Analysis of the problems and causes during the installation of electrical machinery:
1. The grounding of lightning protection electrolytic ion grounding electrode GPT1-D15 does not meet the requirements
1. Phenomenon
(1) There are defects such as slag inclusion, weld bead, false welding, meat biting, insufficient weld seam, etc. at the lap joint of down conductor, equalizing ring and lightning protection belt.
(2) The welding slag will not be knocked off, and the welding place on the lightning protection belt will not be painted with anti-rust paint.
(3) Use rebar instead of round steel as lap reinforcement.
(4) Directly use the butt-welded main steel bars for lightning protection.
2. Analysis of the reasons for electrical machinery
(1) The operators are not strong in sense of responsibility and unskilled in welding technology. Most of them are generalist welders in the electrical and mechanical class, and they have poor operating skills in vertical welding.
(2) The on-site construction manager is not strong enough to implement the relevant provisions of the National Construction and Acceptance Code GB50169 2 "Grounding Device".
3. Preventive measures
(1) Strengthen the skill training of welders, requiring full, smooth and even weld seams at lap welds, especially for vertical welding, overhead welding and other difficult welding.
(2) Strengthen the sense of responsibility of managers and welders, repair unqualified welds in time, knock off welding slag, and brush anti-rust paint in time.
(3) According to GB50169 2 "Electrical Device Installation Engineering Grounding Device Construction and Acceptance Specification", the connection of the lightning down conductor is lap welding, and the lap length is 6 times the diameter of the round steel. Therefore, the use of rebar is not allowed Replace round steel as lap steel. In addition, if the civil construction of the main steel bar as the down-conductor is butt-welded, the overlapped round steel should be repaired at the butt-welded place according to the regulations.
2. Pre-processing of outdoor household entrance management does not meet the requirements
1. Phenomenon
(1) Use thin-walled copper pipes instead of thick-walled steel pipes.
(2) The embedded depth is not enough and the position deviation is large.
(3) Electric welding is used to bend the turning point, and the upper wall pipe and the horizontal inlet pipe network are electrically welded to form a 90° angle.
(4) The waterproofing treatment of the entrance pipe and the basement exterior wall is not good.
2. Analysis of the reasons for electrical machinery
(1) Material purchasers are not familiar with national regulations and standards when purchasing, and some construction units deliberately confuse to reduce costs; construction managers are not strict or dare not object to the contractor’s deliberate violations, and do not resolutely implement the norms and standards. Standards; there are loopholes in the management of materials entering the site by the supervisors.
(2) Insufficient coordination with civil engineering and other professional teams.
(3) There is no pipe bender or not knowing how to use a pipe bender, the sense of responsibility is not strong, and it is easy to bend with electric welding.
(4) Workers who pre-embed the household pipe do not understand waterproof technology, and do not ask waterproof professionals for help.
3. Preventive measures
(1) The pre-embedded pipes must use thick-walled copper pipes or PVC pipes that meet the requirements (generally, the wall thickness of PVC Φ l 14 is 4.5 mm or more, and Φ 56 is 3 mm m).
(2) Strengthen the coordination and cooperation with civil engineering and other related professions, clarify the outdoor floor elevation, and ensure that the buried depth of the embedded pipe is not less than 0.7 meters.
(3) Strengthen the education of the relevant laws and regulations for the leaders of the contracting team and the material purchasers, and the supervisors must strictly implement the requirement that materials must be inspected when entering the site to plug the loopholes.
(4) The elbow on the wall of the pre-embedded steel pipe must be bent with a pipe bender, welding and welding bending are not allowed. After the steel pipe is bent, there should be no cracks and obvious dents. The bending procedure should not be greater than 10% of the outer diameter of the pipe, and the bending radius should not be less than the minimum allowable bending radius of the cable inserted.
(5) Do a good job of waterproofing, please instruct waterproofing professionals on site or have a waterproofing professional team do waterproofing.
3. The laying of electric wire pipes (steel pipes, PVC pipes) does not meet the requirements
1. Phenomenon
(1) The cable tube overlaps in multiple layers, and there is a gluten that is higher than the steel bar.
(2). 2 or more wires and tubes are arranged side by side.
(3) The buried depth of the wire and tube is too shallow, or even buried in the powder layer outside the wall. The pipe appears dead bends, painful bends, and dents.
