Master Electrician (NEC) — All Questions

A single-family dwelling has 2,000 sq ft of habitable floor area. Using the standard calculation method at 3 VA per sq ft, what is the general lighting and general-use receptacle load before any demand factors?

• a.3,000 VA
• b.6,000 VA✓
• c.4,000 VA
• d.8,000 VA

General lighting is figured at 3 VA per sq ft: 2,000 sq ft x 3 VA = 6,000 VA. This value is calculated before applying the general-lighting demand factors.

In the standard dwelling calculation, what is the minimum load to include for two required small-appliance branch circuits plus one laundry branch circuit, before any demand factor?

• a.1,500 VA
• b.4,500 VA✓
• c.6,000 VA
• d.3,000 VA

Each small-appliance and laundry circuit is figured at 1,500 VA. Two small-appliance circuits (2 x 1,500 = 3,000) plus one laundry circuit (1,500) equals 4,500 VA.

A dwelling has 7,200 VA general lighting, 3,000 VA small-appliance, and 1,500 VA laundry. Applying the standard demand factor (first 3,000 VA at 100%, remainder at 35%), what is the net general lighting load?

• a.4,095 VA
• b.11,700 VA
• c.7,200 VA
• d.6,045 VA✓

Sum = 7,200 + 3,000 + 1,500 = 11,700 VA. First 3,000 at 100% = 3,000; remaining 8,700 at 35% = 3,045. Net = 3,000 + 3,045 = 6,045 VA.

Using the demand table for household electric ranges, what is the demand load for one 12-kW electric range in a dwelling (Column C, one appliance)?

• a.9,600 VA
• b.12,000 VA
• c.6,000 VA
• d.8,000 VA✓

For a single household range not over 12 kW, the Column C demand is 8 kW = 8,000 VA. The 12-kW nameplate is reduced to an 8-kW calculated demand for one range.

What is the demand load for two 12-kW household electric ranges served from one feeder (range demand table, Column C, two appliances)?

• a.11,000 VA✓
• b.12,000 VA
• c.19,200 VA
• d.16,000 VA

Two ranges not over 12 kW have a Column C demand of 11 kW = 11,000 VA. This is less than the 24,000 VA connected total because of diversity.

A single household range is rated 16 kW. Using the 5% increase per kW over 12 kW rule on the 8-kW base, what is the demand load?

• a.9,600 VA✓
• b.16,000 VA
• c.10,400 VA
• d.8,000 VA

16 kW is 4 kW over 12 kW, so add 5% x 4 = 20% to the 8-kW base: 8,000 x 1.20 = 9,600 VA.

A dwelling has one 4-kW electric clothes dryer. What value must be used as the dryer demand load in the service calculation?

• a.5,500 VA
• b.4,500 VA
• c.4,000 VA
• d.5,000 VA✓

The dryer load is the nameplate rating or 5,000 VA, whichever is larger. Since 4,000 VA is below 5,000 VA, 5,000 VA must be used.2023 NEC 220.54

A dwelling has four fastened-in-place appliances (dishwasher, disposal, water heater, compactor) totaling 6,000 VA. What is the demand load after applying the fastened-appliance demand factor?

• a.3,000 VA
• b.4,500 VA✓
• c.6,000 VA
• d.7,500 VA

Where four or more fastened-in-place appliances are on the same feeder, a 75% demand factor may be applied: 6,000 x 0.75 = 4,500 VA.2023 NEC 220.53

A dwelling's total calculated load is 24,000 VA on a 240-V, single-phase service. What is the calculated service current?

• a.167 A
• b.100 A✓
• c.120 A
• d.83 A

Current equals volt-amperes divided by voltage: 24,000 VA / 240 V = 100 A.

Using the 75 C column, what is the smallest copper conductor rated to carry a 100-A service load?

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

At 75 C, #4 Cu is rated 85 A and #3 Cu is rated 100 A. The #3 AWG copper is the smallest conductor that meets the 100-A requirement.2023 NEC Table 310.16

For a 200-A dwelling service using the 83% conductor allowance, what is the smallest copper ungrounded conductor (75 C) permitted for the main power feeder?

• a.#1/0 AWG
• b.#3/0 AWG
• c.#2/0 AWG✓
• d.#4/0 AWG

200 A x 0.83 = 166 A required ampacity. At 75 C, #2/0 Cu is rated 175 A, which satisfies 166 A, so #2/0 is the smallest permitted.2023 NEC 310.12

An electric range has a Column C demand of 8,000 VA. Using the 70% neutral demand for ranges, what is the range contribution to the feeder neutral load?

• a.8,000 VA
• b.5,600 VA✓
• c.4,000 VA
• d.7,000 VA

The feeder neutral for a household range may be figured at 70% of the range demand: 8,000 x 0.70 = 5,600 VA.

From the motor full-load current table, what is the full-load current of a 25-HP, 480-V, three-phase induction motor?

• a.28 A
• b.42 A
• c.34 A✓
• d.40 A

The table value for a 25-HP, 460-480-V three-phase motor is 34 A. Table full-load current (FLC), not nameplate, is used for conductor and protection sizing.2023 NEC Table 430.250

A single continuous-duty motor has a table full-load current of 34 A. What minimum conductor ampacity is required for its branch circuit?

• a.50 A
• b.34 A
• c.40 A
• d.42.5 A✓

Motor branch-circuit conductors must be at least 125% of the FLC: 34 A x 1.25 = 42.5 A minimum ampacity.2023 NEC 430.22

A motor with a service factor of 1.15 has a nameplate full-load current of 34 A. What is the maximum overload protection setting at 125%?

• a.42.5 A✓
• b.45.9 A
• c.34 A
• d.39.1 A

For a motor with service factor 1.15 or greater, overload is set at up to 125% of nameplate FLA: 34 x 1.25 = 42.5 A.2023 NEC 430.32

For a motor with a 34-A full-load current, what is the maximum inverse-time circuit breaker for branch-circuit short-circuit and ground-fault protection (250%, then next higher standard size)?

• a.70 A
• b.100 A
• c.90 A✓
• d.80 A

Inverse-time breaker: 250% of FLC = 34 x 2.50 = 85 A. Where this does not correspond to a standard size, the next higher standard rating (90 A) is permitted.2023 NEC 430.52

A feeder supplies three motors with full-load currents of 34 A, 28 A, and 22 A. What minimum conductor ampacity is required for the feeder?

• a.110 A
• b.92.5 A✓
• c.105 A
• d.84 A

Feeder ampacity = 125% of the largest motor FLC plus the sum of the others: (34 x 1.25) + 28 + 22 = 42.5 + 50 = 92.5 A.2023 NEC 430.24

What is the full-load primary current of a 75-kVA, 480-V, three-phase transformer?

• a.72 A
• b.104 A
• c.90 A✓
• d.156 A

Three-phase current = VA / (1.732 x V): 75,000 / (1.732 x 480) = 90.2 A, about 90 A.

What is the full-load secondary current of a 75-kVA, three-phase transformer with a 208-V secondary?

• a.208 A✓
• b.180 A
• c.156 A
• d.90 A

Secondary current = 75,000 / (1.732 x 208) = 208.2 A, about 208 A.

A 75-kVA transformer has a 90-A primary current (over 9 A). With primary-only protection at 125% max, what is the primary overcurrent device rating (next higher standard permitted)?

• a.150 A
• b.100 A
• c.125 A✓
• d.110 A

125% of 90 A = 112.5 A. Where this does not match a standard rating, the next higher standard device (125 A) is permitted for primary-only protection.2023 NEC 450.3(B)

A 120-V branch circuit carries 16 A over a one-way run of 80 ft using #12 Cu (circular mils = 6,530, K = 12.9). What is the approximate voltage drop?

• a.5.1 V✓
• b.7.4 V
• c.3.0 V
• d.2.5 V

Single-phase VD = (2 x K x I x L) / CM = (2 x 12.9 x 16 x 80) / 6,530 = 33,024 / 6,530 = 5.06 V.

Using the previous circuit (5.06-V drop on a 120-V circuit), what is the approximate percent voltage drop?

• a.3.0%
• b.6.0%
• c.4.2%✓
• d.2.1%

Percent VD = 5.06 / 120 = 0.042 = 4.2%, which exceeds the 3% recommended for branch circuits.

A 208-V three-phase feeder carries 40 A over 150 ft using #6 Cu (CM = 26,240, K = 12.9). What is the approximate voltage drop?

• a.3.0 V
• b.7.2 V
• c.9.0 V
• d.5.1 V✓

Three-phase VD = (1.732 x K x I x L) / CM = (1.732 x 12.9 x 40 x 150) / 26,240 = 134,050 / 26,240 = 5.11 V.

For a 112.5-kVA, 208-V, three-phase transformer with 2% impedance, what is the approximate available fault current at the secondary terminals (infinite primary)?

• a.15,617 A✓
• b.20,000 A
• c.6,250 A
• d.10,000 A

Secondary FLA = 112,500 / (1.732 x 208) = 312.3 A. Isc = FLA / %Z = 312.3 / 0.02 = 15,617 A.

A 45-kVA, 208-V, three-phase transformer has 2% impedance. What is the approximate available fault current at its secondary (infinite primary)?

• a.12,500 A
• b.3,120 A
• c.6,245 A✓
• d.9,000 A

Secondary FLA = 45,000 / (1.732 x 208) = 124.9 A. Isc = 124.9 / 0.02 = 6,245 A.

Six current-carrying THHN conductors share one raceway. If the 90 C ampacity of #6 Cu is 75 A, what is the adjusted ampacity after the fill adjustment factor for 4-6 conductors?

• a.55 A
• b.60 A✓
• c.52.5 A
• d.75 A

For 4 to 6 current-carrying conductors, apply an 80% adjustment factor: 75 A x 0.80 = 60 A.2023 NEC Table 310.15(C)(1)

A #3 Cu THHN conductor has a 90 C ampacity of 110 A. In a 50 C ambient (correction factor 0.82), what is the corrected ampacity?

• a.90 A✓
• b.82 A
• c.100 A
• d.110 A

Corrected ampacity = 110 A x 0.82 = 90.2 A, about 90 A, before comparing to the termination temperature limit.2023 NEC Table 310.15(B)(1)

A #2 Cu THHN (90 C ampacity 130 A) runs with 6 current-carrying conductors (0.80 factor) in a 40 C ambient (0.91 factor). What is the adjusted-and-corrected ampacity?

• a.130 A
• b.95 A✓
• c.104 A
• d.115 A

Apply both factors to the 90 C ampacity: 130 x 0.80 x 0.91 = 94.6 A, about 95 A.

An office has 45 general-use receptacle outlets. At 180 VA per outlet, what is the receptacle load before demand factors?

• a.5,400 VA
• b.4,500 VA
• c.9,000 VA
• d.8,100 VA✓

Each general-use receptacle outlet is figured at 180 VA: 45 x 180 = 8,100 VA.2023 NEC 220.14(I)

A commercial building has a 30,000-VA receptacle load. Applying the demand (first 10 kVA at 100%, remainder at 50%), what is the demand load?

• a.25,000 VA
• b.15,000 VA
• c.30,000 VA
• d.20,000 VA✓

First 10,000 VA at 100% = 10,000; remaining 20,000 at 50% = 10,000. Total demand = 20,000 VA.

What is the maximum number of service disconnecting means permitted for a single set of service-entrance conductors (each in a separate enclosure)?

• a.Eight
• b.Six✓
• c.One
• d.Four

A service is limited to a maximum of six disconnecting means. In the 2023 NEC each of the up-to-six disconnects must be in a separate enclosure or be part of listed equipment.2023 NEC 230.71

A service uses #2/0 Cu ungrounded conductors. What is the minimum copper grounding electrode conductor?

• a.#4 AWG✓
• b.#2 AWG
• c.#8 AWG
• d.#6 AWG

For service conductors over 1/0 through 3/0 Cu, the table requires a #4 Cu grounding electrode conductor.2023 NEC Table 250.66

Where the grounding electrode conductor connects only to a made ground rod, what is the largest copper conductor size ever required?

• a.#4 AWG
• b.#6 AWG✓
• c.#8 AWG
• d.#2 AWG

The portion of the GEC connecting solely to a rod, pipe, or plate electrode need not be larger than #6 Cu.2023 NEC 250.66(A)

A branch circuit is protected by a 100-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.#4 AWG
• b.#8 AWG✓
• c.#6 AWG
• d.#10 AWG

The equipment grounding conductor table requires #8 Cu for an overcurrent device rating up to 100 A.2023 NEC Table 250.122

A feeder is protected by a 400-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.#6 AWG
• b.#4 AWG
• c.#1 AWG
• d.#3 AWG✓

For a 400-A overcurrent device the table requires #3 Cu for the equipment grounding conductor.2023 NEC Table 250.122

A service has 500-kcmil Cu ungrounded conductors per phase. What is the minimum copper grounded (neutral) service conductor for bonding purposes?

• a.1/0 AWG✓
• b.#1 AWG
• c.#2 AWG
• d.#4 AWG

The grounded service conductor must be at least the size in Table 250.102(C)(1); for 500-kcmil Cu phase conductors that value is 1/0 Cu.2023 NEC Table 250.102(C)(1)

Service phase conductors total 1,500 kcmil Cu per phase (over 1,100 kcmil). Using the 12.5% rule, what is the minimum copper main bonding jumper?

