Second Year, First Quarter Review Exam

2 350 kcmil Table 250.66 => 2 AWG

A 120/240v 3-phase 4-wire service panelboard is fed with four 350 kcmil conductors. ___ AWG or kcmil wire is the smallest GEC permitted for this installation. REF: 2017 NEC: 250.24(D) | 2017 NEC: 250.66 (Table)

[10 × 10][.2] = 20 20 ÷ .3237 = 61.78 or 61

A section of 10" x 10" wireway is shown in Figure 208.62. The maximum number of 4/0 AWG THHN/THWN conductors that can be installed in the wireway is ___. 2017 NEC: 376.22 | 2017 NEC: Ch 9-T. 5

42-12 = 30

A service lateral is to be installed as direct-buried cable in the bottom of a trench that is 42 inches below finish grade. The trench is to be filled with dirt only. A warning ribbon is required to be installed in the trench at a maximum depth of ___ inches below finish grade. REF: 2017 NEC: 300.5(D)(3)

supply (or Line)

Any equipment that is installed between the utility supply and the service overcurrent protective device(s) is on the ___ side of the service.

18

Figure 207.18 shows luminaires along a driveway to a single-family ranch home. Schedule 40 PVC is the wiring method installed under the 7" thick concrete drive between the luminaires. The minimum dimension permitted for Y is ___ inches. 2017 NEC: 300.5 (Table)

width = (4" × 6) + (3") + (2") + (2") + (2.5") = 33.5 inches

For the pull box shown in Figure 208.52, the minimum calculated width is ___ inches. All conductors enter the bottom and exit the right side of the box. 2017 NEC: 314.28(A)(2)

incorrect 12/2: AC + Iso.Gnd. in AC cable + I.G.Rec. = 2.25 (2 + 1 + 2) = 11.25 cu. in. 14/2: MC + EGC + Sw = 2.00 (2 + 1 + 2) = 10 cu. in. total: 21.25 - 3.2 for plaster ring = 18.05 => 1900 x 11/4" @ 18 in3 is TOO SMALL

Refer to Scenario 208.1. Your journeyman swears he's been doing this long enough to know that a 11/4" deep box and P-ring assembly will not violate the Code. The plaster ring has 3.2 cu. in. stamped into the metal. Your journeyman is ___. 2017 NEC: 314.16

0

Refer to the drawing shown below. These circuits are from a 120/240-volt, 1Ø, 3-wire panel. Each ungrounded conductor carries 16 amps. The neutral in Conduit A will carry ___ amps.

154 Rtoaster = [Erated]² ÷ Prated = [110]² ÷ 700 = 17.2857 Ω & Rtv = Erated ÷ Irated = 130 ÷ 13.4 = 9.7015 Ω Rtotal = Rtoaster + RTV = (17.2857) + (9.7015) = 26.9872 Ω Itotal = Ea ÷ Rtotal = 240 ÷ 26.9872 = 8.8931 amps Etoaster = Itotal × Rtoaster = 8.8931 × 17.2857 = 153.7234 volts

Refer to the wiring diagram shown above in Figure 207.4. What will be the voltage applied (or dropped across) the toaster if the neutral is removed from the neutral bar? Select the closest answer.

II only, 600v 3 pole

The compressor nameplate reads: 480 V 3Ø 60 Hz. Which of the following safety switches is (are) permitted to be used as the disconnecting means for the air compressor shown above in Figure 201.13? I. 250-volt, 2-pole II. 600-volt, 3-pole III. 250-volt, 3-pole 2017 NEC: 110.4

Stranded only

Two ungrounded branch circuit conductors are installed to serve a load. These are installed in PVC. The 8 AWG copper ungrounded conductors are permitted to be ___. I. stranded II. solid III. bare REF: 2017 NEC: 310.106(C) | 2017 NEC: 310.106(D)

1 3/4

Using the standard calculation, the demand load for household electric ranges rated in excess of ___ kW is computed per NEC® Table 220.55.

