InterNACHI Electrical Systems & Safety 4 — Questions and Answers
Question 1: An arc-fault circuit interrupter (AFCI) breaker is designed to protect against which specific hazard?
- Ground faults from contact with water
- Overcurrent from too many devices on one circuit
- Electrical arcing that can ignite nearby combustibles (Correct answer)
- Voltage surges from lightning strikes
Correct answer: Electrical arcing that can ignite nearby combustibles
AFCI breakers detect the unique electrical signature of arcing faults, which can cause fires in walls or other concealed locations.
Question 2: What is the correct term for the main disconnect switch that cuts power to the entire home's electrical system?
- Load center
- Service entrance switch
- Main breaker (Correct answer)
- Transfer switch
Correct answer: Main breaker
The main breaker is the primary overcurrent protection device that disconnects all power to the home's branch circuits and feeders.
Question 3: A home inspector finds knob-and-tube wiring in an attic that has been covered with insulation. Why is this a concern?
- Knob-and-tube wiring requires ventilation to dissipate heat, and insulation prevents this (Correct answer)
- Insulation causes the wire insulation to degrade chemically
- Covering knob-and-tube wiring automatically voids the homeowner's insurance
- Rodents are attracted to insulation near older wiring
Correct answer: Knob-and-tube wiring requires ventilation to dissipate heat, and insulation prevents this
Knob-and-tube wiring relies on open air for heat dissipation, and burying it in insulation can cause dangerous overheating.
Question 4: What does the term 'service drop' refer to in a residential electrical inspection?
- The voltage drop across the main service conductors
- The overhead utility conductors from the pole to the weatherhead (Correct answer)
- The conduit running from the meter to the main panel
- A sudden loss of power from the utility company
Correct answer: The overhead utility conductors from the pole to the weatherhead
The service drop refers to the overhead conductors supplied by the utility company that run from the utility pole to the customer's weatherhead.
Question 5: Which of the following is a common defect found with older two-prong (ungrounded) receptacles?
- They are rated for less amperage than modern receptacles
- They have no equipment grounding conductor, offering no protection against faults (Correct answer)
- They are only rated for 110 volts
- They lack a neutral conductor
Correct answer: They have no equipment grounding conductor, offering no protection against faults
Two-prong receptacles lack the grounding conductor, meaning there is no path to safely divert fault current away from users or equipment.
Question 6: What is the minimum burial depth for UF (underground feeder) cable supplying a residential outdoor circuit?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC requires UF cable to be buried a minimum of 12 inches deep for residential branch circuits, though RMC conduit allows shallower burial.
Question 7: A home inspector observes a sub-panel installed in a bathroom. What is the concern?
- Sub-panels are not permitted in bathrooms due to moisture hazard (Correct answer)
- Sub-panels require a minimum 100-amp service that bathrooms cannot support
- Bathroom sub-panels must use GFCI breakers for all circuits
- There is no concern as long as the panel is NEMA 4X rated
Correct answer: Sub-panels are not permitted in bathrooms due to moisture hazard
NEC prohibits the installation of electrical panels in bathrooms because of the elevated moisture and shock hazard in that environment.
InterNACHI Electrical Systems & Safety 4
An arc-fault circuit interrupter (AFCI) breaker is designed to protect against which specific hazard?