Lesson 115 - Box Fill and Introduction to Series Circuits (Front Bedroom) Homework

is not permitted (2017 NEC: 410.16(B))

A pendant luminaire mounted in a clothes closet ___.

4507 (P = E 2 ÷ R = [208] 2 ÷ [9.6]= 4506.6667 watts)

A piece of equipment has a fixed resistance of 9.6 ohms. How much power will the equipment deliver when connected to a 208-volt circuit?

open

A series circuit consists of a power source, circuit conductors, and a lamp. If the filament in the lamp is broken, this circuit is called a(n) ___ circuit.

either I or II ([9 travelers] + [3 × 2 for devices] = 18 each 14 AWGs 15 × 2.0 in 3 = 30 in 3 [4 CCCs] + [1 EGC] = 5 each 12 AWGs 5 × 2.25 in 3 = 11.25 in 3 (30 + 11.25 in 3) ÷ 3 = 13.75 in 3 -> 2 1/ 2" deep box is OK ( either I or II) )

A shallow box is shown at I and a deep box is shown at II in Figure 115.105. One of these 3-gang masonry boxes will have several EMT conduits connected to it. The box will contain three 3-way switches. Nine 14 AWG "travelers" are pulled into the box along with four 12 AWG circuit conductors. Additionally, a 12 AWG grounding conductor is installed. All conductors are copper THHN/THWN. The box shown at ___ will have sufficient volume for this installation.

6 (2017 NEC: 410.16(C)(2))

A surface-mounted fluorescent luminaire (light fixture) mounted in a clothes closet must maintain a clearance of at least ___ inches to the storage area.

1 (2017 NEC: 314.16(B)(5))

A wire nut is used to connect a grounding conductor that enters a box to another grounding conductor that exits the box. Then a pigtail is connected under the wire nut and goes to a receptacle in the box. For calculating conductor fill, these grounding conductors count as ___ conductor(s).

you have written permission from the manufacturer

Aerial lifts can be modified for the current job if ___.

2 (15 × 150 = 2250 plus 20 × 75 = 1500 P = 2250 + 1500 = 3750 total watts I = P ÷ E = 3750 ÷ 120 = 31.25 total amperage It will take two 20-ampere circuits to cover 31.25 total amperes 2017 NEC: 220.14(J))

Although not limited to 80% by the NEC ®, if 20-amp residential circuits are to be loaded only up to their ratings, how many 20-ampere, 120-volt circuits will be required? The homeowner wants fifteen 150 watt light fixtures and twenty 75 watt fixtures.

increases

As more loads are added to a series circuit, the resistance of the circuit ___.

13 ((20 A × 120 V) ÷ 180 VA = 13.3 -> 13 outlets 2017 NEC: 220.14(I) | 2017 NEC: 220.18)

At 180 VA per outlet, how many outlets can be installed on a 20-ampere circuit (120 volt) if the circuit loading is to remain within its ratings?

60 (E 1 = E 2 = E 3 = E 4 = E T ÷ 4 = 240 ÷ 4 = 60 volts)

Calculations should not include any power requirements for the blower motor in the FBU. The nameplate on the FBU indicates that it will deliver a total of 11.2 kW of heat when the supply circuit is 250 volts. Refer to the illustration of the FBU and the information shown with Figure 115.342. When the supply circuit is exactly 240 volts, the voltage applied to Element 4 (E 4) is ___ volts.

arc-fault circuit interrupter (2017 NEC: 210.12(A))

Convenience receptacles that are installed in bedrooms in a house are required to be protected by a(n) ___.

240

Each heating element has the same power and voltage ratings as the other three. Refer to the pictorial circuit shown in Figure 115.333. If the leads of a voltmeter are placed on T5 and T8, the meter should indicate ___ volts.

80

For residential circuits, a good rule to follow is to never load a branch circuit to more than ___ percent of the rating.

600

For residential wiring, not less than one 15-ampere lighting branch circuit should be provided for every ___ square feet of floor area.

5 (2017 NEC: 314.16)

How many number 12 AWG conductors may be installed in a 4" × 2 1/ 8" × 1 7/ 8" device box?

2

How many single receptacles can be installed in a two-gang box that is made using two single-gang boxes that are ganged together?

All lamps would go out

If lighting fixtures are connected in series, what happens if one of the lamps burns out?

