Chapter 1 Electrical Systems — General Requirements
To provide access to the working space about electric equipment, the following number of entrances of sufficient size must be provided
1 For example, an electrical equipment room in an office building would require only one entrance door to the room. This entrance shall be capable of giving access to and egress from the working space. NEC Section 110.26(C)(1).
The entrance provided to give access to the working space about electric equipment rated over 600 volts must not be less than:
2 feet × 6½ feet Additionally, door(s) shall open in the direction of egress and be equipped with listed panic hardware. NEC Section 110.33(A)(3).
In all cases where there are live parts normally exposed on the front of switchboards or motor control centers, the working space in front of such equipment shall not be less than
3 feet Three feet is judged by the NEC to be adequate space (600 volts or under) so that workers may keep a safe distance from live electrical parts. NEC Table 110.26(A)(1).
The minimum headroom of working spaces about service equipment, switchboards, panelboards, or motor control centers shall be at least:
6½ feet The NEC judges 6½ feet working space, or the height of the equipment, to be adequate above service equipment to provide room for an electrician to service the equipment. This measurement is taken from the floor to ceiling of, say, an electrical equipment room; not from the top of the panelboard. NEC Section 110.26(A)(3).
How tall must a wall, screen, or fence be that encloses an outdoor electrical installation over 600 volts to deter access by unqualified persons?
7 feet NEC Section 110.31 requires a wall, screen, or fence to be not less than 7 feet in height when it is used to enclose an outdoor electrical installation with voltages over 600 volts.
What is the minimum depth of clear working space at electrical equipment rated above 75 kV and classified as Condition 1?
8 feet NEC Table 110.34(A) requires 8 feet minimum depth of clear working space under the conditions described in this question.
A feeder is
A branch circuit that supplies several outlet
What is a branch circuit called that supplies a number of outlets for lighting and appliances?
A general-purpose branch circuit A general purpose branch circuit supplies two or more receptacles or outlets for lighting and appliances. (Circuits feeding any duplex receptacles other than small appliance and laundry equipment are also general purpose branch circuits.) NEC Article 100 — Definitions, Branch Circuit, General Purpose.
A device that establishes a connection between two or more conductors by means of mechanical pressure and without the use of solder is called:
A pressure connector NEC Article 100 — Definitions
An enclosed channel designed expressly for holding wires, cables, or busbars is called:
A raceway A raceway may be conduit or piping, auxiliary wire troughs (gutters), busducts, wire trays, etc. NEC Article 100 — Definitions
A contact device installed at the outlet for the connection of an attachment plug is called:
A receptacle NEC Article 100 — Definitions.
A bonding conductor or jumper is
A reliable conductor to ensure the required electrical conductivity between metal parts to be electrically connected
Which of the following best describes festoon lighting?
A string of outdoor lights that is suspended between two points Defined in NEC Article 100 — Definitions.
What device is now required to detect and protect against arcing in 15- and 20-amp branch circuits supplying outlets installed in dwelling units?
AFCI Outlets installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, laundry rooms. . . . or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type. NEC Section 210.12(A)(1). The definition of arc-fault circuit interrupter has been added to Article 100 — Definitions.
Which of the following must not be allowed to come in contact with interior parts of electrical equipment?
Abrasives NEC Section 110.12(B) states that internal parts of electrical equipment must not be damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives or corrosive residues.
Approved" as used in the NEC means
Acceptable to the authority having jurisdiction In most cases, the local city, county, or state electrical inspector is the "authority" having jurisdiction. NEC Article 100 — Definitions
Which of the following qualifying terms indicate that a circuit breaker can be set to trip at various values of current, time, or both, within a predetermined range?
Adjustable The term "adjustable" (as applied to circuit breakers) means that the circuit breaker can be set to trip at various values of current, time, or both, within a predetermined range. NEC Article 100 — Definitions, Circuit Breaker, Adjustable.
Parts of electric equipment which in ordinary operation produce arcs, sparks, flames, or molten metal shall be enclosed or separated and isolated from
All combustible material. NEC Section 110.18. Special rules apply for motors (430.14) and hazardous locations (Articles 500 through 517).
A conductor encased within material of composition or thickness that is recognized by the NEC as electrical insulation is known as
An insulated conductor NEC Article 100 — Definitions, Conductor, Insulated
A point on the wiring system at which current is taken to supply utilization equipment is known as:
An outlet NEC Article 100 — Definitions.
Where must branch circuits and feeders be identified?
