305
Refer to the drawing of electrical equipment shown below. Which of the connections (#1, #2 & #3) should be installed?(main panel into 2 subpanels)
#3 only
A 225 KVA, 480 delta to 208/120-volt, 3-ph, 4-w transformer is to be installed. • The first set of secondary conductors is installed from the transformer to a 400-A MB panelboard. There will be two parallel conduits to this 400-A panel. Each conduit will contain 4 each 3/0 conductors. • A second set of secondary conductors is installed from the transformer to a 225-A MB panelboard. One conduit will be installed between this 225-amp panel and the transformer. The conduit will contain 4 each 4/0 conductors. You have decided to "ground and bond" everything in the transformer enclosure. Refer to Scenario 305-25 to answer this question. The smallest SBJ you can install for this system is ___ AWG.
1/0
Refer to Figure 305.01. The smallest bonding jumper you can run with each conduit between the transformer and Switch #1 is ___ AWG.
1/0
As shown in Figure 205.5, four parallel conduits will be installed for the service. Each conduit will contain three 3/0 AWG conductors for the ungrounded conductors and one 3/0 AWG conductor for the grounded conductor. The smallest MBJ that can be installed in the panel is a ___ AWG or kcmil
2/0
Panel B, shown in Figure 205.4, is a 120/240-volt, 1-ph, 3-wire service panelboard. Panel B contains a 700-Amp, 2-pole main breaker. There is one 500 kcmil ungrounded conductor for AØ in each conduit and one in each conduit for BØ. There is also a grounded conductor in each conduit. The smallest main bonding jumper that can be installed is a ___ AWG.
2/0
Refer to Figure 205.17. The smallest permitted size system bonding jumper for Panel LK is ___ AWG.
2/0
Refer to Figure 304.06. The MBJ must be at least a ___ AWG or kcmil.
2/0
Refer to Figure 305.01. Where the GEC is run into the transformer, the smallest system bonding jumper you can use to connect XO to the grounding conductors is ___ AWG.
2/0
A 1200-A fused safety switch is supplied from a 120/208-volt, 3Ø, 4-wire service lateral using 3 paralleled Schedule 40 PVC conduits. The load calculation results are as follows: AØ = 1160 amps; BØ = 1180 amps; CØ = 1140 amps; Neutral = 900 amps. Refer to Scenario 304-12, shown above, to answer this question. The smallest main bonding jumper you are permitted to install in the switch is ___ AWG or kcmil.
250
Table ___ of the NEC® is used to size the system bonding jumper of a separately derived AC system.
250.102(C)(1)
Section ___ of the NEC® states that normally non-current-carrying metal parts of portable generators can be bonded to the generator frame.
250.34(A)(2)
A 500 KVA, 480 delta-to-208/120-volt, 3-ph, 4-W transformer is to be installed. You have decided to "ground and bond" everything in the transformer enclosure. • One set of secondary conductors is installed from the transformer to a 400-A Main Breaker (MB) panelboard. There will be two parallel conduits to this 400-A panel. Each conduit will contain 4 each 3/0 conductors. • A second set of secondary conductors is installed from the transformer to a 225-A MB panelboard. One conduit will be installed between this 225-amp panel and the transformer. The conduit will contain 4 each 4/0 conductors. • A third set of secondary conductors is installed from the transformer to a 600-A safety switch fused at 500 amps. Three parallel conduits will be installed between the transformer and this switch. There will be four each 2/0 conductors installed in each of the three conduits. • And finally, a fourth set of secondary conductors is installed from the transformer to a 400-A panelboard that contains a 300-A main. There will be two parallel conduits to this 350-A MB panel. Each conduit will contain 4 each 1/0 conductors. Refer to Scenario 305-10. The smallest bonding jumper you can install between XO and the ground bar that is attached to the transformer enclosure is ___ AWG.
3/0
Service Panel MDP, shown in Figure 205.6, has a 1200-amp main breaker. Each conduit contains 350 kcmil conductors. The minimum size main bonding jumper is ___ AWG or kcmil.
4/0
What is the smallest size wire permitted to be used as a main bonding jumper in a 1200-A fused safety switch? The safety switch is fed from a transformer with four parallel sets of 350 kcmil wire.
4/0 AWG
An 1800-A, 120/208-volt, 3Ø, 4-wire service is to be installed underground using 6 paralleled Schedule 40 PVC conduits. The service equipment will be a fused switchboard. The minimum size of the aluminum main bonding jumper for this service is ___ AWG or kcmil. All conductors are THHN/THWN aluminum.
400
A 112.5 KVA 480 delta to 208/120-volt, 3-ph, 4-W transformer is to be installed. • One set of secondary conductors is installed from the transformer to a 150-A MB panelboard. A short section of FMC will connect the transformer to this 150-A panel. The flex will contain 4 each 1/0 conductors. • A second set of secondary conductors is installed from the transformer to a 225-A MB panelboard. One conduit will be installed between this 225-amp panel and the transformer. The conduit will contain 4 each 4/0 conductors. • You have decided to "ground and bond" everything in the transformer enclosure. The smallest bonding jumper you can run in the flex between the transformer and the 150-A PB is ___ AWG.