True (2017 NEC: 300.21)

Installing receptacles back-to-back on opposite sides of a wall within the same "stud space" offers the advantage of making the installation easier and cheaper. However, if the wall is fire rated, back-to-back installation might violate the Code unless fire-rated "putty" or fire-rated "listed" boxes are used.

offers the advantage that all power in a room will not go out if the overcurrent protective device trips

Many electricians wire the lights and receptacles in a room on different circuits because this ___.

30.0 ( 2 wires for the 10-2 cable = 2 × 2.5 = 5 in3 + 6 wires for the two 12-3 cables = 6 × 2.25 = 13.53 + 1 wire for the largest EGC = 2.5 in3 + 2 wires for the first device = 4.5 in3 + 2 wires for the second device = 4.5 in3 5 + 13.5 + 2.5 + 4.5 + 4.5 = 30 in3 2017 NEC: 314.16)

Refer to Figure 115.104. The minimum volume required for this box is ___ in 3. The Type NM cables each contain grounds. You will install a second receptacle in this box. A flat (0.0 in 3 volume) p-ring is used. The "pigtails" to both of the receptacles are #12 wires. As you can see, the cable connectors are external (outside the box).

No ( 2 wires for the 12-2 cable + 6 wires for the two 12-3 cables + 1 wire for the EGCs + 2 wires for the device 11 #12 wires -> 11 × 2.25 in3 = 24.75 in3 A 3" × 2" × 3½" deep metal device (switch) box will have a volume of only 18 in 3 this box isn't big enough. NO 2017 NEC: 314.16)

Refer to partial circuit plan shown in Figure 115.103. You are required to size the box that will contain a split-wired receptacle. If the cables entering this box were all #12 MC cables, could a 3" × 2" × 3½" deep metal device (switch) box be used here? The MC cables will be connected to the box using external connectors. There are NO cable clamps within this box. Hint: don't forget to count the wires for the device and the ground(s) that are in the MC cable.

1 1/ 2 (2 wires for the 12-2 cable + 6 wires for the two 12-3 cables + 1 wire for the EGCs + 2 wires for the device = 11 #12 wires -> 11 × 2.25 in 3 = 24.75 in 3 If a 4" × 1 1/ 4" box is used, the volume is 18.0 + 6.1 = 24.1 in 3 too small If a 4" × 1 1/ 2" box is used, the volume is 21.0 + 6.1 = 27.1 in 3 big enough 2017 NEC: 314.16)

Refer to partial circuit plan shown in Figure 115.103. You are required to size the box that will contain a split-wired receptacle. If the cables entering this box were all #12 MC cables, what is the smallest 4" square (1900) metal box that could be used here? The box will have a 1"-rise plaster ring installed that adds a volume of 6.1 in 3 to the total volume. The MC cables will be connected to the box using external connectors. There are NO cable clamps within this box. Hint: don't forget to count the wires for the device and the ground(s) that are in the MC cable.

9.17 (R 1 = R 2 = E rated 2 ÷ P rated = (240) 2 ÷ 2200 = 26.1818 ohms R T = R 1 + R 2 = 52.3636 ohms then: I = E a ÷ R T = 480 ÷ 52.3636 = 9.1667 amps)

Refer to the pictorial circuit shown in Figure 115.337. The current flowing through each circuit conductor is ___ amps.

the two "hot" (2017 NEC: 210.11(B))

Section 210.11(B) in the NEC ® requires that loads be evenly proportioned (or balanced) among the different circuits in a panelboard. This means that when everything connected to all circuits is ON then the current in ___ feeder conductors are equal, or as close as possible.

104

See Figure 115.316. The voltage dropped across each element when the boiler is connected to the 208-volt circuit is ___ volts.

more

Since I = E ÷ R lamp then a lamp that is operated at 130 volts will draw ___ current than when operated at 120 volts.

True

Sometimes volt-amps (VA) can be larger than watts (W).

does not (Although the EWR specs limit the number, the NEC ® does not impose a limit for dwellings. 2017 NEC: 220.14(J)(3))

The NEC ® ___ specify the maximum number of lighting fixtures that can be connected to a 120-volt branch circuit in a dwelling.

an unspecified number of (2017 NEC: 220.14(J))

The NEC ® allows ___ receptacle outlets to be connected on a 120-volt residential lighting or small-appliance branch circuit.

series

The duct heater contains two heating elements that are connected as shown. Each of the two elements is rated to deliver 1850 watts when operated at 125 volts. See Figure 115.317. This is a ___ circuit.