• a.4/0 AWG✓
• b.250 kcmil
• c.2/0 AWG
• d.3/0 AWG

Above 1,100 kcmil, the main bonding jumper is at least 12.5% of the phase area: 0.125 x 1,500 = 187.5 kcmil, so 4/0 Cu (211.6 kcmil) is the smallest that qualifies.2023 NEC 250.28(D)

A panelboard is rated 225 A. What is the maximum rating of the overcurrent device that may protect it?

• a.225 A✓
• b.200 A
• c.400 A
• d.250 A

Each panelboard must be protected by an overcurrent device rated no more than the panelboard rating, so 225 A is the maximum.2023 NEC 408.36

Which of the following is the next standard overcurrent device rating above 95 A?

• a.90 A
• b.125 A
• c.110 A
• d.100 A✓

Standard ratings include 90, 100, 110, and 125 A. The next standard size above 95 A is 100 A.2023 NEC 240.6

Absent a specific exception, what is the maximum overcurrent protection for a #12 Cu conductor?

• a.20 A✓
• b.25 A
• c.30 A
• d.15 A

Under the small-conductor rule, #12 Cu is limited to a maximum overcurrent device of 20 A.2023 NEC 240.4(D)

Absent a specific exception, what is the maximum overcurrent protection for a #10 Cu conductor?

• a.25 A
• b.40 A
• c.30 A✓
• d.20 A

The small-conductor rule limits #10 Cu to a maximum 30-A overcurrent device.2023 NEC 240.4(D)

A conductor has an allowable ampacity of 115 A, which is not a standard rating. Under the next-standard-size rule (600 A or less), what is the largest permitted overcurrent device?

• a.125 A✓
• b.100 A
• c.110 A
• d.150 A

When ampacity does not match a standard rating and conditions are met, the next higher standard device (125 A) is permitted for 800-A or smaller circuits.2023 NEC 240.4(B)

What is the smallest conductor size generally permitted to be installed in parallel?

• a.1/0 AWG✓
• b.#1 AWG
• c.2/0 AWG
• d.#2 AWG

Conductors are generally permitted in parallel only in sizes 1/0 AWG and larger.2023 NEC 310.10(G)

Two paralleled sets of 500-kcmil Cu (75 C, 380 A each) supply one feeder. What is the combined ampacity before adjustment?

• a.620 A
• b.760 A✓
• c.380 A
• d.500 A

Paralleled conductor ampacities add: 380 A x 2 = 760 A total for the feeder.2023 NEC Table 310.16

What is the minimum service disconnecting-means rating for a one-family dwelling?

• a.200 A
• b.125 A
• c.60 A
• d.100 A✓

The service disconnecting means for a one-family dwelling must be rated at least 100 A, 3-wire.2023 NEC 230.79

What is the minimum vertical clearance for an overhead service drop, not over 300 V to ground, above a residential driveway that is not subject to truck traffic?

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

Service-drop conductors up to 300 V to ground require 12 ft of clearance over residential property and driveways not subject to truck traffic.2023 NEC 230.24(B)

At a separately derived system such as a transformer, what conductor connects the grounded conductor to the system grounding electrode?

• a.Equipment bonding jumper
• b.Main bonding jumper
• c.Grounding electrode conductor✓
• d.System bonding jumper

Per 2023 NEC 250.30(A)(5), the grounding electrode conductor connects the grounded conductor of a separately derived system to the grounding electrode. Trap: the system bonding jumper (250.30(A)(1)) bonds the grounded conductor to the equipment/enclosure, not to the electrode.2023 NEC 250.30(A)(5)

An emergency system must be capable of supplying power to its loads within what maximum time after normal supply is lost?

• a.120 seconds
• b.10 seconds✓
• c.60 seconds
• d.30 seconds

Emergency systems must restore power to life-safety loads within 10 seconds of loss of the normal source.2023 NEC 700.12

A legally required standby system must supply its loads within what maximum time after loss of normal power?

• a.30 seconds
• b.10 seconds
• c.60 seconds✓
• d.120 seconds

Legally required standby systems must be able to supply their loads within 60 seconds of a normal-source failure.2023 NEC 701.12

Generator output conductors must have an ampacity of at least what percent of the nameplate current?

• a.100%
• b.125%
• c.110%
• d.115%✓

Generator conductors from the terminals to the first overcurrent device must be at least 115% of the nameplate current rating.2023 NEC 445.13

A feeder supplies a 60,000-VA, 208-V, three-phase load. What is the calculated feeder current?

• a.144 A
• b.167 A✓
• c.200 A
• d.150 A

Three-phase current = 60,000 / (1.732 x 208) = 166.6 A, about 167 A.

A 200-A busbar has a 200-A main breaker at one end. Using the 120% rule, what is the maximum back-fed inverter (PV) overcurrent device at the opposite end?

• a.30 A
• b.40 A✓
• c.60 A
• d.20 A

120% of the 200-A busbar = 240 A. Subtract the 200-A main: 240 - 200 = 40 A maximum for the back-fed supply breaker.2023 NEC 705.12(B)

A single made electrode (ground rod) must be supplemented unless its resistance to earth does not exceed what value?

• a.10 ohms
• b.1 ohm
• c.25 ohms✓
• d.5 ohms

A single rod, pipe, or plate electrode must be supplemented by a second electrode unless it has a resistance to earth of 25 ohms or less.2023 NEC 250.53(A)

A metal underground water pipe qualifies as a grounding electrode if it is in direct contact with earth for at least how many feet?

• a.10 ft
• b.3 ft
• c.1 ft
• d.5 ft✓

A metal underground water pipe electrode must have at least 10 ft of contact with earth (bonding connection made within 5 ft of entry).2023 NEC 250.52(A)(1)

A concrete-encased electrode (Ufer) must consist of at least how many feet of #4 or larger rebar or bare #4 Cu conductor?

• a.20 ft✓
• b.15 ft
• c.25 ft
• d.10 ft

A concrete-encased electrode requires at least 20 ft of 1/2-in (or larger) rebar or 20 ft of bare #4 Cu encased in the concrete footing/foundation.2023 NEC 250.52(A)(3)

A location where ignitable concentrations of flammable gases or vapors exist under normal operating conditions is classified as:

• a.Class II, Division 1
• b.Class I, Division 2
• c.Class I, Division 1✓
• d.Class III

Class I covers flammable gases/vapors; Division 1 means ignitable concentrations can exist under normal operation, so it is Class I, Division 1.2023 NEC 500.5(B)(1)

A location made hazardous by combustible dust is classified as which class?

• a.Class I
• b.Class IV
• c.Class III
• d.Class II✓

Class II locations are those hazardous because of the presence of combustible dust.2023 NEC 500.5(C)

In a Class I, Division 1 location, a sealing fitting must be installed within what distance of an enclosure containing arcing devices?

• a.18 in✓
• b.24 in
• c.12 in
• d.36 in

Seals are required within 18 in of enclosures that contain devices which may produce arcs, sparks, or high temperatures.2023 NEC 501.15(A)

What is the minimum number of receptacles required at a general care (Category 2) patient bed location?

• a.6
• b.4
• c.14
• d.8✓

General care patient bed locations require a minimum of 8 receptacles, served from the normal and/or essential systems.2023 NEC 517.18(B)

What is the minimum number of receptacles required at a critical care (Category 1) patient bed location?

• a.14✓
• b.12
• c.8
• d.10

Critical care patient bed locations require a minimum of 14 receptacles.2023 NEC 517.19(B)

The equipotential bonding grid around a permanently installed pool must use a solid copper conductor no smaller than:

• a.#4 AWG
• b.#8 AWG✓
• c.#6 AWG
• d.#10 AWG

Pool equipotential bonding must use an insulated, covered, or bare solid copper conductor not smaller than #8 AWG.2023 NEC 680.26(B)

A required convenience receptacle for a dwelling pool must be located not less than what distance from the inside pool wall?

• a.5 ft
• b.8 ft
• c.10 ft
• d.6 ft✓

At least one receptacle is required between 6 ft and 20 ft from the inside wall; the minimum setback is 6 ft.2023 NEC 680.22(A)

A wet-niche underwater luminaire operating without GFCI protection is limited to a maximum of:

• a.24 V
• b.15 V✓
• c.120 V
• d.30 V

Underwater luminaires must be GFCI protected unless they operate at not more than the low-voltage contact limit of 15 V.2023 NEC 680.23(A)

A motor disconnecting means must have an ampere rating of at least what percent of the motor full-load current?

• a.125%
• b.115%✓
• c.100%
• d.110%

The disconnecting means for a motor must be rated at least 115% of the motor full-load current.2023 NEC 430.110(A)

A single hermetic refrigerant motor-compressor has a rated-load current of 24 A. What minimum branch-circuit conductor ampacity is required?

• a.30 A✓
• b.24 A
• c.28 A
• d.36 A

Conductors to a single motor-compressor must be at least 125% of the rated-load or branch-circuit selection current: 24 x 1.25 = 30 A.2023 NEC 440.32

A hermetic compressor has a rated-load current of 24 A. What is the maximum branch-circuit short-circuit and ground-fault device at 175% (next standard size)?

• a.40 A
• b.60 A
• c.45 A✓
• d.50 A

175% of 24 A = 42 A; the next standard overcurrent size is 45 A, which is the maximum permitted for short-circuit/ground-fault protection.2023 NEC 440.22(A)

Which nameplate value on an air-conditioning unit is used to size the branch-circuit conductors?

• a.Maximum overcurrent protection
• b.Rated-load amps only
• c.Nameplate horsepower
• d.Minimum circuit ampacity✓

Conductors are sized to the marked minimum circuit ampacity (MCA); the maximum overcurrent protective device (MOCP) sizes the breaker or fuse.2023 NEC 440.4

A Class 2 power-limited circuit at 30 V or less is limited to a maximum power of:

• a.100 VA✓
• b.250 VA
• c.1,000 VA
• d.500 VA

Class 2 circuits are inherently limited low-energy circuits; a typical alternating-current source limit is 100 VA at up to 30 V for reliable low-energy protection.2023 NEC Chapter 9 Table 11(B)

Cables listed for power-limited fire alarm use are marked with which type designation?

• a.CMR
• b.CL2
• c.TC
• d.FPL✓

Power-limited fire alarm cables carry the FPL family markings (FPL, FPLR riser, FPLP plenum).2023 NEC 760.179

Two 10-HP, 460-V motors (14 A each) are supplied by one feeder. What minimum feeder conductor ampacity is required?

• a.28 A
• b.31.5 A✓
• c.25 A
• d.35 A

125% of the largest motor plus the other: (14 x 1.25) + 14 = 17.5 + 14 = 31.5 A.2023 NEC 430.24

A motor without a marked service factor (or with SF under 1.15) has a full-load current of 28 A. What is the maximum overload protection at 115%?

• a.30 A
• b.35 A
• c.28 A
• d.32.2 A✓

For motors with a service factor less than 1.15, overload protection is limited to 115% of nameplate FLA: 28 x 1.15 = 32.2 A.2023 NEC 430.32(A)

Which wiring method is acceptable in a Class I, Division 2 location?

• a.Type AC
• b.Nonmetallic Romex
• c.Type MC with listed fittings✓
• d.Type NM

Class I, Division 2 permits methods such as threaded rigid metal conduit and Type MC cable with listed fittings; ordinary NM/AC cable is not permitted.2023 NEC 501.10(B)

A required branch circuit that supplies a sign or outline lighting system must be rated at least:

• a.40 A
• b.30 A
• c.15 A
• d.20 A✓

Each commercial building must have at least one dedicated 20-A branch circuit for a sign or outline lighting outlet.2023 NEC 600.5(B)

Low-voltage lighting systems covered by Article 411 are limited to a maximum circuit voltage of:

• a.12 V
• b.30 V✓
• c.15 V
• d.24 V

Article 411 low-voltage lighting systems operate at not more than 30 V (or 60 V DC for wet contact limits), commonly through a listed power supply.2023 NEC 411.5

Electrical equipment supplying a decorative fountain must have what protection?

• a.Surge protection
• b.GFCI✓
• c.AFCI
• d.Isolation transformer only

All electrical equipment associated with fountains, including luminaires and pumps, must be protected by a ground-fault circuit interrupter.2023 NEC 680.51(A)

The equipotential plane bonding conductor in an agricultural building must be:

• a.#8 Cu only if insulated
• b.Copper conductor not smaller than #8✓
• c.#6 Cu maximum
• d.Insulated conductor only

Bonding of the equipotential plane in agricultural buildings uses a copper conductor not smaller than #8 AWG, solid or the equivalent.2023 NEC 547.10

A motor feeder supplies motors whose largest branch device is 90 A, plus other motors with 50 A total full-load current. What is the maximum feeder short-circuit/ground-fault device (not to exceed the sum, next standard down)?

• a.110 A
• b.175 A
• c.125 A✓
• d.150 A

The feeder device may not exceed the largest branch-circuit device (90 A) plus the other FLCs (50 A) = 140 A; the largest standard rating not exceeding 140 A is 125 A.2023 NEC 430.62

A load draws 80 kW of real power and 100 kVA of apparent power. What is the power factor?

• a.1.0
• b.0.6
• c.0.8✓
• d.0.9

Power factor = real power / apparent power = 80 kW / 100 kVA = 0.8.

For a load of 80 kW real and 100 kVA apparent, what is the reactive power?

• a.80 kVAR
• b.60 kVAR✓
• c.40 kVAR
• d.100 kVAR

Reactive power = sqrt(kVA^2 - kW^2) = sqrt(100^2 - 80^2) = sqrt(3,600) = 60 kVAR.

