Journeyman Electrician (NEC) — All Questions

Article 100 defines a continuous load as one where the maximum current is expected to continue for how long?

• a.More than 24 hours
• b.Any duration over 100 amperes
• c.Only at night
• d.3 hours or more✓

A continuous load is one where the maximum current is expected to continue for 3 hours or more, which is why such loads are sized at 125 percent. See NEC Article 100.

A dwelling feeder supplies three fastened-in-place appliances other than ranges, dryers and heating or air-conditioning equipment. What demand factor may be applied to their nameplate total?

• a.65 percent
• b.75 percent
• c.100 percent✓
• d.50 percent

The 75 percent demand factor requires four or more such fastened-in-place appliances; with only three, no reduction is permitted. See NEC 220.53.

Under the current code, how must two to six service disconnects for a single service be arranged?

• a.Behind a single main breaker feeding sub-disconnects
• b.All mounted on a single removable panel
• c.Each in a separate enclosure, or in a listed assembly with individual enclosures, all grouped✓
• d.In any convenient locations throughout the building

The 2020 and 2023 codes require each of up to six service disconnects to be in a separate enclosure or a listed assembly with individual disconnect enclosures, grouped together. See NEC 230.71(B).

Receptacles installed outdoors in wet or damp locations must be which listed type?

• a.Twist-lock
• b.Weather-resistant✓
• c.Hospital-grade
• d.Isolated-ground

Fifteen- and 20-ampere, 125- and 250-volt receptacles in damp or wet locations must be listed weather-resistant. See NEC 406.9(A) and 406.9(B).

A 15-kVA, single-phase transformer has a 480-volt primary and is protected by primary overcurrent protection only at 125 percent. What is the maximum standard primary overcurrent device rating?

• a.35 amperes
• b.45 amperes
• c.40 amperes✓
• d.50 amperes

Primary full-load current = 15,000 / 480 = 31.25 A, and 31.25 x 1.25 = 39.06 A. The next standard rating is 40 A. See NEC 450.3(B).

What is the primary purpose of a lockout/tagout procedure?

• a.To improve the power factor of the circuit
• b.To increase the available fault current
• c.To reduce conductor voltage drop
• d.To prevent the unexpected energization or startup of equipment during servicing✓

Lockout/tagout keeps a disconnecting means in the open position so equipment cannot be unexpectedly energized or started while a worker is servicing it. This reflects OSHA 1910.147 and NFPA 70E safe-work practice.

Using the optional dwelling calculation, the general loads total 30 kVA. What is the demand load for these general loads?

• a.30 kVA
• b.22 kVA
• c.12 kVA
• d.18 kVA✓

The optional method takes the first 10 kVA at 100 percent and the remainder at 40 percent: 10 + (20 x 0.40) = 18 kVA. See NEC 220.82(B).

The point of attachment of overhead service-drop conductors to a building must be at least how far above finished grade?

• a.10 feet✓
• b.12 feet
• c.8 feet
• d.15 feet

The point of attachment of the service-drop or overhead service conductors must be at least 10 feet above finished grade and positioned to maintain the required conductor clearances. See NEC 230.26.

Which of the following is a recognized equipment grounding conductor?

• a.Electrical nonmetallic tubing
• b.Rigid metal conduit installed under its article✓
• c.A nonmetallic pull string
• d.Rigid PVC conduit

Metal raceways such as rigid metal conduit, intermediate metal conduit and EMT are recognized equipment grounding conductors; nonmetallic raceways are not. See NEC 250.118.

What is the maximum weight of a ceiling-suspended paddle fan that may be supported solely by a listed fan-rated outlet box without additional independent support?

• a.70 pounds✓
• b.50 pounds
• c.90 pounds
• d.35 pounds

A fan-listed outlet box may support a fan up to 70 pounds; a fan exceeding 70 pounds must be supported independently of the box. See NEC 314.27(C).

A Class A ground-fault circuit interrupter is designed to trip when the difference between the ungrounded and grounded conductor currents reaches approximately what value?

