CMI Electrical Systems Inspection 1 — Questions and Answers
Question 1: According to NEC 230.79, what is the minimum service ampacity required for a single-family dwelling?
- 60 amps
- 100 amps (Correct answer)
- 150 amps
- 200 amps
Correct answer: 100 amps
NEC 230.79 requires a minimum 100-amp service for single-family dwellings, though 200 amps is the modern standard for new construction.
Question 2: Which type of wiring commonly found in homes built before 1950 is flagged during inspections primarily because it lacks a ground conductor?
- Romex (NM-B)
- Knob-and-tube wiring (Correct answer)
- Aluminum branch-circuit wiring
- BX armored cable
Correct answer: Knob-and-tube wiring
Knob-and-tube wiring has only two conductors (hot and neutral) with no ground wire, and its cloth insulation is often degraded, making it a safety concern.
Question 3: Under current NEC standards, bedrooms must be protected by which device to guard against arc-fault-initiated fires?
- GFCI outlets at the first location in the circuit only
- Standard 15-amp breakers with surge protection
- AFCI circuit breakers or combination AFCI devices (Correct answer)
- Double-pole breakers sized at 20 amps
Correct answer: AFCI circuit breakers or combination AFCI devices
The NEC requires Arc Fault Circuit Interrupter (AFCI) protection for bedroom circuits because arcing in wiring or cords is a leading cause of residential fires.
Question 4: A home inspector observes two conductors connected under a single breaker terminal in the main panel. What deficiency does this represent?
- Two circuits properly sharing an appropriately rated breaker
- A 240V circuit correctly wired with both legs to one terminal
- A panel that has been properly upgraded to increase capacity
- Double-tapping: two conductors under a terminal not listed for that configuration, creating a fire and fault risk (Correct answer)
Correct answer: Double-tapping: two conductors under a terminal not listed for that configuration, creating a fire and fault risk
Double-tapping means two wires share a breaker terminal not rated for dual conductors, which can cause loose connections, arcing, and overheating.
Question 5: Per NEC 240.24, the center of the operating handle of a circuit breaker in the highest position must not exceed what height from the floor?
- 5 feet 6 inches
- 6 feet 0 inches
- 6 feet 7 inches (Correct answer)
- 7 feet 0 inches
Correct answer: 6 feet 7 inches
NEC 240.24(A) limits the center of the grip of the operating handle to a maximum of 6 feet 7 inches (2.0 m) above the floor so breakers remain accessible.
Question 6: When inspecting bathroom receptacle outlets, which statement best describes the GFCI protection requirement under current NEC?
- GFCI is required only within 3 feet of the sink
- GFCI is required only for outlets adjacent to the bathtub
- GFCI is required only within 6 feet of any water source
- All bathroom receptacle outlets require GFCI protection regardless of distance from water (Correct answer)
Correct answer: All bathroom receptacle outlets require GFCI protection regardless of distance from water
The NEC requires GFCI protection for all receptacle outlets in bathrooms regardless of their location within the room.
Question 7: What is the correct copper wire gauge for a 20-amp dedicated circuit, such as a kitchen small-appliance circuit?
- 14 AWG
- 10 AWG
- 8 AWG
- 12 AWG (Correct answer)
Correct answer: 12 AWG
12 AWG copper wire is rated for 20-amp circuits; using 14 AWG (rated 15 amps) on a 20-amp breaker would be an over-fusing hazard.
CMI Electrical Systems Inspection 1
According to NEC 230.79, what is the minimum service ampacity required for a single-family dwelling?