What is the real power of a three-phase load at 480 V, 50 A, and 0.85 power factor?

• a.35,326 W✓
• b.24,960 W
• c.30,000 W
• d.41,568 W

P = 1.732 x V x I x PF = 1.732 x 480 x 50 x 0.85 = 35,326 W.

In a balanced wye (star) three-phase system, the line current is:

• a.0.577 times the phase current
• b.Equal to the phase current✓
• c.1.732 times the phase current
• d.2 times the phase current

In a wye connection the same conductor carries phase and line current, so line current equals phase current.

In a balanced delta three-phase system, the line current equals:

• a.3 times the phase current
• b.0.577 times the phase current
• c.The phase current
• d.1.732 times the phase current✓

In a delta connection the line current is the square root of 3 (1.732) times the phase (winding) current.

In a 208Y/120-V wye system, what is the phase (line-to-neutral) voltage?

• a.208 V
• b.120 V✓
• c.277 V
• d.240 V

Line-to-neutral voltage = line-to-line / 1.732 = 208 / 1.732 = 120 V.

In a 480Y/277-V system, what is the line-to-neutral voltage?

• a.240 V
• b.120 V
• c.277 V✓
• d.208 V

Line-to-neutral = 480 / 1.732 = 277 V.

An 80-kW load at 0.80 power factor is to be corrected to 0.95. How many kVAR of capacitance are required (tan 36.87 = 0.75, tan 18.19 = 0.329)?

• a.48 kVAR
• b.60 kVAR
• c.33.7 kVAR✓
• d.20 kVAR

Qc = kW x (tan(theta1) - tan(theta2)) = 80 x (0.750 - 0.329) = 80 x 0.421 = 33.7 kVAR.

In a three-phase, four-wire wye system serving nonlinear loads, which harmonic order adds arithmetically in the neutral?

• a.7th
• b.2nd
• c.5th
• d.3rd✓

Triplen harmonics, principally the 3rd, are in phase across all three phases and add in the neutral rather than canceling.

On a feeder with significant harmonic (nonlinear) load, the neutral conductor is treated as:

• a.Not a current-carrying conductor
• b.A current-carrying conductor✓
• c.An ignored conductor
• d.A half current-carrying conductor

Where the major portion of the load is nonlinear, the neutral carries harmonic current and must be counted as a current-carrying conductor for adjustment.2023 NEC 310.15(E)

A three-phase panel has phase loads of A = 40 A, B = 30 A, C = 20 A. What is the ideal balanced current per phase?

• a.20 A
• b.40 A
• c.25 A
• d.30 A✓

Total = 40 + 30 + 20 = 90 A; balanced across three phases = 90 / 3 = 30 A per phase.

A single-line (one-line) diagram represents an electrical system by:

• a.Only the branch-circuit wiring
• b.The physical layout of raceways
• c.One line for each circuit or set of conductors✓
• d.Each individual conductor drawn separately

A one-line diagram uses a single line and standard symbols to represent circuits and equipment, simplifying analysis of the power system.

A transformer steps 480 V down to 120 V. What is its turns (voltage) ratio?

• a.4:1✓
• b.8:1
• c.2:1
• d.1:4

Turns ratio = primary voltage / secondary voltage = 480 / 120 = 4:1.

A transformer has a 4:1 turns ratio and a 10-A primary current. What is the secondary current (ideal)?

• a.2.5 A
• b.40 A✓
• c.10 A
• d.20 A

Current is inversely proportional to the turns ratio: Is = Ip x (Np/Ns) = 10 x 4 = 40 A.

An AC circuit at 240 V draws 12 A. What is the circuit impedance?

• a.0.05 ohms
• b.2 ohms
• c.20 ohms✓
• d.288 ohms

By Ohm's law for AC, Z = V / I = 240 / 12 = 20 ohms.

A continuous load draws 40 A. At what minimum ampacity must the branch-circuit conductors and overcurrent device be rated?

• a.50 A✓
• b.32 A
• c.40 A
• d.45 A

Continuous loads require 125% sizing: 40 A x 1.25 = 50 A for the conductors and overcurrent device.2023 NEC 210.20(A)

The demand factor of a system is defined as:

• a.Connected load divided by maximum demand
• b.A value always greater than 1
• c.Maximum demand divided by total connected load✓
• d.Always equal to 1

Demand factor = maximum demand / total connected load; it is 1 or less and reflects load diversity.

What are the commonly recommended maximum voltage-drop limits for a branch circuit and for the combined feeder plus branch circuit?

• a.2% and 4%
• b.3% and 5%✓
• c.5% and 8%
• d.1% and 3%

The informational recommendation is 3% maximum on a branch circuit and 5% maximum for feeder plus branch circuit combined.

For equipment operating at 0-150 V to ground under Condition 1, what is the minimum depth of working space in front of the equipment?

• a.4 ft
• b.2.5 ft
• c.2 ft
• d.3 ft✓

Condition 1 (exposed live parts on one side, no grounded parts opposite) requires a minimum working clearance of 3 ft for 0-150 V.2023 NEC 110.26(A)(1)

What is the minimum required width of working space in front of electrical equipment?

• a.36 in always
• b.24 in
• c.18 in
• d.30 in or the width of the equipment, whichever is greater✓

The working space width must be at least 30 in or the width of the equipment, whichever is greater, and must permit a 90-degree door opening.2023 NEC 110.26(A)(2)

What is the minimum headroom (height) of working space about electrical equipment such as panelboards?

• a.8 ft
• b.6 ft
• c.6.5 ft✓
• d.7 ft

The minimum headroom of working space is 6.5 ft (or the height of the equipment, whichever is greater).2023 NEC 110.26(A)(3)

The dedicated equipment space above a panelboard extends how far above the equipment (or to a structural ceiling if lower)?

• a.4.5 ft
• b.7 ft
• c.6 ft✓
• d.3 ft

The dedicated electrical space extends from the equipment to 6 ft above it, or to a structural ceiling if lower, and must be kept clear of foreign systems.2023 NEC 110.26(E)(1)

Equipment rated at what current or more requires two entrances to and egress from the working space when the space is large or contains overcurrent devices?

• a.1000 A
• b.600 A
• c.1200 A✓
• d.800 A

For equipment rated 1,200 A or more and over 6 ft wide, two entrances/egress paths to the working space are required.2023 NEC 110.26(C)(2)

For a circuit rated 100 A or less, conductor ampacity is generally based on which temperature column unless the equipment is listed otherwise?

• a.90 C
• b.75 C
• c.105 C
• d.60 C✓

Terminations on equipment rated 100 A or less are based on the 60 C column unless the equipment and conductors are listed for a higher temperature.2023 NEC 110.14(C)(1)

For circuits rated over 100 A, conductor ampacity for terminations is generally based on which temperature column?

• a.Nameplate only
• b.90 C
• c.75 C✓
• d.60 C

Terminations on equipment over 100 A are based on the 75 C column unless listed and marked for a higher rating.2023 NEC 110.14(C)(1)

Which standard governs electrical safety-related work practices, including arc-flash and shock protection?

• a.OSHA 1910 only
• b.NFPA 70E✓
• c.NFPA 72
• d.NEC (NFPA 70)

NFPA 70E, Standard for Electrical Safety in the Workplace, covers safe work practices, arc-flash boundaries, and PPE selection.

Under safe electrical work practices, what is the preferred condition before working on or near exposed conductors?

• a.Energized with a permit
• b.An electrically safe (de-energized and verified) work condition✓
• c.Wearing rubber gloves
• d.Under observation

The safest and preferred approach is to place equipment in an electrically safe work condition: de-energize, lock out, and verify absence of voltage before work.

What is the primary purpose of a lockout/tagout (LOTO) procedure under Cal/OSHA?

• a.To install ground rods
• b.To label panel directories
• c.To test GFCI devices
• d.To isolate and control hazardous energy during servicing✓

LOTO isolates and controls hazardous energy sources so equipment cannot be re-energized while workers are servicing it.

During electrical construction, a rough-in (rough) inspection is generally performed:

• a.After the final inspection
• b.After energizing the system
• c.Before wiring is concealed or covered✓
• d.Only at final occupancy

The rough inspection occurs after wiring is installed but before walls or wiring are covered, so the inspector can verify concealed work.

Who is responsible for interpreting and enforcing the requirements of the NEC?

• a.The authority having jurisdiction (AHJ)✓
• b.The serving utility
• c.The NFPA
• d.The equipment manufacturer

The authority having jurisdiction enforces the Code, makes interpretations, and grants any special permission where allowed.2023 NEC 90.4

The NEC generally does not cover which of the following installations?

• a.Dwelling branch circuits
• b.Utility-owned generation and distribution under exclusive utility control✓
• c.Commercial feeders
• d.Industrial services

The Code does not apply to installations under the exclusive control of an electric utility for generation, transmission, or distribution of power.2023 NEC 90.2(B)

Service equipment (other than dwellings) must be field marked with what value related to fault protection?

• a.Maximum available fault current✓
• b.Phase rotation
• c.Installation date only
• d.The panel interrupting rating only

Service equipment must be legibly field marked with the maximum available fault current and the date of the calculation.2023 NEC 110.24(A)

Equipment likely to be examined or serviced while energized must carry what type of field-applied marking?

• a.Voltage rating only
• b.Phase-sequence label
• c.An arc-flash hazard warning label✓
• d.Equipment grounding conductor size

An arc-flash warning label must be applied to warn qualified persons of the potential arc-flash hazard before energized examination or servicing.2023 NEC 110.16

A one-family dwelling has a total general load (lighting, small-appliance, laundry, fastened appliances, ranges) of 40,000 VA before HVAC. Using the optional method of 220.82(B), what is the demand for these general loads?

• a.22,000 VA✓
• b.16,000 VA
• c.40,000 VA
• d.28,000 VA

2023 NEC 220.82(B) takes 100% of the first 10 kVA plus 40% of the remainder: 10,000 + 0.40 x 30,000 = 10,000 + 12,000 = 22,000 VA. Trap: 16,000 VA applies 40% to the whole 40,000; the first 10 kVA must stay at 100%.2023 NEC 220.82(B)

Under the optional dwelling calculation, central electric space-heating load is included at what percent of nameplate?

• a.100%
• b.65%✓
• c.40%
• d.75%

2023 NEC 220.82(C)(3) permits central electric space heating at 65% of nameplate. Trap: the 40% figure (220.82(C)(5)) applies only to four or more separately controlled electric-heat units, not to central heat.2023 NEC 220.82(C)

A 10,000 sq ft office building is calculated for general lighting using the 2023 unit-load table for office/bank occupancies. What is the general lighting load?

• a.25,000 VA
• b.20,000 VA
• c.30,000 VA
• d.35,000 VA✓

2023 NEC Table 220.42(A) lists 3.5 VA per sq ft for banks and office buildings: 10,000 x 3.5 = 35,000 VA. Trap: 30,000 VA uses the 3 VA/sq ft dwelling/store value.2023 NEC Table 220.42(A)

A 6,000 sq ft retail store is calculated for general lighting using the 2023 unit-load table. What is the general lighting load?

• a.18,000 VA✓
• b.12,000 VA
• c.21,000 VA
• d.15,000 VA

2023 NEC Table 220.42(A) lists 3 VA per sq ft for stores: 6,000 x 3 = 18,000 VA. Trap: 21,000 VA mistakenly uses the 3.5 VA/sq ft office value.2023 NEC Table 220.42(A)

A commercial service supplies several motors; the largest has a 40-A full-load current. How much is added to the service calculation for the largest-motor factor?

• a.50 A
• b.40 A
• c.10 A✓
• d.8 A

2023 NEC 430.24 (with 220.50) requires 25% of the largest motor FLC be added on top of the motor loads: 0.25 x 40 = 10 A. Trap: 50 A adds 125% of the motor, double-counting the FLC that is already in the load.2023 NEC 430.24

A commercial kitchen has six kitchen-equipment units totaling 60 kW. Applying the demand factor for six or more units, what is the demand load?

• a.60 kW
• b.39 kW✓
• c.45 kW
• d.42 kW

2023 NEC Table 220.56 allows 65% for six or more units: 60 x 0.65 = 39 kW (result may not be less than the sum of the two largest units). Trap: 45 kW uses 75%, the four-appliance dwelling factor, not the commercial-kitchen table.2023 NEC 220.56

Transformer secondary conductors run 8 ft to a panelboard under the 10-ft secondary rule. Their ampacity must be not less than:

• a.10% of the primary overcurrent device rating
• b.the primary conductor ampacity
• c.the rating of the device or busbar they supply✓
• d.at least 300% of the transformer's rated secondary current

2023 NEC 240.21(C)(2) allows unprotected secondary conductors up to 10 ft if their ampacity is at least the calculated load and at least the rating of the device or busbar they terminate in. Trap: the 1/10 rule belongs to the 10-ft feeder tap 240.21(B)(1), not the transformer-secondary rule.2023 NEC 240.21(C)(2)

A 75-kVA, 480-208Y/120-V transformer feeds a panel through 20-ft secondary conductors under 240.21(C)(6). What is the minimum secondary conductor ampacity?

• a.208 A✓
• b.167 A
• c.260 A
• d.104 A

Secondary FLC = 75,000 / (1.732 x 208) = 208 A. 240.21(C)(6) requires the 20-ft secondary conductors to have ampacity at least equal to the transformer secondary current (208 A) and to terminate in a single OCPD not exceeding that ampacity. Trap: 260 A is 125% of secondary current, which would size the OCPD, not the minimum conductor.2023 NEC 240.21(C)(6)

A 400-A feeder overcurrent device supplies a 10-ft tap. Under the 10-ft feeder tap rule, what minimum tap-conductor ampacity comes from the 1/10 provision?