• a.100 milliamperes
• b.20 amperes
• c.4 to 6 milliamperes✓
• d.1 ampere

A Class A GFCI trips when the ground-fault (imbalance) current reaches 4 to 6 milliamperes, the level intended to protect people from electrocution, not to protect the circuit conductors.

A commercial building has 40 general-use receptacle outlets. Using the standard method, what receptacle load must be calculated before demand factors?

• a.6,000 volt-amperes
• b.4,800 volt-amperes
• c.7,200 volt-amperes✓
• d.7,920 volt-amperes

Non-dwelling receptacle outlets are calculated at 180 VA each: 40 x 180 = 7,200 VA. See NEC 220.14(I).

What is the minimum vertical clearance of overhead service conductors above a roof not readily accessible where the voltage does not exceed 300 volts to ground?

• a.8 feet✓
• b.10 feet
• c.12 feet
• d.3 feet

Overhead service conductors must maintain at least 8 feet of vertical clearance above the roof surface, over an area 3 feet in all directions from the roof edge, with reduced clearances only under specific listed conditions. See NEC 230.24(A).

Rigid PVC conduit requires an expansion fitting where the expected length change due to temperature is at least what value?

• a.1/8 inch
• b.1 inch
• c.1/2 inch
• d.1/4 inch✓

Expansion fittings are required for PVC conduit where the length change is expected to be 1/4 inch or more. See NEC 352.44.

A cord-and-plug-connected room air conditioner shares its branch circuit with lighting outlets. Its total marked rating must not exceed what percentage of the branch-circuit rating?

• a.100 percent
• b.80 percent
• c.50 percent✓
• d.125 percent

Where lighting units or other appliances are also supplied, a room air conditioner may not exceed 50 percent of the branch-circuit rating; if it is the only load, the limit is 80 percent. See NEC 440.62(B) and (C).

A retail store has 15 linear feet of show window. What show-window load must be included?

• a.1,800 volt-amperes
• b.1,500 volt-amperes
• c.2,700 volt-amperes
• d.3,000 volt-amperes✓

Show-window lighting is calculated at 200 VA per linear foot of show window: 15 x 200 = 3,000 VA. See NEC 220.14(G).

Overhead service conductors must maintain what minimum clearance from a window designed to be opened?

• a.6 feet
• b.3 feet✓
• c.5 feet
• d.10 feet

Service conductors must keep 3 feet of clearance from windows designed to open, doors, porches, decks, stairs and similar locations. Conductors above the top of a window are exempt. See NEC 230.9(A).

How many 12 AWG conductors may be installed in a 21.0-cubic-inch box with no clamps, devices or fittings?

• a.8
• b.10
• c.9✓
• d.11

Each 12 AWG conductor requires 2.25 cubic inches: 21.0 / 2.25 = 9.33, rounded down to 9 conductors. See NEC 314.16(A) and (B).

Capacitor circuit conductors must have an ampacity of at least what percentage of the rated current of the capacitor?

• a.135 percent✓
• b.150 percent
• c.125 percent
• d.115 percent

Conductors supplying a capacitor must be sized at not less than 135 percent of the rated current of the capacitor. See NEC 460.8(A).

A store lighting load of 20 amperes operates continuously. What is the minimum standard branch-circuit overcurrent device rating?

• a.20 amperes
• b.30 amperes
• c.35 amperes
• d.25 amperes✓

The device must be at least 125 percent of the continuous load: 20 x 1.25 = 25 A, which is a standard rating. See NEC 210.20(A).

What is the minimum clearance for overhead service conductors passing over a public street or road?

• a.15 feet
• b.12 feet
• c.10 feet
• d.18 feet✓

Overhead service conductors over public streets, roads, alleys and parking areas subject to truck traffic require 18 feet of clearance. See NEC 230.24(B).

What is the maximum permitted conductor fill of a metal wireway?

• a.31 percent
• b.53 percent
• c.20 percent✓
• d.40 percent

The conductors in a metal wireway may not fill more than 20 percent of its interior cross-sectional area. See NEC 376.22(A).

