What is the minimum size for single conductors used in a fire alarm system?

In fire alarm systems, the minimum size for single conductors is 18 AWG (American Wire Gauge). This size is commonly specified to ensure adequate performance and safety for the components of the fire alarm system. A conductor's diameter affects its current-carrying capacity, resistance to voltage drop, and overall reliability in transmitting signals.

Using 18 AWG wire strikes a balance between providing sufficient current-carrying capability and maintaining flexibility for installation within the system. It is also consistent with various codes and standards that govern fire alarm system installations, ensuring that the wiring can handle the required loads while minimizing the risk of overheating or signal loss.

While the other options presented are different wire sizes, they do not meet the minimum requirements established by standard practices for fire alarm systems. Conductors that are too small might compromise the functionality and safety of the alarm system, potentially leading to failures in critical moments.