• a.200 A
• b.133 A
• c.13 A
• d.40 A✓

2023 NEC 240.21(B)(1) requires the 10-ft tap ampacity to be at least 1/10 of the 400-A device: 400 / 10 = 40 A (and at least the load served). Trap: 133 A is the 1/3 value that belongs to the 25-ft tap rule 240.21(B)(2).2023 NEC 240.21(B)(1)

A 600-A feeder overcurrent device supplies a 25-ft tap. Under the 25-ft feeder tap rule, what minimum tap-conductor ampacity is required?

• a.60 A
• b.200 A✓
• c.300 A
• d.150 A

2023 NEC 240.21(B)(2) requires the 25-ft tap ampacity to be at least 1/3 of the 600-A device: 600 / 3 = 200 A. Trap: 60 A applies the 1/10 rule, which is only for the 10-ft tap.2023 NEC 240.21(B)(2)

A 75-kVA transformer with a 208-A secondary (over 9 A) is protected on both the primary and the secondary. What is the maximum secondary overcurrent device (next higher standard permitted)?

• a.300 A✓
• b.260 A
• c.250 A
• d.225 A

Table 450.3(B) allows up to 125% on the secondary where both sides are protected: 208 x 1.25 = 260 A. Since 260 A is not a standard size, Note 1 permits the next higher standard rating, 300 A. Trap: 250 A is the next lower standard and would be too small to carry full secondary load.2023 NEC 450.3(B)

From the motor full-load current table, what is the full-load current of a 50-HP, 460-V, three-phase induction motor?

• a.52 A
• b.80 A
• c.65 A✓
• d.48 A

2023 NEC Table 430.250 lists 65 A for a 50-HP, 460-V three-phase motor. This table FLC (not nameplate) is used for branch-circuit and feeder sizing. Trap: 52 A is the 40-HP value.2023 NEC Table 430.250

A motor with a 34-A full-load current is protected by a non-time-delay (one-time) fuse. At 300%, what is the maximum branch-circuit short-circuit/ground-fault fuse (next standard size)?

• a.90 A
• b.100 A
• c.125 A
• d.110 A✓

Table 430.52 allows 300% for non-time-delay fuses: 34 x 3.00 = 102 A. Where this is not a standard size, 430.52(C)(1) Exception 1 permits the next higher standard fuse, 110 A. Trap: a time-delay (dual-element) fuse uses only 175% (60 A).2023 NEC 430.52

The optional calculation for a multifamily dwelling (220.84) may be used only where the building has at least how many dwelling units?

• a.3✓
• b.2
• c.5
• d.10

2023 NEC 220.84 applies to multifamily dwellings of three or more units that meet the stated conditions (single feeder per unit, electric cooking, and electric heat or air-conditioning). Trap: 5 confuses this with range-table diversity, not the unit-count threshold.2023 NEC 220.84

A feeder supplies five household electric ranges, each rated 12 kW. Using Column C of the range demand table, what is the demand load?

• a.17,000 VA
• b.25,000 VA
• c.20,000 VA✓
• d.21,000 VA

2023 NEC Table 220.55, Column C, gives 20 kW for five ranges not over 12 kW: 20,000 VA. Trap: 21,000 VA is the six-range value; 25,000 VA wrongly prorates 5 x 5 kW.2023 NEC Table 220.55

A service neutral carries a maximum unbalanced load of 250 A. Applying the neutral demand allowance, what is the calculated neutral load?

• a.250 A
• b.235 A✓
• c.225 A
• d.210 A

2023 NEC 220.61(B) permits 70% on the portion of neutral load over 200 A: 200 + 0.70 x 50 = 200 + 35 = 235 A. Trap: 250 A ignores the reduction; only the amount above 200 A is reduced.2023 NEC 220.61(B)

When more than two conductors are pulled into a single conduit, what maximum percent of the conduit's cross-sectional area may they occupy?

• a.53%
• b.31%
• c.60%
• d.40%✓

2023 NEC Chapter 9, Table 1: over two conductors is limited to 40% fill. Trap: 53% is the limit for one conductor and 31% for exactly two.2023 NEC Chapter 9 Table 1

A box contains eight #12 AWG conductors and nothing else. Using the box-fill volume allowance, what minimum box volume is required?

• a.16.0 cu in
• b.20.0 cu in
• c.18.0 cu in✓
• d.22.5 cu in

2023 NEC Table 314.16(B) assigns 2.25 cu in to each #12 conductor: 8 x 2.25 = 18.0 cu in. Trap: 16.0 uses the 2.0 cu in #14 value; 22.5 uses the 2.5 cu in #10 value.2023 NEC Table 314.16(B)

Under the optional method for adding load to an existing dwelling (220.83), after taking 100% of the first 8 kVA, the remaining other loads are calculated at what percent?

• a.40%✓
• b.35%
• c.50%
• d.65%

2023 NEC 220.83(B) takes 100% of the first 8 kVA and 40% of the remainder of the other load where additional air-conditioning or space-heating is being added. Trap: 35% is the general-lighting remainder factor from the standard method 220.42, not 220.83.2023 NEC 220.83(B)

A large multifamily building has 900,000 VA of connected load and an applicable 220.84 demand factor of 32%. What is the calculated demand load?

• a.450,000 VA
• b.900,000 VA
• c.288,000 VA✓
• d.360,000 VA

The optional multifamily method multiplies connected load by the Table 220.84 demand factor: 900,000 x 0.32 = 288,000 VA. Trap: 360,000 VA uses 40%; the demand factor falls as the number of units rises.2023 NEC 220.84

A transformer (separately derived system) has 3/0 AWG copper derived (secondary) phase conductors. What is the minimum copper grounding electrode conductor for the SDS?

• a.#6 AWG
• b.#2 AWG
• c.#1 AWG
• d.#4 AWG✓

2023 NEC 250.30(A)(5) sizes the SDS grounding electrode conductor from Table 250.66 using the derived phase conductors: 2/0-3/0 Cu requires #4 Cu. Trap: #6 is the maximum only when the GEC connects solely to a rod, pipe, or plate, not for the transformer GEC to building steel or water pipe.2023 NEC 250.30(A)(5)

A separately derived system has 250-kcmil copper derived conductors. Using the bonding table, what is the minimum copper system/supply-side bonding jumper?

• a.#2 AWG✓
• b.#4 AWG
• c.#1 AWG
• d.1/0 AWG

2023 NEC 250.30(A)(2) with Table 250.102(C)(1): over 3/0 through 350 kcmil Cu requires a #2 Cu bonding jumper. Trap: #4 is the value for 2/0-3/0 Cu, one row too small for 250 kcmil.2023 NEC 250.102(C)(1)

Overcurrent devices in an emergency system (Article 700) that supply life-safety loads must be:

• a.series rated only
• b.all the same ampere rating
• c.selectively coordinated✓
• d.ganged together

2023 NEC 700.32 requires emergency-system OCPDs to be selectively coordinated with all supply-side devices so that a downstream fault opens only the nearest device. Trap: series rating addresses interrupting capacity, not coordination of tripping.2023 NEC 700.32

A 400-A feeder is run as two parallel sets in separate metal raceways. What size copper equipment grounding conductor is required in each raceway?

• a.#6 AWG, half in each raceway
• b.#3 AWG in each raceway✓
• c.a single #3 AWG total
• d.#8 AWG in each raceway

2023 NEC 250.122(F) requires a full-size EGC in each raceway sized to the 400-A device; Table 250.122 gives #3 Cu for 400 A, so each raceway carries a full #3 Cu. Trap: the EGC is never divided between the parallel raceways.2023 NEC 250.122(F)

Service-entrance conductors supply a 200-A continuous load. What minimum conductor ampacity is required?

• a.160 A
• b.200 A
• c.230 A
• d.250 A✓

2023 NEC 230.42(A) requires the service conductors to carry 125% of the continuous load: 200 x 1.25 = 250 A. Trap: 200 A ignores the continuous-load multiplier.2023 NEC 230.42(A)

A service has 500-kcmil copper ungrounded conductors. What is the minimum copper bonding jumper for the metal underground water pipe?

• a.1/0 AWG✓
• b.#2 AWG
• c.#4 AWG
• d.#3 AWG

2023 NEC 250.104(A)(1) sizes the water-pipe bonding jumper from Table 250.66: over 350 through 600 kcmil Cu requires 1/0 Cu. Trap: #2 is the value for 250-350 kcmil, one row too small for 500 kcmil.2023 NEC 250.104(A)

Under 110.9, a circuit breaker or fuse intended to interrupt fault current must have an interrupting rating that is:

• a.equal to the load current
• b.125% of the continuous load
• c.at least the available fault current at its terminals✓
• d.the same as the largest downstream conductor ampacity

2023 NEC 110.9 requires the device's interrupting rating to be at least the available fault current where it is applied. Trap: ampacity and load current size the device for normal operation, not for interrupting a fault.2023 NEC 110.9

A downstream circuit breaker has an interrupting rating below the available fault current. It may still be applied if:

• a.it is derated 20% for continuous-duty operation inside a sealed enclosure
• b.it is part of a listed, tested series combination with the line-side device✓
• c.it is a molded-case type
• d.the connected load is noncontinuous

2023 NEC 240.86 permits a lower-rated downstream breaker only as part of a tested, marked series combination with the line-side OCPD (or under engineering supervision). Trap: derating a breaker does not raise its interrupting (fault) rating.2023 NEC 240.86

How many overload (running-protection) units are required for a three-phase AC motor?

• a.1
• b.2
• c.3✓
• d.4

2023 NEC Table 430.37 requires three overload units, one in each phase, for a three-phase AC motor. Trap: two units apply to certain single-phase configurations, not to three-phase motors.2023 NEC Table 430.37

An indoor dry-type transformer rated over 112.5 kVA with standard insulation generally must be installed:

• a.on any combustible wall surface
• b.within 6 in of any exposed combustible building material
• c.in a ventilated attic space
• d.in a transformer room of fire-resistant construction✓

2023 NEC 450.21(B) requires indoor dry-type transformers over 112.5 kVA to be in a fire-resistant transformer room, unless the unit uses Class 155 C or higher insulation with the specified clearances/barriers. Trap: units up to 112.5 kVA only need 12-in separation from combustibles.2023 NEC 450.21(B)

An adjustable-speed drive (VFD) has a rated input current of 30 A. What minimum branch-circuit conductor ampacity is required?

• a.37.5 A✓
• b.30 A
• c.40 A
• d.45 A

2023 NEC 430.122(A) sizes conductors to a power-conversion drive at 125% of the rated input current: 30 x 1.25 = 37.5 A. Trap: use the drive's rated input current, not the motor nameplate FLC, for a VFD circuit.2023 NEC 430.122(A)

Atmospheres containing acetylene are classified in which hazardous (classified) location group?

• a.Group D
• b.Group A✓
• c.Group C
• d.Group B

2023 NEC 500.6(A)(1) places acetylene in Class I, Group A. Trap: Group D (propane, gasoline vapor, etc.) is the most common and often assumed, but acetylene is the single Group A gas.2023 NEC 500.6(A)

The disconnecting means for air-conditioning and refrigerating equipment must be located:

• a.only at the main service panel of the building, wherever it sits
• b.at least 25 ft from the unit
• c.inside a locked room
• d.within sight from and readily accessible to it✓

2023 NEC 440.14 requires the A/C disconnect to be within sight from and readily accessible from the equipment. Trap: locating it only at the service panel does not satisfy the within-sight requirement for the unit.2023 NEC 440.14

In patient care spaces, branch-circuit wiring to receptacles and fixed equipment must provide grounding by:

• a.an insulated EGC plus the metal raceway or cable armor✓
• b.the metal raceway or cable armor alone serving as the only ground path
• c.an isolated ground connection only
• d.the grounded (neutral) conductor

2023 NEC 517.13 requires redundant grounding: an insulated copper equipment grounding conductor AND a metal raceway or cable with a metallic grounding path. Trap: the raceway alone is not sufficient in patient care spaces.2023 NEC 517.13

What three-phase transformer kVA rating corresponds to a full-load current of 100 A at 480 V?

• a.48 kVA
• b.144 kVA
• c.83 kVA✓
• d.100 kVA

kVA = (1.732 x V x I) / 1000 = (1.732 x 480 x 100) / 1000 = 83.1 kVA. Trap: 48 kVA omits the 1.732 three-phase factor.

A single-phase load draws 30 A at 240 V with a 0.90 power factor. What is the real power?

• a.7,200 W
• b.6,480 W✓
• c.5,760 W
• d.6,000 W

P = V x I x PF = 240 x 30 x 0.90 = 6,480 W. Trap: 7,200 W is the apparent power (VA) before power factor is applied.

A resistive heating element carries 10 A and has a resistance of 2 ohms. What power does it dissipate?

• a.20 W
• b.40 W
• c.100 W
• d.200 W✓

P = I^2 x R = 10^2 x 2 = 100 x 2 = 200 W. Trap: 20 W multiplies I x R, which gives the voltage drop (20 V), not power.

A motor delivers 10 HP of mechanical output while drawing 8,300 W of electrical input. What is its approximate efficiency?

