InterNACHI Electrical Systems & Safety 5 — Questions and Answers
Question 1: What is the primary purpose of an equipment grounding conductor (EGC) in a branch circuit?
- To carry the return current of normal circuit operation
- To provide a low-impedance fault path back to the source (Correct answer)
- To balance the load between hot and neutral conductors
- To reduce electromagnetic interference in the circuit
Correct answer: To provide a low-impedance fault path back to the source
The EGC provides a low-impedance path for fault current so that overcurrent devices trip quickly and safely during a ground fault.
Question 2: Which of the following panels is commonly flagged by home inspectors due to recalled breakers and a history of fires?
- Square D QO series
- Siemens ITE
- Zinsco (Sylvania) panels (Correct answer)
- Cutler-Hammer panels
Correct answer: Zinsco (Sylvania) panels
Zinsco (also sold as Sylvania) panels have been documented to have breakers that weld shut and fail to trip, posing a significant fire hazard.
Question 3: When a home inspector identifies reversed polarity at a receptacle, what does that mean?
- The hot and neutral wires are connected to the wrong terminals (Correct answer)
- The ground and neutral wires have been swapped
- The receptacle is wired in a series rather than parallel circuit
- The receptacle has too high a voltage for its rating
Correct answer: The hot and neutral wires are connected to the wrong terminals
Reversed polarity means the hot wire is connected to the neutral terminal and vice versa, which can make some appliances dangerous even when switched off.
Question 4: What is a 'bootleg ground' (also called a false ground) in a receptacle?
- A ground wire run externally along the baseboard
- A jumper wire connecting the neutral terminal to the ground terminal (Correct answer)
- An improper ground installed in a two-wire circuit using EMT conduit
- A ground rod driven outside the foundation without bonding
Correct answer: A jumper wire connecting the neutral terminal to the ground terminal
A bootleg ground uses a jumper between the neutral and ground slots, making a tester show 'correct' but providing no real shock protection.
Question 5: How many circuits are permitted to share a single neutral conductor in a multi-wire branch circuit (MWBC)?
- One circuit per neutral
- Two circuits sharing one neutral on different hot legs (Correct answer)
- Three circuits sharing one neutral on the same hot leg
- Unlimited circuits if the neutral is oversized
Correct answer: Two circuits sharing one neutral on different hot legs
An MWBC allows two 120V circuits on opposite hot legs to share one neutral, as the neutral currents cancel each other out under load.
Question 6: What does 'service ampacity' refer to when a home inspector evaluates an electrical service?
- The voltage rating of the utility transformer supplying the home
- The maximum current the service entrance conductors and main breaker are rated to carry (Correct answer)
- The total wattage of all appliances connected to the panel
- The number of circuit breaker slots available in the panel
Correct answer: The maximum current the service entrance conductors and main breaker are rated to carry
Service ampacity is the rated capacity of the service entrance conductors and main overcurrent protection, commonly 100A, 150A, or 200A for residential homes.
Question 7: A home inspector finds that junction box covers are missing throughout the home. What hazard does this present?
- It allows moisture to enter the wiring, causing corrosion
- It exposes live wire connections and increases the risk of shock or arc faults (Correct answer)
- It reduces the ampacity of the circuits by increasing heat dissipation
- It is only a concern in bathrooms and kitchens
Correct answer: It exposes live wire connections and increases the risk of shock or arc faults
Open junction boxes expose energized wire splices to accidental contact, creating shock and arc flash hazards for occupants.
InterNACHI Electrical Systems & Safety 5
What is the primary purpose of an equipment grounding conductor (EGC) in a branch circuit?