In the field of building electrical safety, flame-retardant cables are the 'invisible firewalls' that prevent the spread of fires. However, in the face of the complex level markings such as ZA, ZB, ZC, B1, B2, etc., how to accurately select has become a pain point in the industry. This article is based on two core standards, GB/T 19666-2019 and GB 31247-2014, to deeply analyze the grading logic of the cable.

　　1、 Bundle flame retardant system: gradient protection of ZA/ZB/ZC

GB/T 19666-2019 classifies flame-retardant cables into three levels: ZA, ZB, and ZC. The core difference lies in the non-metallic material content and combustion test strength

ZA (high flame retardant): Each meter of cable contains 7 liters of non-metallic material and must undergo a 40 minute vertical combustion test with a carbonization height not exceeding 2.5 meters. Suitable for ultra high risk locations such as nuclear power plants and data centers.

ZB grade (higher flame retardant): The non-metallic material content has been reduced to 3.5 liters/meter, and the fire supply time is still 40 minutes. The carbonization standard is the same as ZA. Commonly found in densely populated places such as hospitals and shopping malls.

ZC level (basic flame retardant): non-metallic material content of 1.5 liters/meter, fire supply time shortened to 20 minutes, suitable for ordinary buildings such as residential and office buildings.

Typical case: In a super high-rise complex project, the fire pump room uses ZA-YJV cables to ensure continuous power supply for 90 minutes in a 950 ℃ flame; Ordinary lighting circuits use ZC-BV wires to balance cost and safety.

　　2、 Classification of Combustion Performance: Quantitative Standards for B1/B2

GB 31247-2014 introduces stricter quantitative indicators, dividing flame-retardant cables into four levels: A, B1, B2, and B3

B1 level (flame retardant): flame spread ≤ 1.5 meters, peak heat release rate ≤ 30kW, smoke density transmittance ≥ 60%. Suitable for special fire prevention places such as subway tunnels and large exhibition centers.

B2 level (flammable): flame spread ≤ 1.5 meters, but peak heat release rate relaxed to 150 kW, smoke density transmittance ≥ 30%. Mostly used in ordinary public buildings.

Technological breakthrough: B1 level cables adopt ceramic silicon rubber sheaths, which form a dense ceramic layer at high temperatures of 800 ℃, effectively blocking the spread of flames and toxic gases.

　　3、 The Golden Rule of Selection: Scene based Matching

1. Dense places: B1 or ZA cables must be used. For example, Shanghai center Building uses B1 mineral insulated cables to meet the 180 minute fire resistance requirements.

2. Special industrial environment: Chemical enterprises need to choose ZA+corrosion-resistant coating cables. For example, a certain refinery of Sinopec uses ZA-YJH22 cables, which pass halogen-free testing with HCL release ≤ 5mg/g.

3. Cost sensitive projects: Residential buildings can use ZC grade cables, but it is necessary to ensure that the smoke toxicity level meets the t0 (non-toxic) standard.

　　4、 Future trend: Intelligent flame retardant

The new generation of smart cables has been implemented:

1. Temperature self sensing: The built-in fiber optic sensor monitors the temperature of the wire core in real time. For example, Hengtong Optoelectronics' B1 level smart cable can warn of overheating risks 30 minutes in advance.

2. Flame retardant adjustable: Nanomaterials automatically form a carbonized layer at high temperatures, reducing the flame spread rate by 80%.

Conclusion: The classification of flame-retardant cables is essentially a triangular balance of 'risk performance cost'. Behind every letter from ZA to B1 is a solemn commitment to life safety. With the full implementation of the mandatory standard GB 31247-2014, the Chinese cable industry is moving towards a more precise era of fire prevention.