1/0 500 kcmil is the largest ungrounded conductor in conduit => 1/0 AWG

What is the smallest size copper wire permitted to be used as a main bonding jumper in a 400-A main breaker panelboard? The panel is fed from a transformer a single conduit containing four 500kcmil conductors. 2017 NEC: 250.28(D) | 2017 NEC: 250.102(C)(1) (Table)

I = [16000 × 125%] ÷ 240 = 83.33 amps => 4 AWG

What minimum size copper THHN/THWN conductors are required to feed a 16-KW, 240-volt electric furnace operated at 240 volts? REF: 2017 NEC: 240.4(B) | 2017 NEC: 210.20(A) | 2017 NEC: 424.3(B)

II or III only

Where a 120/240-volt, 1Ø, 3-wire multiwire branch circuit is connected to a "split-wired" duplex receptacle in a barber shop, the branch-circuit OCPD/disconnect is permitted to be ___. I. two single-pole circuit breakers without handle ties II. two single-pole circuit breakers with identified handle ties III. a 2-pole circuit breaker

mandatory

Where used in the NEC®, the term shall not indicates that an action is ___. An example of this usage appears below. 210.9 Circuits Derived from Autotransformers. Branch circuits shall not be derived from autotransformers unless the circuit supplied has a grounded conductor that is electrically connected to a grounded conductor of the system supplying the autotransformer. 2017 NEC: 90.5(A)

7" < 8" OPENING = 3 inches beyond opening plus 4-inch depth to opening = 7 inches

Measured from the point in the box where the conductors emerge from the conduit in the back of the junction box, shown in Figure 207.13, the minimum length of the conductors is ___". The junction box has a depth (d) of 4" and is 6" wide by 6" high. 2017 NEC: 300.14

1

Per Section 110.26(A)(1) in the NEC®, where the wall opposite a panelboard is constructed of sheetrock attached to 7/8" hat channel that is attached to CMUs (concrete masonry units or "concrete blocks"), Condition ___ applies to the clearance requirements.

10

Refer to Figure 203.5. The minimum clearance at C, above the sidewalk, is ___ feet for this 120/240-volt, 1Ø, 3-wire triplex drop. 2017 NEC: 240.24(B)(1)

43 3 wires + 3 wires + 3 wires = 9 current-carrying conductors = 70% correction 6 AWG THHN ampacity = 75 amps 75 × .70 = 52.5 amps and 121°F => .82 correction 52.5 × .82 = 43.05 => 43 amps

Refer to Figure 204.3. The wire to Load #3 is 6 AWG, the wire to Load #2 is 1 AWG, and the wire to Load #1 is 2/0 AWG. Each of the loads is 3Ø, 3-wire. In the conduit with 9 conductors, how much current can the wire to Load #3 carry in the high-temperature area where the temperature is 121°F? 2017 NEC: 310.15(B)(2)(a) (Table) 2017 NEC: 310.15(B)(3)(a) (Table) 2017 NEC: 310.15(B)(16) (Table)

6 AWG => Feeder OCP ÷ 10 = 300 ÷ 10 = 30 amps => 10 AWG @ 75°C terminations versus sized to carry load: 52 amps => 6 AWG

Refer to Figure 204.7. Load #3 will draw 52 amps. What is the smallest size wire permitted for the wire between Pull Box 2 and FD #3 (Fused Disconnect for Load #3)? The circuit breaker is rated for 300 amps and the wire connected to it is 350 kcmil. The distance from FD #3 to pull box 2 is 4 feet. Don't forget that the switches have 75ºC lugs so you will select your wire from the 75ºC column. REF: 2017 NEC: 240.21(B)(1) | 2017 NEC: 310.15(B)(16) (Table)

branch circuit

Refer to Figure 204.7. The conductors in the conduit between FD #1 and Load #1 are ___ conductors. 2017 NEC: 240.2 | 2017 NEC: 100_Feeder | 2017 NEC: 100_Branch Circuit

x

Refer to Figure 205.2. Point ___ is the main bonding jumper. 2017 NEC: 100 | 2017 NEC: 250

6

Refer to Figure 207.18 where luminaires have been installed along a driveway to a single-family ranch home. RMC is the wiring method installed between the luminaires and along the side of the driveway. The minimum dimension permitted for X is ___ inches. 2017 NEC: 300.5 (Table)

