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Commercial & Industrial Systems Flashcards

7 cards from real CEI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Commercial & Industrial Systems flashcards as text

  1. What is the minimum headroom clearance required in front of electrical equipment rated 600V or less in a commercial occupancy per NEC 110.26?

    Answer: 3 ft 0 in

    NEC 110.26(A)(1) requires a minimum working clearance of 3 ft (900 mm) for equipment rated 600V or less.

  2. A 480V, 3-phase industrial motor has a full-load current of 40A. What is the maximum allowable branch-circuit short-circuit and ground-fault protection for an inverse-time breaker?

    Answer: 150A

    NEC 430.52 and Table 430.52 permit inverse-time breakers at 250% of FLC for motors; 40A × 250% = 100A, but the next standard size up to 150A is permitted when 100A does not allow starting.

  3. Which NEC article governs the installation of busways (bus ducts) in commercial and industrial facilities?

    Answer: Article 368

    NEC Article 368 covers busways, including their installation, support, and use in commercial and industrial applications.

  4. In an industrial facility, a 480/277V panelboard supplies lighting circuits. What is the maximum voltage-to-ground permitted for lighting circuits in commercial occupancies?

    Answer: 277V

    NEC 210.6(D) permits lighting circuits up to 277V to ground in commercial and industrial occupancies when installed in approved luminaires.

  5. What type of grounding electrode is required to be used when a building has a metal water pipe that is at least 10 ft of the pipe in contact with the earth?

    Answer: Metal water piping system

    NEC 250.52(A)(1) requires the metal underground water piping system with at least 10 ft in contact with earth to be used as a grounding electrode.

  6. An industrial control panel contains a transformer that steps 480V down to 120V for control circuits. What is the maximum overcurrent protection permitted on the 120V secondary if the secondary conductors are 12 AWG copper?

    Answer: 20A

    NEC 240.4(D) limits 12 AWG copper conductors to a maximum of 20A overcurrent protection.

  7. Per NEC 230.71, what is the maximum number of service disconnecting means permitted for a single set of service entrance conductors supplying a commercial building?

    Answer: 6

    NEC 230.71(A) limits the number of service disconnecting means to a maximum of six for a single set of service-entrance conductors.