Lesson 110 - Voltage Drop, Cable, Conduit, and Tubing Homework

I, II & III

Allied's TRUE COLOR TM EMT is available with an outer finish that is ___ in color. I. yellow II. blue III. green

7.35 (V d = 2KIL ÷ cma = (2)(12)(10)(200) ÷ 6530 = 7.35 volts)

A 240-volt branch circuit supplies a resistive heating load of 10 amps. The distance from the panel to the heater is 200'. Using 12 AWG THHN copper, what is the voltage drop on the wire? Use K = 12.

3/ 4 inch (2017 NEC: 360.20(B))

According to the NEC ®, what is the largest size of flexible metallic tubing (FMT) that can be used?

II only

The fitting shown can be used on Type MC or AC cables with ___ armor. I. aluminum II. steel

1 (2017 NEC: 350.30(A))

The maximum distance permitted between a box and the first strap (support) for an installation using 1" LFMC (liquidtight flexible metal conduit) is ___ ft.

3 (Voltage at the fixtures = 211 - V d = 208 -> V d = 3 volts cma = 2KIL ÷ V d = (2 × 12 × 15.182 × 350) ÷ 3 = 42510 cmils 3 AWG 2017 NEC: Ch 9-T. 8)

Refer to Figure 110.16. You are to run 320 feet of PVC underground from a panel to a 30-foot-tall parking lot light pole. Install copper THHN/THWN circuit conductors from the breaker to the luminaires on top of the pole. The luminaires will draw a total current of 15.182 amps. The voltage measured at the circuit breaker is 211 volts. In order to supply at least 208 volts to the luminaires, the smallest size wire is ___ AWG. Use NEC ® Chapter 9, Table 8 and K=12.

resistance

Voltage drop problems can be caused by any of the following conditions: • wire too small for load served • circuit conductors too long • poor or corroded connections at terminals • conductors operating at high temperatures (higher temperatures increase resistance) The presence of one or more of these conditions causes an increase in the total ___ of the circuit.

3.46 (V d = 2KIL ÷ cma = (2)(12)(30)(50) ÷ 10380 = 3.46 volts)

What is the voltage drop on a 120-volt circuit consisting of 10 AWG copper wire where the load is 30 amps and the distance between the panel and the load is 50 ft (Use K=12)

straps, expansion fittings (2017 NEC: 352.44 | 2017 NEC: 352.30(B))

When PVC is run horizontally on the exterior back wall of a strip shopping center, ___ are to be installed. The distance between pull boxes is 60 feet and the summer/winter temperature difference is 90°F.

internal bonding strip

Armored cable includes a(n) ___ to ensure a low-impedance grounding path.

False

If circuit current travels through your body, the circuit breaker will trip. This is a ___ statement.

3 (2017 NEC: 352.30 (Table))

Trade size 3/ 4 Schedule 40 PVC (rigid polyvinyl chloride conduit) shall be supported at a minimum of every ___ feet.

4 (V d = 2.5% × 240 volts = (.025)(240) = 6 volts cma = (2)(K)(I)(L) ÷ V d = (2)(12)(42.7)(167) ÷ (6) = 28524 cmils -> 4 AWG)

A 42.7-amp 240-volt load is located 167 feet from the panel. The circuit is connected to a 2-pole circuit breaker in a 120/240-volt, 1Ø, 3-wire panelboard. The smallest wire that can be used for the circuit is ____ AWG. Use K = 12 and limit the voltage dropped in the circuit conductors to 2.5%.

ground-fault circuit interrupter

A(n) ___ is required for all construction personnel while using 15- or 20-amp, 120-volt receptacles. It shuts off electricity if a ground fault occurs.

14 (2017 NEC: 344.30(B)(2) (Table))

Although frequently referred to as galvanized rigid conduit (GRC), the NEC ® identifies this wiring method as rigid metal conduit (RMC). Where trade size 1 1/ 2 RMC is threaded (screwed wrenchtight) together between boxes or enclosures, the maximum distance permitted between straps (supports) is ___ feet. The distance between the boxes for this straight run of conduit is almost 200 feet.