As defined in Article 100, what does 'in sight from' mean in terms of distance?

• a.Anywhere on the same floor level
• b.Visible and not more than 50 feet away✓
• c.Within 75 feet whether visible or not
• d.Visible and not more than 25 feet away

'In sight from' means the equipment is visible and not more than 50 feet distant from the other equipment. See NEC Article 100.

A feeder supplies 50 amperes of continuous load plus 40 amperes of noncontinuous load. Using 75 degrees C copper terminations, what is the minimum conductor size?

• a.1 AWG
• b.2 AWG✓
• c.3 AWG
• d.4 AWG

Required ampacity = noncontinuous + 125 percent continuous = 40 + (50 x 1.25) = 102.5 A. In the 75 degrees C column 3 AWG (100 A) fails and 2 AWG (115 A) qualifies. See NEC 215.2(A)(1) and Table 310.16.

Ground-fault protection of equipment is required for a solidly grounded wye service of more than 150 volts to ground when the disconnect is rated at least what value?

• a.1,000 amperes✓
• b.1,200 amperes
• c.600 amperes
• d.800 amperes

The threshold is a service disconnect rated 1,000 amperes or more on a solidly grounded wye system of more than 150 volts to ground but not over 1,000 volts phase-to-phase, such as 480Y/277. The 1,200-ampere figure is the maximum GFPE setting, not the trigger. See NEC 230.95.

A raceway enters a building underground from an outside source. What is required at the point of entry?

• a.It must be sealed or plugged to prevent moisture from entering the building✓
• b.It must be left open for ventilation
• c.It must be filled completely with concrete
• d.It must be bonded but is never sealed

Conduits and raceways entering a building underground must be sealed or plugged with an identified compound to stop moisture and gases from entering. See NEC 300.5(G).

A 40-horsepower, 460-volt, three-phase motor has a table full-load current of 52 amperes. What minimum ampere rating must the disconnecting means have?

• a.46 amperes
• b.65 amperes
• c.52 amperes
• d.59.8 amperes✓

The disconnecting means must be at least 115 percent of the full-load current: 52 x 1.15 = 59.8 A, so a 60-ampere or larger switch would be selected. See NEC 430.110(A).

Four current-carrying 10 AWG THHN copper conductors share one raceway at a 30 degrees C ambient. What is the adjusted ampacity of each before termination limits?

• a.28 amperes
• b.30 amperes
• c.32 amperes✓
• d.35 amperes

The 90 degrees C ampacity of 10 AWG copper is 40 A, and the 4 to 6 conductor adjustment is 80 percent: 40 x 0.80 = 32 A. The final overcurrent device is still limited to 30 A by NEC 240.4(D). See NEC 310.15(C)(1).

Neutral current that flows onto metal enclosures and grounding conductors because of an improper neutral-to-ground connection is known as what?

• a.Inductive reactance
• b.Fault current
• c.Displacement current
• d.Objectionable current✓

A neutral-to-ground bond made on the load side of the service creates parallel neutral paths, and the resulting current on grounding paths is objectionable current, which must be eliminated by correcting the connection. See NEC 250.6 and 250.142(B).

Type NM cable entering a single-gang nonmetallic box that has no cable clamps must be secured within what distance of the box?

• a.24 inches
• b.8 inches✓
• c.3 feet
• d.4 and 1/2 feet

Where a single-gang nonmetallic box without internal clamps is used, the NM cable must be secured within 8 inches of the box. See NEC 314.17(C) Exception and 334.30(A).

A 5-horsepower, 460-volt, three-phase motor has a table full-load current of 7.6 amperes. Using 75 degrees C copper, what is the minimum branch-circuit conductor size?

• a.16 AWG
• b.14 AWG✓
• c.12 AWG
• d.10 AWG

The conductor must carry 7.6 x 1.25 = 9.5 A. 14 AWG copper (20 A at 75 degrees C) is adequate; motor branch-circuit conductors are sized under Article 430 and are not restricted by the small-conductor rule of 240.4(D). See NEC 430.22.