I only 4 hots + 5 neutrals + 1 Gnd + 2 for device = 12 #12s 12 × 2.25 cu. inches = 27.0 cu. in. required 4 x 4 x 11/2 w/5.0 in3 ring: 21.0 + 5.0 = 26 => .0 => too small => violation 411/16 x 411/16 x 11/4 w/4.2 in3 ring: 25.5 + 4.2 = 29.7 => big enough 4 x 4 x 21/8 w/3.6 in3 ring: 30.3 + 3.6 = 33.9 => big enough

Refer to Figure 208.36. Which industrial cover/box combination will violate the NEC®? All the conductors are 12 AWG. I. 4" x 1 ½ square with 5.0 in³ industrial cover II. 4" 11/16 x 1 ¼ square box with a 4.2 in³ industrial cover III. 4 x 2 ⅛ square box with a 3.6 in³ industrial cover

4.26 × 80/100 = 3.408

Schedule 40 PVC is to be installed in a straight run between two junction boxes on the back exterior wall of a strip shopping center. The summertime temperature is 100°F and the wintertime temperature is -5°F. An expansion fitting would be required in this 80' run of PVC because it would expand ___ inches between winter and summer. REF: 2017 NEC: 352.44 | 2017 NEC: 352.44 (Table)

all except 2, 5, 7 & 9

The kitchen plan view in Figure 201.63 is for a kitchen in a house. Which receptacles are required by the NEC® to be GFCI protected? REF: 2017 NEC: 210.8(A)(6)

25

The largest 3-pole circuit breaker that can be used to protect a 10 AWG copper Type SJTO flexible cord is ___ A. The provisions of NEC® 240.4 are N/A to flexible cords. REF: 2017 NEC: 240.5 | 2017 NEC: 400.5(A)(1) (Table)

1 (4 × .0133) + (3 × .0211) + (2 × .0507) = .2179 sq. in. => 1" per Table 4

The minimum trade size EMT required is ___. This is a run that is 45' long. The following conductors will be installed: four-#12 THHN/THWN + three-#10 THHN/THWN + two-#6 THHN/THWN. REF: 2017 NEC: 250.24(D) | 2017 NEC: 250.66 (Table)

Any of the below: a. a fusible switchboard with a maximum of 6 switches b. a main breaker panelboard with eight individual 3-pole circuit breakers c. not more than 6 separate circuit breaker enclosures, each with a 3-pole breaker

The service disconnecting means for a 3-phase service is permitted to consist of ___. 2017 NEC: 230.71(A)

100 A => 8 AWG

Three 8 AWG conductors are installed in the flex between the breaker enclosure, containing a 100-A breaker, and the motor. The smallest EGC that can be installed in the flex in Figure 205.15 is ___ AWG.

I only

Which of the drawings below meets the NEC® requirements where equipment 1 and equipment 2 are required to be within sight from each other?

1/0

Which of the following THHN/THWN copper conductors is the smallest size permitted for a feeder where a 150 A breaker protects the feeder? The feeder originates in the 120/240-volt, 1-ph, 3-wire service panel in a bakery. 2017 NEC: 310.15(B)(16) (Table)

PVC or RMC only

Which of the following conductor arrangements is permitted by the NEC®? 2017 NEC: 300.3(B)(1) | 2017 NEC: 300.3(B)(1) Exc

120/240-volt, 3-ph, 4-W

You are sent on a service call to install some equipment. The main service equipment is a 42-circuit panelboard that does not have the system voltage stamped on it. There is a sticker on the cover that reads: Proudly Installed by BOOTLEG BROTHERS ELECTRIC After removing the panelboard cover and deadfront you see that the main breaker is a 3-pole 200 Amp and that the feeder consists of three conductors colored brown, red and blue. The feeder also has a gray-colored conductor that is connected to the neutral bar. To verify the system voltage, you check with your voltmeter and get the following readings: AØ to neutral = 120 volts BØ to neutral = 208 volts CØ to neutral = 120 volts You have now determined that the system is ___.