InterNACHI Electrical Systems & Safety 2 — Questions and Answers
Question 1: What is the minimum clearance required between the top of a residential electrical panel and the ceiling?
- 3 feet
- 6 feet (Correct answer)
- 6.5 feet
- No minimum required
Correct answer: 6 feet
NEC requires a minimum headroom clearance of 6 feet above electrical panels to allow safe working access.
Question 2: A home inspector observes double-tapped circuit breakers in a panel. What does this mean?
- Two wires are connected to a single breaker terminal not rated for it (Correct answer)
- The panel has twice the normal capacity
- A tandem breaker is properly installed
- The panel uses a dual-bus design
Correct answer: Two wires are connected to a single breaker terminal not rated for it
Double-tapping means two conductors are connected to a breaker terminal designed for only one, which is a safety defect unless the breaker is listed for two conductors.
Question 3: Which wire color in a standard 120V residential circuit is the grounded conductor?
- Black
- White (Correct answer)
- Green
- Red
Correct answer: White
The white wire is the grounded (neutral) conductor in a standard 120V residential circuit.
Question 4: What does an open ground condition mean at a three-prong receptacle?
- The neutral wire is disconnected
- The hot wire is reversed with the neutral
- The ground wire is missing or not connected (Correct answer)
- The receptacle has too many devices plugged in
Correct answer: The ground wire is missing or not connected
An open ground means the equipment grounding conductor is absent or disconnected, leaving no path for fault current.
Question 5: InterNACHI inspectors should report aluminum branch circuit wiring (post-1972) because it poses what risk?
- It corrodes faster than copper in wet environments
- Connections can loosen over time causing overheating and fire (Correct answer)
- It has lower ampacity than copper of the same gauge
- It is not permitted in any residential application
Correct answer: Connections can loosen over time causing overheating and fire
Aluminum wiring connections can oxidize and loosen, increasing resistance and creating a fire hazard at termination points.
Question 6: What is the standard amperage rating for a 240V dryer circuit in a residential home?
- 15 amps
- 20 amps
- 30 amps (Correct answer)
- 50 amps
Correct answer: 30 amps
A 240V electric dryer circuit is typically protected by a 30-amp double-pole breaker per NEC requirements.
Question 7: A home inspector finds a Federal Pacific Stab-Lok electrical panel. What should the inspector note?
- It is a high-quality panel with enhanced safety features
- These panels have a documented history of breaker failure and fire risk (Correct answer)
- It requires immediate red-tag condemnation
- It is only a concern if the home is over 50 years old
Correct answer: These panels have a documented history of breaker failure and fire risk
Federal Pacific Stab-Lok panels have a well-documented history of failing to trip under overcurrent conditions, posing a fire hazard.
InterNACHI Electrical Systems & Safety 2
What is the minimum clearance required between the top of a residential electrical panel and the ceiling?