6
A 225 KVA, 480 delta to 208/120-volt, 3-ph, 4-w transformer is to be installed. Secondary conductors are installed from the transformer to a 600-A MB panelboard. There will be four parallel flexible metal conduits to this 600-A panel. Each conduit will contain 4 each 1/0 conductors. You have decided to "ground and bond" everything in the panelboard. Refer to Scenario 305-24 to answer this question. The smallest bonding jumper you can run in each of the sections of flex is ___ AWG.
6
For high-impedance grounded neutral systems, the grounded system conductor shall have an ampacity of not less than the maximum current rating of the grounding impedance and shall be ___ AWG copper, or larger.
8
The minimum size of a main bonding jumper selected from Table 250.102(C)(1) shall be ___.
8 AWG
Where a 3Ø, 4-wire main lug only panelboard in a building (of steel construction) is fed from another building, which action below is not required by 250.32(D)?
A main bonding jumper must be installed between the neutral bar and the ground bar in the panelboard.
The neutral and EGC connections required to be made in a sub-panel in Bldg B are shown below at ___.
B( to GE from ground bar, no bonding)
Where multiple branch circuits are to be installed and there is not an existing grounding electrode at the second building or structure, ___.
Both one or more grounding electrodes must be installed at the second building and an equipment ground must be installed with the branch circuits
Refer to figure 305.14. If the conductor connected to L2 inside the 240 volt motor enclosure came into contact with the metal enclosure, the ground fault current would travel through conductors ___ to cause the 2 pole circuit breaker to trip.
E-D-B-A
When a transformer feeds a 120/208 volt, 3phase, 4wire main breaker panel, the system bonding jumper and grounding electrode conductor are required to be installed at ___.
Either the transformer or the panel
Bonding is the process of connecting one or more conductive objects to the earth.
False
High-impedance grounded neutral systems are permitted to serve 277-volt loads.
False
You are going to run a 120/208-volt, 3Ø, 4-wire feeder (with EGC) in PVC from one building to another. The panel at the second building has an insulated neutral bar and a ground bar that is bonded to the metal panel can (enclosure). A GEC has also been installed from the ground bar to the grounding electrode. You will ___. I. connect the neutral to the neutral bar II. connect the EGC to the ground bar III. install a main bonding jumper between the neutral bar and the ground bar
I & II only
A 120/240-volt, 3-ph, 4-wire feeder with an EGC, without GFPE, is to be installed underground in Schedule 40 PVC to feed a main breaker panelboard that is located in another building. The feeder originates from a 200-A safety switch that contains two each 200-A fuses and a 150-A fuse. In the panel at the 2nd building, all ungrounded conductors are connected to the main breaker and the EGC is connected to the ground bar. Refer to Scenario 305-1. The following conductors will be installed in the PVC: • Two 3/0 conductors and one 1/0 AWG ungrounded circuit conductor • One 6 AWG grounded circuit conductor The panel at the second building has an insulated neutral bar and a ground bar that is bonded to the metal panel can (enclosure). A GEC has also been installed from the ground bar to the grounding electrode. How should the feeder neutral be connected in the panel at second building? I. Connect the neutral to the neutral bar. II. Use a main bonding jumper to connect the neutral bar to the ground bar.
I only
A 240/480 to 120/240-volt, single-phase transformer is supplied from a 480-volt circuit and delivers power to a 120-volt load. X2-X4 is connected to 120-volt load terminal L1 and X1-X3 is connected to load terminal L2. If X1-X3 is also connected to a grounding electrode conductor, ___. I. the secondary voltage to ground is stabilized II. the secondary fuses will open if the secondary is fused III. the secondary windings will rapidly overheat and burn in two, unless the secondary is fused
I only
When ___ are installed in a conduit from one building to a 2nd building, the NEC® requires that one or more grounding electrodes be installed. There is not an existing grounding electrode at the 2nd building. The circuits originate from a 120/208-volt, 3Ø, 4-W panel in the main building and include an EGC in the conduit. I. two "hots" (for a 208-volt load) plus one "hot" with a neutral for 120-volt loads II. three "hots" and one neutral - these serve only 120-volt loads
I only
Where the main bonding jumper is a screw only, the NEC requires that it be identified with ___. I. a green finish, visible when the screw is installed II. a hexagonal head III. a listing mark, visible when the screw is installed
I only
A 120/208-volt, 3-ph, 4-wire feeder is installed underground to serve 120-volt convenience receptacles, 120-volt lighting, and a 208-volt 1Ø window unit AC/HTR in the parking attendant's "shack" at Park-and-Fly. The feeder is run from a 3-pole breaker in a panelboard that is located inside the vehicle maintenance building. One circuit will be required for the receptacles, one circuit for the lighting, and one circuit for the window unit. The feeder at the shack is permitted to be connected to ___. All spaces in the panel will be occupied by breakers .I. a 12-circuit MB panel II. a 6-circuit MLO panel III. a 24-circuit MLO panel
