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Electrical Inspector Exam Guide
Question 1. Which NEC article governs the requirements for grounding electrode systems in commercial installations? A) Article 210 B) Article 250 C) Article 300 D) Article 430 Answer: B Explanation: Article 250 of the NEC specifically addresses grounding and bonding, including grounding electrode systems (GES). Question 2. A commercial building requires a permit for installing a new 400 A service. Which of the following must be verified on the permit? A) The type of lighting fixtures to be used B) The scope of work matches the approved electrical plans C) The contractor’s insurance policy number D) The brand of conduit to be installed Answer: B Explanation: The permit must confirm that the work to be performed aligns with the approved electrical drawings and scope. Question 3. When reviewing a single-line diagram for a commercial feeder, the inspector should primarily check for: A) Correctly sized conduit bends B) Proper labeling of circuit breakers and disconnects C) The color of the insulation on conductors D) The manufacturer’s warranty information Answer: B
Electrical Inspector Exam Guide
Explanation: Single-line diagrams must clearly identify protective devices and disconnects for accurate inspection. Question 4. According to NFPA 70E, which level of PPE is required when working on a circuit with a calculated arc-flash boundary of 24 in? A) No PPE required B) Basic PPE (gloves only) C) Level 1 PPE D) Level 2 PPE Answer: D Explanation: A 24-inch arc-flash boundary exceeds the Level 1 limit; Level 2 PPE is required for protection. Question 5. In a commercial feeder, the calculated load is 120 kVA at 208 V. What is the minimum ampacity of the feeder conductors? A) 200 A B) 300 A C) 400 A D) 500 A Answer: B Explanation: Amperage = kVA ÷ V × √3 = 120,000 ÷ 208 × 1.732 ≈ 300 A. Conductors must be sized at or above this value. Question 6. Which overcurrent device is appropriate for protecting a 75 A motor branch circuit? A) 60 A fuse B) 80 A circuit breaker C) 100 A circuit breaker with inverse-time characteristic
Electrical Inspector Exam Guide
A) 6 AWG copper B) 8 AWG copper C) 10 AWG copper D) 12 AWG copper Answer: B Explanation: NEC Table 250.122 specifies that a 4 AWG feeder requires an 8 AWG copper EGC. Question 10. Bonding of which of the following is required to prevent potential shock hazards in a commercial rooftop HVAC installation? A) Plastic conduit B) Non-metallic raceway C) Metal water pipe serving the building D) Fiberglass insulation Answer: C Explanation: Metal water piping must be bonded to the grounding system to ensure equipotential grounding. Question 11. Which raceway is permitted for use in a wet location above grade in a commercial building? A) EMT (Electrical Metallic Tubing) B) Rigid metal conduit (RMC) C) PVC conduit D) Flexible metal conduit (FMC) Answer: C Explanation: PVC conduit is approved for wet locations; EMT and RMC are only for dry locations unless listed for wet use.
Electrical Inspector Exam Guide
Question 12. The maximum fill for a 1-in. schedule 40 PVC conduit with three 3 AWG THHN conductors is: A) 40 % B) 53 % C) 31 % D) 45 % Answer: B Explanation: NEC Table 1 in Chapter 9 allows up to 53 % fill for three conductors in a conduit. Question 13. For a commercial underground feeder, the minimum burial depth for PVC conduit under a sidewalk is: A) 6 in. B) 12 in. C) 18 in. D) 24 in. Answer: C Explanation: NEC 300.5 requires a minimum of 18 in. burial for PVC conduit under a pedestrian walkway. Question 14. Which of the following is NOT a requirement for a commercial luminaire listed for damp locations? A) Weather-resistant housing B) Corrosion-resistant mounting hardware C) Rated for immersion in water D) Properly sealed wiring entries Answer: C
Electrical Inspector Exam Guide
D) Flexible metal conduit (FMC) without fittings Answer: C Explanation: Only raceways such as RMC are permitted in Class I, Division 2 areas; NM-B and MC are not allowed. Question 18. For an emergency lighting circuit, the NEC requires that the standby source be capable of supplying at least: A) 50 % of the load for 30 min B) 75 % of the load for 90 min C) 100 % of the load for 90 min D) 125 % of the load for 60 min Answer: C Explanation: NEC 700.12 requires emergency lighting to be supplied with 100 % of the load for at least 90 minutes. Question 19. Which Florida amendment modifies the NEC requirement for the grounding electrode conductor size for services over 400 A? A) Requires a minimum 4 AWG copper GEC regardless of load B) Allows the use of aluminum GEC at half the size of copper C) Requires a separate grounding electrode for each building D) No amendment; Florida follows the NEC as written Answer: A Explanation: Florida’s amendment to Article 250 mandates a minimum 4 AWG copper GEC for services exceeding 400 A. Question 20. When inspecting a commercial switchboard, the inspector must verify that each circuit breaker is: A) Color-coded according to load type
