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Low-voltage and fire protection cable trays are shared

Fiber and communications infrastructure knowledge brief Published 29 Mar 2026

Use this reference to prepare product questions for BAGYOU FIBRE. Check interfaces, capacity, protection and installation requirements against the current product documentation.

Low-voltage fire protection cables (PLFA circuits) can be shared with other low-voltage or communication cables in the same tray if installed according to code, but physical separation and protection are strongly recommended.

Regulatory Guidance

According to the National Electrical Code (NEC), power-limited fire alarm circuits (PLFA) are generally permitted to share a cable tray or raceway with communications circuits, as both are low-voltage systems (NEC 760. 139). This includes Class 2 and Class 3 circuits, which can coexist in the same tray provided proper installation methods are followed.

However, high-voltage circuits must remain segregated from low-voltage fire alarm circuits to prevent induced voltages or interference.

Practical Considerations

Even though code allows sharing, best practices recommend physical separation to protect the fire alarm system from mechanical damage and electromagnetic interference (EMI). Shared trays can expose fire alarm cables to accidental cuts, pinching, or stress during maintenance of data or communication cables.

EM

I from nearby data cables, especially unshielded twisted pair (UTP) Ethernet, can degrade fire alarm signaling or network performance.

Recommended Measures

Use divider brackets or compartmentalized trays to separate fire alarm and data cables within the same tray. Maintain minimum spacing (commonly 6 inches) between fire alarm and other low-voltage circuits when dividers are not used. Secure cables properly with metal supports or approved cable ties to prevent movement and maintain spacing.

Follow manufacturer and local code requirements for fire-resistant or enhanced fire-resisting cables in critical areas.

Summary

While sharing cable trays is allowed for low-voltage fire protection and communication circuits, it is frowned upon in practice due to safety and reliability concerns. Using dedicated pathways or physical separation within shared trays ensures the integrity of life safety systems, reduces EMI, and simplifies inspection and maintenance.

Low-voltage and fire protection cable trays are shared - BAGYOU FIBRE NETWORKS [PDF]

Low-voltage and fire protection cable trays are shared

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Technical note

This reference is intended for preliminary fiber and communications infrastructure research. Optical interface, fiber type, port or core capacity, electrical input and output, enclosure protection, cooling, installation limits and applicable standards must be verified for the specific project.

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