Journeyman Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsHard
A technician is installing a fire alarm control panel (FACP) in a commercial occupancy. The power-limited fire alarm (PLFA) circuit conductors are run in a raceway. What is the minimum permissible separation required between these PLFA circuit conductors and Class 1, nonpower-limited fire alarm (NPLFA), or medium-power network-powered broadband communications circuits in the same raceway, according to NEC?
- ANo minimum separation is required if all conductors are insulated for the maximum voltage of any circuit in the raceway.
- B0.25 inches (6.4 mm)
- C1.0 inches (25.4 mm)
- D0.5 inches (12.7 mm)
Show answer & explanationAnswer & explanation
Correct answer: B. 0.25 inches (6.4 mm)
NEC 760.136(D) requires that power-limited fire alarm (PLFA) circuit conductors be separated from Class 1, nonpower-limited fire alarm (NPLFA), or medium-power network-powered broadband communications circuits by a barrier, or by a minimum of 0.25 inches (6.4 mm) if no barrier is used, within the same raceway. This prevents interference and ensures proper operation of safety systems.
Why the other options are wrong
- A. While insulation is important, a physical separation or barrier is specifically required to prevent interference and ensure safety for these critical circuits, as per the NEC.
- C. 1.0 inches is not the specified minimum for this application.
- D. 0.5 inches is not the specified minimum for this application.
PLFA Circuit Separation
Power-limited fire alarm (PLFA) circuit conductors must maintain a minimum 0.25-inch separation or use a barrier when run with Class 1, NPLFA, or medium-power network-powered broadband communications circuits within the same raceway.
- Applies to PLFA circuits (NEC Article 760).
- Prevents electrical interference and ensures reliability.
- Separation is 0.25 inches without a barrier.
Memory trick: Fire alarm wires: Keep 'Quarter-inch' apart for clear signals.