• a.90%✓
• b.85%
• c.80%
• d.75%

10 HP = 7,460 W of output (746 W/HP). Efficiency = output / input = 7,460 / 8,300 = 0.90 = 90%. Trap: 75% forgets to convert HP to watts.

Equipment operating at 151-600 V to ground under Condition 3 requires what minimum depth of working space?

• a.3 ft
• b.3.5 ft
• c.4 ft✓
• d.5 ft

2023 NEC Table 110.26(A)(1): for 151-600 V, Condition 3 (exposed live parts on both sides of the working space) requires 4 ft. Trap: 3 ft is the Condition 1 value at this voltage.2023 NEC Table 110.26(A)(1)

Equipment that is listed or labeled must be installed and used:

• a.entirely at the discretion of the installing electrician on the job site
• b.per any instructions included in its listing or labeling✓
• c.only by the original manufacturer
• d.without regard to the product label

2023 NEC 110.3(B) requires listed or labeled equipment to be installed and used in accordance with any instructions included in the listing or labeling. Trap: field practice cannot override the listing instructions.2023 NEC 110.3(B)

A one-family dwelling has 2,500 sq ft of habitable floor area. Using the standard method at 3 VA per sq ft, what is the general lighting and general-use receptacle load before demand factors?

• a.9,000 VA
• b.5,000 VA
• c.6,000 VA
• d.7,500 VA✓

2023 NEC 220.41 figures dwelling general lighting at 3 VA/sq ft: 2,500 x 3 = 7,500 VA, calculated before the 220.42 demand factors are applied.

A dwelling has 9,000 VA general lighting, 3,000 VA small-appliance, and 1,500 VA laundry. Applying the standard general-lighting demand (first 3,000 VA at 100%, remainder at 35%), what is the net general lighting load?

• a.6,675 VA✓
• b.7,275 VA
• c.13,500 VA
• d.4,725 VA

Sum = 9,000 + 3,000 + 1,500 = 13,500 VA. First 3,000 at 100% = 3,000; remaining 10,500 at 35% = 3,675. Net = 6,675 VA (2023 NEC 220.42).

Using Column C of the household-range demand table, what is the demand load for three 12-kW electric ranges served by one feeder?

• a.11,000 VA
• b.16,000 VA
• c.12,000 VA
• d.14,000 VA✓

2023 NEC Table 220.55, Column C, gives 14 kW for three ranges not over 12 kW: 14,000 VA.

A single household electric range is rated 14 kW. Using the 5%-per-kW-over-12 rule on the 8-kW Column C base, what is the demand load?

• a.10,000 VA
• b.9,600 VA
• c.8,800 VA✓
• d.8,000 VA

2023 NEC Table 220.55 Note 1: 14 kW is 2 kW over 12, so add 5% x 2 = 10% to the 8-kW base: 8,000 x 1.10 = 8,800 VA.

A dwelling feeder supplies four electric clothes dryers, each rated 5.5 kW. Applying the dryer demand factor, what is the demand load?

• a.22,000 VA✓
• b.27,500 VA
• c.20,000 VA
• d.16,500 VA

2023 NEC Table 220.54: 1-4 dryers are taken at 100%. 4 x 5,500 (each above the 5,000 VA minimum) = 22,000 VA.

A feeder supplies five electric clothes dryers, each rated 5 kW. Applying the dryer demand factor for five dryers, what is the demand load?

• a.21,250 VA✓
• b.25,000 VA
• c.23,750 VA
• d.18,750 VA

2023 NEC Table 220.54 lists 85% for five dryers: 5 x 5,000 x 0.85 = 21,250 VA (each dryer is figured at the 5,000 VA minimum).

A dwelling has five fastened-in-place appliances (dishwasher 1,200, disposal 900, water heater 4,500, compactor 1,000, wine cooler 600 VA) totaling 8,200 VA. What is the demand after the fastened-appliance factor?

• a.6,560 VA
• b.8,200 VA
• c.4,100 VA
• d.6,150 VA✓

2023 NEC 220.53 permits a 75% demand factor for four or more fastened-in-place appliances on the same feeder: 8,200 x 0.75 = 6,150 VA.

A dwelling's total calculated load is 27,600 VA on a 240-V, single-phase service. What is the calculated service current?

• a.100 A
• b.120 A
• c.115 A✓
• d.96 A

Current = volt-amperes / voltage: 27,600 / 240 = 115 A.

Under the optional dwelling method, the general loads (lighting, small-appliance, laundry, appliances, range) total 32,000 VA. Applying 220.82(B) (100% of the first 10 kVA, 40% of the remainder), what is the demand?

• a.12,800 VA
• b.18,800 VA✓
• c.22,000 VA
• d.32,000 VA

2023 NEC 220.82(B): 10,000 + 0.40 x 22,000 = 10,000 + 8,800 = 18,800 VA. The first 10 kVA stays at 100%.

Under the optional dwelling method a home has 5,000 VA of air-conditioning and 9,000 VA of central electric space heating (not run together). What single value is included for the heating/cooling load?

• a.5,000 VA
• b.5,850 VA✓
• c.9,000 VA
• d.14,000 VA

2023 NEC 220.82(C) takes the largest of the listed heating/cooling figures: A/C at 100% = 5,000 VA versus central heat at 65% = 5,850 VA. The larger, 5,850 VA, is used.

A 45-unit multifamily building has 720,000 VA of connected load and an applicable 220.84 demand factor of 26%. What is the calculated demand load?

• a.230,400 VA
• b.720,000 VA
• c.187,200 VA✓
• d.288,000 VA

2023 NEC 220.84 multiplies connected load by the Table 220.84 demand factor: 720,000 x 0.26 = 187,200 VA.

Three 12-kW household ranges on a feeder have a Column C demand of 14,000 VA. Using the range neutral allowance, what is the range contribution to the feeder neutral?

• a.8,400 VA
• b.11,000 VA
• c.14,000 VA
• d.9,800 VA✓

2023 NEC 220.61(B)(1) allows the feeder neutral for household ranges at 70% of the range demand: 14,000 x 0.70 = 9,800 VA.

A feeder neutral carries a maximum unbalanced load of 300 A. Applying the neutral demand allowance, what is the calculated neutral load?

• a.300 A
• b.250 A
• c.235 A
• d.270 A✓

2023 NEC 220.61(B)(2): 70% applies to the portion over 200 A: 200 + 0.70 x 100 = 200 + 70 = 270 A.

A 40-HP, 460-V, three-phase induction motor has a table full-load current of 52 A. What minimum branch-circuit conductor ampacity is required?

• a.52 A
• b.50 A
• c.65 A✓
• d.72 A

2023 NEC 430.22: motor branch-circuit conductors must be at least 125% of the table FLC: 52 x 1.25 = 65 A.

A 30-HP, 460-V, three-phase motor has a table full-load current of 40 A. What is the maximum inverse-time circuit breaker for branch-circuit short-circuit and ground-fault protection?

• a.100 A✓
• b.90 A
• c.125 A
• d.110 A

2023 NEC 430.52: inverse-time breaker at 250% of FLC = 40 x 2.50 = 100 A, which is a standard rating (240.6).

A 30-HP, 460-V, three-phase motor has a table full-load current of 40 A. What is the maximum time-delay (dual-element) fuse for branch-circuit short-circuit/ground-fault protection?

• a.80 A
• b.90 A
• c.60 A
• d.70 A✓

2023 NEC 430.52: time-delay fuses at 175% of FLC = 40 x 1.75 = 70 A, which is a standard fuse size.

A motor with a service factor of 1.15 has a nameplate full-load current of 40 A. What is the maximum overload protection at 125% of nameplate?

• a.46 A
• b.54 A
• c.44 A
• d.50 A✓

2023 NEC 430.32(A)(1): motors with a service factor of 1.15 or more may set overload at 125% of nameplate FLA: 40 x 1.25 = 50 A.

A feeder supplies a 50-HP (65 A) and a 30-HP (40 A) motor, both 460-V three-phase. What minimum feeder conductor ampacity is required?

• a.131.25 A
• b.121.25 A✓
• c.105 A
• d.115 A

2023 NEC 430.24: 125% of the largest motor FLC plus the sum of the others: (65 x 1.25) + 40 = 81.25 + 40 = 121.25 A.

What is the full-load primary current of a 112.5-kVA, 480-V, three-phase transformer?

• a.104 A
• b.117 A
• c.156 A
• d.135 A✓

Three-phase current = VA / (1.732 x V): 112,500 / (1.732 x 480) = 135 A.

What is the full-load secondary current of a 112.5-kVA, three-phase transformer with a 208-V secondary?

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

Secondary current = 112,500 / (1.732 x 208) = 312 A.

A 45-kVA, 480-V, three-phase transformer (primary FLC 54 A, over 9 A) has primary-only overcurrent protection at 125% maximum. What is the primary device rating (next higher standard permitted)?

• a.60 A
• b.80 A
• c.70 A✓
• d.90 A

2023 NEC Table 450.3(B): 125% of 54 A = 67.7 A; not a standard size, so the next higher standard device, 70 A, is permitted for primary-only protection.

A 150-kVA, 480-208Y/120-V transformer (secondary FLC 416 A) is protected on both sides. What is the maximum secondary overcurrent device at 125% (next higher standard permitted)?

• a.450 A
• b.600 A✓
• c.500 A
• d.520 A

2023 NEC Table 450.3(B): 416 x 1.25 = 520 A on the secondary; not a standard size, so the next higher standard rating, 600 A, is permitted.

A 120-V branch circuit carries 20 A over a one-way run of 100 ft using #10 Cu (CM = 10,380, K = 12.9). What is the approximate voltage drop?

• a.5.0 V✓
• b.6.2 V
• c.3.0 V
• d.2.5 V

Single-phase VD = (2 x K x I x L) / CM = (2 x 12.9 x 20 x 100) / 10,380 = 51,600 / 10,380 = 4.97 V.

A 480-V, three-phase feeder carries 60 A over 200 ft using #4 Cu (CM = 41,740, K = 12.9). What is the approximate voltage drop?

• a.3.2 V
• b.6.4 V✓
• c.4.8 V
• d.9.0 V

Three-phase VD = (1.732 x K x I x L) / CM = (1.732 x 12.9 x 60 x 200) / 41,740 = 268,100 / 41,740 = 6.42 V.

Using the previous feeder (6.42-V drop on a 480-V, three-phase feeder), what is the approximate percent voltage drop?

• a.3.0%
• b.1.3%✓
• c.0.7%
• d.2.7%

Percent VD = 6.42 / 480 = 0.0134 = 1.3%, within the 3% recommendation for a feeder.

A 240-V, single-phase circuit carries 24 A over a one-way run of 150 ft (K = 12.9). What is the smallest copper conductor that keeps voltage drop at or below 3% (7.2 V)?

• a.#10 AWG
• b.#8 AWG✓
• c.#12 AWG
• d.#6 AWG

Required CM = (2 x K x I x L) / Vdrop = (2 x 12.9 x 24 x 150) / 7.2 = 12,900 CM. #10 (10,380) is too small; #8 (16,510 CM) is the smallest that satisfies it.

Nine current-carrying #8 THHN conductors share one raceway. If the 90 C ampacity of #8 Cu is 55 A, what is the adjusted ampacity after the fill adjustment factor for 7-9 conductors?

• a.38.5 A✓
• b.44 A
• c.33 A
• d.55 A

2023 NEC Table 310.15(C)(1): 7 to 9 current-carrying conductors take a 70% factor: 55 x 0.70 = 38.5 A.

A #1/0 Cu THHN conductor has a 90 C ampacity of 170 A. In a 46 C ambient (correction factor 0.82), what is the corrected ampacity?

• a.125 A
• b.139 A✓
• c.170 A
• d.150 A

2023 NEC Table 310.15(B)(1): 170 x 0.82 = 139.4 A, about 139 A, before comparison to the termination temperature limit.

A #3 Cu THHN (90 C ampacity 110 A) runs with 8 current-carrying conductors (0.70 factor) in a 38 C ambient (0.91 factor). What is the adjusted-and-corrected ampacity?

• a.70 A✓
• b.77 A
• c.100 A
• d.85 A

Apply both factors to the 90 C ampacity: 110 x 0.70 x 0.91 = 70.1 A, about 70 A.

An office has a 10,800-VA general receptacle load. Applying the demand (first 10 kVA at 100%, remainder at 50%), what is the demand load?

• a.10,800 VA
• b.10,000 VA
• c.5,400 VA
• d.10,400 VA✓

2023 NEC 220.44 / Table 220.44: first 10,000 VA at 100% + remaining 800 VA at 50% = 10,000 + 400 = 10,400 VA.

A box contains five #12 AWG and three #10 AWG conductors and nothing else. Using the box-fill volume allowances, what minimum box volume is required?

• a.16.5 cu in
• b.20.0 cu in
• c.17.25 cu in
• d.18.75 cu in✓

2023 NEC Table 314.16(B): #12 = 2.25, #10 = 2.5 cu in. (5 x 2.25) + (3 x 2.5) = 11.25 + 7.5 = 18.75 cu in.

A device box has six #12 conductors, one #12 equipment grounding conductor, and one duplex receptacle. Using box-fill rules, what minimum box volume is required?

• a.22.5 cu in
• b.15.75 cu in
• c.20.25 cu in✓
• d.18.0 cu in

2023 NEC 314.16(B): six conductors = 6, all grounds count as one = 1, the device counts as two based on its largest conductor = 2. (6 + 1 + 2) x 2.25 = 20.25 cu in.

