1.1 Metal conduits and conduits must be grounded (PE) or zero-connected (PEN) reliably and meet the following requirements:
1. Galvanized steel conduit, flexible conduit and metal trunking shall not be welded to bridge the grounding wire. The connecting wire between the two cards that are bridged by a special grounding card shall be a copper-core flexible wire with a cross-sectional area of not less than 4mm2;
2 When the non-galvanized steel conduit is connected by thread, the two ends of the connection shall be welded with a jumper grounding wire; when the galvanized steel conduit is connected by a thread, the two ends of the connection shall be fixed with a special grounding clip to connect the jumper grounding wire;
3. The metal trunking is not used as the grounding conductor of the equipment. When there is no design requirement, the metal trunking shall be connected to the grounding (PE) or zero (PEN) trunk line at no less than 2 places along the entire length;
4 The two ends of the connecting plate between the non-galvanized metal wire troughs are connected to the copper core grounding wire, and the two ends of the connecting plate between the galvanized wire troughs are not connected to the grounding wire, but there are no less than two anti-loosening screws at both ends of the connecting plate. caps or lock washers to attach the fixing bolts.
1.2 Metal conduits are strictly prohibited from butt fusion welding; galvanized and steel conduits with a wall thickness of less than or equal to 2mm are not allowed to be welded by the casing.
1.3 The explosion-proof conduit should not be connected with an inverted buckle; when the connection is difficult, an explosion-proof union should be used, and the joint surface should be tight.
1.4 When the insulating conduit is grooved and buried on the masonry, it should be protected by cement mortar with a strength grade of not less than M10, and the thickness of the protective layer is greater than 15mm.
1.2 General items
2.1 The buried depth of cable conduits laid outdoors shall not be less than 0.7m. Steel wire conduits with a wall thickness of less than or equal to 2mm should not be buried in outdoor soil.
2.2 The orifice of the outdoor duct shall be set in the box or box. For the nozzle in the floor-standing distribution box, if there is no sealing plate at the bottom of the box, the nozzle should be 50-80mm higher than the base surface. All nozzles should be sealed after penetrating wires and cables. For conduits leading from box-type substations or floor-standing distribution boxes to buildings, the conduit openings on one side of the building should be located in the building.
2.3 The bending radius of the cable conduit shall not be less than the minimum allowable bending radius of the cable, and the minimum allowable bending radius of the cable shall comply with the provisions in Table 12.2.1-1 of this code. page 37
2.4 The inner and outer walls of the metal conduit shall be treated with anti-corrosion; the inner wall of the conduit buried in the concrete shall be treated with anti-corrosion, and the outer wall may not be treated with anti-corrosion.
2.5 The conduit openings entering the floor-standing cabinets, tables, boxes and trays indoors should be higher than the base of the cabinets, tables, boxes, and trays.
Base surface 50 ~ 80mm.
2.6 For concealed conduits, the distance between the buried depth and the surface of buildings and structures should not be less than 15mm; for exposed conduits, they should be arranged neatly, with uniform spacing between fixed points and firm installation; There are pipe clamps within the range of 150-500mm from the edge of the plate, plate, etc., and the maximum distance between the pipe clamps in the middle straight section shall comply with the provisions of Table 14.2.6.
surface
2.6 Maximum distance between pipe clamps
Catheter diameter (mm)
15～20
25～32
32～40
50～65
65 and above
laying method
Type of catheter
Maximum distance between tube cards (m)
Wall thickness > 2mm rigid steel conduit
1.5
2.0
2.5
2.5
3.5
Wall thickness≤2mm rigid steel conduit
1.0
1.5
2.0
bracket or along
exposed wall
Rigid Insulated Conduit
1.0
1.5
1.5
2.0
2.0
2.7 The wiring groove should be installed firmly without distortion, and the nut of the fastener should be outside the wire groove.
2.8 The laying of explosion-proof conduits shall meet the following requirements:
1. The threaded connections between conduits and lamps, switches, junction boxes, etc. are tight and firm. Except for special requirements in the design, the connection is not connected to the ground wire, and the threads are coated with power compound ester or conductive anti-rust ester;
2 The installation is firm and straight, and the galvanized layer is rusted or peeled off with anti-corrosion treatment.
2.9 The laying of insulating conduits shall meet the following requirements:
1. The mouth of the pipe is flat and smooth; when the pipe and pipe, pipe and box (box), and other devices are connected by the insertion method, the joint surface of the joint shall be coated with special glue, and the interface shall be firmly sealed;
2 For rigid insulating conduits directly buried in the ground or in the floor, protective measures shall be taken at the section that penetrates the ground or the floor and is susceptible to mechanical damage;
3 When there is no design requirement, the insulating conduit buried in the wall or concrete shall be of medium-sized or larger;
4 Install temperature compensation devices along the surface of buildings, structures, and rigid insulating conduits laid on supports according to design requirements.
2.10 The laying of metal and non-metal flexible conduits shall meet the following requirements:
1 Rigid conduit are connected to electrical equipment and appliances through flexible conduits. The length of flexible conduits is not greater than 0.8m in power engineering and 1.2m in lighting engineering;
2 Special joints shall be used for the connection between flexible metal pipes or other flexible conduits and rigid conduits or electrical equipment and appliances; the joints of composite flexible metal pipes or other flexible conduits shall be well sealed, and the liquid-proof covering layer shall be intact;
3 Flexible metal conduits and metal flexible conduits cannot be used as grounding (PE) or zero (PEN) connection conductors.
2.11 Compensation devices shall be provided for conduits and trunkings at the deformation joints of buildings.