60°C (2017 NEC: 320.80(A))

Although the 90°C column is permitted to be used for ampacity corrections to Type AC cable with THHN conductors, the NEC ® requires that the ___ column of Table 310.15(B)(16) be used to determine ampacity when used for premises wiring (to determine maximum uncorrected ampacity).

True

Although the National Electrical Code contains requirements for making holes and notches in framing members, in order to protect the cables installed in them, electricians must also be aware that building codes also have requirements for holes and notches in framing members, in order not to weaken the structure of the building.

used to support luminaires (2017 NEC: 352.10 | 2017 NEC: 352.12(B))

As covered by Article 352, rigid nonmetallic conduit is permitted to do all of the following, except where ___.

10 (2017 NEC: 322.104)

Flat cable assemblies shall have conductors of ___ AWG special stranded copper wires.

192 (E wire = (2 × 12.845 × 42 × 250) ÷ 16510 = 16.338 volts E load = 208 - 16.338 = 191.662 volts)

For a 208-volt circuit that feeds a 42-amp load located 250 feet from the panel, 8 AWG copper wire is used. Use K = 12.845 and find the voltage that is applied to the load.

6 (2017 NEC: 352.30 (Table))

Horizontal runs of trade size 3 Schedule 40 PVC conduit must be supported at ___ ft intervals.

1/ 16 (2017 NEC: 300.4(A)(1) | 2017 NEC: 300.4(A)(2))

If cable holes through studs cannot be bored to meet the requirements of NEC ® 300.4(A)(1) or if cables are to be laid in notches or grooves cut into the face of the stud, a steel plate, sleeve, or clip at least ___-inch in thickness must be used to protect the cable from driven nails or screws.

a circuit that is too long, poor connections at the terminals, a conductor that is too small for the load

Low voltage at the load served (high voltage drop in the circuit conductors) in a home can be caused by ____.

3 15/ 16 (7 × 9/ 16 = 315/16 inches 2017 NEC: 330.24(B))

Refer to Figure 110.12. Per NEC ® Article 330, 10-3 Type MC (corrugated sheath metal-clad) cable is permitted to be bent so that the bending radius is no smaller than ___ inches. The diameter of the cable is 9/ 16".

8.61 (I = P ÷ E = (6)(20) ÷ (12) = 10 amps V d = [2KIL] ÷ cma = [(2)(11.6)(10)(60)] ÷ [4110] = 3.3869 volts V at fixtures = 12 - 3.3869 = 8.6131 volts)

Six 20 watt, 12-volt luminaires (lighting fixtures) are supplied from a small, 12-volt transformer that is 60 feet away from the fixtures. The wire used is 14 AWG. What is the voltage applied to the fixtures? Use K = 11.6.

3 5 (2017 NEC: 210.19(A)(1) I-Note 4)

The Code recommends a voltage drop no greater than ___ percent for feeders and no greater than ___ percent total for feeders and branch circuits together.

MC

Type ___ cable has plastic binder tape wrapped around all the conductors within the cable assembly.

3 (2017 NEC: 344.30(A)(1))

What is the maximum distance permitted between a box and the first strap (support) for an installation using 1" RMC? ___ feet

No (2017 NEC: 320.30(C))

When Type AC cable is installed in horizontal runs through the holes in sheet metal studs and joists, do additional supports have to be installed (Caddy clips, for example)? The AC cable is securely fastened within the required distance from any boxes or enclosures and the framing members are on 24-inch centers.

