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General wiring practice questions

44 questions from the nec code knowledge (2023) practice test.

General wiring practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

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Sample questions

A 120/240 V panelboard is 20 in. wide. What is the minimum width of the working space in front of it?

  1. 20 in.
  2. 24 in.
  3. 30 in.
  4. 36 in.
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C. 30 in.

The working space must be as wide as the equipment or 30 in., whichever is greater. Matching the 20 in. width of the panel is the common mistake.

Reference: NEC 2023, 110.26(A)(2)

What is the minimum depth of working space in front of a 120/240 V dwelling panelboard that may need servicing while energized?

  1. 2.5 ft
  2. 3 ft
  3. 3.5 ft
  4. 4 ft
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B. 3 ft

At 150 volts to ground or less the required depth is 3 ft for every condition. The 3.5 ft and 4 ft depths apply only to higher voltages to ground with grounded surfaces or live parts across the space.

Reference: NEC 2023, 110.26(A)(1)

The dedicated space above a panelboard, reserved for electrical equipment, extends to the structural ceiling or how far above the equipment, whichever is lower?

  1. 3 ft
  2. 4 ft
  3. 6 ft
  4. 8 ft
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C. 6 ft

The dedicated electrical space is the width and depth of the equipment and runs from the floor to 6 ft above the equipment or to the structural ceiling, whichever is lower. Foreign piping and ducts must stay out of that zone.

Reference: NEC 2023, 110.26(E)(1)

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