In general, non-fire conditions do not require special power system requirements. Therefore, standard electrical wiring can be used as per regular specifications. However, for fire-fighting electrical equipment, the power supply must ensure continuous operation during a fire and maintain the integrity of the circuit to guarantee the system's normal function. Additionally, it is essential to consider the fire hazards of wires and cables, preventing them from becoming a fire source due to short circuits or overloads. The impact of external fires should also be minimized to avoid fire spread, and the release of harmful gases from organic insulation layers should be reduced to prevent secondary disasters.
**Selection of Non-Fire Electrical Circuits**
- Ordinary wires can be used for general equipment, with buried installation or concealed conduit (1).
- Fire-retardant wires and cables are recommended for wire bundles (2).
- In secondary areas, halogen-free and low-smoke cables are required; in special and first-class locations, halogen-free low-smoke cables should be used (3).
- For special-grade buildings, especially important loads in first-class locations, mineral-insulated cables are mandatory (4).
**Selection of Fire Electrical Circuits**
- Fire-resistant wires or mineral-insulated cables should be used. When installed in open metal troughs or metal pipes, or in flame-retardant rigid plastic conduits, fire-resistant wires are suitable for long-term use (≥1 hour) (1).
- For shorter durations (≤1 hour), flame-retardant and fire-resistant wires can be used. If installed in refractory metal troughs or coated metal pipes, flame-retardant wires may suffice. Main power lines for fire equipment should use fire-retardant fire-resistant cables or mineral-insulated cables (2).
- General wires and cables can be used, but for distribution lines with surface coating, the thickness of the protective layer should be at least 30 mm. Fireproof cable trays or mica-insulated fire-resistant cables should be used when laying in closed metal channels (3).
- Mica-insulated fire-resistant cables can be used in open areas if the usage time is less than 20 minutes. Distribution lines should be protected by metal pipes or enclosed trunking with fire-retardant coatings (4).
**Fire-Fighting Equipment Electrical Wiring Measures**
To ensure the integrity and fire resistance of the distribution lines, fire-resistant and heat-resistant wiring should be designed according to technical regulations. The conductor cross-section should be appropriately sized to prevent increased resistance due to elevated ambient temperatures during a fire, which could cause voltage drop and affect the performance of fire-fighting equipment.
- Ordinary wires and cables can be installed in metal pipes or flame-retardant rigid plastic conduits (oxygen index ≥30) when buried in non-combustible structures (1).
- Metal pipes or metal surfaces coated with fire-retardant paint can improve flame resistance. Flame-retardant wires and cables, along with copper trunk protection, should be used. Laying in enclosed cable trunks with fire prevention measures in cable shafts or ceilings is also recommended (2).
- Fire-resistant barriers should separate the two systems. If non-flammable cables are used in shafts or metal troughs, metal tube protection may not be necessary. However, if cables are laid in the same shaft, additional precautions are required (3).
- Flame-retardant rigid plastic pipes or plastic trunking can be used for fire protection circuits within ceilings. Metal pipes or trunking should be used for fire circuits inside flame-retardant ceilings (4).
- Distribution lines protected by metal pipes can be laid close to air duct walls. However, if flammable materials are present in the ceiling cavity, the lines must not pass through the air duct’s interior or be placed on its outer wall. In such cases, metal pipe protection is mandatory (5).
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