I or II only
Refer to Figure 303.04. In each raceway between the transformer and Switch 1, 350 kcmil conductors are installed. • Switch 3 is rated at 200 A, F 175 A with 2/0 AWG conductors installed to the wireway. • Switch 2 is rated at 60 A, F 60 A with 6 AWG conductors installed to the wireway. • The 200-A PB has a 200 A main with 3/0 AWG conductors run into the wireway. • The 100-A PB has a 100 A main with 3 AWG conductors run into the wireway .The SBJ and GEC to building steel can be installed in ___. I. the transformer II. Switch #1 III. the wireway IV. Switches 2 & 3, the 100-A PB, and the 200-A PB
I or II only
The system bonding jumper and grounding electrode conductor are permitted to be installed in the ___ where a transformer feeds a fused safety switch and then a main-lug only panel. I. transformer II. safety switch III. panelboard
I or II only
Sections 250.24(A) and 250.28 require which of the following to be connected together at the service entrance? I. grounded conductor (neutral) II. MBJ III. GEC
I, II & III
Refer to the installation shown in Figure 304.21. Safety switches B, C, and E are fused. Switches B and E feed main lug only panels inside the building. Panel A is a main breaker panel. Panel D is MLO and is fed from Switch C. MBJs should be installed in ___. I. the wireway II. Switches B, C & E III. Panel A IV. Panel D
II & III only
The grounded secondary conductor shown at ___ below is correctly identified as the neutral.
II & III only
Which of the following is not required by section 250.24 for the main bonding jumper?
It shall be re-identified at the terminals when furnished with insulation in any color other than green or natural gray
One, 20 amp, 120/240-volt, 1Ø multi-wire branch circuit is installed underground (in PVC) to serve receptacles and lighting in the parking attendant's "shack" at Park-and-Fly. Do you need to connect the neutral and the ground bar together in the safety switch on the "shack"?
No
___ of the NEC is normally used to size the main bonding jumper.
Table 250.102(C)(1)
Since Section 250.32(B) identifies the supply conductors to a second building as a "feeder or branch circuit," all equipment grounding conductors are sized according to ___.
Table 250.122
High impedance grounded neutral systems require the installation of ground detectors.
True
NEC® Article 250 covers requirements for the main bonding jumper used at services. Requirements for bonding of switchboards and panelboards used as service equipment are covered in Section 408.3(C).
True
On a portable generator, the neutral conductor is required to be bonded to the frame of the generator.
True
Static electricity is a hazard common to a wide variety of industries.
True
Taking the time to bond or ground when working around flammable vapors, gases, and dusts will help prevent a serious accident.
True
All of the following are acceptable as a grounding electrode at a separate building or structure EXCEPT ___.
a 1/2-inch trade size rigid metal conduit
A grounding electrode is required at a separate building or structure under which of the following conditions?
all of the above
When a 480 to 120/208-volt, 3Ø, 4-wire transformer feeds a main breaker panelboard, the neutral is permitted to be connected to the grounding electrode conductor and the equipment grounding conductor(s) ___
either a or b
The conductor shown at Point B in Figure 306.52 is a(n) ___.
grounded conductor
Under what conditions is the main bonding jumper permitted to be larger than required by 250.28(D)?
it may always be larger
One commercial building is supplied with 208/120-volt, 4-wire, three-phase power from another building on the same property and under the same management. The feeder is protected in the first building with a 200-ampere circuit breaker, and the conductors are run underground in PVC. Three ungrounded conductors, a neutral conductor, and an equipment grounding conductor are contained in the PVC. At the second building, the neutral and equipment grounding conductors are required to be ___.
kept separated, and the equipment grounding conductor is required to be connected to a grounding electrode
The ___ connects the equipment grounding conductors to the grounded (neutral) conductors.
main bonding jumper
A 600-amp main breaker service panel will have a 225-A breaker installed in it to feed a 225-amp, 1Ø, 3-wire main breaker panel. You will install three 4/0 conductors to the new panel. You will install a ___ AWG MBJ in this new 225-amp panel.
none of these(2,3,4)
A static spark occurs when ___.
one surface is charged positively and one surface is charged negatively
For existing installations and under certain circumstances, the grounded circuit conductor ___ used for grounding equipment on the line (supply) side or within the enclosure of the main disconnecting means for separate buildings.
shall be permitted to be
One way of preventing static electricity as an ignition source can be accomplished through ___.
substituting non-conductive pads when grounding or bonding is not possible
A static spark can occur when an electrical charge accumulates on the surfaces of ___ materials that have been brought together and then separated.
two
Section 250.32(B) defines the grounding requirements for a grounded system supplying two or more buildings, and Section 250.32(C) defines the requirements for a(n) ___ system.
ungrounded