At the disconnecting means NEC Section 110.22 requires circuit identification at the disconnecting means. This is usually at the main distribution panel for feeders and at subpanels for branch circuits. If overcurrent protective devices are located properly, this is the location where the circuits should be identified. The marking shall be able to withstand the environment involved.
A device that, by insertion in a receptacle, establishes connection between the conductors of the attached flexible cord and the conductors connected permanently to the receptacle is called one of the following:
Attachment plug Also called a plug cap or plug. NEC Article 100 — Definitions.
A "bathroom" is an area that includes a basin with one or more of the following:
Bidet The definition of "bathroom" was revised in 2011 to include "a urinal" and "a bidet, or similar plumbing fixtures." NEC Article 100 — Definitions.
Externally operable means
Capable of being operated without exposing the operator to contact with live parts
A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating is called a
Circuit breaker NEC Article 100 — Definitions
Which circuits must not be connected to any system containing trolley wires with a ground return?
Circuits for lighting and power No other "live" or ungrounded conductors may be connected except those specifically designed for trolley operation. NEC Section 110.19.
A separate portion of a conduit or tubing system that provides access through a removable cover(s) to the interior of the system at a junction of two or more sections of the system or at a terminal point of the system is defined as a
Conduit body NEC Article 100 — Definitions
A device used to govern, in some predetermined manner, the electric power delivered to an electric apparatus is called a:
Controller A wall switch controlling a lighting fixture is one. A motor starter or controller is another example. A rheostat or electronic dimmer used to vary the light intensity is also a controller. NEC Article 100 — Definitions.
The ratio of the maximum demand of a system, or part of a system, to the total connected load of the system or the part of the system under consideration is known as:
Demand factor The NEC recognizes that every electrical outlet or piece of electric equipment will not all be operating simultaneously. Therefore, the NEC allows a demand factor for certain installations. NEC Article 100 — Definitions.
What is the term used to describe an enclosing case constructed so that dust will not enter under specified test conditions?
Dust tight NEC Article 100 — Definitions
In locations where electric equipment would be exposed to physical damage, the following must be provided
Enclosures or guards
Electric parts that are not suitably guarded, isolated, or insulated and are capable of being inadvertently touched or approached nearer than a safe distance by a person are known as:
Exposed A switchboard with knife switches, for example, has exposed live electrical parts. NEC Article 100 — Definitions.
Accessories such as locknuts, bushings, etc. are known as:
Fittings A fitting can be a locknut, bushing, or other part of a wiring system that is intended to perform a mechanical rather than an electrical function. NEC Article 100 — Definitions.
An unintentional, electrically conductive connection between an ungrounded conductor and the normally non-current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth, is called:
Ground fault The definition of "Ground Fault" has been relocated from NEC Section 250.2 to Article 100 — Definitions.
A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a class A device.
Ground-fault circuit-interrupter (GFCI) Class A GFCIs trip when the current to ground has a value in the range of 4-6 mA. Ground-fault circuit-interrupters are required on all residential receptacles installed outdoors, in bathrooms and kitchens, and in garages, etc. NEC Article 100 — Definitions.
The NEC definition of "Qualified Person" is one who:
Has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved A licensed electrician and a professional electrical engineer are two such "qualified" persons. NEC Article 100 — Definitions.
What must be provided for in all working spaces above service equipment?
Illumination. A light fixture must be installed for the working spaces about any switchboards, panelboards, etc. so adequate illumination (light) will be available for operation or repairs. Such lighting shall not be controlled by automatic means only. NEC Section 110.26 (D).
Entrances to all rooms or other enclosures containing exposed live parts operating at over 600 volts, nominal, shall be:
Kept locked NEC Section 110.34(C) requires that entrances to all buildings, vaults, rooms, or enclosures containing exposed live parts or exposed conductors operating at over 600 volts, nominal, be kept locked unless such entrances are under the observation of a qualified person at all times. In addition, permanent "danger" signs shall be provided that meet the requirements in NEC Section 110.21(B).
Indoor electrical installations over 600 volts that are open to unqualified persons shall be made with:
Metal-enclosed equipment Equipment accessible to unqualified persons shall be metal-enclosed. NEC Section 110.31(B)(1). In addition, associated equipment over 600 volts shall be marked with appropriate caution signs. NEC Section 110.34(C).
What is an assembly of one or more enclosed sections having a common power supply (bus) and principally containing motor control units called?
Motor control center NEC Article 100 — Definitions states that the described apparatus is referred to as a "motor control center."
