1. Key points for conduit laying and embedded construction
Low-voltage conduit laying is a key part of concealed works and must strictly follow GB 50303-2015 and GB 50312-2016. Main technical requirements: metal conduits shall use hot-dip galvanized steel pipes Φ20-Φ50, with wall thickness ≥1.5 mm for exposed installation or ≥2.0 mm for concealed installation; conduit bending radius shall be no less than 6 times the pipe diameter for concealed installation or 4 times for exposed installation; pipe clamp fixing spacing shall be no more than 1.5 m, with one fixing point at each end of a bend; the spacing between power and low-voltage conduits shall be ≥300 mm for parallel laying and ≥100 mm for crossing.
2. Equipment installation and termination process requirements
Low-voltage equipment installation must meet the requirements of equipment technical manuals and design drawings. Core points: cabinet base height ≥300 mm; cabinet verticality deviation ≤1.5 mm/m and horizontality deviation ≤2 mm/m; patch panel termination shall adopt the T568B standard, with untwisted pair length ≤13 mm, and cable labels after termination shall be clear and durable; camera installation height 2.5-5 m indoors or 3.5-10 m outdoors, with no obstruction in the viewing area, and IP protection rating ≥IP66 outdoors.
3. System grounding and equipotential bonding
Low-voltage system grounding is key to ensuring stable system operation and lightning protection. Technical requirements are based on GB 50174-2017 and GB 50057-2010: the low-voltage system shall adopt a common grounding method with grounding resistance ≤1 ohm; the low-voltage equipment room shall be provided with an equipotential grounding grid using copper bars 25 mm x 3 mm or BV-25 sqmm conductors, with a grid size of 600 mm x 600 mm; all metal conduits, cable trays, and cabinets shall have reliable grounding connections.
4. System commissioning and integrated commissioning acceptance
Low-voltage system commissioning follows the principles of single equipment before system, local before remote, and subnet before backbone. Commissioning process: single equipment commissioning with point-by-point I/O testing, sensor accuracy calibration, and actuator stroke testing; subsystem commissioning with DDC controller PID parameter tuning and logic verification; network commissioning with IP address allocation, VLAN division, route configuration, and BACnet device discovery; linkage commissioning with fire linkage, security linkage, and BA linkage.