Master Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsMedium
A master electrician is installing a communication system in a commercial building. The system includes a power-limited fire alarm circuit that extends beyond the building. According to NEC, what is the minimum required separation distance between the exposed communication cables and exposed electric light or power conductors that are not in a raceway or cable, if the power conductors operate at 300 volts or less?
- A6 inches
- B12 inches
- C4 inches
- D2 inches
Show answer & explanationAnswer & explanation
Correct answer: C. 4 inches
NEC Section 805.133(A)(1)(c) specifies that exposed communication cables must be separated by a minimum of 4 inches from exposed electric light or power conductors operating at 300 volts or less, unless the power conductors are in a raceway or cable. This separation prevents induction and potential contact hazards.
Why the other options are wrong
- A. 6 inches is a larger separation than the minimum required, though it would be compliant.
- B. 12 inches is significantly more than the minimum required and typically applies to higher voltage power conductors or specific outdoor installations.
- D. 2 inches is insufficient separation; the NEC requires a greater distance for safety.
Communication/Power Cable Separation
The minimum required separation distance between exposed communication cables and exposed electric light or power conductors (300V or less, not in raceway/cable) as per the NEC.
- Prevents electrical interference and hazards.
- Applies to exposed conductors.
- NEC Article 805 covers communication systems.
Memory trick: Communication and power, exposed and bare, four inches minimum, safety's care!