What is the minimum conductor size for single conductors in fire rated cable installations?

• A. 26 AWG
• B. 18 AWG
• C. 20 AWG
• D. 22 AWG

Answer: (B)

In fire-rated cable installations, the conductor size must be large enough to carry the necessary signaling current and to remain compatible with the fire-rating of the cable assembly. The standard minimum for single conductors in these systems is 18 AWG. This size provides adequate current-carrying capability and mechanical robustness while still fitting within typical fire-rated cables and terminations. Smaller conductors (higher AWG numbers) would raise the risk of overheating and may not be covered by the listing for the fire-rated cable, potentially compromising the assembly’s fire performance. So, 18 AWG is the smallest size that meets the requirement.