E2 Systems and Equipment 3 — Questions and Answers
Question 1: When inspecting a commercial fire alarm system, the inspector notes that the NAC (Notification Appliance Circuit) uses Class B wiring. What distinguishes Class B from Class A wiring?
- Class B uses shielded cable; Class A does not
- Class B has no return path and a single open fault can disable devices beyond the fault (Correct answer)
- Class B requires 2-hour fire-rated cable throughout
- Class B allows wireless devices only
Correct answer: Class B has no return path and a single open fault can disable devices beyond the fault
Class B (Style B) NAC circuits do not loop back to the panel, so a single wire break can disable all devices beyond that point.
Question 2: A 480V, 3-phase transformer feeding a 120/208V panelboard in a commercial building must have its secondary protected at no more than what percentage of the transformer's rated secondary current when using a standard fuse?
- 100%
- 125% (Correct answer)
- 250%
- 300%
Correct answer: 125%
NEC 450.3(B) allows secondary overcurrent protection up to 125% of the transformer's rated secondary current for a supervised installation.
Question 3: In a commercial occupancy, the NEC requires that luminaires installed in a clothes closet must maintain what minimum clearance from the storage area?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC 410.16(C) requires incandescent and LED luminaires to maintain at least 12 inches of clearance from the defined storage space in closets.
Question 4: An inspector finds that a commercial building's panelboard has all circuit breakers fully populated with no spare spaces. Under the NEC, this is:
- Acceptable if the load is under 80% of panel capacity (Correct answer)
- A violation — all panelboards must have at least 20% spare capacity
- Not a code violation but a violation of NFPA 70E
- Acceptable only if a written load calculation is posted
Correct answer: Acceptable if the load is under 80% of panel capacity
The NEC does not require spare breaker spaces in a panelboard; 100% population is permitted as long as the calculated load does not exceed the panelboard rating.
Question 5: For a commercial elevator installation, the NEC requires a separate branch circuit for which of the following?
- The elevator motor and cab lighting on the same circuit
- The elevator cab lighting, receptacle, and ventilation on a separate circuit from the motor (Correct answer)
- The hoistway lighting only
- No separate circuit is required — one feeder may serve all elevator loads
Correct answer: The elevator cab lighting, receptacle, and ventilation on a separate circuit from the motor
NEC 620.22 requires a separate branch circuit for elevator car lighting, receptacle outlets, and ventilation, independent of the elevator motor circuit.
Question 6: When inspecting a commercial pool pump motor installation, which bonding requirement is unique compared to standard motor installations?
- The motor frame must be bonded to the equipment grounding conductor only
- All metal parts within 5 feet of the pool, including the motor, must be bonded together with a solid copper conductor no smaller than 8 AWG (Correct answer)
- The pool pump motor requires a dedicated grounding rod
- Bonding is not required if GFCI protection is provided
Correct answer: All metal parts within 5 feet of the pool, including the motor, must be bonded together with a solid copper conductor no smaller than 8 AWG
NEC 680.26 requires all metal parts within 5 feet of the pool water surface to be bonded together using a solid copper bonding conductor not smaller than 8 AWG solid.
Question 7: A commercial building's uninterruptible power supply (UPS) system has a bypass switch. The NEC requires this bypass to:
- Be rated only for the UPS input current
- Allow maintenance without de-energizing the critical load (Correct answer)
- Disconnect the battery bank automatically
- Be located in a separate room from the UPS
Correct answer: Allow maintenance without de-energizing the critical load
NEC 700.3(F) requires UPS systems serving emergency loads to have a bypass that allows maintenance without interrupting power to the critical load.
E2 Systems and Equipment 3
When inspecting a commercial fire alarm system, the inspector notes that the NAC (Notification Appliance Circuit) uses Class B wiring.
What distinguishes Class B from Class A wiring?