Do mineral cables need to be placed in cable trays

Mineral-insulated (MI) cables do not strictly require cable trays; they can be installed in trays, conduits, or directly supported, depending on the application and code requirements.

Installation Flexibility

MI cables are highly durable and fire-resistant, making them suitable for direct installation without trays in many applications. According to the Cable Tray Institute, MI cables have been permitted in Class I, Division 1 and Class II, Division 1 hazardous locations since the 1962 NEC and can be installed in cable trays if desired, but trays are not mandatory . They can also provide fire protection when installed without trays, which is one of their key advantages.

When Cable Trays Are Used

Cable trays are often used for MI cables to:

• Organize and support multiple cables in industrial or commercial installations
• Maintain spacing and separation between different cable types
• Facilitate future maintenance or cable additions
• Ensure compliance with ampacity and heat dissipation requirements Cable trays must comply with NEC Article 318 regarding fill, spacing, grounding, and segregation of cable types. MI cables installed in trays must also have approved termination fittings for the location .

Considerations

• In hazardous locations, MI cables can be installed in trays, but the tray must only contain cable types permitted for that classification .
• MI cables are robust enough to be directly supported on brackets or hangers without a tray, especially in vertical runs or where fire protection is critical.
• Using a tray may affect ampacity due to heat accumulation, so spacing and tray type should be considered .

Summary

While MI cables can be installed in cable trays, they do not require them. The choice depends on installation convenience, code compliance, environmental conditions, and maintenance considerations. Trays are optional support systems rather than a mandatory requirement for MI cable installations .