A motor feeder's largest branch-circuit short-circuit device is 110 A; the other motors on the feeder total 68 A of full-load current. What is the maximum feeder short-circuit/ground-fault device?

• a.150 A
• b.200 A
• c.178 A
• d.175 A✓

2023 NEC 430.62: the feeder device may not exceed the largest branch device (110 A) plus the other FLCs (68 A) = 178 A; the largest standard rating not exceeding 178 A is 175 A.

A commercial kitchen has eight kitchen-equipment units totaling 80 kW. Applying the demand factor for six or more units, what is the demand load?

• a.45 kW
• b.60 kW
• c.52 kW✓
• d.48 kW

2023 NEC Table 220.56 allows 65% for six or more units: 80 x 0.65 = 52 kW (not less than the sum of the two largest units).

In a commercial service calculation, the largest motor has a 65-A full-load current. How much is added for the largest-motor 25% factor?

• a.13 A
• b.81.25 A
• c.16.25 A✓
• d.65 A

2023 NEC 430.24 / 220.50: 25% of the largest motor FLC is added on top of the motor loads: 0.25 x 65 = 16.25 A.

An 800-A feeder overcurrent device supplies a 25-ft tap. Under the 25-ft feeder tap rule, what minimum tap-conductor ampacity is required?

• a.80 A
• b.160 A
• c.266.667 A✓
• d.200 A

2023 NEC 240.21(B)(2): the 25-ft tap ampacity must be at least 1/3 of the 800-A device: 800 / 3 = 267 A.

A 600-A feeder overcurrent device supplies a 10-ft tap. Under the 10-ft feeder tap rule, what minimum ampacity comes from the 1/10 provision?

• a.40 A
• b.60 A✓
• c.200 A
• d.133 A

2023 NEC 240.21(B)(1): the 10-ft tap ampacity must be at least 1/10 of the 600-A device: 600 / 10 = 60 A (and at least the load served).

A 112.5-kVA, 480-208Y/120-V transformer feeds a panel through 25-ft secondary conductors under 240.21(C)(6). What is the minimum secondary conductor ampacity?

• a.156 A
• b.260 A
• c.312 A✓
• d.390 A

Secondary FLC = 112,500 / (1.732 x 208) = 312 A. 2023 NEC 240.21(C)(6) requires the secondary conductors to have ampacity at least the transformer secondary current and terminate in a single OCPD not exceeding that ampacity.

A 150-kVA, 208-V, three-phase transformer has 2% impedance. What is the approximate available fault current at its secondary terminals (infinite primary)?

• a.8300 A
• b.10410 A
• c.20818 A✓
• d.15600 A

Secondary FLA = 150,000 / (1.732 x 208) = 416 A. Isc = FLA / %Z = 416 / 0.02 = 20,820 A.

A 300-kVA, 480-V, three-phase transformer has 5% impedance. What is the approximate available fault current at its secondary (infinite primary)?

• a.3600 A
• b.18040 A
• c.14432 A
• d.7217 A✓

Secondary FLA = 300,000 / (1.732 x 480) = 361 A. Isc = 361 / 0.05 = 7,217 A.

A feeder supplies a 100-A continuous load and a 50-A noncontinuous load. What minimum conductor ampacity is required?

• a.187.5 A
• b.175 A✓
• c.150 A
• d.200 A

2023 NEC 215.2(A)(1): 125% of the continuous load plus 100% of the noncontinuous load: (100 x 1.25) + 50 = 125 + 50 = 175 A.

A feeder supplies a 120-A continuous load and a 40-A noncontinuous load. What is the minimum standard overcurrent device rating?

• a.225 A
• b.190 A
• c.175 A
• d.200 A✓

215.3: device >= 125% continuous + noncontinuous = (120 x 1.25) + 40 = 190 A; the next standard size (240.6) is 200 A.

A feeder supplies six household clothes dryers, each rated 5 kW. Applying the dryer demand factor for six dryers, what is the demand load?

• a.18,000 VA
• b.25,500 VA
• c.22,500 VA✓
• d.30,000 VA

2023 NEC Table 220.54 lists 75% for six dryers: 6 x 5,000 x 0.75 = 22,500 VA.

A feeder supplies five household electric ranges, each rated 14 kW. Using Column C plus the over-12-kW adjustment, what is the demand load?

• a.20,000 VA
• b.22,000 VA✓
• c.24,000 VA
• d.25,000 VA

Table 220.55 Column C for five ranges = 20 kW; Note 1 adds 5% per kW over 12 (14 kW is 2 over): 20,000 x 1.10 = 22,000 VA.

A 208-V, three-phase service carries a calculated load of 90,000 VA. What is the calculated service current?

• a.250 A✓
• b.144 A
• c.216 A
• d.433 A

Three-phase current = 90,000 / (1.732 x 208) = 250 A.

A 480-V, three-phase feeder carries a calculated 150-A load. What transformer kVA does this correspond to?

• a.72 kVA
• b.104 kVA
• c.144 kVA
• d.125 kVA✓

kVA = (1.732 x V x I) / 1000 = (1.732 x 480 x 150) / 1000 = 124.7 kVA, about 125 kVA.

A box has internal cable clamps and contains eight #14 AWG conductors. Using box-fill rules, what minimum box volume is required?

• a.18.0 cu in✓
• b.22.5 cu in
• c.20.25 cu in
• d.16.0 cu in

2023 NEC 314.16(B): where clamps are present, add one conductor volume of the largest conductor. (8 conductors + 1 clamp allowance) x 2.0 (#14) = 9 x 2.0 = 18.0 cu in.

A #6 Cu THHN conductor (90 C ampacity 75 A) is run with twelve current-carrying conductors in one raceway. What is the adjusted ampacity?

• a.45 A
• b.37.5 A✓
• c.52.5 A
• d.26.25 A

2023 NEC Table 310.15(C)(1): 10 to 20 current-carrying conductors take a 50% factor: 75 x 0.50 = 37.5 A.

A retail show window is 30 ft long. Using the show-window unit load, what is the calculated show-window load?

• a.3,000 VA
• b.6,000 VA✓
• c.9,000 VA
• d.5,400 VA

2023 NEC 220.43(A) requires 200 VA per linear foot of show window: 30 x 200 = 6,000 VA.

An 8,000 sq ft office building is calculated for general lighting using the 2023 unit-load table. What is the general lighting load?

• a.24,000 VA
• b.32,000 VA
• c.16,000 VA
• d.28,000 VA✓

2023 NEC Table 220.42(A) lists 3.5 VA per sq ft for office/bank occupancies: 8,000 x 3.5 = 28,000 VA.

A service uses #3/0 AWG copper ungrounded conductors. What is the minimum copper grounding electrode conductor?

• a.#8 AWG
• b.#6 AWG
• c.#2 AWG
• d.#4 AWG✓

2023 NEC Table 250.66: for service conductors over 1/0 through 3/0 Cu, the grounding electrode conductor is #4 Cu.

A service uses 400-kcmil copper ungrounded conductors. What is the minimum copper grounding electrode conductor?

• a.1/0 AWG✓
• b.#2 AWG
• c.#3 AWG
• d.#1 AWG

2023 NEC Table 250.66: over 350 through 600 kcmil Cu requires a 1/0 Cu grounding electrode conductor.

Where the grounding electrode conductor connects solely to a concrete-encased (Ufer) electrode, what is the largest copper size it is ever required to be?

• a.#2 AWG
• b.#4 AWG✓
• c.#8 AWG
• d.#6 AWG

2023 NEC 250.66(B): the portion of the GEC that connects only to a concrete-encased electrode need not be larger than #4 Cu.

A branch circuit is protected by a 60-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.#12 AWG
• b.#8 AWG
• c.#6 AWG
• d.#10 AWG✓

2023 NEC Table 250.122: overcurrent devices up to 60 A require a #10 Cu equipment grounding conductor.

A feeder is protected by a 200-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.#6 AWG✓
• b.#4 AWG
• c.#8 AWG
• d.#10 AWG

2023 NEC Table 250.122: a 200-A overcurrent device requires a #6 Cu equipment grounding conductor.

A feeder is protected by a 600-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.#1 AWG✓
• b.#3 AWG
• c.#2 AWG
• d.1/0 AWG

2023 NEC Table 250.122: a 600-A overcurrent device requires a #1 Cu equipment grounding conductor.

A service has 3/0 AWG copper ungrounded conductors. What is the minimum copper grounded (neutral) service conductor for bonding purposes?

• a.#6 AWG
• b.#4 AWG✓
• c.#2 AWG
• d.#8 AWG

2023 NEC 250.24(C) with Table 250.102(C)(1): for 2/0-3/0 Cu phase conductors, the grounded service conductor is at least #4 Cu.

Service ungrounded conductors are 350-kcmil copper per phase. Using the bonding table, what is the minimum copper main bonding jumper?

• a.#1 AWG
• b.#2 AWG✓
• c.#4 AWG
• d.1/0 AWG

2023 NEC 250.28(D)(1) with Table 250.102(C)(1): over 3/0 through 350 kcmil Cu requires a #2 Cu main bonding jumper.

Service phase conductors total 2,000 kcmil Cu per phase (over 1,100 kcmil). Using the 12.5% rule, what is the minimum copper main bonding jumper?

• a.3/0 AWG
• b.350 kcmil
• c.250 kcmil✓
• d.4/0 AWG

2023 NEC 250.28(D)(2): above 1,100 kcmil the main bonding jumper is at least 12.5% of the phase area: 0.125 x 2,000 = 250 kcmil.

A feeder supplies a detached building. Under 2023 NEC 250.32, the feeder must include which of the following?

• a.an equipment grounding conductor run with the feeder to the building✓
• b.a separate utility service
• c.no grounding conductor if the feeder is under 100 A
• d.a bonded neutral serving as the only ground path

2023 NEC 250.32(B) requires an equipment grounding conductor run with the supply to the separate building, with the neutral kept isolated from ground at the second building.

Where two ground rods are used as the grounding electrode, what is the minimum required spacing between them?

• a.8 ft
• b.3 ft
• c.10 ft
• d.6 ft✓

2023 NEC 250.53(A)(3): rod, pipe, or plate electrodes that supplement each other must be at least 6 ft apart.

A driven ground rod electrode must have a minimum length in contact with the soil of:

• a.10 ft
• b.6 ft
• c.4 ft
• d.8 ft✓

2023 NEC 250.52(A)(5) and 250.53(G): rod electrodes must be at least 8 ft in length and installed with at least 8 ft in contact with the soil.

Overhead service-drop conductors must maintain what minimum vertical clearance above public streets, roads, and alleys?

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

2023 NEC 230.24(B)(4): 18 ft over public streets, alleys, roads, and areas subject to truck traffic.

Absent a specific exception, what is the maximum overcurrent protection for a #14 Cu conductor?

• a.25 A
• b.10 A
• c.20 A
• d.15 A✓

2023 NEC 240.4(D): under the small-conductor rule, #14 Cu is limited to a 15-A overcurrent device.

A conductor has an allowable ampacity of 240 A, which is not a standard rating. Under the next-standard-size rule (800 A or less), what is the largest permitted overcurrent device?

• a.225 A
• b.250 A✓
• c.300 A
• d.240 A

2023 NEC 240.4(B): when ampacity does not match a standard rating and conditions are met, the next higher standard device is permitted; the next standard size above 240 A is 250 A.

A 400-A feeder is run as two parallel sets of conductors in separate raceways. What is required for the equipment grounding conductor in each raceway?

• a.a #6 Cu EGC, split half in each raceway
• b.a #8 Cu EGC in each raceway
• c.a single #3 Cu total for the run
• d.a full-size EGC in each raceway, sized to the 400-A device (#3 Cu)✓

2023 NEC 250.122(F): each parallel raceway must contain a full-size EGC sized to the feeder device; Table 250.122 gives #3 Cu for 400 A. The EGC is never divided among the raceways.

A service has 250-kcmil copper ungrounded conductors. What is the minimum copper grounded (neutral) service conductor required by 250.24(C)?

• a.1/0 AWG
• b.#4 AWG
• c.#2 AWG✓
• d.#1 AWG

2023 NEC 250.24(C) with Table 250.102(C)(1): over 3/0 through 350 kcmil Cu (which includes 250 kcmil) requires a #2 Cu grounded conductor.

A 208-V, three-phase feeder supplies a 120,000-VA load. What is the calculated feeder current?

• a.577 A
• b.288 A
• c.333 A✓
• d.200 A

Three-phase current = 120,000 / (1.732 x 208) = 333 A.

A 225-A busbar is fed by a 225-A main breaker at one end. Using the 120% rule, what is the maximum back-fed inverter (PV) supply breaker at the opposite end?

• a.60 A
• b.45 A✓
• c.40 A
• d.30 A

2023 NEC 705.12(B)(3): 120% of the 225-A busbar = 270 A; subtract the 225-A main: 270 - 225 = 45 A maximum for the back-fed supply breaker.

A feeder is protected by a 500-A overcurrent device. What is the minimum copper equipment grounding conductor?

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

2023 NEC Table 250.122: a 500-A overcurrent device requires a #2 Cu equipment grounding conductor.

A feeder is protected by an 800-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.1/0 AWG✓
• b.#2 AWG
• c.#1 AWG
• d.2/0 AWG

2023 NEC Table 250.122: an 800-A overcurrent device requires a 1/0 Cu equipment grounding conductor.

A feeder is protected by a 1,200-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.3/0 AWG✓
• b.4/0 AWG
• c.#1 AWG
• d.2/0 AWG

2023 NEC Table 250.122: a 1,200-A overcurrent device requires a 3/0 Cu equipment grounding conductor.

A service uses 1/0 AWG copper ungrounded conductors. What is the minimum copper grounding electrode conductor?

