2023 NEC · 25 questions

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25 questions: 15 calculations and 10 challenging code questions based on the 2023 NEC.

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01 [Calculation] A 4,000 ft² office uses a 1.3 VA/ft² general-lighting unit load. What is its general-lighting load before any other loads?

A4,000 VAB5,200 VAC6,000 VAD8,000 VA

02 [Calculation] A commercial lighting circuit has 16 A of continuous load. What minimum branch-circuit conductor ampacity is required before adjustment factors?

A16 AB18 AC20 AD25 A

03 [Calculation] A 45 kVA, three-phase transformer has a 480 V primary. Approximately what is the primary full-load current?

A27 AB54 AC94 AD162 A

04 [Calculation] A 25 kVA single-phase transformer has a 240 V primary. Approximately what is the primary full-load current?

A52 AB78 AC104 AD208 A

05 [Calculation] A continuous-duty motor has a table full-load current of 28 A. What is the minimum single-motor branch-circuit conductor ampacity?

A28 AB30 AC35 AD56 A

06 [Calculation] A feeder supplies two motors with table currents of 28 A and 14 A. What minimum feeder ampacity does the basic motor rule yield?

A42 AB45.5 AC49 AD52.5 A

07 [Calculation] For a three-phase squirrel-cage motor (other than a Design B energy-efficient motor) with a 28 A table full-load current, what is 250% for an inverse-time circuit breaker under the table value rule?

A35 AB56 AC70 AD80 A

08 [Calculation] A single dwelling electric clothes dryer is nameplate-rated 4,500 W. What load is used under the 2023 NEC dryer minimum?

A3,500 VAB4,500 VAC5,000 VAD6,000 VA

09 [Calculation] A single dwelling electric clothes dryer is rated 6,000 W. What load is used before any multi-dryer demand factor?

A5,000 VAB5,500 VAC6,000 VAD7,500 VA

10 [Calculation] Under Table 220.55 Column C, what is the demand for one 12 kW household range?

A6 kWB8 kWC10 kWD12 kW

11 [Calculation] Under Table 220.55 Column C, what is the demand for two 12 kW household ranges?

A8 kWB10 kWC11 kWD24 kW

12 [Calculation] A box has six 12 AWG insulated conductor allowances and one 12 AWG device yoke (two allowances). Ignoring all other fill, what volume is required?

A13.5 in³B16 in³C18 in³D20.25 in³

13 [Calculation] A raceway has 0.533 in² internal area and contains more than two conductors. What is its maximum general fill area?

A0.165 in²B0.213 in²C0.282 in²D0.533 in²

14 [Calculation] A 120 V, 1,800 W resistive load draws what current?

A10 AB12 AC15 AD20 A

15 [Calculation] A 2,400 ft² dwelling is assigned 3 VA/ft² of general lighting load for this exercise. What is the undemanded lighting load?

A2,400 VAB4,800 VAC7,200 VAD9,600 VA

16 [Code] A feeder is installed as parallel sets in separate metal raceways, with a wire-type equipment grounding conductor in each raceway. How is each equipment grounding conductor generally sized?

ADivide the table size by the number of racewaysBFrom the feeder overcurrent device using Table 250.122CFrom the neutral conductor size onlyDUse 12 AWG regardless of the feeder rating

17 [Code] A pull box contains conductors 4 AWG and larger arranged as an angle pull. Which rule determines the distance from a raceway entry to the opposite wall?

AEight times the smallest racewayBSix times the largest raceway in the row plus the other raceway sizes in that row on the same wallCFour times the largest conductor diameterDThe sum of all raceways on every wall

18 [Code] A four-wire, three-phase wye circuit supplies mostly nonlinear loads. How is its neutral treated for conductor ampacity adjustment?

AAlways excludedBCounted only if smaller than the phase conductorsCCounted as a current-carrying conductorDCounted as an equipment grounding conductor

19 [Code] Which installation is excluded from the next-higher standard overcurrent device allowance in 240.4(B)?

AA feeder with a nonstandard conductor ampacityBA branch circuit supplying more than one receptacle for cord-and-plug-connected portable loadsCA circuit with a next standard rating below 800 ADA feeder using a standard-size breaker

20 [Code] A 25-foot feeder tap qualifies under 240.21(B)(2). Which combination is required?

AOne-tenth ampacity and any number of terminating breakersBOne-third of feeder OCP rating, a single terminating breaker or fuse set limiting load to tap ampacity, and physical protectionCFull feeder ampacity with no termination protectionDOne-half ampacity and exposed conductors

21 [Code] For a continuous-duty motor over 1 hp with a marked service factor of 1.15, a separate overload device is initially selected using which value?

A125% of motor nameplate currentB125% of NEC table currentC250% of motor nameplate currentD115% of NEC table current

22 [Code] Which proposed parallel phase-conductor installation fails the matching requirements, even if both conductors have adequate ampacity?

ASame length and insulation typeBSame circular-mil area and termination methodCOne copper and one aluminum conductor on the same phaseDIdentical copper conductors electrically joined at both ends

23 [Code] Emergency conductors share an enclosure with normal wiring at transfer equipment. Is the general separation rule alone enough to reject the installation?

AYes, no exceptions existBNo; 700.10(B) permits specified wiring in transfer equipment enclosuresCNo; all emergency and normal wiring may share any racewayDYes, unless both systems are under 50 V

24 [Code] A grounding electrode conductor is spliced in a wireway. Which splice method is permitted by the general continuity rule?

AA twist-on connectorBAny removable mechanical lugCIrreversible compression connectors listed for grounding and bonding or exothermic weldingDSolder alone

25 [Code] A conductor has 90°C insulation, but equipment terminals are rated 75°C. Which statement describes use of the 90°C ampacity column?

AIt always determines the final allowable loadBIt may be used for adjustment or correction, but the result cannot exceed the applicable terminal-temperature limitCIt is never permitted in calculationsDIt eliminates ambient-temperature correction

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