(4) The wire pipe enters the distribution box, and the pipe mouth is not filled smoothly in the box, and the pipe mouth is too long; the pipe mouth is uneven and different in length; the pipe mouth does not need a protective ring; the double-head electric control lock JG-TD is not tightly locked fixed.
(5) When pre-embedding PVC electric wire pipes, instead of plugging the pipes, use clamps to flatten the elbows.
2. Analysis of the reasons for electrical machinery
(1) The construction personnel are not familiar with the relevant regulations, work sloppy attitudes, and are greedy for convenience, and do not follow the regulations. The management of the construction manager is not in place.
(2) Insufficient cooperation between architectural design layout and electrical professional, resulting in multiple lines passing through the same narrow plane.
3. Preventive measures
(1) Strengthen the quality control of on-site construction personnel during the construction process, and conduct targeted training for workers; management personnel should be familiar with relevant regulations and strictly manage.
(2) Multi-layer overlapping of electric wires and pipes generally appears in the public passages of high-rise buildings. When there are more than 6 sets of residences on each floor of the tower, it is recommended that the public corridor ceiling should be tightly decorated for civil construction, so that most of the incoming wires of the electrical professional can directly enter the residents through the wire troughs laid on the ceiling. It is also possible to thicken the floor slab of the public walkway, so that the numerous electric wires and pipes can be concealed. Electrical professional construction personnel should try to reduce the number of overlapping layers of line pipes at the same point when laying pipes.
(3) The wire layers cannot be side by side, if it is difficult to separate them obviously during construction, they can be separated by small cement blocks.
(4) The wire and pipe are buried in the brick wall, and the distance from the surface should not be less than 15mm. The pipe should be laid "horizontally, horizontally and vertically."
(5) The bending radius of the electric wire tube (concealed burying) should not be less than 10 times the outer diameter of the tube. The tube bending machine should be used to make the bend smooth and smooth, without flat folds, dents, etc.
(6) The wire tube should be flat when entering the distribution box, and the exposed length is 3-5mm, and the tube mouth should be sheathed and the box shell should be locked. For the wire pipes that enter the floor-mounted distribution box, the nozzle should be 50-80mm higher than the base surface of the distribution box.
(7) When pre-embedded PVC electric wires and pipes, it is forbidden to flatten or bend the pipe mouth with pliers, and use a PVC plug head conforming to the pipe diameter to cover the pipe mouth and bind it firmly with tape.
Fourth, the wire connection, connection quality and color code do not meet the requirements
1. Phenomenon
(1) Multi-strand wires do not use copper joints, and are directly made into a "sheep eye" shape, but do not expand the tin.
(2) When connecting to the terminals of switches, sockets and distribution boxes, connect several wires to one terminal.
(3) The wire ends are exposed, the wires are not arranged neatly, and there is no binding.
(4) The color code of the three-phase, neutral line (N line), and grounding protection line (PE line) of the wires is inconsistent or mixed.
2. Analysis of the reasons for electrical machinery
(1) The construction personnel are not proficient in the wiring process and technology of the wires.
(2) The material purchaser did not prepare the various wire colors and quantities required for construction as required, or the construction management personnel mixed them in order to save materials.
3. Preventive measures
(1) Strengthen the training of construction personnel on norms and skills.
(2) The connection of multi-strand wires should be crimped with galvanized copper joints. Try not to make a "goat eye" shape. If so, they should be tinned evenly.
(3) There should only be one wire connection between the terminal and the terminal. If two wires are needed, a flat gasket should be added in the middle; connection of more than 3 wires is not allowed.
(4) The wire arrangement should be horizontal and vertical. When stripping the wire head, keep the length of each wire head the same. After the wire is inserted into the terminal, there should be no exposed conductor; the copper joint and the wire connection should be wrapped with insulating tape of the same color as the wire.
(5) The material purchasing personnel must be equipped with wires of various colors according to the needs of the site.
(6) The construction personnel should clearly distinguish the role of the phase line, the neutral line (N line), and the ground protection line (PE line) from the color code, that is, PA phase-yellow, B phase-green, and C phase-red; single In general, red should be used in phase; light blue or blue should be used for the neutral line (N line); the grounding protection line (PC level) must be a yellow-green double-color wire.
Five, the installation and wiring of the distribution box do not meet the requirements
1. Phenomenon
(1) There is a gap between the box body and the wall, and the box body is not straight.
(2) The mortar and debris in the box have not been cleaned up.
