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Wiring & Protection — NASCLA Electrical Practice Questions

17 questions · 17% of the NASCLA Electrical exam

Worked questions

1. On a restaurant build-out during plan review, what is the primary hazard addressed by arc-fault circuit-interrupter protection?

  • Hazardous-arcing ignition
  • BUtility frequency variation
  • CMechanical overspeed
  • DExcessive water pressure

Why A is correct

AFCI technology detects characteristic arcing associated with damaged wiring and connections; it does not replace all overload or ground-fault protection. The best answer is therefore “Ignition from hazardous arcing conditions.” The other choices either address a different system, rely on an unsafe shortcut, or make a conclusion not supported by the stated facts.

2. On a warehouse conversion during plan review, a design requires surge-protective equipment at a dwelling service; what installation principle is important?

  • ARemove grounding electrodes
  • Use listed equipment with short conductors
  • CInstall an unlisted plug strip inside the panel
  • DIncrease breaker size instead

Why B is correct

A listed SPD depends on correct connection and low-impedance lead routing; ordinary plug strips and larger breakers do not satisfy service protection. The best answer is therefore “Use listed equipment at the required location with conductors kept appropriately short.” The other choices either address a different system, rely on an unsafe shortcut, or make a conclusion not supported by the stated facts.

3. On a single-family remodel at final inspection, ground-fault protection of equipment trips during commissioning; what is the proper response?

  • ABypass it permanently
  • BIncrease every breaker rating
  • CDisconnect grounding electrodes
  • Diagnose before energizing

Why D is correct

A trip can indicate misconfiguration or a real fault; defeating protection removes an essential safeguard and obscures the cause. The best answer is therefore “Investigate settings, sensing, wiring, and actual leakage before energizing service.” The other choices either address a different system, rely on an unsafe shortcut, or make a conclusion not supported by the stated facts.

4. On a restaurant build-out at final inspection, a contractor wants to rely on a series-rated combination; what must be verified?

  • AThe downstream device has the lower price
  • BThe devices share the same enclosure color
  • An approved marked device combination
  • DBoth devices are from any manufacturer

Why C is correct

Series performance is established for tested combinations, not inferred from individual ratings or appearance. The best answer is therefore “The specific upstream and downstream devices are part of an approved marked combination.” The other choices either address a different system, rely on an unsafe shortcut, or make a conclusion not supported by the stated facts.

5. On a warehouse conversion at final inspection, a dwelling service calculation exceeds the proposed main rating; what is the compliant response?

  • AChange the panel label
  • BAssume loads never overlap
  • CReduce grounding-electrode size
  • Add capacity or load management

Why D is correct

Service capacity must accommodate the calculated demand; unsupported diversity assumptions and labeling do not reduce that demand. The best answer is therefore “Increase capacity or revise loads using a permitted load-management method.” The other choices either address a different system, rely on an unsafe shortcut, or make a conclusion not supported by the stated facts.

6. On a multifamily project at final inspection, a portable generator inlet can energize utility conductors because no transfer mechanism is installed; what is required?

  • ARemoval of the neutral
  • BA warning sign only
  • Isolating transfer equipment
  • DA larger extension cord

Why C is correct

Source isolation prevents dangerous backfeed and unintended paralleling; instructions alone are not a physical safeguard. The best answer is therefore “Approved transfer equipment or interlocking that prevents simultaneous source connection.” The other choices either address a different system, rely on an unsafe shortcut, or make a conclusion not supported by the stated facts.

10 more in the bank

Answers and explanations for these are in the app.

  • The load schedule identifies the branch load as continuous. What minimum standard overcurrent rating is generally needed?
  • On a single-family remodel during plan review, a receptacle is installed in a location included in the current GFCI requirements; what does GFCI protection address?
  • On a small hospital renovation during plan review, a conductor ampacity is lower than the proposed standard overcurrent device and no permitted exception applies; what must change?
  • On a school modernization during plan review, why are motor overload protection and branch-circuit short-circuit protection treated separately?
  • A fault occurs at the terminal shown on the critical-system one-line. What must selective coordination demonstrate?
  • On a retail shell project during plan review, a transformer installation is sized from secondary load alone with no review of primary protection; what is missing?
  • On a tenant improvement at final inspection, a feeder tap is proposed without protection at its supply point; what determines whether it is permitted?
  • On a small hospital renovation at final inspection, an ungrounded conductor of a multiwire branch circuit is disconnected while the other remains energized; what feature improves safe simultaneous isolation?
  • On a school modernization at final inspection, many current-carrying conductors share a raceway; what must be checked before selecting protection?
  • On a retail shell project at final inspection, a photovoltaic source is added to a building; what overcurrent review is necessary?

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