120

The duct heater contains two identically rated heating elements that are connected as shown. See Figure 115.311. If the leads of a voltmeter were placed on T3 & T4, the meter should indicate ___ volts.

0

The duct heater contains two identically-rated heating elements that are connected as shown. See Figure 115.312. If the leads of a voltmeter were placed on T3 & T2, the meter should indicate ___ volts.

208

The duct heater contains two identically-rated heating elements that are connected as shown. See Figure 115.312. If the leads of the voltmeter were moved to T1 & T4, the meter should indicate ___ volts.

the same as (2017 NEC: 410.16(C)(3) | 2017 NEC: 410.16(C)(4))

The required minimum clearances for a recessed-mounted fluorescent luminaire installed in clothes closets are ___ those for a recessed-mounted incandescent or LED luminaire with a trim ring that has a glass lens.

greater than (2017 NEC: 410.16(C)(1) | 2017 NEC: 410.16(C)(2))

The required minimum clearances for surface-mounted incandescent or LED luminaires installed in clothes closets are ___ those for fluorescent luminaires.

5.45 (R T = R 1 + R 2 = 22 + 22 = 44 ohms then: I = E a ÷ R T = 240 ÷ 44 = 5.4545 amps)

This duct heater contains two heating elements that are connected as shown. The fixed or "hot" resistance of each of the two elements is 22 ohms. See Figure 115.314. What is the total current drawn by the duct heater when connected to the 240-volt circuit?

44

This duct heater contains two heating elements that are connected as shown. The fixed or "hot" resistance of each of the two elements is 22 ohms. See Figure 115.314. What is the total resistance of the duct heater (both elements)?

3 1/ 2 ( 3 wires for the 12-3 cable (home run) + 2 wires for the 12-2 cable (to recept) + 3 wires for the 12-3 cable (to fan/lt) + 1 wire for the EGCs + 2 wires for the first device + 2 wires for the second device 13 #12s = 13 × 2.25 = 29.25 in3 We need to divide this volume by two to get the minimum volume of each of the two boxes. 29.25 ÷ 2 = 14.62 in 3 -> 3" × 2" × 31/2" box 2017 NEC: 314.16)

Two 3" × 2" metal device (switch) boxes are ganged together to form a 2-gang box. A light switch and a fan switch are to be installed in this 2-gang box assembly for a ceiling fan/light kit. A 12-3 cable is run from the panel to the 2-gang box. One circuit feeds power to the switches and the other circuit is connected to a 12-2 cable that supplies power to a receptacle box on the same wall. A 12-3 cable exits the box assembly to supply the fan/light. The cable clamps are of the external type. All cables are Type AC with ground. The shallowest switch boxes you can use for the 2-gang box assembly are 3" × 2" × ___" deep.

104

Two identical (same voltage and power ratings) heating elements are connected to a 2-pole 208-volt circuit breaker as shown. Refer to the pictorial circuit shown in Figure 115.315. If the leads of a voltmeter were placed on L1 and L2 on the lower element, the meter should indicate ___ volts.

208

Two identical (same voltage and power ratings) heating elements are connected to a 2-pole 208-volt circuit breaker as shown. Refer to the pictorial circuit shown in Figure 115.315. If the two voltmeter leads were placed on the breaker lugs, the meter should indicate ___ volts.

12 watts (P T = P 1 + P 2 = 6 + 6 = 12 W)

What is the total power used by a 12-volt circuit having two 6 watt loads connected in series?

plaster ring

When a switch is to be installed in a 4 11/ 16" square (2100 or 411) box, a(n) ___ must be installed on the box.

manufacturer-provided anchor points on the lift

When working in an aerial lift, you are required to tie off. It is permitted to tie off to ___.

160.8 (I = P ÷ E a = 38600 ÷ 240 = 160.83 amps)

Where a piece of equipment is connected to a 2-pole breaker in a 120/240-volt 3Ø, 4-wire panel, each circuit conductor to the equipment will have to carry ___ amps of current. The equipment has a nameplate rating of 38.6 KVA @ 240 volts 1-ph.

Above certain electric baseboard heaters (2017 NEC: 210.52 I-Note)

Where are electrical receptacle outlets not permitted to be located?