The agency that publishes the NEC is abbreviated:
NFPA The National Fire Protection Association
A bare conductor is one with
No covering or insulation whatsoever A bare conductor, such as a service grounding wire, has no cover or insulation. NEC Article 100 — Definitions,
What is the name of an electrical load where the wave shape of the steady-state current does not follow the wave shape of the applied voltage?
Nonlinear load NEC Article 100 — Definitions.
When the electrical equipment exceeds 6½ feet in height, what is the required minimum headroom?
Not less than the height of the equipment NEC Section 110.26(A)(3) requires a minimum headroom working space of 6½ feet; the minimum headroom shall not be less than the height of the equipment if the equipment exceeds 6½ feet in height.
The NEC uses the term "isolated" to mean:
Not readily accessible to persons unless special means for access are used For example, a safety switch with a means of locking the access door to live interior parts would be considered to be not readily accessible. NEC Article 100 — Definitions.
An arrangement of incandescent lamps or electric discharge lighting to call attention to certain features such as the shape of a building is called:
Outline lighting Lighting fixtures of many types, but especially neon, are used to highlight signs, buildings, and the like. Las Vegas gambling casinos are a good example of how outline lighting is used to highlight and outline buildings or windows. NEC Article 100 — Definitions.
Operation of equipment in excess of normal, full-load rating is known as:
Overload For example, a conductor operating in excess of its rated ampacity that, if it persists for a sufficient length of time, would cause damage or dangerous overheating. A fault, such as a short circuit or ground fault, is not an overload. NEC Article 100 — Definitions.
Where switches, or other equipment operating at 600 volts, nominal, or less, are installed in a room or enclosure where there are exposed energized parts or wiring operating at over 600 volts, the high-voltage equipment shall be effectively separated from the space occupied by the low-voltage equipment by a suitable:
Partition, fence or screen A partition to prevent contact between the two systems must be installed. NEC Section 110.34(B).
A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system is a:
Plenum NEC Article 100 — Definitions.
When an enclosure has been constructed so that exposure to a beating rain will not result in the entrance of water under specified test conditions, the enclosure is known as:
Raintight This type of enclosure is designed to keep rain water out of the device. NEC Article 100 — Definitions.
Any electric circuit that controls any other circuit through a relay is called a:
Remote-control circuit NEC Article 100 — Definitions.
Concealed" as applied to electrical wiring means
Rendered inaccessible by the structure or finish of the building For example, cables or raceways installed within, say, a drywalled partition are not accessible without damaging the finished wall and are considered to be concealed. Wires in concealed raceways are considered concealed, even though they may become accessible by withdrawing them. NEC Article 100 — Definitions.
The value of current, time, or both at which an adjustable circuit breaker is set to trip is known as:
Setting The setting of a circuit breaker is the value of current, time, or both at which an adjustable circuit breaker is set to trip. NEC Article 100 — Definitions, Circuit Breaker, Setting.
Any electric circuit that energizes signaling equipment is known as a:
Signaling circuit For example, a circuit consisting of a low-voltage transformer, pushbuttons, door chime, and conductors is a signaling circuit; so is a security alarm system. NEC Article 100 — Definitions.
Working space in rooms containing electrical equipment shall not be used for
Storage. The area around electrical equipment must be kept clear of foreign matter so that maintenance and repairs may be readily made. NEC Section 110.26 (B).
A large single panel, frame, or assembly of panels, on which are mounted on the face, back, or both, switches, overcurrent and other protective devices will fall under the definition of:
Switchboard Switchboards are generally accessible from the rear as well as from the front and are not intended to be installed in cabinets. NEC Article 100 — Definitions
Ampacity is defined as
The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating NEC Article 100 — Definitions
A continuous load is a load where the maximum current is expected to continue for a certain length of time. This time is:
Three hours or more For example, electric baseboard heaters in the coldest weather will more than likely operate for longer than three hours. Therefore, circuits feeding these units must be rated as "continuous." NEC Article 100 — Definitions.
How many access entrances are required to working space about electrical equipment rated 1200 amperes or more and over 6 feet wide?
Two, one at each end of the area NEC Section 110.26(C)(2) requires one entrance not less than 24 inches wide and 6½ feet high at each end of the work space to allow entrance to and egress from the work space. Additional requirements apply to the installation and hardware requirements of such doors
A raceway is an enclosed channel designed for holding:
Wires, cables or busbars A conduit, such as rigid steel conduit, unlike plumbing pipe, is designed to contain electrical conductors. A raceway is identified within specific article definitions. NEC Article 100 — Definitions.
Which of the following anchors may not be used to secure electrical equipment to masonry walls?
Wooden plugs driven into holes in the masonry for holding wood screws NEC Section 110.13(A)
