305

Scenario 305.2A 400-amp, 120/208-volt, 3-ph, 4-wire feeder (without GFPE) is installed underground in PVC from one building to deliver power to a 400-A main breaker panel installed on another building. The maximum load calculated for the neutral is 40 amps. The feeder consists of three each 600 kcmil conductors for the "hots." All grounded conductors at the 2nd building are connected to an insulated neutral bar. All equipment grounding conductors at the 2nd building are connected to a ground bar.Refer to Scenario 305.2. The building steel is connected to the ground bar using a ___ AWG as the minimum size permitted.

1/0

The ground clamp, for attachment to an aluminum grounding electrode conductor, is not permitted to be located within ___" of the earth.

18

A ground ring must be at least ___ feet long.

20

A 2000 A switchgear is fed from a transformer with five parallel sets of 600 kcmil wire in five parallel conduits. ___ AWG or kcmil wire is the smallest GEC permitted to the main water pipe.

3/0

The maximum size GEC required from the service equipment to the rebar in the bottom of the grade beam (poured concrete slab for a building) is ___ AWG.

4

Although metal water piping alone is not permitted to serve as a grounding electrode conductor, the first ___ of metal water pipe entering the building is permitted to serve as part of the grounding electrode.

5 feet

When a metal water pipe is used as the grounding electrode for a separately-derived system, the connection of the grounding electrode conductor is required to be made ___ where the pipe enters the building.

5 feet or closer to the point

Scenario 305.2A 400-amp, 120/208-volt, 3-ph, 4-wire feeder (without GFPE) is installed underground in PVC from one building to deliver power to a 400-A main breaker panel installed on another building. The maximum load calculated for the neutral is 40 amps. The feeder consists of three each 600 kcmil conductors for the "hots." All grounded conductors at the 2nd building are connected to an insulated neutral bar. All equipment grounding conductors at the 2nd building are connected to a ground bar.Refer to Scenario 305.2. The ground rod is connected to the ground bar using a ___ AWG as the minimum size permitted.

6

The maximum size copper GEC required for a 200-amp service panel to a 1" × 10' ground rod is ___ AWG.

6

Electrical Nonmetallic Tubing may be used to protect a grounding electrode conductor from physical damage.

False

Schedule 40 PVC (rigid polyvinyl chloride conduit) may be used to protect a grounding electrode conductor from physical damage.

False

If a GEC were to be installed inside a "conduit" to protect it from physical damage, which of the following "conduits" could be used?I. Schedule 80 PVC II. EMT III. FMC

I & II only

The grounding electrode conductor can be ___.I. covered II. stranded III. copper

I, II & III

Underground steel or copper water piping systems were traditionally used for grounding electrodes because they provided a large metal surface in direct contact with the earth.

True

Table 250.66 permits an aluminum grounding electrode conductor to be used with ___ service-entrance conductors.

aluminum or copper

A grounding electrode conductor may be ___. -copper -copper clad aluminum -aluminum

any of these

Where exothermic or irreversible compression connections are used, the connections made to fireproofed structural members ___ required to be accessible.

are not

Article 250 requires that when metal underground water piping is used as the only grounding electrode, it shall ___.

be supplemented by an additional electrode

A concrete-encased electrode is effective because ___. I. concrete retains moistureII. concrete provides a large contact area with the earth and the building weight maintains contact between concrete and earth

both I and II

When a grounding electrode conductor is installed in a metal raceway, it shall be bonded to the raceway at ___.

both ends

Which of the following does NEC® Section 250.62 not specify for the grounding electrode conductor?

connector types permitted

To avoid heating problems due to induction, the Code generally prohibits installing a single conductor of an alternating-current (ac) system in a metallic raceway. Which of the following single conductors of an ac system is permitted to be installed by itself in a metallic raceway?

grounding electrode conductor

The grounding electrode conductor sizes specified in Table 250.66 are ___ sizes.

minimum

When a GEC is installed in a metal conduit, the GEC is connected in ___ with the conduit.

parallel

Section 250.58 states that when two or more grounding electrodes are bonded together, they shall be considered as a(n) ___.

single grounding electrode system

Where a 1/0 AWG bare copper ground ring is installed, the minimum size GEC permitted from the service equipment to the ground ring is ___ AWG. A 4 AWG GEC is the minimum required size to building steel.

