A space in a panelboard (or switchboard) where a branch circuit protective device can be attached to connect a branch circuit to the bus bars (buses) and protect the branch circuit from overload. |
| Power Panelboard
| Any panelboard that does not qualify as a lighting and appliance panelboard. It is used to feed lighting and appliance panelboards and three-phase motor loads. Also can power small transformers to provide other voltage levels. |
| Pull Box
| A top-mounted pull section. |
| Pull Section
| A common switchboard component, a blank enclosure containing empty space through which cables can be pulled. |
| Rear Alignment
| A type of switchboard arrangement where only the rear faces of the switchboard sections are aligned. |
| Series Rated Method
| A method of selecting circuit protection devices where the main upstream circuit protection device must have an interrupting rating equal to or greater than the available fault current of the system, but downstream devices connected in series can be rated at lower values. |
| Service Entrance
| The single point at which electrical power enters a building. |
| Service Entrance Equipment
| The term used to describe a panelboard or switchboard used as a service entrance. |
| Service Section
| This section of the switchboard is where upstream power enters. It always contains a main disconnect and usually also has utility and/or customer metering equipment. |
| Six Subdivisions of the Main Rule
| An NEC ruling which states that you must be able to throw no more than six handles into the off position to disconnect electrical service. If throwing more than six handles would be required, one upstream disconnect must be provided to disconnect all the branch circuits at once. |
| Space
| A specification when ordering a switchboard. Room is purposely left for a protective device to be installed in a later expansion of service. Bus bars are in place. The customer needs to buy and install a protection device and connect a branch circuit to it. |
| Spare
| A specification when ordering a switchboard. An extra protection device is bolted in place and connected to the bus. For future service expansion, all the customer has to do is connect a branch circuit to it. |
| Surface-Mounted
| Attached to (and projects out from) the wall. |
| Switchboard
| A floor-standing electrical power distribution device for use in commercial and industrial applications. It divides large blocks of electrical current into smaller blocks of current used by electrical equipment.NEC defines it as a large single panel, frame, or assembly of panels on which are mounted, on the face or back, or both, switches overcurrent and other protective devices, buses and usually instruments. |
| Vertical Bus
| Distributes power through the circuit protection devices of a switchboard to the branch circuits. |
| Voltage Rating
| A rating of the voltage at which a piece of equipment is designed to operate. |