A feeder neutral has a maximum unbalanced load of 250 amperes of non-nonlinear line-to-neutral load. Applying the permitted demand factor, what is the calculated neutral load?

• a.175 amperes
• b.250 amperes
• c.225 amperes
• d.235 amperes✓

For a feeder or service, the first 200 A of unbalanced neutral load is taken at 100 percent and the portion over 200 A at 70 percent: 200 + (50 x 0.70) = 235 A. See NEC 220.61(B).

On the load side of the service disconnecting means, may the grounded neutral conductor be used to ground equipment enclosures?

• a.Yes, where the neutral is 6 AWG copper or larger
• b.Yes, in any subpanel fed from the service equipment
• c.No; a separate equipment grounding conductor must be used✓
• d.Yes, but only in dwelling units

Downstream of the service disconnect the neutral and equipment grounding conductor must be kept separate so load current does not travel on enclosures and raceways. See NEC 250.142(B).

May a raceway be used as a means of support for another raceway or box?

• a.Yes, in all cases
• b.Yes, for spans under 6 feet
• c.Only where the raceway is nonmetallic
• d.No, except where the raceway is identified for that purpose or specifically permitted✓

Raceways may not be used to support other raceways, cables or nonelectrical equipment unless identified for the purpose or specifically permitted. See NEC 300.11(C).

A continuous-duty motor over 1 horsepower is marked with a temperature rise of 40 degrees C. What percentage of nameplate full-load current sets the maximum overload device?

• a.140 percent
• b.115 percent
• c.125 percent✓
• d.130 percent

A motor with a marked temperature rise not over 40 degrees C, like one with a service factor of 1.15 or greater, is permitted overload protection at 125 percent of nameplate current. See NEC 430.32(A)(1).

A branch circuit supplies a 44-ampere continuous load. What is the minimum standard overcurrent device rating?

• a.50 amperes
• b.55 amperes
• c.70 amperes
• d.60 amperes✓

44 x 1.25 = 55 A, which is not a standard rating, so the next standard size of 60 A must be used. See NEC 210.20(A) and 240.6(A).

A 30 kVA, three-phase transformer has a 480-volt primary and is protected by primary overcurrent protection only at 125 percent. What is the maximum standard primary overcurrent device rating?

• a.60 amperes
• b.50 amperes✓
• c.45 amperes
• d.40 amperes

Primary full-load current = 30,000 / (1.732 x 480) = 36.1 A, and 36.1 x 1.25 = 45.1 A. Because that exceeds the standard 45-ampere rating, the next standard size of 50 A is permitted. See NEC 450.3(B).

A junction box contains four 12 AWG and three 10 AWG conductors with no devices, clamps or fittings. What minimum box volume is required?

• a.16.5 cubic inches✓
• b.17.5 cubic inches
• c.14.0 cubic inches
• d.15.75 cubic inches

Each conductor is counted at the allowance for its own size: four 12 AWG at 2.25 = 9.0, and three 10 AWG at 2.50 = 7.5, for 16.5 cubic inches. See NEC 314.16(B)(1).

A feeder supplies a 30-horsepower motor (40 amperes), a 20-horsepower motor (27 amperes) and a 10-horsepower motor (14 amperes), all 460 volts three-phase. What minimum conductor ampacity is required?

• a.91 amperes✓
• b.101.25 amperes
• c.81 amperes
• d.95 amperes

Feeder ampacity = 125 percent of the largest motor plus the sum of the others: (40 x 1.25) + 27 + 14 = 50 + 41 = 91 A. See NEC 430.24.

A 120-volt branch circuit shows a measured voltage drop of 4.8 volts. What is the percentage voltage drop?

• a.4 percent✓
• b.5 percent
• c.3 percent
• d.2 percent

Percentage voltage drop = 4.8 / 120 = 0.04, or 4 percent, which exceeds the 3 percent branch-circuit guideline. See the Informational Note to NEC 210.19.

