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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Installation of electrical wiring. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Electric installation work Wiring is divided into power and lighting, trunk and distributione. To speed up the installation process, wire harnesses for the same type of products are manufactured separately from the devices. Harness - this is a bundle of wires laid and interconnected, terminated with lugs for connection to circuit elements or products. The bundle combines direct and reverse conductors with industrial frequency currents according to its scheme. The wires used in high-frequency devices are not bundled, as this increases the capacitance between the conductors. Bundles are made with a sheath for fastening and shielding, as well as without a sheath. The wires of the bundles are fastened with a bandage of cotton threads, and for the operation of the electrical circuit at elevated temperatures - with glass threads, followed by impregnation of the bandage with wax or paraffin, sometimes they are fastened with varnish or glue. Shells can be tubular, tape, strip and wicker. Tubular shells can be soft and hard. For soft shells, PVC tubes are used, for hard shells, aluminum tubes are used, which ensure safety under significant mechanical loads. In addition, they perform the functions of electrical shielding. The manufacture of harnesses includes the following operations:
When installed inside and outside buildings and structures, lighting and power wiring with voltages up to 1000 V are made with insulated wires of various grades and sections, as well as unarmored cables with rubber insulation with a cross section of up to 16 mm2. Wiring Requirements: 1) in rooms without an increased risk of electric shock, the wires should be located at a height not less than 2 m, and in rooms with increased or special danger - at least 2,5 m from the floor; 2) the wires are laid along the upper part of the wall at a distance of 150-200 mm from the ceiling, and the wires to the lamps of the general lighting - on the ceiling; 3) if the height of the room does not allow maintaining the specified dimensions, then the wires are laid in pipes or hidden in thicker than the walls of the room. This requirement does not apply to cable runs to light switches and sockets in rooms without an increased risk of electric shock. Installation rules: 1) in one pipe (box or tray), a closed channel of a building structure, it is prohibited to lay mutually redundant circuits, emergency and working lighting circuits, lighting circuits and power, lighting circuits with voltage up to 42 V with voltage circuits above 42 V; 2) in dry and wet rooms with non-combustible structures, all types of wiring are allowed. In dusty, damp and especially damp rooms, wiring on rollers is not allowed; 3) in especially damp rooms and in rooms with a chemically active environment, it is impossible to lay wires in plastic pipes, under plaster and on rollers; 4) in fire hazardous premises, it is not allowed to lay wires in plastic pipes, on cables and cable wire, on rollers, and in case of combustible structures - under plaster and in vinyl plastic pipes; 5) all conductors of flexible wires and cables (including grounding) must be in a common sheath, braid or have a common insulation. The insulation of wires and cables must correspond to the rated voltage of the network; 6) when choosing wires for electrical wiring, their mechanical strength is taken into account. For example, for aluminum wires, the smallest sections for inputs to consumers and wiring to electric meters are 4 mm2, for wires on insulators, the distance between which is up to 6 m - 4 mm2, up to 12 m - 10 mm2, up to 25 m - 16 mm2; 7) in places where mechanical damage to electrical wiring is possible, openly laid wires and cables must be protected by sheaths or pipes, boxes, fences. The installation of electrical wiring is carried out strictly according to the design documentation, which describes the brands of wires and cables, installation locations for electrical equipment and lamps, starting and switching devices, passages through ceilings or walls, wiring route, etc. Installation of electrical wiring involves the following operations: 1) markup; 2) installation of rollers, insulators, brackets; 3) punching furrows, etc.; 4) laying of wires; 5) wire connection; 6) installation of wiring accessories, apartment shields, lamps, etc.; 7) termination of wires and their connection to electrical receivers; 8) performing measurements; 9) commissioning. After the completion of the installation work, the entire wiring diagram is assembled, the connections are checked for correctness, and the assembled control and signaling circuits are fully tested. Measurements and testing of electrical wiring made by the personnel of installation organizations during the installation process, as well as by commissioning personnel immediately before commissioning, are drawn up by the relevant acts and protocols. Let's take a look at each of the above steps in turn.. Marking is carried out before the start of plastering, painting and other finishing works. This takes into account the ease of use and maintenance of wiring during operation, subject to the rules of electrical and fire safety. The marking of the route and the main axes for the placement of electrical equipment and lamps is carried out as follows: marks are made on the floor or ceiling in the form of a black strip 