When the trunking is installed vertically in layers, the cables shall be arranged from top to bottom according to the following specified sequence: instrument signal line; Safety interlocking line; AC and DC power supply lines.
C.
The distance between the power line and the weak electrical signal line is not enough, and sometimes it is laid side by side.
when threaded connection is used between pipes, the thread length of pipe end shall not be less than 1 / 2 of the length of pipe joint, and the thread surface shall be smooth There shall be no corrosion or defect, and the thread shall be coated with electric compound full grease or conductive anti-corrosion grease.
This PE line must be connected to each junction box it passes through.
If jumper connection is required, round steel jumper connection can be adopted between black iron pipes and between black iron pipes and junction box, which shall be welded on one side, and the jumper length shall not be less than 6 times of the diameter of the jumper round steel; When the black iron pipe is connected with the galvanized bridge, a copper bolt shall be welded at the end of the black iron pipe, and the copper wire not less than 4mm shall be connected with the galvanized bridge.
When strong and weak current cables are laid in parallel or cross, the spacing is less than 0.3m, and when communication lines are laid in parallel or cross with other weak wires, the spacing is less than 0.1M, which is strictly prohibited in the specification.
If it must be laid in parallel, the distance between them should be greater than 0.5m.
The layout of weak current cables is not straight, resulting in twisting and looping, and some cables are squeezed and damaged by external forces.
The grounding device of weak current system requiring grounding shall meet the following requirements: (1) when galvanized electric pipe is used for piping, except where it is clearly specified in the design, it is not necessary to cross connect after connecting pipe and pipe, pipe and metal box, but the following provisions shall be observed: a.
When the signal cable (line) crosses the power cable, it should be at right angles; When laid in parallel, the distance between them shall meet the design requirements.
Solid Lifting Socket Cross Pin
3.
2.
Cables with different signals and voltage levels in the same trunking shall be arranged by category; For AC power lines and interlocking lines, partition boards shall be used to lay them separately from unshielded signal lines.
2.
The clear distance between the signal line laid in the open and the electrical equipment with strong magnetic field and strong electric field should be greater than 1.5m; When shielded cable or metal protective pipe is used and laid in trunking, it should be greater than 0.8m.
During weak current construction, the installation of cabinet is often ignored.
4.
When the cable is laid along the support or in the trunking, it shall be firmly fixed at the following places: (1) When the cable slope exceeds 45 ° or is arranged vertically, it shall be on each support.
when the casing with set screw is used for connection between pipes, the screw shall be tightened; In places with vibration, anti loosening measures shall be taken for set screws.
Different grounding has different requirements, and the grounding construction shall be determined according to the design.
1、 Ten common problems of property weak current construction weak current construction is restricted by relevant standards and specifications, and a qualified weak current construction team should also master them skillfully.
5.
4.
The installation of cabinet shall be stable and firm, and shall be reinforced according to the guidelines and requirements of construction drawings.
the exposed piping shall not be bridged by fusion welding, but shall be bridged by the special wire clip specified in the design.
B.
C.
(2) When the inclined gradient of the cable is not more than 45 ° and the cable is arranged horizontally, it shall be on every 1 ~ 2 supports.
The grading ring in the machine room is not grounded.
if there is bare soft PE copper wire in the pipe, the pipe may not be bridged.
9.
(5) 150 ~ 300mm in front of the lead-in junction box and junction box.
However, it is often ignored in actual construction.
when there is a PE line in the weak current pipe, each junction box shall be connected with the PE line.
7.
3、 Five precautions for the construction of weak current lightning protection and grounding of the property: 1.
The outdoor buried weak current piping shall be laid with PVC pipe, while the weak current construction specification emphasizes the laying with steel pipe.
5.
Protective grounding is divided into: anti electric shock grounding, lightning protection grounding, anti-static grounding and anti-corrosion grounding; Functional grounding is divided into working grounding, logic grounding, shielding grounding and signal grounding.
10.
However, in specific projects, there will be some small problems, which are also common problems in weak current construction: 1.
2、 Five precautions for weak current wiring construction of the property: 1.
(2) When galvanized electric pipes are used for piping and the design stipulates that the pipes need to be bridged, the following provisions shall be observed: a.
D.
(3) When the black iron pipe is used for piping, if the design does not require jumper connection, it is not necessary to jumper connection.
B.
the electric pipe buried or buried in concrete shall not be bridged by line card, but can be bridged by fusion welding.
8.
(4) When PVC pipes are used for strong and weak current, in order to avoid interference, the weak current piping shall be laid in parallel with the strong current piping as far as possible.
6.
the connection between the pipe and the box shall not use plastic container, but conductive metal container.
The horizontal distance from the detector to the wall and beam edge is less than 0.5m due to weak fire current.
The grounding of weak current system can be divided into protective grounding and functional grounding according to its purpose.
The bridge crossing the floor is not blocked with fireproof mud or not at all.
In weak current construction, the construction unit pays attention to the use function of each subsystem and ignores sensory acceptance, that is, the possible phenomena are poor wiring, disordered arrangement of information panels, no identification and so on.
(4) 300 ~ 400mm in front of the instrument panel (box).
2.
Weak current construction often ignores that surge absorbing devices should be installed on the low-voltage bus in the special distribution box of the main engine room, and the surge absorbing devices must be specified in the national test report.
After connection, 2 ~ 3 threads should be exposed.
3.
The low-voltage circuit under the raised floor in the machine room does not use copper core shielded conductor or copper core shielded cable.
(5) When the strong and weak current are laid in trunking, the strong and weak trunking should be separated; When it needs to be laid in the same slot, the strong and weak currents shall be separated by metal partitions…
(3) And the first and second supports on both sides of the compensation redundancy and both ends of the protective tube.
