What is the fire rating of ordinary fire-resistant cable trays

Ordinary fire-resistant cable trays typically have fire resistance ratings of E30, E60, or E90, indicating the number of minutes they maintain circuit integrity under fire conditions.

Fire Resistance Ratings

Fire-resistant cable trays are designed to maintain the functionality of electrical circuits during a fire, ensuring critical systems like emergency lighting, alarms, and smoke extractors continue to operate. The most common ratings are:

• E30: Maintains circuit integrity for 30 minutes
• E60: Maintains circuit integrity for 60 minutes
• E90: Maintains circuit integrity for 90 minutes, often used in industrial or high-risk environments

These ratings are determined by standardized fire tests, such as DIN 4102-12, which involve placing the complete cable tray system—including cables, supports, and accessories—inside an oven and exposing it to temperatures up to 1000°C for the specified duration . The system passes the test if the cables remain functional and the tray maintains structural integrity throughout the fire exposure.

Factors Affecting Fire Resistance

The actual fire performance of a cable tray system depends on several variables:

• Tray material and thickness: Steel or coated metal trays generally perform better than unprotected aluminum or plastic trays
• Cable loading and packing density: Overloaded trays may reduce fire resistance
• Mounting orientation and support spacing: Proper installation ensures maximum fire performance
• Joint detailing and accessories: Fireproof cleats, wraps, or coatings can enhance resistance

Practical Considerations

• E30 trays are suitable for low-risk or secondary circuits.
• E60 trays are commonly used in commercial buildings and infrastructure projects.
• E90 trays are preferred in industrial, petrochemical, or public spaces where evacuation times are longer and critical systems must remain operational .

In summary, ordinary fire-resistant cable trays are tested and rated to maintain circuit integrity for 30, 60, or 90 minutes, with E90 being the most robust standard under DIN 4102-12 and similar international testing protocols. Proper selection should consider the risk level, cable type, and installation environment to ensure safety and compliance.