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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Installation of hidden electrical wiring. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Electric installation work Concealed wiring mounted in parts. Flush wires can be laid inside walls, ceilings, foundations, ceilings, under removable floors and in other structural elements of buildings. This is done before plastering and laying a clean floor. Wires can be placed in pipes, flexible metal hoses, in the voids of building structures, in grooves under plaster. They can be embedded in building structures during their manufacture. In order to stretch the wires into the voids of the floor slabs and lead them to the lamps, holes are punched or drilled in the slabs. The wires are pulled using a steel wire or cable with a diameter of 3-4 mm, which are laid in the channels (voids) of the plates. The wires to be drawn are firmly attached to one end of the wire and pulled to the point of their exit from the plate. Marking the installation sites of fixtures is carried out in the same way as when installing open wiring. The wiring route is carried out in the following order. Horizontal laying along the walls is carried out, as a rule, parallel to the lines of intersection of the walls with the ceiling at a distance of 10-20 cm from the ceiling or 5-10 cm from the cornice or beam. The mains of the socket outlets should be laid along a horizontal line connecting the sockets. Descents and ascents to lamps, switches, socket outlets should be carried out along vertical lines. On ceilings (in plaster, cracks, voids or floor slabs), wires must be laid along the shortest distance between the junction box and the luminaires. When crossing pipelines with flammable liquids and gases, wires should be laid at a distance of 10 cm from the pipeline or in furrows in insulating pipes. When crossing wires with pipelines with heated surfaces (hot pipelines) or when laying them parallel to these pipelines, the wires must be protected from high temperatures. When laying in parallel, the wires are placed at a distance of at least 10 cm from hot pipelines, and from pipelines with flammable liquids - at least 25 cm. Crossing of flat wires with each other should be avoided. If such an intersection is necessary, the wire insulation at the intersections must be reinforced with three to four layers of rubberized or PVC adhesive tape. When using three-core flat wires in lighting networks, the cores separated by a wide film should be used for circuits of different phases, and the third core should be used as a neutral wire. The exit of hidden wires to the surface of walls or ceilings (for example, to connect to a lamp or to a non-recessed switch, socket) should be carried out through insulating tubes, porcelain or plastic bushings or funnels. Connections and branches of wires must be made in junction boxes. Boxes may be plastic or other insulating material. It is allowed to use metal boxes with insulating gaskets inside them. Branches of wires can be made in the introductory boxes of switches, sockets and lamps. Connections and branches of hidden flat wires should be made with a wire margin of at least 5 cm. Direct suspension of the wire on flat wires is not allowed. Metal boxes at the points of entry of flat wires should have bushings made of insulating material, or additional insulation should be applied to the wire (three to four layers of insulating tape). A flexible copper wire with a cross section of at least 0,5 mm2 is used to connect luminaires to the lighting electrical network. The length of the wires from the lighting network to the lamp in damp, damp rooms (in toilets, showers, in the hallways of houses) should be minimal. Wiring should be placed outside these rooms, and lamps - on the wall closest to the electrical wiring. Hidden laying of flat wires on ceilings is carried out in one of the following ways: - under a layer of wet plaster of the ceiling of fireproof slabs, similar to laying on fireproof walls and partitions under a layer of wet plaster; - in voids of reinforced concrete slabs and panels; - in the gaps between prefabricated reinforced concrete slabs with their subsequent sealing with alabaster mortar; - in the gaps between the brickwork (Fig. 38).
Before plastering, the wires are temporarily fixed in separate places by “freezing” with alabaster mortar (Fig. 39), the distance between the “freezing” points is not more than 25 cm.