What is the secondary full-load current of a 112.5 kVA transformer with a 208Y/120-volt three-phase secondary?

• a.541 amperes
• b.312 amperes✓
• c.270 amperes
• d.156 amperes

Secondary current = VA / (1.732 x E) = 112,500 / (1.732 x 208) = 112,500 / 360.3, about 312 amperes. Dividing by voltage alone gives the 541-ampere trap.

What is the minimum trade size of EMT required for six 10 AWG THHN conductors?

• a.One inch
• b.Three-quarter inch✓
• c.One-half inch
• d.One and one-quarter inch

Annex C, Table C1 shows one-half-inch EMT holds five 10 AWG THHN and three-quarter-inch EMT holds ten, so three-quarter inch is the minimum for six. See NEC Annex C, Table C1.

A single receptacle is installed on an individual 20-ampere branch circuit. What is the minimum ampere rating of that receptacle?

• a.20 amperes✓
• b.30 amperes
• c.25 amperes
• d.15 amperes

A single receptacle on an individual branch circuit must have an ampere rating not less than the branch-circuit rating: 20 A. See NEC 210.21(B)(1).

How is the bonding jumper for exposed structural metal building framing sized?

• a.From Table 250.66, based on the ungrounded service conductor size✓
• b.Always 6 AWG copper regardless of service size
• c.From Table 310.16, by the service ampacity
• d.From Table 250.122, by the overcurrent device rating

The bonding jumper for exposed structural metal that is likely to become energized is sized from Table 250.66 using the ungrounded service-entrance conductors. See NEC 250.104(C).

A metal outlet box is supplied by a wiring method that includes an equipment grounding conductor. How must the box be treated?

• a.It must be left isolated from ground
• b.It must be connected to the grounded neutral bar
• c.It must be connected to the equipment grounding conductor✓
• d.It need be bonded only in a wet location

A metal box must be connected to an equipment grounding conductor so it is bonded and any fault will clear. See NEC 250.148 and 314.4.

What is the maximum continuous load permitted on a 15-ampere branch circuit?

• a.18 amperes
• b.12 amperes✓
• c.15 amperes
• d.10 amperes

A continuous load may not exceed 80 percent of the overcurrent device rating: 15 x 0.80 = 12 A. See NEC 210.20(A).

For a separately derived system, the grounding electrode conductor connects to the grounded conductor at the same point where what is installed?

• a.The largest branch-circuit overcurrent device
• b.The main bonding jumper at the service
• c.The system bonding jumper✓
• d.Every downstream equipment grounding bus

The grounding electrode conductor for a separately derived system connects the grounded conductor to the electrode at the same single point where the system bonding jumper is installed. See NEC 250.30(A).

An insulated bushing or fitting to protect conductors from abrasion is required where conductors of what size or larger enter a raceway or enclosure?

• a.1 AWG
• b.4 AWG✓
• c.8 AWG
• d.6 AWG

Where ungrounded conductors of 4 AWG or larger enter a raceway in a cabinet, box or enclosure, a fitting providing a smoothly rounded insulating surface, such as an insulating bushing, is required. See NEC 300.4(G).

A dwelling has a combined general lighting, small-appliance and laundry load of 8,000 volt-amperes. Applying the standard demand factors, what is the demand load?

• a.4,750 volt-amperes✓
• b.8,000 volt-amperes
• c.2,800 volt-amperes
• d.5,000 volt-amperes

The dwelling lighting demand table takes the first 3,000 VA at 100 percent and the remainder at 35 percent: 3,000 + (5,000 x 0.35) = 4,750 VA. See NEC Table 220.45 (renumbered from Table 220.42 in the 2023 NEC).

A supply-side bonding jumper on the line side of the service is sized from which table?

• a.Table 220.55
• b.Table 250.102(C)(1)✓
• c.Table 310.16
• d.Table 250.122

Supply-side bonding jumpers are sized from Table 250.102(C)(1), based on the ungrounded supply conductors, not from the equipment grounding conductor table. See NEC 250.102(C).