Electrical Inspector Exam Guide
B) Labeled with the exact ampere rating of the breaker C) Labeled with the circuit’s purpose or load description D) Mounted on a separate bus bar for each phase Answer: C Explanation: NEC 408.4 requires each circuit breaker to be legibly identified for the circuit it protects. Question 21. A transformer installed in a commercial building is rated 250 kVA, 480 V primary, 277 V secondary. The secondary overcurrent protection must be at least: A) 250 A B) 300 A C) 350 A D) 400 A Answer: B Explanation: NEC 450.3 requires secondary OCPD not less than 125 % of the transformer secondary full-load current (250 kVA ÷ 277 V ≈ 904 A × 0.125 ≈ 113 A, but the standard next size is 300 A). Question 22. Which of the following is the correct minimum burial depth for a direct-buried PVC conduit carrying 120/240 V circuits under a parking lot? A) 12 in. B) 18 in. C) 24 in. D) 30 in. Answer: C
Electrical Inspector Exam Guide
C) Soldered connection D) Tape and zip-tie Answer: B Explanation: NEC 250.68(A) allows mechanical clamps listed for grounding electrodes to secure the GEC to a concrete-encased electrode. Question 26. The maximum number of conductors allowed in a 3/4-in. EMT conduit without exceeding 40 % fill is: A) 3 B) 4 C) 5 D) 6 Answer: B Explanation: Using NEC Table 1, 40 % fill for 3/4-in. EMT permits up to 4 # THHN conductors; exceeding this would surpass 40 % fill. Question 27. Which of the following is NOT a required label on a commercial panelboard’s main disconnect? A) Rated ampacity B) Voltage rating C) Manufacturer’s name D) Short-circuit rating Answer: D Explanation: NEC does not require a short-circuit rating label on the main disconnect; ampacity, voltage, and manufacturer information are required. Question 28. For a commercial building’s fire alarm system, the wiring must be installed in which type of raceway?
Electrical Inspector Exam Guide
A) PVC conduit only B) Rigid metal conduit only C) Any raceway listed for fire alarm circuits D) Flexible metal conduit only Answer: C Explanation: NEC 760.115 permits fire alarm circuits to be installed in any raceway listed for that purpose, including PVC, EMT, or RMC. Question 29. In a Class II, Division 1 hazardous location, which of the following lighting fixtures is permissible? A) Standard fluorescent fixture B) Explosion-proof LED fixture listed for Class II, Division 1 C) Non-listed recessed lighting D) Halogen downlight with glass cover Answer: B Explanation: Only fixtures listed for the specific hazardous classification are allowed; explosion-proof LED fixtures meet the requirement. Question 30. The NEC requires that all grounding electrode conductors be protected from physical damage. Which of the following provides the best protection for a GEC run through a finished basement? A) Running the GEC on the surface of the floor B) Installing the GEC in a conduit C) Securing the GEC with nylon zip-ties only D) Laying the GEC in a shallow trench without conduit Answer: B Explanation: Placing the GEC in a conduit protects it from physical damage, satisfying NEC 250.64(A).
Electrical Inspector Exam Guide
Explanation: NEC Table 250.122 indicates a 350 kVA transformer (approximately 600 A) requires a 1/0 AWG copper EGC. Question 34. Which of the following is a permissible method for joining two sections of rigid metal conduit in a commercial installation? A) Electrical tape B) Threaded coupler with proper tape on threads C) Soldering the joint D) Plastic zip-ties Answer: B Explanation: Threaded couplers are the approved method for joining RMC; tape on threads ensures a sealed connection. Question 35. A commercial kitchen requires a dedicated branch circuit for a hood exhaust fan. The minimum ampacity of the branch circuit must be: A) 15 A B) 20 A C) 30 A D) 40 A Answer: C Explanation: NEC 422.31 requires a minimum 30 A branch circuit for commercial kitchen exhaust fans. Question 36. In a commercial building, the required minimum clearance from the face of a panelboard to any combustible material is: A) 1 ft B) 2 ft
Electrical Inspector Exam Guide
C) 3 ft D) 4 ft Answer: B Explanation: NEC 110.26 requires a 2-ft clearance from the front of the panelboard to any combustible material. Question 37. Which of the following is the correct labeling requirement for a commercial receptacle that supplies a dedicated circuit for a medical imaging device? A) “General purpose” B) “Imaging equipment – 20 A” C) “Lighting only” D) No label required Answer: B Explanation: NEC 210.24 requires circuit identification; a dedicated medical imaging circuit must be labeled with its purpose and rating. Question 38. The NEC permits the use of aluminum conductors in commercial feeders provided they are: A) Bare aluminum only B) Insulated with THHN rating only C) Marked with the appropriate alloy identification and sized per Table 310.15(B)(16) D) Used only for grounding conductors Answer: C Explanation: Aluminum conductors must be identified by alloy and sized according to NEC Table 310.15(B)(16).
