In general, for non-fire conditions, the power system can be designed according to standard requirements. However, when it comes to fire-fighting electrical equipment, the power supply must ensure continuous operation during a fire and maintain the integrity of the circuit to support the proper functioning of critical systems. Additionally, the risk of fire caused by wires and cables due to short circuits or overloads must be considered. The impact of external fires should not contribute to the spread of flames, and materials used should minimize harmful gases released from organic insulation, thereby preventing secondary disasters.
**Selection of Non-Fire Electrical Circuits**
For general applications, ordinary wires and cables can be used. For concealed installations, they can be buried or installed in conduits. Ordinary cables are suitable for standard equipment wiring. In areas where fire resistance is required, flame-retardant wires and cables should be selected. For cable bundles, flame-retardant types are recommended. In secondary locations, halogen-free and low-smoke cables are preferred. In special and first-class locations, halogen-free low-smoke cables are mandatory. For special-grade facilities and important loads in first-class buildings, especially wooden structures, mineral-insulated cables are required.
**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 concealed flame-retardant rigid plastic conduits, cables with at least 1 hour of fire endurance are necessary. In cases where the power demand is shorter (≤1 hour), flame-retardant and fire-resistant wires can be used. For main power lines of fire equipment, fire-retardant fire-resistant cables or mineral-insulated cables are recommended. For short-term power needs (<20 minutes), mica-insulated fire-resistant cables can be used in open areas, while distribution lines should be protected by metal pipes or enclosed trunking with fire-retardant coatings. General cables may be used in such cases.
**Fire-Fighting Equipment Electrical Wiring Measures**
To ensure the integrity and fire resistance of the electrical distribution system, fire-resistant and heat-resistant wiring should be implemented in accordance with technical regulations. The cross-sectional area of conductors should be appropriately increased to prevent excessive resistance caused by high ambient temperatures during a fire, which could lead to voltage drops and affect the performance of fire-fighting equipment.
When laying cables in non-combustible structures, ordinary wires and cables can be installed in metal pipes or flame-retardant rigid plastic conduits (with an oxygen index of at least 30). The pipe should be protected with a layer of at least 30 mm thickness. Metal pipes or pipes coated with fire-retardant paint can improve flame resistance. Flame-retardant cables and copper trunk protection are also acceptable, with fireproof cable trays or mica-insulated fire-resistant cables used in enclosed metal bridges.
When two circuits are separated by fire-resistant barriers, non-flammable cables can be used in shafts or ceilings without additional metal tubing, provided that metal trough sealing is applied. However, if cables are laid in the same shaft, metal tubes are still required. Flame-retardant rigid plastic pipes with an oxygen index of 50 can be used in ceilings for fire protection wiring. Metal pipes or trunking should be used for internal fire electrical circuits within the ceiling. In flame-retardant ceilings, similar precautions apply.
Distribution lines protected by metal pipes can be placed directly against the outer wall of air ducts. However, if flammable materials are present in the ceiling cavity, these lines must not pass through the interior of the ducts or be laid on their outer walls. In such cases, metal tube protection is mandatory.
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