No (2017 NEC: 330.30(C))

When Type MC cable is installed in horizontal runs through the holes in sheet metal studs and joists, do additional supports have to be installed (Caddy clips for example)? The MC cable is securely fastened within the required distance from any boxes or enclosures and the framing members are on 24" centers.

is (2017 NEC: 348.60)

When a 3' long piece of trade size 3/ 4 flexible metal conduit is installed (for flexibility) so that the connected equipment can vibrate freely, an equipment grounding conductor ___ required to be installed with the circuit conductors. The "flex" and the fittings are listed for grounding.

No

You can count on being safe around ___ voltages.

you are sweating

Your body is a better conductor when ___.

25,714 (cma = 2KIL ÷ V d = (2)(12)(50)(75) ÷ 3.5 = 25,714 cmils)

What is the cross-sectional area in circular mils of a copper conductor needed to supply a circuit 75 feet from the panel, with a load of 50 amperes and a voltage drop not to exceed 3.5 volts? (Use K=12)

4 1/ 2 (2017 NEC: 320.30(B))

What is the maximum distance permitted between straps (supports) where 12-2 Type AC cable is run for some distance between boxes or enclosures? ___ feet

6 (2017 NEC: 330.30(B))

What is the maximum distance permitted between straps (supports) where 12-2 Type MC cable is run for some distance between boxes or enclosures? ___ feet

10 (2017 NEC: 330.108)

What size equipment grounding conductor is contained in 10-3 Type MC cable?

320 (2017 NEC: 320)

___ is the Code Article that provides the requirements for Type AC cable.

3 m (10 ft), 900 mm (3 ft) (2017 NEC: 358.30(A))

EMT shall be securely fastened in place at least every ___. In addition, each EMT run between termination points shall be securely fastened within ___ of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination.

10 (2017 NEC: 358.30(A))

The maximum distance permitted between straps (supports) where trade size 1/ 2 EMT ( Electrical Metallic Tubing) is run for some distance straight between boxes or enclosures is ___ feet.

202.8 (208 - (208)(.025) = 202.8 volts)

The specifications require that you limit the voltage drop on any circuit to 2.5%. For a 208-volt circuit, this means that the voltage applied to any load cannot be less than ___ volts.

362.30 (2017 NEC: 362.30)

The support requirements for ENT are located in the NEC ® in Section ___.

8 ((.05) × (120) = 6 volts cma = 2KIL ÷ V d = (2)(12)(8)(500) ÷ 6 = 16000 -> 8 AWG)

The total length of cable to a 120-volt 1/ 2 hp, 8-amp motor load is 500'. Determine the wire size necessary for the voltage drop not to exceed 5%. Use K = 12.

increases

The voltage (volts) dropped in circuit conductors ___ when the circuit length is increased.

7.35 volts

What is the voltage drop on a 120-volt circuit? The circuit uses 12 AWG copper conductors and has a load of 20 amperes. There is a distance of 100 feet from the panel to the load. (Use K=12)

True

When MC cable is used as the wiring method, the fittings used with the MC cable are required to be listed for MC cable.

liquidtight flexible nonmetallic conduit (2017 NEC: 356.10(1))

When connections to motorized appliances such as food waste disposers, washers, dryers, air-conditioners, and heat pumps that may be subject to vibration are made, ___ is an acceptable choice for the wiring method.

conductor

When there's a current leakage from a tool or piece of equipment, the current will flow through any available ___ until it reaches a grounded surface or grounding conductor.

1 (2017 NEC: 358.22)

When using EMT, the maximum number of conductors shall not exceed that permitted by the percentage fill specified in Chapter 9, Table ___.

12 in (2017 NEC: 330.30(B))

Where 12-2 Type MC cable is installed, the maximum distance permitted between a box and the first strap (support) is ___.

12 in (2017 NEC: 320.30(B))

Where 12-4 Type AC cable is installed, the maximum distance permitted between a box and the first strap (support) is ___.

Rigid

Which of the following wiring methods provides the best protection against physical damage?

An 8 AWG conductor has a greater resistance per foot than a 6 AWG conductor. (2017 NEC: Ch 9-T. 8)

Which of the statements below is true?