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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. A design specifies a listed surge protective device at the service. Which installation principle helps it perform as intended?

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

Where to look it up

https://www.se.com/us/en/faqs/FAQ000240088/

Why B is correct

Use the specified listed equipment and follow its connection instructions, keeping leads appropriately short. Longer leads add impedance and can increase the voltage reaching protected equipment during a surge. Neither a larger breaker nor an unlisted strip substitutes for the designed SPD.

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

Where to look it up

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.334

Why D is correct

Before reenergizing, determine that the equipment and circuit can be safely energized. Investigate the protection setup and any actual fault rather than bypassing protection, repeatedly resetting it or arbitrarily increasing ratings. Follow the applicable testing procedure with qualified personnel.

4. A contractor proposes a tested, listed series-rated combination of protective devices. What must be verified for that proposed combination?

  • 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

Where to look it up

https://www.eaton.com/us/en-us/products/low-voltage-power-distribution-control-systems/series-rating.html

Why C is correct

Verify that the actual upstream and downstream devices, equipment and ratings match the approved combination and its application conditions. Appearance, price or two unrelated individual ratings do not establish that tested combination. This question does not evaluate an engineered series-rating approach.

5. Plan review establishes that the calculated service demand exceeds the proposed main rating. Which response addresses the design mismatch?

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

Where to look it up

Explicit exercise assumptions; not a universal code requirement.

Why D is correct

Revise the design so the service capacity accommodates the applicable calculated demand, or use a load revision or management method only where permitted and properly evaluated. Relabeling equipment, reducing grounding size or unsupported assumptions about simultaneous use do not resolve the mismatch.

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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