In modern building construction, fire safety is a paramount concern. Among the critical components ensuring safety is the selection of appropriate wiring. Halogen-free cables, also known as Low Smoke Zero Halogen (LSZH) cables, have become increasingly mandatory in Chinese building projects due to stringent fire regulations. This article provides an in-depth look at the specifications, standards, and applications of halogen-free cables for Chinese building wire.

Understanding Halogen-Free Cables

Traditional PVC cables release halogen gases (chlorine, fluorine, bromine) when burned. These gases form corrosive acids and dense toxic smoke, endangering lives and damaging equipment. Halogen-free cables use thermoplastic or cross-linked polyolefin compounds that emit minimal smoke and no halogen gases during combustion. In China, these cables are typically designated as WDZ or WDZN types, where "WD" stands for "low smoke and halogen-free" (无卤低烟), "Z" for flame-retardant, and "N" for fire-resistant.

Key Chinese Standards

The primary specification governing halogen-free building wire in China is GB/T 19666-2019, titled "Flame retardant and fire resistant wires and cables — General principles." This standard defines the classification, technical requirements, and test methods for LSZH cables. Additional references include GB 50217-2018 for power cable design in electrical engineering and JGJ 16-2018 for building electrical design.

Critical Performance Parameters

1. Halogen Content: The chlorine, bromine, and fluorine content must be less than 0.5% by weight. Tested per GB/T 17650 (IEC 60754-1).

2. Smoke Density: Under combustion, the light transmittance of smoke must exceed 60% (measured per GB/T 17651, equivalent to IEC 61034). This ensures visibility during evacuation.

3. Flame Retardancy: Cables must pass the vertical flame spread test per GB/T 18380 (IEC 60332-1 or IEC 60332-3 for bunched cables).

4. Fire Resistance (for WDZN types): Cables must maintain circuit integrity for 90 minutes at 750°C or 180 minutes at 950°C, per GB/T 19216 (IEC 60331).

5. Toxicity Index: The total toxic gas yield must pass GB/T 20285 (equivalent to NF F 16-101).

Material Construction

A typical halogen-free building wire consists of:

- Conductor: Class 1 or 2 stranded annealed copper (per GB/T 3956), offering low resistance and flexibility.

- Insulation: Halogen-free cross-linked polyethylene (XLPE) or polyolefin compound, providing moisture and heat resistance.

- Sheath: LSZH copolymer jacket, often colored red, yellow, green, or blue for phase identification.

Common cable types include:

- WDZ-BYJ: Halogen-free flame-retardant copper core cross-linked polyethylene insulated wire (rated 450/750V).

- WDZN-BYJ: Halogen-free fire-resistant copper core XLPE insulated wire.

- WDZ-YJY: Halogen-free armored power cable, used for main distribution.

Applications in Chinese Buildings

Halogen-free cables are mandated in:

- High-rise residential and commercial buildings (above 54 meters in height).

- Hospitals, schools, and public transportation hubs.

- Underground spaces, tunnels, and data centers.

- Fire alarm, emergency lighting, and sprinkler pump circuits.

The China Code for Fire Protection of Building Design (GB 50016) explicitly requires flame-retardant and low-smoke wiring in critical safety systems.

Installation Best Practices

- Bending radius: For single-core cables, min 15D (cable diameter); for multi-core, min 12D.

- Temperature range: Typically -20°C to +90°C for fixed installation.

- Avoid direct sunlight exposure (use UV-resistant LSZH compounds for outdoor runs).

- Ensure proper grounding and bonding as per GB 50217.

Market and Quality Assurance

Leading Chinese manufacturers like Far East Cable, ZTT, and Baosheng specialize in LSZH cables. Buyers should demand third-party test reports from CNAS-accredited labs (e.g., China Electric Equipment Institute) and certificates like CCC (China Compulsory Certification) for fixed building wiring.

Conclusion

Halogen-free cables are not just a specification; they are a life-safety imperative in Chinese building wire. By adhering to GB/T 19666, ensuring low halogen content, high smoke transmittance, and proven flame retardancy, these cables significantly reduce fire hazards. As Chinese building codes tighten, specifying LSZH cables becomes a baseline requirement for responsible design. Always verify compliance with local fire authorities and choose trusted manufacturers to guarantee safety and performance in every building project.