It should be noted that the alabaster solution hardens very quickly and at the same time acquires increased strength; therefore, 1-2 minutes after applying the alabaster lumps, they should be flattened to the wire insulation. Then, all sections of the electrical wire should be ringed with a tester; if the result is positive, the grooves can be plastered. It is possible to fasten the wires with brackets or clamps made of plastic, rubber, cotton tape. When laying wires in the gaps between brickwork (without subsequent plastering), the wire is fixed in the furrow with a cement mortar with a thickness of at least 5 mm. When laying wires with subsequent plastering, a furrow depth for wires of less than 5 mm is allowed, with a thickness of the plaster layer of at least 5 mm. Hidden laying of flat wires on wooden bases should be carried out under a layer of plaster with a lining under the wires of a layer of sheet asbestos with a thickness of at least 3 mm or over plaster with a thickness of at least 5 mm. In this case, asbestos or a layer of plaster must be laid on top of the shingles, or the shingles must be cut to the width of the asbestos gasket. Asbestos or a layer of plaster must protrude at least 5 mm on each side of the wire. Fastening flat wires directly with nails with any method of hidden wiring is unacceptable. Hidden laying of APPVS, APN, APV wires along wooden walls and partitions covered with dry gypsum plaster is carried out in the gap between the wall and the plaster in a continuous layer of alabaster plaque or between two layers of sheet asbestos. The thickness of sheet asbestos must be at least 3 mm, and the alabaster layer - 5 mm. A layer of alabaster or asbestos on each side of the wire must protrude at least 5 mm. Fastening with brackets or clamps made of plastic, rubber, cotton tape is allowed. The length of the strips for making staples should be 8 cm. Switches and sockets with hidden wiring are fixed using U19B type steel boxes, into which switches and sockets are built. The steel box is smeared into the nest with alabaster mortar. The diameter of the socket must be at least 8 cm, the depth must be at least 4,5 cm. To connect the flat wire to the terminals of the switch or the socket, the separating film must be cut or cut out at the connection area. Metal boxes at the points of entry of flat wires must have bushings made of insulating material, or additional insulation should be applied to the wire (3-4 layers of rubberized insulating tape or sticky PVC). Cable wiring installation Vertical suspension strings are installed, as a rule, in places where junction boxes, plug connectors and lamps are fixed. The distance between the points of intermediate fastening of the cable should be no more than 12 m. For vertical suspension strings, it is recommended to use galvanized steel wire with a diameter of 2-3 mm for power wiring and 1,5-2 mm for lighting. All metal parts of cable wiring - bare parts of the cable, tensioners, cable clamps, end anchor structures, wire hangers, braces - must be lubricated with grease. Rope electrical wiring can be carried out with special rope wires of the AVTS, AVT, APT brands with a supporting steel cable, as well as protected wires and cables of the corresponding brands and unprotected insulated wires of the APV, APRV brands, cables of the AVRG, ANRG, AVVG, APVG brands suspended from the supporting steel cable (Fig. 40).
Steel ropes-cables with a diameter of 1,95-6,5 mm, woven from galvanized steel wires, are used as load-bearing cables. It is allowed to use hot-rolled steel wire (rolled wire) with a diameter of 5-8 mm instead of a carrier cable. When hanging, the cable must be well tensioned. The pulling force should not exceed 0,7 of the force that is allowed for a given carrier cable. It is best to carry out the installation and tensioning of the load-bearing cables at an ambient temperature of at least 20 °C. When hanging unprotected insulated wires on cables, the distance between the wire attachment points should not exceed: - for unprotected insulated wires laid on cable hangers, with a cross section of 2,5-6 mm2 - 1,5 m; - for wires laid directly, with a cross section of 2,5-6 mm2 - 0,5 m; - for cables in all cases - 0,5 m. For tensioning steel ropes during cable wiring, tension couplings of the K798, K804, K805 types are used, and for tensioning steel ropes or steel wire during the installation of cable wiring, couplings of the MN type are used. The permissible tensile load must not exceed 3 kN. For the end fastening of steel ropes or steel wire with a diameter of 6-8 mm, an anchor of the K675 type is used when installing cable wiring. The permissible load on it should not exceed 16 kN. For fastening steel ropes or wire to the walls, an anchor type K809 is used with a tension force of not more than 16 kN. For connection of wire suspensions, stretch marks, guy lines with the carrying cable of the electrical wiring, a K296 type clamp is used. The permissible load on it should not exceed 7,2 kN. To fasten a loop made at the end of a steel cable (rope), with a diameter of 6-8 mm, a cable clamp type K676 is used. The permissible load on the clamp is 16 kN. For branching wires from the main, as well as for connecting fixtures with cable wiring, cable boxes of the U245, U246 type are used, equipped with a screw for grounding (connecting the neutral wire of the network), and boxes of the U230, U231 type, used for branching from cable wiring made with APT wires , ABTB (up to three electrical receivers can be connected to one box). Branch boxes type U257 are used to make detachable connections of fixtures to the main lighting network. The box is equipped with a three-pole socket. Author: Korshevr N.G.
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