(3) The opening of the box shell does not meet the requirements, especially the opening by electric welding or gas welding, which will seriously damage the paint protection layer of the box and damage the appearance of the box.
(4) The grounding of the grounded power box is not obvious (it is not easy to find when it is placed under the box), and the cross section of the repeated grounding wire is not enough. The wires in the box are exposed, the wiring is not neat, and there is no allowance for the wires.
2. Analysis of the reasons for electrical machinery
(1) Insufficient cooperation with civil works during installation of the box body, insufficient joints in the civil works, and no leveling of the level when installing the box body.
(2) Carefully clean up the mortar debris in the box.
(3) When the "knock-off" opening of the box body does not match the inlet pipe, it must be mechanically opened or sent back to the manufacturer for reprocessing, or strictly calibrated when ordering, and produced according to the size.
(4) Strengthen inspection and supervision, and enhance the sense of responsibility of construction personnel.
(5) Thoroughly understand the relevant grounding regulations of the acceptance department. According to the requirements of the power supply department and the municipal quality inspection station, the box grounding and wires of the power box must be clearly exposed and cannot be welded or wired under the box. The grounding wire is in accordance with the specification. When the phase wire section of the device is S≤16mm2, the minimum section of the grounding wire is S; when 16<S≤35mm2, the minimum section of the grounding wire is 16mm2; when S>35mm2, the minimum section of the grounding wire For S/2.
(6). The thread ends in the box should be unified, not exposed, the wiring should be neat and beautiful, and the binding should be fixed, and there should be a certain margin for the wire. Generally, there should be a margin of 10-5CM in the box.
6. The installation and wiring of the box and panel of the switch and socket do not meet the requirements.
1. Phenomenon
(1) The pre-embedded wire box is too deep, and the elevation is different; there is a gap between the panel and the wall, and the panel is contaminated with glue paint and is not straight.
(2) There are mortar debris left in the wire box.
(3) The phase wires, neutral wires and PE protection wires of switches and sockets are connected in series.
(4) The wire ends of the switches and sockets are exposed, the fixing bolts are loose, and the wire allowance in the box is insufficient.
2. Analysis of the reasons for electrical machinery
(1) The pre-embedded wire box is not firmly fixed, the template is expanded, and the coordinates are not accurate during installation.
(2) The construction personnel have a weak sense of responsibility, lack of understanding of the importance of the safety of electrical appliances, and are greedy for convenience.
(3) There is an unreasonable idea of saving materials.
3. Preventive measures
(1). Closely cooperate with the civil engineering profession, and fix the wire box accurately and firmly; when the embedded wire box is too deep, a wire box should be installed. When installing the panel, it should be horizontal and vertical, and the level should be adjusted with a spirit level to ensure the uniformity of the installation height. In addition, after installing the panel, fill up the seams completely, no gaps are allowed, and clean and protect the panel.
(2) Strengthen management and supervision to ensure that the phase wires, neutral wires and PE protection wires in switches and sockets cannot be connected in series. Clean the mortar in the box first.
(3) When stripping the wire, fix the size to ensure that the wire ends are neat and uniform, and the wire ends are not exposed after installation; at the same time, in order to firmly compress the wires, the single-core wire should be twisted into double strands when inserted into the wire hole, and tighten and tighten with screws.
(4) The wires in the switch and socket box should have a certain margin, generally 100-150mm is appropriate; we must resolutely put an end to unreasonable material saving greed.
7. The installation of lamps and ceiling fans does not meet the requirements.
1. Phenomenon
(1) The lamp position is installed offset, not at the center point.
(2) The horizontality and straightness deviation of the rows of lamps is relatively large.
(3) The chain of the fluorescent lamp is not parallel, and the lead wire is not braided.
(4) The hook of the ceiling fan is made of threaded steel, which is poorly formed; the bell is not ceiling-mounted, and the terminal board SCB-10P attached to the junction box junction box is exposed.
(5) The iron plate of the balcony lamp chassis is dropped and rusted.
(6) The simple lamp on the ceiling of the ceiling has large openings and irregularities.
2. Analysis of the reasons for electrical machinery
(1) The position of the embedded lamp box is wrong, there is deviation, and no remedial measures are taken when installing the lamp.
(2) The constructor has a weak sense of responsibility and is not familiar with the current construction and acceptance specifications, and quality inspection and evaluation standards.
