The wiring between the fire alarm control unit and the control appliance or relay for an emergency function cannot be of which class?

The wiring between the fire alarm control unit and the control appliance or relay for an emergency function cannot be of which class?

• A. Class A
• B. Class B
• C. Class C
• D. Class D

Answer: (C)

Emergency-function wiring must stay reliable and supervised so the control appliances or relays operate even if part of the circuit is damaged. Class A circuits are looped, which provides fault tolerance so a single fault doesn’t take the whole path down. Class B circuits are also designed for reliable signaling, with proper supervision. Class C, however, does not meet the life-safety requirements for these emergency controls because it lacks the necessary fault tolerance or supervision. That’s why the connection between the fire alarm control unit and an emergency-function device cannot be Class C.

Emergency-function wiring must stay reliable and supervised so the control appliances or relays operate even if part of the circuit is damaged. Class A circuits are looped, which provides fault tolerance so a single fault doesn’t take the whole path down. Class B circuits are also designed for reliable signaling, with proper supervision. Class C, however, does not meet the life-safety requirements for these emergency controls because it lacks the necessary fault tolerance or supervision. That’s why the connection between the fire alarm control unit and an emergency-function device cannot be Class C.