• a.#4 AWG
• b.#2 AWG
• c.#6 AWG✓
• d.#8 AWG

2023 NEC Table 250.66: service conductors of 1 or 1/0 Cu require a #6 Cu grounding electrode conductor.

A service uses 750-kcmil copper ungrounded conductors. What is the minimum copper grounding electrode conductor?

• a.2/0 AWG✓
• b.3/0 AWG
• c.1/0 AWG
• d.#1 AWG

2023 NEC Table 250.66: over 600 through 1,100 kcmil Cu requires a 2/0 Cu grounding electrode conductor.

A separately derived system (transformer) has 600-kcmil copper derived conductors. What is the minimum copper supply-side bonding jumper?

• a.1/0 AWG✓
• b.#1 AWG
• c.2/0 AWG
• d.#2 AWG

2023 NEC 250.30(A)(2) with Table 250.102(C)(1): over 350 through 600 kcmil Cu requires a 1/0 Cu bonding jumper.

Service-entrance conductors supply a 150-A continuous load. What minimum conductor ampacity is required?

• a.187.5 A✓
• b.150 A
• c.200 A
• d.165 A

2023 NEC 230.42(A): service conductors must carry at least 125% of the continuous load: 150 x 1.25 = 187.5 A.

A service has 3/0 AWG copper ungrounded conductors. What is the minimum copper bonding jumper for the metal underground water pipe?

• a.#2 AWG
• b.#6 AWG
• c.#4 AWG✓
• d.#8 AWG

2023 NEC 250.104(A)(1) sizes the water-pipe bonding jumper from Table 250.66: 2/0-3/0 Cu service conductors require a #4 Cu bonding jumper.

Under 2023 NEC 110.9, a circuit breaker or fuse intended to interrupt fault current must have an interrupting rating that is:

• a.125% of the continuous load
• b.equal to the connected load current
• c.at least the available fault current at its line terminals✓
• d.the same as the largest downstream conductor ampacity

2023 NEC 110.9 requires the device's interrupting rating to be at least the available fault current where it is applied; ampacity and load current size the device only for normal operation.

A downstream circuit breaker has an interrupting rating below the available fault current. It may still be applied only if:

• a.the connected load is noncontinuous
• b.it is a molded-case type
• c.it is derated 20% for continuous operation
• d.it is part of a listed, tested series combination with the line-side device✓

2023 NEC 240.86 permits a lower-rated downstream breaker only as part of a tested, marked series combination with the line-side OCPD (or under engineering supervision). Derating does not raise interrupting rating.

Service phase conductors total 1,100 kcmil Cu per phase. Using the bonding table, what is the minimum copper main bonding jumper?

• a.1/0 AWG
• b.2/0 AWG✓
• c.#1 AWG
• d.3/0 AWG

2023 NEC 250.28(D)(1) with Table 250.102(C)(1): over 600 through 1,100 kcmil Cu requires a 2/0 Cu main bonding jumper.

What is the maximum rating of the overcurrent device that may protect a 400-A-rated panelboard?

• a.350 A
• b.450 A
• c.400 A✓
• d.500 A

2023 NEC 408.36: a panelboard must be protected by an overcurrent device rated no more than the panelboard rating, so 400 A is the maximum.

A single made electrode (ground rod) must be supplemented by a second electrode unless its resistance to earth does not exceed:

• a.1 ohm
• b.5 ohms
• c.25 ohms✓
• d.10 ohms

2023 NEC 250.53(A)(2): a single rod, pipe, or plate electrode must be supplemented unless it has a resistance to earth of 25 ohms or less.

A branch circuit is protected by a 30-A overcurrent device. What is the minimum copper equipment grounding conductor?

• a.#12 AWG
• b.#10 AWG✓
• c.#14 AWG
• d.#8 AWG

2023 NEC Table 250.122: overcurrent devices from 30 through 60 A require a #10 Cu equipment grounding conductor.

A single hermetic refrigerant motor-compressor has a rated-load current of 28 A. What minimum branch-circuit conductor ampacity is required?

• a.35 A✓
• b.28 A
• c.40 A
• d.31.5 A

2023 NEC 440.32: conductors to a single motor-compressor must be at least 125% of the rated-load current: 28 x 1.25 = 35 A.

A hermetic compressor has a rated-load current of 28 A. What is the maximum branch-circuit short-circuit and ground-fault device at 175% (next standard size)?

• a.50 A✓
• b.40 A
• c.45 A
• d.60 A

2023 NEC 440.22(A): 175% of 28 A = 49 A; the next standard overcurrent size is 50 A, the maximum permitted for short-circuit/ground-fault protection.

An A/C unit has a compressor rated-load current of 20 A and a fan motor of 3 A. What minimum branch-circuit conductor ampacity is required?

• a.30 A
• b.25 A
• c.28 A✓
• d.23 A

2023 NEC 440.33/440.34: 125% of the largest motor plus the other loads: (20 x 1.25) + 3 = 25 + 3 = 28 A.

A location where ignitable concentrations of flammable gas or vapor are present only under abnormal (fault or leak) conditions is classified as:

• a.Class I, Division 1
• b.Class I, Division 2✓
• c.Class III
• d.Class II, Division 1

2023 NEC 500.5(B)(2): Class I, Division 2 covers flammable gases or vapors normally confined but present only under abnormal conditions.

A location made hazardous by easily ignitable fibers or flyings that are not likely to be suspended in the air is classified as:

• a.Class IV
• b.Class II
• c.Class I
• d.Class III✓

2023 NEC 500.5(D): Class III locations are hazardous because of easily ignitable fibers or flyings, such as textile mills and woodworking areas.

Atmospheres containing propane, gasoline, or natural-gas vapor fall into which hazardous-location group?

• a.Group D✓
• b.Group B
• c.Group A
• d.Group C

2023 NEC 500.6(A)(4): Group D includes the common flammable gases and vapors such as propane, gasoline, and natural gas.

In a Class I, Division 1 location, where a conduit leaves the classified area into an unclassified area, a seal is required:

• a.never, if rigid metal conduit is used
• b.only at the service equipment
• c.only if the conduit is over 2 in trade size
• d.within 10 ft of the boundary, with no coupling or fitting between the seal and the boundary except as permitted✓

2023 NEC 501.15(A)(4): a seal is required within 10 ft of the boundary where a raceway leaves a Class I, Division 1 location, with no unions, couplings, or fittings between the seal and the point of exit (other than as allowed).

A hospital's essential electrical system for a Type 1 facility is divided into which branches?

• a.isolated and grounded branches
• b.life safety, critical, and equipment branches✓
• c.emergency and legally required branches
• d.normal and standby branches only

2023 NEC 517.30: the Type 1 essential electrical system consists of the life safety branch, the critical branch, and the equipment branch.

In a wet procedure location where interruption of power is not permitted, protection is provided by:

• a.double-insulated equipment only
• b.an AFCI on the branch circuit
• c.standard 15-A receptacles only
• d.an isolated power system (or GFCI where interruption can be tolerated)✓

2023 NEC 517.20: wet procedure locations require GFCI protection or an isolated power system; where power interruption cannot be tolerated, an isolated (ungrounded) power system is used.

Luminaires and lighting outlets installed over a permanently installed pool must be mounted at least what height above the maximum water level (for new installations without special protection)?

• a.8 ft
• b.12 ft✓
• c.10 ft
• d.5 ft

2023 NEC 680.22(B): luminaires over the pool and the area extending 5 ft horizontally must be at least 12 ft above the maximum water level for new work.

The equipotential bonding required around a permanently installed pool must extend horizontally what distance from the inside pool wall?

• a.5 ft
• b.2 ft
• c.3 ft✓
• d.6 ft

2023 NEC 680.26(B)(2): the perimeter surface equipotential bonding extends 3 ft horizontally beyond the inside walls of the pool.

Outlets supplying a self-contained spa or hot tub must be protected by:

• a.an isolation transformer only
• b.a ground-fault circuit interrupter (GFCI)✓
• c.an arc-fault circuit interrupter
• d.a surge protective device

2023 NEC 680.44: the outlet(s) that supply a self-contained or packaged spa or hot tub must be GFCI protected.

A motor controller (other than certain small or torque motors) must have a horsepower rating that is:

• a.equal to the branch-circuit device rating
• b.at least 250% of the motor horsepower
• c.at least equal to the motor horsepower at the application voltage✓
• d.not more than the motor full-load current

2023 NEC 430.83(A): the controller must have a horsepower rating not lower than the motor horsepower rating at the application voltage, so it can make and break the motor current.

An adjustable-speed drive (VFD) has a rated input current of 24 A. What minimum branch-circuit conductor ampacity is required?

• a.36 A
• b.30 A✓
• c.24 A
• d.28 A

2023 NEC 430.122(A): conductors supplying a power-conversion drive are sized at 125% of the rated input current: 24 x 1.25 = 30 A. Use the drive input current, not the motor FLC.

The disconnecting means for a sign or outline lighting system must be:

• a.at the utility transformer only
• b.within sight of the sign or controller, or capable of being locked open✓
• c.inside a locked electrical room only
• d.at least 25 ft from the sign

2023 NEC 600.6(A): the sign disconnect must be within sight of the sign or outline lighting it controls, or be lockable in the open position where out of sight.

Each commercial building or occupancy accessible to pedestrians must have at least one dedicated sign or outline-lighting branch circuit rated at least:

• a.20 A✓
• b.30 A
• c.40 A
• d.15 A

2023 NEC 600.5(A): at least one dedicated 20-A branch circuit is required for a sign or outline-lighting outlet at each entrance of a commercial occupancy.

Article 411 low-voltage lighting systems are limited to a maximum circuit voltage of:

• a.30 V✓
• b.24 V
• c.15 V
• d.12 V

2023 NEC 411.5: low-voltage lighting systems operate at a maximum of 30 V ac (or 60 V dc for dry locations), typically through a listed power supply.

Electrical equipment associated with a fountain, including submersible pumps and luminaires, must be protected by:

• a.an isolation transformer only
• b.an arc-fault circuit interrupter
• c.a ground-fault circuit interrupter (GFCI)✓
• d.a surge arrester

2023 NEC 680.51(A): fountain luminaires and other electrical equipment associated with the fountain must be GFCI protected.

In agricultural buildings, the site-isolating disconnecting means at the distribution point must:

• a.be a service disconnect at each building only
• b.provide a means to disconnect all site conductors and be identified as the site-isolating device✓
• c.be limited to 60 A maximum
• d.be a snap switch inside the barn

2023 NEC 547.9/547.25: the site-isolating device at the agricultural distribution point disconnects the site conductors and must be pole-mounted or otherwise identified as such.

A feeder supplies a 50-HP (65 A), a 30-HP (40 A), and a 20-HP (27 A) motor, all 460-V three-phase. What minimum feeder conductor ampacity is required?

• a.156 A
• b.140 A
• c.132 A
• d.148.25 A✓

2023 NEC 430.24: 125% of the largest motor FLC plus the sum of the others: (65 x 1.25) + 40 + 27 = 81.25 + 67 = 148.25 A.

A motor marked with a temperature rise of 40 C (and no service factor) has a nameplate full-load current of 52 A. What is the maximum overload protection?

• a.52 A
• b.59.8 A
• c.65 A✓
• d.60 A

2023 NEC 430.32(A)(1): motors marked with a temperature rise not over 40 C may set overload at 125% of nameplate FLA: 52 x 1.25 = 65 A.

In a Class II, Division 1 (combustible dust) location, enclosures for arcing equipment must be:

• a.identified (listed) as dust-ignitionproof for the location✓
• b.explosionproof for Class I only
• c.weatherproof rated
• d.ordinary NEMA 1 enclosures

2023 NEC 502.115/502.6: Class II, Division 1 arcing equipment must be in enclosures identified as dust-ignitionproof; Class I explosionproof enclosures are not necessarily suitable for dust.

An indoor dry-type transformer rated 45 kVA with standard (Class 105) insulation must maintain what minimum separation from combustible material unless otherwise protected?

• a.18 in
• b.3 in
• c.12 in✓
• d.6 in

2023 NEC 450.21(A): dry-type transformers 112.5 kVA and under must be separated at least 12 in from combustible material unless the unit has a listed fire-resistant barrier or Class 155 (or higher) insulation.

Which value from a motor nameplate must be used with the tables to size branch-circuit short-circuit protection and conductors, per 430.6(A)?

• a.the nameplate full-load amperes
• b.the service-factor amps
• c.the locked-rotor current
• d.the table full-load current, not the nameplate current rating✓

2023 NEC 430.6(A)(1): for general motor applications, the full-load current values in Tables 430.247-430.250 (not the nameplate FLA) are used to size conductors and short-circuit/ground-fault protection. Overload protection uses the nameplate FLA.

The disconnecting means for air-conditioning or refrigerating equipment with a motor-compressor must be located:

• a.only at the main service panel
• b.inside a locked mechanical room only
• c.at least 25 ft away
• d.within sight from and readily accessible from the equipment✓

2023 NEC 440.14: the disconnect must be within sight from, and readily accessible from, the air-conditioning or refrigerating equipment.

How many overload (running-protection) units are required for a three-phase alternating-current motor?

