Fire-resistant electrical wires are crucial. In case of fire, critical systems like alarms, smoke extraction, and emergency lighting all depend on them – they are truly a "lifeline." But how do you choose the right fire-resistant wires? Actually, just remember these four types, and you too can become an expert!
What types of fire-resistant wires are there? According to the "General Principles for Flame-Retardant and Fire-Resistant Wires and Cables," fire-resistant wires are mainly divided into the following four types:
Flame-retardant cables (ZR): If these cables encounter fire, they won't burn immediately, but will burn slowly. Once the fire is extinguished, they will stop burning themselves, preventing the fire from spreading further. They are suitable for general fire safety equipment, such as manual alarm buttons.
Fire-resistant cables (NH): These can withstand high temperatures of 750℃ and can continuously supply power for 90 minutes. Their insulation layer uses mica tape, which is particularly heat-resistant. Equipment that is particularly important during a fire, such as smoke exhaust fans, fire pumps, and emergency lighting, requires this type of cable.
Mineral insulated cables (BTTZ): These have a copper core and magnesium oxide insulation. Their advantage is that they can withstand high temperatures of 950℃ and are also waterproof and explosion-proof. They are essential for ensuring power supply safety in places with extremely high safety requirements, such as super high-rise buildings, tunnels, and nuclear power plants.
Halogen-free low-smoke cables (WD): When these cables burn, they produce very little smoke and no toxic gases. According to the standard, the light transmittance can reach over 60%. Therefore, they are safer in densely populated areas such as subways, hospitals, and schools, reducing the harm caused by smoke and toxic gases during a fire.
5 tips for choosing fire-resistant wires:
Consider the building type: For super high-rise buildings or underground projects, mineral insulated cables (BTTZ) are a must, as only they can guarantee stable power supply in such extremely complex and dangerous environments. For ordinary commercial buildings, it's best to use a combination of fire-resistant (NH) and halogen-free low-smoke (WD) cables. This ensures both safety and meets practical needs.
Select based on system importance: For critical equipment like fire pumps and smoke exhaust fans, which play a crucial role in fire fighting, mineral insulated cables must be used, as their stable operation is vital to the success of the entire fire protection system. For secondary load equipment like emergency lighting, fire-resistant (NH) cables are sufficient and more cost-effective.
Choose based on the installation environment: If installed in damp places, such as basements or swimming pools, cross-linked polyethylene insulated (YJV) cables should be used, and the waterproof rating must be IP67 or higher to prevent water from affecting the cable's normal operation. In corrosive environments, such as near chemical plants, armored cables like NH-YJV22 should be used, as their outer sheath can resist corrosive substances such as acids and alkalis.
Consider cost: If you want to save money, use flame-retardant cables (ZR) and supplement them with fire-resistant cables (NH) in critical areas. This ensures basic safety while controlling costs. If you prioritize extremely high reliability and don't mind spending more, use mineral insulated cables (BTTZ) throughout the entire system, although this will increase costs by approximately 30% to 50%.
Follow regulations: If fire protection power lines are laid openly, they must be routed through metal conduits or enclosed metal trunking and coated with fire-retardant paint to further enhance fire safety.
How to check the quality after selection:
Check certificates: When purchasing cables, the supplier should provide a third-party test report containing key data such as fire resistance time and smoke density. This report confirms whether the cable meets the standards.
Test performance: Samples can be sent to a professional institution for testing. The insulation resistance should be tested, and it must be above 20MΩ. Fire resistance should also be thoroughly tested to determine the actual quality of the cable.
Inspection of markings: Legitimate cables will have clear markings such as "NH" and "WD" printed on the outer sheath, indicating the cable type. These markings should be clear and not easily rubbed off. If the markings are unclear or easily erased, the cable is likely defective.
Future trends in fire-resistant cables:
Flexible mineral-insulated cables: These cables may gradually replace traditional BTTZ cables in the future because they have a smaller bending radius, making installation easier and increasing construction efficiency by 50%. This will save considerable time and labor costs.
Intelligent monitoring cables: These cables are equipped with temperature sensors. If the line temperature becomes too high, an alarm will be triggered immediately, allowing for early detection of potential hazards and preventing fires. This is particularly helpful for fire safety.
Environmentally friendly materials: According to industry forecasts for 2025, the proportion of halogen-free, low-smoke cables will increase to 80%. More and more places will use these more environmentally friendly and safer cables in the future, reducing the harm to the environment and people during fires.