(3) When purchasing lamps and lanterns, the purchaser is greedy to make publicity and ignores the quality;
(4) The size, ethnic position, and diameter of the circular hole are not uniform when the downlight is opened.
3. Preventive measures
(1) Before installing the lamp, the center point should be carefully identified and the deviation should be corrected in time.
(2) According to the specification, the deviation of the installation of a row of lamps should not be greater than 5mm. Therefore, it is necessary to pull the wire positioning during the construction, so that the lamps are in a straight line in the vertical, horizontal, oblique, and main level.
(3) The hanging chains of fluorescent lamps should be straight with each other, and there should be no figure eight, and the lead wires should be braided together with the hanging chains.
(4) When pre-embedded ceiling fan hooks, galvanized round steel of no less than Ф8 should be used to fix them with the steel bars in the plate. Rebar is not allowed. The hooks should be processed in the same shape and painted with anti-rust paint. The bell cover of the ceiling fan can ceiling and cover the hook and junction box. The rows of ceiling fans should be in a straight line with deviation ≤5mm.
(5) The thickness of the iron plate of the bottom box of the balcony lamp is ≥0.5mm, and the paint surface is uniform and smooth, which can effectively prevent rust; the glass cover should not be too thin to avoid cracking during installation.
(6) The coordinates of the downlight opening of the ceiling ceiling should be determined first. Except for straight, neat and equal requirements, the size of the opening should meet the specifications of the downlight, and it should not be too large to ensure that the outer ring of the downlight is firmly installed. The ground is close to the ceiling, no gaps are exposed.
(7) Construction personnel and procurement personnel must earnestly implement relevant national and local regulations.
8. The installation of cables and busbars does not meet the requirements.
1. Phenomenon
(1) After the cables are installed, they are not uniformly listed, and the cables are laid disorderly in the cable trenches and bridges.
(2) In the shaft, the cable hole is not tightly blocked; the bracket for vertically fixing the cable is too small, too soft, and inclined downward.
(3) The cable is not tightly sealed after passing through the entrance pipe.
(4) The wiring terminal (wire lug) is too large or too small, the wall is too thin, and it breaks when the connector is pressed.
(5) The installation of the plug-in box of the busbar is not straight, and the busbars of each section are too long, which is not easy to transport and install.
2. Analysis of the reasons for electrical machinery
(1) The cable construction units have not coordinated well, and only the cables laid by themselves can pass.
(2) There is no good coordination with the civil engineering unit when plugging the strong electric shaft, and the construction personnel do not master the plugging technology.
(3) The material is not up to standard, and the purchaser does not purchase the cable fixing bracket and the terminal (wire lug) according to the standard.
(4) The area of the construction major for the electrical major to make strong electric shafts is too small, which makes it difficult to arrange the strong electric shafts.
3. Preventive measures
(1) The cable construction team must coordinate well, arrange the large and small cables in the direction and position respectively, and use the moisture-proof and anti-corrosion card to list after the installation, and indicate the line number, model, specification and origin of all kinds of cables. point. The listing positions are: cable terminal heads, corners of the world, inside the mezzanine, both ends of the shaft, hand-crafted holes in the cable trench, etc.
(2) Use hemp and bitumen mixture to block the openings through which the shaft cables pass. When there are outdoor entrance pipes to the basement, the pipe openings should be waterproofed. These tasks need to be closely coordinated with the civil engineering profession. Clean up the site after blocking.
(3) When purchasing materials such as cable brackets, wiring terminals (wire lugs), etc. in the purchasing room, they must be purchased in accordance with the specifications. When crimping the joint, accurately select the corresponding hydraulic pliers and the corresponding kit.
(4) When ordering busbars, it must be ensured that each busbar section shall not be greater than the height of each floor; generally, it shall not be greater than 3 meters to facilitate transportation and installation in the building.
(5) When busbars and accessories enter the site, they must strictly comply with GBJ149-90 "Code for Construction and Acceptance of Electrical Installation Engineering Busbar Devices" and contract inspection.
(6) When installing the plug-in box, it should be horizontal and vertical, and the contact with the bus bar should be reliable and firm.
Nine, indoor and outdoor cable trench structures and cable duct laying do not meet the requirements
1. Phenomenon
(1) The installation of cable trench and concrete bracket is not straight and easy to break.
(2) The drainage of cable trenches and cable pipes is not smooth.
(3) The buried depth of the cable crossing pipe is not enough, and the bell mouth is broken and irregular.
