InterNACHI - International Association of Certified Home Inspectors Electrical Systems and Safety Questions and Answers — Questions and Answers
Question 1: An inspector opens a main service panel and observes two white neutral conductors terminated under a single screw on the neutral bus bar. Which of the following is the most accurate description of this defect?
- Over-fused circuit
- Reversed polarity
- A bonded neutral bus
- Double-tapped neutrals (Correct answer)
Correct answer: Double-tapped neutrals
This condition is commonly called "double-tapped neutrals." Most panelboard lugs are designed for only one conductor. Terminating two wires under one screw can lead to a loose connection over time due to expansion and contraction, which can cause overheating, arcing, and a potential fire hazard.
Question 2: According to the National Electrical Code (NEC), what is the minimum required clear working space in front of a residential electrical panel?
- 24 inches deep and 24 inches wide
- 30 inches deep and 36 inches wide
- 36 inches deep and 30 inches wide (Correct answer)
- 48 inches deep and 48 inches wide
Correct answer: 36 inches deep and 30 inches wide
The NEC Section 110.26 requires a clear working space of at least 36 inches of depth in front of the panel, 30 inches of width (or the width of the equipment, whichever is greater), and a height of 6.5 feet. This space allows a service person to work safely and provides an escape path in an emergency.
Question 3: While inspecting a home built in 1935, an inspector observes electrical wiring consisting of single insulated conductors supported by white ceramic knobs and protected by ceramic tubes where they pass through wood framing. What is a primary safety concern associated with this type of wiring?
- The copper conductors are typically undersized for modern loads.
- This wiring system is inherently prone to voltage surges.
- It was designed to dissipate heat in open air and becomes a fire hazard if covered by thermal insulation. (Correct answer)
- The ceramic components can release hazardous materials as they age.
Correct answer: It was designed to dissipate heat in open air and becomes a fire hazard if covered by thermal insulation.
This describes knob-and-tube wiring. A major hazard is that the system was designed for heat to dissipate into open air. When modern thermal insulation is blown or packed around it, the wires can overheat, leading to the breakdown of their insulation and creating a significant fire risk. Other concerns include the lack of a ground wire and damage from improper modifications.
Question 4: In a modern home, which of the following locations requires receptacles to have BOTH arc-fault (AFCI) and ground-fault (GFCI) protection?
- Hallways and closets
- Attached garages
- Bedrooms
- Kitchens and laundry areas (Correct answer)
Correct answer: Kitchens and laundry areas
The National Electrical Code requires AFCI protection for 15- and 20-amp branch circuits in most living areas of a dwelling, including kitchens and laundry rooms, to protect against fire hazards from arcing. It also requires GFCI protection for receptacles in locations with a high risk of shock, such as those near water in kitchens and laundry areas. Therefore, these locations require both forms of protection.
Question 5: What is the primary safety purpose of bonding the metallic gas piping system to the electrical system's grounding electrode system?
- To use the gas pipe as a primary grounding electrode for the electrical system.
- To ensure that any electrical fault energizes the gas meter, causing it to shut off the gas flow.
- To create an equipotential plane, preventing a voltage difference between the gas pipe and other grounded objects during a fault or lightning strike. (Correct answer)
- To allow low-voltage appliance control signals to travel through the home's piping.
Correct answer: To create an equipotential plane, preventing a voltage difference between the gas pipe and other grounded objects during a fault or lightning strike.
Bonding connects all metallic systems (gas pipes, water pipes, etc.) to the electrical ground to keep them at the same electrical potential. In the event of a lightning strike or an electrical fault that energizes the piping, this connection prevents a dangerous voltage difference from developing between the pipe and another grounded appliance, which could cause an arc and potential fire or explosion. The gas pipe must be bonded, but it is prohibited from being used as the grounding electrode itself.
Question 6: An inspector observes an overhead service drop that is attached to a mast on the roof. The conductors pass within 2 feet horizontally of the side of a window that is designed to be opened. What should the inspector report?
- This is an acceptable installation as long as the conductors are more than 8 feet above the roof surface.
- The conductors must be at least 10 feet away from any window, regardless of whether it opens.
- This is a safety hazard, as a minimum clearance of 3 feet is required from the sides of operable windows. (Correct answer)
- The clearance is adequate, as the requirement is only for conductors running directly above or below a window.
Correct answer: This is a safety hazard, as a minimum clearance of 3 feet is required from the sides of operable windows.
NEC Section 230.9(A) requires overhead service conductors to maintain a clearance of at least 3 feet from the sides, top, and bottom of windows that can be opened. This is a critical safety rule to prevent accidental contact with energized conductors by a person or an object passed through the window. An inspector should report this as a safety hazard.
InterNACHI - International Association of Certified Home Inspectors Electrical Systems and Safety Questions and Answers
An inspector opens a main service panel and observes two white neutral conductors terminated under a single screw on the neutral bus bar.
Which of the following is the most accurate description of this defect?