Practice Test Geeks(CEI) Certified Electrical Inspector Practice Test
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Commercial & Industrial Systems Flashcards

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  1. In an industrial plant, a 200A feeder supplies a subpanel. The feeder conductors are 3/0 AWG THWN copper in conduit. What is the allowable ampacity of these conductors at 75°C?

    Answer: 200A

    Per NEC Table 310.16, 3/0 AWG THWN copper has an allowable ampacity of 200A at 75°C.

  2. Which of the following grounding and bonding requirements applies to metal raceways in a commercial building?

    Answer: Metal raceways that qualify must be bonded to form a continuous EGC path

    NEC 250.118 lists metal raceways such as RMC, IMC, and EMT as acceptable equipment grounding conductors when properly installed and bonded.

  3. A commercial kitchen uses a 208V, single-phase, 20A branch circuit for a commercial dishwasher. The circuit conductors must be at least what AWG size (copper, THHN, 75°C terminals)?

    Answer: 12 AWG

    A 20A branch circuit requires conductors with an ampacity of at least 20A; 12 AWG copper at 75°C has an ampacity of 20A per NEC Table 310.16.

  4. Per NEC Article 440, what determines the branch-circuit rating for a hermetic refrigerant motor-compressor?

    Answer: Rated-load current (RLC) or branch-circuit selection current (BCSC), whichever is greater

    NEC 440.22 requires that the branch-circuit short-circuit protection be based on the greater of the RLC or the BCSC as marked on the nameplate.

  5. In a commercial building, what is the minimum burial depth for rigid metal conduit (RMC) installed under a parking lot?

    Answer: 12 in

    NEC Table 300.5 requires RMC to be buried a minimum of 6 in, but under a parking lot (not a road subject to heavy vehicles), the standard minimum of 6 in for RMC applies; however, NEC 300.5 Column 1 sets 6 in for RMC in all locations.

  6. What is the purpose of a transfer switch in a commercial building's standby power system?

    Answer: To prevent simultaneous connection of the utility and generator to the load

    A transfer switch ensures the load is connected to only one source at a time, preventing backfeed from the generator onto the utility line.

  7. Under NEC 517, a Type 1 Essential Electrical System in a hospital must restore power to life safety branch circuits within what time frame?

    Answer: 10 seconds

    NEC 517.31 and 517.34 require the life safety branch of the Essential Electrical System to be restored within 10 seconds of a power interruption.