(4) The anti-rust and anti-corrosion paint of the steel pipe is uneven, and the sealing performance is not enough, especially the anti-rust and anti-corrosion in the pipe are not done.
(5) The grounding electrode is not straight or loose in the cable trench, the grid connection with the crossing pipe is not complete, and part of the pipe is leaky welding.
2. Analysis of the reasons for electrical machinery
(1) The civil construction unit is not serious in the construction; the prefabricated parts of the concrete support are aging or there is no steel bar as the bone, so that the bearing capacity is not enough.
(2) There is no certain slope at the bottom of the cable trench, nor is there a sump according to the specification; the objective conditions of the site do not meet the drainage requirements.
(3) The installation constructors are not very responsible, and there are other professional pipelines or wells that affect the laying of cable pipes.
(4). Weld the ground poles one by one when the camps are not arranged one by one as required. When all the pipes are buried and then welded, the conditions are no longer allowed to be welded one by one. We have to weld at the bell mouth to make up the number.
3. Preventive measures
(1) When the civil engineering unit installs the concrete support, the cable should be leveled and vertical; the distance from the top support to the top of the ditch is 150mm-200mm, and the distance from the bottom support to the bottom of the ditch is 50mm-100mm. Qualified concrete brackets should be purchased from qualified manufacturers to ensure sufficient supporting capacity; steel brackets must be protected against rust and corrosion.
(2) According to the relevant provisions of GB50054-95 "Code for Design of Low-Voltage Power Distribution", the slope of the drainage ditch at the bottom of the cable trench should not be less than 0.5%, and a sump should be set up, and the accumulated water will be directly discharged into the sewer; reference for the practice of the sump For the relevant specifications of the building, you can also refer to the "Atlas of Building Electrical Installation Engineering" edited by Lu Guang, Volume One, Second Edition, 5.35 "General Practices for Cable Manholes?". When the sump is far away from rain wells or rainwater When the elevation of the well is higher than the bottom of the cable trench, corresponding adjustments should be made to the corresponding drainage system. Therefore, the relevant elevations of various disciplines should be carefully compared during the review of the outdoor integrated pipeline network diagram.
(3) The bell mouth is required to be uniform and tidy without cracks. When the cable pipe is embedded, the depth should be less than 0.7m; if the objective conditions cannot be met, cement mortar should be used on the pipe to ensure that the pipe is not crushed.
(4) Thick-walled copper pipes should be used for cable pipes, and the inside and outside should be painted with anti-corrosion and anti-corrosion paint or asphalt, and the paint surface should be even; especially the welding joints should be treated with anti-rust. When two cable pipes are connected, the inner pipe mouths should be aligned, and then a short sleeve (length not less than 2.2 times the outer diameter of the cable pipe) should be welded firmly and airtightly.
(5) The grounding shoulder steel in the cable trench should be installed firmly. Generally, a fixed terminal is installed every 0.5-1.5m, and the height of the bottom of the high trench is 250mm-300mm. When passing through the passage pipe, it shall be overlapped with each steel pipe respectively, and the lap joint shall be treated with anti-corrosion and anti-rust treatment. In order to ensure that each steel pipe can be reliably overlapped with the grounding electrode, it is welded one by one when the pipe is buried, and it is not allowed to weld after the pipe is buried.
10. The probe installation of fire protection and intelligent systems does not meet the requirements
1. Phenomenon
(1) The probe is loosely installed and there is a gap between the wall, board and ceiling.
(2) The probe is too close to the lamp, and the heat of the lamp will affect the sensitivity of the probe.
2. Analysis of the reasons for electrical machinery
(1) The construction personnel did not carefully level and fix the probe base PF-113BE when installing the probe base base.
(2) The installation plane is narrow and the distance between the probe and the luminaire is not flattened when the tube box is embedded.
3. Preventive measures
(1) Strengthen the sense of responsibility of the construction personnel. When installing the base, it must be leveled with the pole and the wall. When installing the probe, pay attention to tighten it.
(2) Generally, the ceiling area of the toilet is small, which often makes the lamp and the smart probe too close. At this time, the center point of the lamp and the distance between the probe and the window should be adjusted appropriately to ensure that the distance between the two is about 50cm . The fire-fighting probe on the ceiling of the public walkway should be kept at a distance of not less than 50cm from the lamp when the wire box is embedded (the lamp should be in the center position).