1, the length of the flexible conduit for lighting / power exceeds the specification requirements;
2, in the pipeline at the turn of the junction box (box) is not set, directly replace the flexible conduit;
3, more than one circuit of the conductor directly bifurcated in flexible conduit, do not use the Junction box; connection without the use of special connectors, connectors are not fixed or the use of tape wrapped connection;
4, the metal flexible has a retreat, disconnection phenomenon;
5, not to do across the ground, or the metal flexible conduit for grounding the connection instead.
Hazard
1, flexible conduit is too long, in the flexible conduit at the turn of the hose instead of junction box, multiple circuits of wires directly in the conduit within the bifurcation, without the use of junction boxes, will make threading difficult, difficult to fix, is not easy to line inspection, maintenance, replacement; 2, the connection does not use a special connector, flexible conduit is not securely fixed, the flexible conduit back out of the joints, the conduit is unprotected;
3, the metal flexible conduit is not grounded or the metal flexible conduit to do grounding of the continuous conductor, there is a potential safety hazard.
Reasons
1, flexible conduit is too long, directly on the flexible conduit bifurcation, etc. Caused by unfamiliar with the specification requirements, the desire to save trouble, random construction. Pre-embedded wiring distance from the lamps, appliances, equipment is too large, resulting in the length of flexible conduit more than the specification requirements, especially ceiling-mounted lamps and lanterns power line conduit; construction personnel do not want to save trouble bending operation, in the pipeline at the corner of the junction box should be set up to omit, and casually use the flexible conduit instead.
2, directly in the flexible conduit bifurcation wiring, eliminating the junction box, and then wrapped in adhesive tape package, flexible conduit wall thickness is very thin, its strength than the same kind of rigid conduit is much lower than the joints can not be fixed, thereby reducing the ability to protect the wire.
3, flexible conduit connection is not used in the special joints, the reason is difficult to buy the matching joints, expensive, easy to use tape instead.
4, the construction process due to the many types of work, more personnel, it is inevitable to injure the flexible conduit, conduit has the phenomenon of retreating, etc., but the construction workers are not strong sense of responsibility, did not repair the damaged conduit, is the conductor leakage, the loss of protection.
5, the construction workers believe that the metal flexible conduit connection are all metal objects, the metal flexible conduit do not have to do across the grounding, so that the metal management to lose the electrical continuity.
6, in order to save materials, greedy for convenience, the metal conduit to do the grounding of the connecting conductor, there will be serious problems, because the metal conduit is too thin, in the event of a ground fault, the short-circuit stability is greatly reduced, and will make the need to ground the equipment grounding is not reliable.
Prevention measures
1, the length of the hose for lighting is not greater than 1.2m, the length of the hose for power is not more than 0.8m, the quality of the project should be in line with the specification requirements, in the pipeline at the turn, set up junction boxes as needed, can not be replaced by a hose, the wire in the middle of the bifurcation of the connection should be carried out in the conductor box should not be directly bifurcated on the hose;
2, flexible metal conduit or other flexible conduit or electrical equipment, appliances between the connection should be used for special joints; metal flexible conduit disconnection phenomenon, should be rectified in a timely manner;
3, the construction of a good job of technical briefing before construction, construction to strengthen the parallel inspection, inspection efforts to ensure that the metal flexible conduit grounding is reliable.
4, can not be made of metal flexible conduit grounding connection instead of metal flexible conduit since its own grounding; and equipment, appliances, metal shell should be a special grounding protection line, and grounding trunk connection. Relevant norms: "Building Electrical Engineering Construction Quality Acceptance Specification" GB 50303-2015 Article 12.2.8: Bendable metal conduit and flexible conduit laying should be in accordance with the following provisions:
1 Rigid conduit through the flexible conduit and electrical equipment, appliances and connecting the flexible conduit, flexible conduit length in the power engineering should not be greater than 0.5m, in the lighting project should not be greater than 1. 2m. 2m.
2 bendable metal conduit or flexible conduit and rigid conduit or electrical equipment, appliances should be connected using a special connector; anti-liquid bendable metal conduit or flexible conduit connections should be well sealed, anti-liquid cover should be intact yuan damage.
3 bendable metal conduit and metal flexible conduit should not be used to protect the conductor of the connecting conductor.
3.