10-12 mm wide and 120-150 mm long. Marking is done with the help of tape measures, and the lines are beaten off with a cord dyed with blue or dry ocher. The taut cord is pulled back and abruptly released to strike the surface. The location of the fasteners is marked with transverse risks on the broken line. The route for open wiring should be parallel to the lines of building structures. When marking, determine the location of the transition boxes, fastening of electrical wiring, holes for wires, cables, pipes and niches for shields. After that, the dimensions of the electrical wiring elements and their configuration are specified. At the harvesting site, in accordance with field measurements of the routes, wires are cut for each section of the route. The ends of wires and cables must be prepared for connections, branches and connections to equipment (luminaires): they are cleaned of insulation, the connection diagrams are checked and the wiring is marked. Prepared sections of electrical wiring are mounted at the installation site using various fasteners. In order to protect the wires from mechanical damage, sections of metal or insulating pipes, respectively, are laid into the holes for their passage through the wooden or brick internal walls of the house and interfloor ceilings. They must be aligned with the wiring lines so that there are no additional bends in the wires before entering the pipe. The ends of the pipes should protrude 10 mm from the walls and ceilings, and the upper end of the pipe laid through the ceiling should rise at least 1,5 m above the floor of the second floor. The ends of the pipes on both sides are made out with porcelain or plastic bushings. They lay a tube of PVC or semi-hard rubber with a diameter of about 15 mm and such a length that its ends protrude from the bushings by 10 mm. Then a wire is laid through the tube.
In this case, connections and branches of wires are allowed to be made only inside the branch boxes. Routes are laid along the shortest distance between connected devices, parallel and perpendicular to walls, ceilings and columns, with a minimum number of turns, intersections with technological communications and the smallest number of detachable pipe connections; away from technological equipment that is subject to frequent disassembly, from places dangerous for maintenance personnel, where heating to temperatures above 60 ° C and mechanical and chemical damage are possible; in places convenient for installation, maintenance and repair. Routes for laying plastic pipes and unarmored cables on open structures and outdoor installations are selected taking into account their protection by building elements, flyovers from direct sunlight. When the directions of pipe wiring and other electrical networks coincide, it is recommended that they be combined, if this is permissible under the conditions of joint laying, in common channels, tunnels and overpasses. Pipe bending radii must be at least 10 outer cable diameters at temperatures up to -40 °C, for areas with low temperatures down to -50 °C, the allowable bending radius must be at least 20 cable outer diameters. When laying technological pipes and electrical wiring jointly along the installed prefabricated structures, the cables are placed below the pipes. The distance between ducts and pipelines with hot liquids or gases must be: in parallel laying - to pipelines passing from either side, at least 250 mm; when crossing - to pipelines passing under the boxes or from their sides, at least 100 mm; above them - at least 250 mm. The route line is applied along the walls, columns, ceilings, then the places of attachment and installation of supporting structures and other elements of the route are marked, the correctness of the route breakdown is checked for compliance with its project. Multi-hollow reinforced concrete panels are used as interfloor floors in residential and civil buildings. The voids of these panels are often used for laying wiring in them. In places where it is required to lead wires to the lamp and for its fastening on the ground floor, they punch passages (usually using a powder shock column UK-6). The holes are marked so that they are, if possible, in the center of the voids of the panel. To do this, you need to familiarize yourself with the dimensions of the structures, keeping in mind that the panels are standard. In each individual case, it is necessary to first check these distances on the panels used at this object, and then proceed to the marking. Furrows are punched for concealed electrical wiring in brick, concrete and gypsum building structures. Punching grooves in reinforced concrete is generally unacceptable. To form furrows 8 mm wide and 20 mm deep in plaster or brick, a furrower is used, in which the working tool is a disk cutter - a steel disk with VK6 grade hard alloy plates arranged radially in the form of teeth. Each insert has a clearance cutting angle of 15°. Work is started after marking the furrows, checking the serviceability of the furrower by testing its work in vain. During operation, the power handle is held with the right hand. As the dust container fills, it is cleaned. Large transverse grooves are punched with an electric or pneumatic hammer or a manual puncher. To obtain grooves of the correct shape, after preliminary marking with a furrow maker, contour lines are outlined, and then the middle part is pierced with a hammer or a manual puncher. Author: Bannikov E.A.
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