ch 7 Flashcards
A ? is a conductor installed on the supply side of a service or separately derived system to ensure the required electrical conductivity between metal parts required to be electrically connected.
supply-side bonding jumper
A(n) ? is the connection between two or more portions of the equipment grounding conductor.
equipment bonding jumper
When two conductive parts are connected together to establish electrical continuity and conductivity between them, they are ? .
bonded
A system bonding jumper is the connection between the grounded conductor and the equipment grounding conductor or ? , or both, at a separately derived system.
supply-side bonding jumper
Bonding of electrical equipment is important for a grounded system because it accomplishes all but which of the following?
It eliminates voltage gradients in the Earth
It establishes continuity between metal equipment.
List the three elements that an effective ground-fault return path is required to perform in order to maintain and provide adequate safety.
Be electrically continuous.
Have sufficiently low impedance to limit the voltage to ground and to facilitate the operation of the circuit protective devices
Have the capacity to conduct safely any fault current likely to be imposed on it.
Which of the following is recognized in the Code as an acceptable method of attaching bonding jumpers to circuits and equipment?
Connections that are part of a listed assembly
Exothermic welding
Listed clamps
Machine screw fasteners that engage not less than two threads or are secured with a nut
Pressure connectors listed as grounding and bonding equipment
Terminal bars
According to the NEC Style Manual, the phrase “likely to become energized” is best described by which of the following?
Failure of insulation on
Which part of Article 250 provides specific electrical bonding requirements?
part V
Note: Mention the general performance requirements for bonding in Sections 250.4(A)(3) and (4) and 250.4(B)(2) and (3). The question asks for specific bonding requirements. These are the general performance criteria on which the specific (prescriptive) rules are based.
Fittings for wiring methods such as electrical metallic tubing and rigid metal conduit are required to be ? .
listed
Effective bonding of metal parts is required to maintain effective continuity from the service to the ? .
farthest outlet supplied by the system
first panelboard enclosure
first receptacle in the branch circuit
first system overcurrent device
Where loosely jointed metal raceways are used and, especially where there are expansion joints or telescoping sections of raceways, the National Electrical Code requires that they be made electrically continuous by the use of a(n) ? unless the fitting is listed for use without a field inspected equipment bonding jumper.
equipment bonding jumper
Reducing washers are not suitable for non-service bonding in circuits over and under 250 volts to ground.
false
Where concentric, eccentric, or oversized knockouts are encountered in circuits over 250 volts phase to ground, one of the bonding methods in Section 250.92(B)(2) through (4) must be applied to ensure the required continuity and conductivity.
true
Which of the following methods is not suitable for establishing bonding connections for circuits over 250 volts phase to ground?
A locknut on the outside and a bushing on the inside of metal enclosure
Standard boxes with concentric and eccentric knockouts that are listed as suitable for bonding can be used in circuits over and under 250 volts phase-to-ground.
true
Nonconductive coatings on equipment to be grounded shall be removed from threads and other contact surfaces to ensure good electrical continuity or be connected by means of fittings designed so as to make such removal unnecessary.
true
250.12
An aluminum equipment bonding jumper installed on the load side of a 400-ampere overcurrent device must not be smaller than ? .
1 awg
What is the minimum-size copper supply-side bonding jumper for a 600-ampere service supplied with two 400 kcmil conductors (800 kcmil is the largest ungrounded service-entrance conductor per phase) if all the conductors are in a single six-inch raceway?
2/0 awg
Where more than one raceway enters or leaves a switchboard, pull or junction box, or other equipment, it is permissible to use a single conductor to bond these raceways to the equipment where sized appropriately.
true
A(n) ? is generally required to connect the grounding terminal of a grounding-type receptacle to a grounded box.
equipment bonding jumper
Which NEC table is used to size equipment bonding jumpers on the load side of a fuse or circuit breaker?
Table 250.122
What is the minimum-size aluminum equipment bonding jumper required for a range receptacle installed in a metal box where the branch circuit is protected by a 60-ampere circuit breaker?
8 awg
An equipment bonding jumper from a metal box to a grounding-type receptacle is not necessary for a self-grounding type receptacle.
true
? requires that metal water piping systems and other metal piping systems installed within or attached to buildings or structures be bonded.
Section 250.104
The metal water piping system is permitted to be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where large enough, or to one or more grounding ? .
electrodes
What is the minimum-size copper bonding jumper required for an interconnected exposed structural metal if the service is rated 1,000 amperes and supplied by two parallel 600 kcmil copper conductors for each ungrounded service phase conductor?
3/0 AWG
The bonding connection for a metal water piping system is required to be readily accessible unless it is a buried connection or a connection made using the exothermic welding process.
false
Explain that there is a difference between the terms accessible and readily accessible. The other factor in this question is the fact that Section 250.104(A) does not currently offer an exception for the required accessibility for the bonding connection to a metal water pipe. This relates back to old requirements for testing and being able to disconnect this connection during testing procedures.
Where a building or structure is supplied by a feeder or branch circuit, the bonding jumper to the metal water piping system(s) is required to be sized according to ? , based on the size of the feeder or branch circuit that supplies the building or structure.
Table 250.102(C)(1)
The grounded conductor of each separately derived system shall be bonded to the nearest available point of the metal water piping system(s) in the area served by the separately derived system.
true
An equipment bonding jumper is permitted to be installed either inside or outside of a raceway or enclosure.
true
When an equipment bonding jumper is installed on the outside of flexible metal conduit or liquidtight flexible metal conduit, the length of the jumper is generally limited to not exceeding ? in length.
6 feet
Where a feeder supplies a separate building or structure, and a metal frame of that structure must be bonded, what NEC table is used to size the bonding jumper?
Table 250.102(C)(1)
When a gas furnace is supplied by a 30-ampere branch circuit, what is the minimum size bonding conductor or jumper required for bonding the metal gas piping system?
10 AWG copper
Refer students to 250.104(B), where the bonding for the gas piping system can be accomplished using the branch circuit equipment grounding conductor for the circuit supplying the equipment. Also point out that Informational Note No. 2 refers users to additional bonding requirements that are provided in Section 7.13 of NFPA 54, National Fuel Gas Code. The question asks for the minimum, and the type of gas piping system is not provided in the question.
Referring to the drawing, what is the minimum size required for the copper supply-side bonding jumper in this service?
2 AWG
Referring to the drawing, what is the minimum size required for the copper supply-side bonding jumper in this service and what is the minimum size required for a copper load-side bonding jumper?
2 AWG / 4 AWG
Which of the following tables is used to size bonding conductors or jumpers for interior metal water piping systems?
Table 250.102(C)(1)
What is the minimum size copper bonding conductor for an interior metal water piping system if the building is supplied by a service that has a large ungrounded service entrance conductor size of 2,500 kcmil?
350 kcmil
Note: 2,500 kcmil x 12.5% = 312,500 kcmil round up to the next standard available size is 350 kcmil based on Table 8, Chapter 9 and Table 250.102(C)(1).
The largest size bonding jumper or conductor for interconnected exposed structural metal building frames is 3/0 copper or 250 aluminum.
false
Note: The NEC now requires interior metal water piping systems and exposed interconnected structural metal building framing to be bonded with conductors or jumpers not smaller than the sizes in Table 250.102(C)(1).
Bonding wedges are suitable for use to accomplish the bonding required by 250.92(B)(2) through (4).
true