• a.one
• b.three✓
• c.four
• d.two

2023 NEC Table 430.37: a three-phase AC motor requires three overload units, one in each phase.

In patient care spaces, grounding of receptacles and fixed electrical equipment must be accomplished by:

• a.an isolated ground only
• b.the metal raceway alone as the only ground path
• c.the grounded (neutral) conductor
• d.an insulated copper equipment grounding conductor plus a metal raceway or cable armor (redundant ground)✓

2023 NEC 517.13: patient care spaces require redundant grounding - an insulated copper EGC AND a metallic raceway or cable that itself qualifies as a grounding path.

The disconnecting means for a motor must have an ampere rating of at least what percentage of the motor full-load current?

• a.115%✓
• b.125%
• c.100%
• d.110%

2023 NEC 430.110(A): the disconnecting means for a motor circuit must be rated at least 115% of the motor full-load current.

A load draws 60 kW of real power and 100 kVA of apparent power. What is the reactive power?

• a.60 kVAR
• b.40 kVAR
• c.80 kVAR✓
• d.100 kVAR

Reactive power = sqrt(kVA^2 - kW^2) = sqrt(100^2 - 60^2) = sqrt(6,400) = 80 kVAR.

A load has a current lagging the voltage by a phase angle of 30 degrees. What is its power factor?

• a.0.50
• b.0.87✓
• c.0.71
• d.0.94

Power factor = cos(theta) = cos(30 degrees) = 0.866, about 0.87.

What is the real power of a three-phase load at 480 V, 40 A, and 0.90 power factor?

• a.19,200 W
• b.24,000 W
• c.29,930 W✓
• d.33,254 W

P = 1.732 x V x I x PF = 1.732 x 480 x 40 x 0.90 = 29,930 W.

What is the real power of a single-phase load drawing 25 A at 240 V with a 0.85 power factor?

• a.6,000 W
• b.5,100 W✓
• c.7,200 W
• d.4,335 W

P = V x I x PF = 240 x 25 x 0.85 = 5,100 W.

In a balanced wye (star) three-phase system, the line-to-line voltage equals:

• a.2 times the line-to-neutral voltage
• b.0.577 times the line-to-neutral voltage
• c.1.732 times the line-to-neutral voltage✓
• d.the line-to-neutral voltage

In a wye system the line-to-line voltage is the square root of 3 (1.732) times the phase (line-to-neutral) voltage.

In a 240/120-V, three-phase, four-wire high-leg delta system, what is the voltage from the high (stinger) leg to the neutral?

• a.240 V
• b.277 V
• c.208 V✓
• d.120 V

The high leg to neutral in a 240-V delta is 240 x (sqrt(3)/2) = 208 V; that phase must never supply line-to-neutral loads.

An 80-kVA transformer serves a single-phase load at 240 V. What is the full-load current?

• a.333 A✓
• b.577 A
• c.240 A
• d.192 A

Single-phase current = VA / V = 80,000 / 240 = 333 A.

A 100-kW load at 0.70 power factor is corrected to 0.90 (tan of the 0.70 angle = 1.020, tan of the 0.90 angle = 0.484). How many kVAR of capacitance are required?

• a.20 kVAR
• b.48 kVAR
• c.100 kVAR
• d.53.6 kVAR✓

Qc = kW x (tan(theta1) - tan(theta2)) = 100 x (1.020 - 0.484) = 100 x 0.536 = 53.6 kVAR.

A transformer steps 480 V down to 240 V. What is its turns (voltage) ratio?

• a.8:1
• b.1:2
• c.2:1✓
• d.4:1

Turns ratio = primary voltage / secondary voltage = 480 / 240 = 2:1.

A transformer has a 10:1 turns ratio and a 5-A primary current. What is the ideal secondary current?

• a.5 A
• b.50 A✓
• c.15 A
• d.0.5 A

Current is inversely proportional to the turns ratio: Is = Ip x (Np/Ns) = 5 x 10 = 50 A.

A purely resistive load connected to 120 V draws 10 A. What is its resistance?

• a.130 ohms
• b.12 ohms✓
• c.1,200 ohms
• d.0.083 ohms

By Ohm's law, R = V / I = 120 / 10 = 12 ohms.

A resistive heating element rated 240 V has a resistance of 12 ohms. What power does it dissipate?

• a.28,800 W
• b.2,880 W
• c.20 W
• d.4,800 W✓

P = V^2 / R = 240^2 / 12 = 57,600 / 12 = 4,800 W.

A single-phase load draws 50 A at 240 V. What is the apparent power?

• a.12 kVA✓
• b.24 kVA
• c.6 kVA
• d.12 kW

Apparent power = V x I = 240 x 50 = 12,000 VA = 12 kVA (kW would require the power factor).

A motor delivers 25 HP of mechanical output. Ignoring losses, how many watts of output is that?

• a.25,000 W
• b.746 W
• c.33,540 W
• d.18,650 W✓

1 HP = 746 W, so 25 HP = 25 x 746 = 18,650 W of mechanical output.

A motor delivers 20 HP of mechanical output at 92% efficiency. What is its electrical input power?

• a.14,920 W
• b.13,726 W
• c.20,000 W
• d.16,217 W✓

Output = 20 x 746 = 14,920 W. Input = output / efficiency = 14,920 / 0.92 = 16,217 W.

A feeder conductor carries 20 A and has a total resistance of 0.5 ohm. What is the power lost as heat in the conductor?

• a.2,000 W
• b.200 W✓
• c.10 W
• d.40 W

Line loss = I^2 x R = 20^2 x 0.5 = 400 x 0.5 = 200 W.

What is the apparent power of an 80-kW load operating at a 0.80 power factor?

• a.80 kVA
• b.64 kVA
• c.125 kVA
• d.100 kVA✓

Apparent power = real power / power factor = 80 / 0.80 = 100 kVA.

For a 120-V rms sinusoidal supply, what is the approximate peak voltage?

• a.120 V
• b.170 V✓
• c.240 V
• d.85 V

Peak = rms x 1.414: 120 x 1.414 = 169.7 V, about 170 V.

In a three-phase, four-wire wye system with heavy nonlinear (electronic) load, why can the neutral current exceed the phase current?

• a.the neutral carries the vector sum of balanced fundamentals
• b.reactive current cancels in the neutral
• c.third-harmonic (triplen) currents are in phase across all three legs and add in the neutral✓
• d.the neutral is undersized by code

Triplen harmonics, principally the 3rd, are in phase across all three phases and add arithmetically in the neutral rather than canceling, so the neutral can carry more than a phase conductor.

A balanced three-phase panel has phase loads of A = 48 A, B = 36 A, C = 24 A. What is the ideal per-phase current if the loads were perfectly balanced?

• a.36 A✓
• b.24 A
• c.40 A
• d.48 A

Total = 48 + 36 + 24 = 108 A; perfectly balanced = 108 / 3 = 36 A per phase.

What three-phase transformer kVA rating corresponds to a full-load current of 200 A at 240 V?

• a.48 kVA
• b.100 kVA
• c.83 kVA✓
• d.144 kVA

kVA = (1.732 x V x I) / 1000 = (1.732 x 240 x 200) / 1000 = 83.1 kVA.

A 60-Hz sinusoidal waveform has a period of approximately:

• a.1.0 s
• b.8.3 ms
• c.60 ms
• d.16.7 ms✓

Period = 1 / frequency = 1 / 60 = 0.0167 s = 16.7 ms.

For equipment operating at 151-600 V to ground under Condition 2, what is the minimum depth of working space in front of the equipment?

• a.5 ft
• b.3.5 ft✓
• c.4 ft
• d.3 ft

2023 NEC Table 110.26(A)(1): for over 150 to 600 V, Condition 2 (grounded parts on the opposite side) requires 3.5 ft of clear working depth.

For equipment operating at 0-150 V to ground, what is the minimum depth of working space regardless of condition?

• a.3 ft✓
• b.3.5 ft
• c.2.5 ft
• d.4 ft

2023 NEC Table 110.26(A)(1): at 0-150 V to ground the working depth is 3 ft for Conditions 1, 2, and 3.

Personnel doors for electrical equipment rated at what current or more must open in the direction of egress and be equipped with panic hardware?

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

2023 NEC 110.26(C)(3): where equipment rated 800 A or more has a personnel door within 7.6 m (25 ft) of the working space, the door must open in the direction of egress and have listed panic hardware.

Under 2023 NEC 110.22, each disconnecting means must be:

• a.legibly marked to indicate its purpose unless located and arranged so the purpose is evident✓
• b.installed only by the utility
• c.rated at least 100 A
• d.painted red

2023 NEC 110.22(A): each disconnecting means must be legibly marked to indicate its purpose unless located and arranged so the purpose is evident.

Under 2023 NEC 110.14(D), terminations that are marked with a tightening torque must be:

• a.tightened until the conductor deforms
• b.tightened to the specified value using a calibrated torque tool✓
• c.left finger-tight for expansion
• d.hand-tightened only

2023 NEC 110.14(D): where a tightening torque is indicated on equipment or in instructions, a calibrated torque tool must be used to achieve the specified value.

One of the primary purposes of system grounding under 2023 NEC 250.4(A)(1) is to:

• a.limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines✓
• b.carry normal load current
• c.eliminate the need for overcurrent protection
• d.reduce conductor resistance

2023 NEC 250.4(A)(1): system grounding limits the voltage imposed by lightning, line surges, and unintentional contact with higher-voltage lines and stabilizes voltage to earth during normal operation.

Under 2023 NEC 408.4(A), every circuit and circuit modification in a panelboard must be:

• a.numbered only, with no description
• b.marked only if over 100 A
• c.legibly identified as to its clear, evident, and specific purpose in a circuit directory✓
• d.identified only for motor circuits

2023 NEC 408.4(A): each circuit must be legibly identified as to its clear, evident, and specific purpose on a directory located at the panelboard.

In the 2023 NEC, the word 'shall' indicates a requirement that is:

• a.mandatory✓
• b.permissive
• c.advisory only
• d.a recommendation

2023 NEC 90.5(A): mandatory rules use the word 'shall'; permissive rules use 'shall be permitted'; explanatory material is informational.

Under 2023 NEC 110.12, electrical equipment must be installed in a manner that is:

• a.energized before inspection
• b.at the installer's sole discretion
• c.concealed from view
• d.neat and workmanlike✓

2023 NEC 110.12: electrical equipment must be installed in a neat and workmanlike manner, with unused openings closed and internal parts kept free of foreign material.

Under 2023 NEC 110.2, conductors and equipment covered by the Code are acceptable only if:

• a.approved by the authority having jurisdiction✓
• b.rated over 600 V
• c.installed by a master electrician
• d.manufactured domestically

2023 NEC 110.2: conductors and equipment required or permitted by the Code are acceptable only if approved (accepted as suitable) by the authority having jurisdiction.

Under 2023 NEC 110.11, equipment must be selected considering:

• a.the utility's meter type
• b.only the ambient temperature
• c.the installer's warranty period
• d.any deteriorating agents or environmental conditions present at the installation✓

2023 NEC 110.11: equipment must be identified for the environment; presence of moisture, corrosive vapors, dust, or other deteriorating agents must be considered in selection and installation.

Service equipment (other than one- and two-family dwellings) rated 1,200 A or more must be legibly field marked with:

• a.the installer's license number
• b.the maximum available fault current and the date of the calculation✓
• c.the panel's short-circuit color code
• d.the phase rotation only

2023 NEC 110.24(A): service equipment must be field marked with the maximum available fault current, including the date of the calculation, so the interrupting/short-circuit ratings can be verified.

In the NEC definitions, a 'continuous load' is one where the maximum current is expected to continue for:

• a.30 minutes or more
• b.8 hours or more
• c.1 hour or more
• d.3 hours or more✓

2023 NEC Article 100: a continuous load is one where the maximum current continues for 3 hours or more, which triggers the 125% conductor and device sizing rules.

Under 2023 NEC 110.26, the working space in front of energized electrical equipment must:

• a.be reduced to 24 in for panelboards
• b.be kept clear and not be used for storage✓
• c.double as an egress corridor only
• d.be usable for storage when de-energized

2023 NEC 110.26(B): the required working space must be kept clear and must not be used for storage; when normally enclosed live parts are exposed for service, the space must be guarded.

For equipment operating at 151-600 V to ground under Condition 1, what is the minimum depth of working space?

• a.3 ft✓
• b.4 ft
• c.2.5 ft
• d.3.5 ft

2023 NEC Table 110.26(A)(1): at over 150 to 600 V, Condition 1 (no grounded or live parts on the opposite side) requires 3 ft of working depth.

Because jurisdictions adopt different Code editions and amendments, a master electrician sizing a service should always:

• a.assume the newest published NEC applies everywhere
• b.use whichever edition is most economical
• c.verify the NEC edition and any local amendments the jurisdiction has adopted✓
• d.follow the manufacturer's catalog instead of the Code

The NEC is adopted (often with amendments) on a state/local basis, and Article 220 was renumbered in the 2023 edition; always verify the edition and local amendments your jurisdiction has adopted before finalizing a calculation.

Under 2023 NEC 110.14(C), the temperature rating of a conductor used for ampacity at a termination is governed by:

• a.the ambient temperature only
• b.the lowest temperature rating of any connected termination, conductor, or device✓
• c.the 90 C column in all cases
• d.the highest-rated component in the circuit

2023 NEC 110.14(C): the conductor ampacity at a termination is based on the lowest temperature rating of any connected termination, conductor, or device, so the 90 C column is generally usable only for derating, not for final termination sizing.