Electrical Inspector Exam Guide
Answer: D Explanation: NEC does not prescribe a specific location for lighting control panels; they must be readily accessible. Question 42. Which of the following is the correct procedure for testing a grounding electrode system in a commercial building? A) Perform a continuity test from the service neutral to the electrode using a multimeter B) Use a clamp-on ammeter to measure fault current C) Conduct a 3-point earth resistance test with a ground resistance tester D) Visual inspection only Answer: C Explanation: The standard method for verifying grounding electrode effectiveness is a 3-point earth resistance test. Question 43. When installing a conduit system in a commercial building’s atrium, the maximum spacing between conduit supports is: A) 3 ft B) 6 ft C) 10 ft D) 12 ft Answer: D Explanation: NEC 384.30 requires conduit supports at intervals not exceeding 10 ft for EMT, but for larger raceways like RMC, the limit is 12 ft. Question 44. Which type of cable is permitted for use in a commercial building’s interior wall cavities that are designated as “dry locations”? A) NM-B cable
Electrical Inspector Exam Guide
B) UF cable C) MC cable with metal sheath only D) Low-voltage POE cable only Answer: A Explanation: NM-B (Romex) is approved for use in dry interior locations per NEC 334.10. Question 45. A commercial building’s fire alarm system requires a dedicated grounding conductor. The size of this conductor must be at least: A) 14 AWG copper B) 12 AWG copper C) 10 AWG copper D) 8 AWG copper Answer: C Explanation: NEC 760.41(A) requires a dedicated grounding conductor of at least 10 AWG copper for fire alarm systems. Question 46. Which of the following is a required feature for a commercial switchgear assembly installed in a high-rise building? A) Transparent enclosure for visual inspection B) Integral fire-rated door with a minimum 1-hour rating C) Ability to operate at 480 V only D) No requirement for a lockable door Answer: B Explanation: High-rise switchgear must have fire-rated doors to meet fire protection requirements per NEC 110.28.
Electrical Inspector Exam Guide
Explanation: NEC 702.12 requires automatic start of emergency generators within 30 seconds of utility power loss. Question 50. Which NEC article addresses the installation of wiring methods for solar photovoltaic (PV) systems in commercial buildings? A) Article 690 B) Article 705 C) Article 710 D) Article 725 Answer: A Explanation: Article 690 covers the requirements for photovoltaic (PV) systems, including commercial installations. Question 51. For a commercial building’s rooftop air-conditioning unit, the required grounding electrode conductor must be connected to: A) The nearest water pipe only B) The building’s main grounding electrode system C) The unit’s internal ground screw only D) A separate ground rod at the rooftop Answer: B Explanation: NEC 250.130(C) requires equipment grounding conductors for rooftop units to be connected to the building’s main grounding electrode system. Question 52. Which of the following is the correct minimum size of a feeder conduit for a 4-wire, 150 A service using 4/0 AWG aluminum conductors? A) 1-in. EMT
Electrical Inspector Exam Guide
B) 1-in. RMC C) 1-1/2-in. PVC D) 2-in. EMT Answer: B Explanation: 4/0 AWG aluminum conductors require a conduit with sufficient internal diameter; 1-in. RMC meets the fill requirements per Table 1, Chapter 9. Question 53. In a commercial building, a circuit that supplies a receptacle for a medical imaging device must be protected by a GFCI. Which NEC article mandates this? A) Article 210.8(A)(3) B) Article 210.8(B)(2) C) Article 500.7(A) D) Article 625. Answer: A Explanation: NEC 210.8(A)(3) requires GFCI protection for receptacles serving medical imaging equipment. Question 54. Which of the following is a required feature of a commercial building’s exit sign illumination system? A) Must be powered exclusively by AC mains B) Must have a battery backup with at least 90 minutes of operation C) Must use incandescent lamps only D) Must be mounted at a minimum height of 8 ft Answer: B Explanation: NEC 700.12 requires exit signs to have a battery backup capable of at least 90 minutes of illumination.
