Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsHard
An electrician is installing a new 20-amp, 120-volt circuit for a dedicated refrigerator outlet in a commercial kitchen. The circuit will pass through a 2-hour fire-rated wall. What is the minimum fire rating required for the firestop system used to seal the penetration around the raceway?
- A1-hour fire rating
- B2-hour fire rating
- C3-hour fire rating
- D1 1/2-hour fire rating
Show answer & explanationAnswer & explanation
Correct answer: B. 2-hour fire rating
According to NEC 300.21, electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be so made that the possible spread of fire or products of combustion will not be substantially increased. This implies that penetrations through fire-rated walls must maintain the fire rating of the wall. Therefore, a 2-hour fire-rated wall requires a firestop system with at least a 2-hour fire rating.
Why the other options are wrong
- A. Incorrect. A 1-hour fire rating would compromise the integrity of the 2-hour fire-rated wall.
- C. Incorrect. While a 3-hour rating would provide sufficient protection, it is not the *minimum* required; a 2-hour rating is the minimum to match the wall.
- D. Incorrect. A 1 1/2-hour fire rating is insufficient for a 2-hour fire-rated wall.
Firestop System Rating
The fire resistance rating required for materials or assemblies used to seal penetrations through fire-rated walls, floors, or ceilings.
- Must match or exceed the fire rating of the penetrated assembly.
- Prevents spread of fire and smoke.
- NEC 300.21 addresses this general requirement.
Memory trick: Match the Wall's Hour, or More Power.