1/0

A commercial service entrance is rated at 100 amperes and the service-entrance conductors are size 3 AWG. An 8 ft. ground rod is driven as the grounding electrode for the building. The minimum size GEC permitted to the ground rod is a ___ AWG.

8

A dwelling service entrance is rated at 125 amperes and the service-entrance conductors are size 2 AWG with 75°C insulation and terminations. The minimum size grounding electrode conductor permitted to the metal underground water pipe is ___ AWG.

8

Which of the following is a Ufer ground? I. 40 feet of 1/2" diameter rebar in the bottom of a concrete footing II. 25' of 1 AWG bare copper laid in the bottom of a concrete grade beamIII. 20' of 4 AWG laid directly on the sand base below a 5" concrete slab

I & II only

Which of the following materials are considered to be ferrous?I. RMC II. copper conductors III. EMT

I & III only

The purpose of a grounding electrode is to enable electrons to flow into the earth when ___ occur. I. lightning strikes II. ground faults

I only

Where a GEC is installed at 18 inches above grade on the exterior wall of a ___, the AHJ would most likely consider this a location that would NOT be subject to physical damage. I. house behind a flower bedII. building between a sidewalk and the building where grass is mowed with a tractorIII. restaurant in the back alley where delivery trucks drive

I only

A wire-type GEC being installed from the service to the main water pipe is too short. According to the NEC®, another piece of wire may be spliced onto the short wire using ___. I. exothermic welding II. listed split-boltsIII. listed "crimp-on" splice connectors

I or III only

Sections 250.52(A)(7) and 250.53(A)(5) require plate electrodes made of iron or steel to ___. I. have a 2-square-foot surface area II. be 1/4 inch thickIII. be buried at a depth of not less than 30 inches

I, II & III

The purpose of a grounding electrode is to ___. I. "drain" static electricity from a nearby thunderstorm harmlessly into the earth II. maintain all grounded non-current-carrying surfaces at ground potentialIII. provide a path to earth for lightning or line surges

I, II & III

Which of the following could be used as the GEC from the service equipment to building steel? I. structural metal frame II. solid copperIII. other conductors resistive to corrosion

I, II & III

Which of the following could be used as the GEC from the service equipment to building steel? I. THHN/THWN aluminumII. THHN/THWN copperIII. bare copper

I, II & III

Which of the following GECs is required to be protected, by installing it inside EMT or some equivalent means of protection, where it is NOT subject to physical damage? I. 6 AWG II. 4 AWG III. 8 AWG

III only

2/0

Panel B, shown above in Figure 205.4, is a 120/240 volt 1-ph, 3-wire service panelboard. Panel B contains a 700 Amp 2-pole breaker 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 GEC to building steel that can be installed is a ___ AWG.

6

Refer to Figure 205.7, shown above. Panel LD has a 600-amp main breaker and is supplied power by the transformer with a set of 350 kcmil conductors in each of two parallel conduits. From Panel LD, the minimum size GEC to the ground rod is ___ AWG. The GEC will not be subject to physical damage.

2

Refer to the service equipment in Figure 304.20. Both the switch and the panelboard are rated for 400 amps. Each conduit into the top of the switch contains two each 3/0 and two each 1/0 AWG conductors. The switch will contain two 400-A fuses and one 300-A fuse. The minimum size GEC permitted from the service switch to the building steel is ___ AWG. This is a 480/277-volt, 3-ph, 4-wire service.

A GEC to a ground rod is installed in 1/2" EMT. The EMT is connected to the ground rod, and the bare GEC is connected to the ground rod. A set-screw connector is installed through a 1/2" KO in the metal panel enclosure and secures the EMT to the service panel. The 1/2" KO is within an eccentric set of 11/4" to 1/2" KOs. Is a bonding jumper required from the ground bar to the set-screw connector?

Yes

Is a grounding electrode conductor ever permitted to be smaller than the main bonding jumper?

Yes

Under what condition(s) does Section 250.60 permit the grounding electrode conductor for the lightning protection system to also serve as the primary grounding electrode? -for buildings or structures less than three stories in height -for residential occupancies only -for all occupancies, other than health care facilities

none of these

Section 250.52(A)(3) allows concrete metallic reinforcing bar (rebar) to be used as a grounding electrode where all the following conditions are satisfied, except when ___.

the rebar has a diameter of 3/8"