CMI Electrical Systems Inspection 2 — Questions and Answers
Question 1: Why do home inspectors flag Federal Pacific Electric (FPE) Stab-Lok panels during inspections?
- They are modern, high-efficiency panels that exceed current code
- They use fuses instead of circuit breakers, requiring a licensed upgrade
- Their breakers have been documented to fail to trip under overload conditions, creating a fire risk (Correct answer)
- They require three-phase power that is unusual in residential settings
Correct answer: Their breakers have been documented to fail to trip under overload conditions, creating a fire risk
FPE Stab-Lok breakers have been documented to fail to trip when overloaded, leaving circuits unprotected and posing a significant fire hazard.
Question 2: What is the primary inspection concern when 15-amp branch circuits in a home are wired with single-strand aluminum instead of copper?
- Aluminum conducts electricity too efficiently, causing general circuit overheating
- Aluminum wiring is too large in diameter to fit standard junction boxes
- Aluminum cannot be used for 120-volt circuits under any NEC edition
- Aluminum connections can loosen over time and overheat at devices and terminations not listed for aluminum conductors (Correct answer)
Correct answer: Aluminum connections can loosen over time and overheat at devices and terminations not listed for aluminum conductors
Aluminum expands and contracts more than copper with temperature changes, causing connections to loosen at terminals not rated for aluminum, leading to overheating and fire risk.
Question 3: When inspecting the service entrance cable at the exterior of a home, which combination of items should the inspector evaluate?
- The cable's amperage label and color coding only
- Weatherhead height, drip loop presence, clearance from windows and doors, and proper sealing at the entry point (Correct answer)
- Only whether the cable is in conduit or open air
- The manufacturer's label on the cable and cable age
Correct answer: Weatherhead height, drip loop presence, clearance from windows and doors, and proper sealing at the entry point
A complete service entrance inspection checks weatherhead height above grade, a drip loop to prevent water ingress, NEC-required clearances from openings, and a sealed penetration through the structure.
Question 4: A home inspector finds 14 AWG wiring (15-amp capacity) protected by a 30-amp circuit breaker. What deficiency is present?
- The breaker is properly sized; 14 AWG can handle 30 amps intermittently
- Under-fusing: the breaker is too small for the wire gauge installed
- This configuration is acceptable for circuits exceeding 20 feet in length
- Over-fusing: the breaker rating far exceeds the wire's safe ampacity, creating a fire hazard (Correct answer)
Correct answer: Over-fusing: the breaker rating far exceeds the wire's safe ampacity, creating a fire hazard
Over-fusing occurs when overcurrent protection (the breaker) is rated higher than the wire it protects, allowing the wire to overheat and ignite before the breaker trips.
Question 5: Per NEC 110.26(A)(1), what minimum depth of clear working space is required in front of a residential electrical panel (0–150V to ground)?
- 18 inches
- 24 inches
- 36 inches (Correct answer)
- 30 inches
Correct answer: 36 inches
NEC 110.26(A)(1) requires at least 36 inches of clear working depth in front of electrical equipment operating at 0–150V to ground to allow safe access for electricians.
Question 6: Under which circumstances should a home inspector recommend immediate further evaluation of a residential electrical panel by a licensed electrician?
- Only when the panel brand is identified as a recalled product
- Whenever the panel is located in a garage or utility room
- When the inspector observes double-tapping, improper breaker sizing, evidence of overheating, or other unsafe conditions (Correct answer)
- Only when the panel is more than 40 years old
Correct answer: When the inspector observes double-tapping, improper breaker sizing, evidence of overheating, or other unsafe conditions
Defects such as double-tapped breakers, mismatched wire/breaker sizes, and signs of overheating indicate active safety hazards that require prompt professional correction.
Question 7: What is 'backstabbing' when referring to electrical receptacles and switches, and why is it a concern?
- Installing a receptacle in an inverted orientation, violating NEC conventions
- Using two separate circuits to power a single duplex outlet
- Running unprotected cable through a wall cavity without conduit
- Inserting conductors into the push-in release-hole terminals rather than using the screw terminals, which can cause loose, arcing connections (Correct answer)
Correct answer: Inserting conductors into the push-in release-hole terminals rather than using the screw terminals, which can cause loose, arcing connections
Push-in (stab-in) terminals on the back of devices can loosen over time, leading to high-resistance connections, overheating, and arcing that may cause fires or outlet failure.
CMI Electrical Systems Inspection 2
Why do home inspectors flag Federal Pacific Electric (FPE) Stab-Lok panels during inspections?