Electrical wiring: general information
Electrical wiring is called the set of insulated conductors and cables with elements of their fastening, the protective and supporting designs.
The electrical wiring provides the electric power supply to the consumer's electroreceivers. At design of electroconductings it is necessary to be guided by existing "Regulations for electrical installation" (REI), "Norms of technology design of electric units" and "Construction norms of the ipravilama" (Construction Norms and Regulations).
Internal and outside electrical wiring
The electrical wiring laid indoors is internal.
The wiring laid on outside walls of buildings and constructions under canopies, etc. and also between buildings on support (no more than four flights 25 m long) out of streets and roads is called outside.
Open and hidden electrical wiring
The conductings laid on the surface of walls, ceilings, on support, farms and other construction elements of buildings and constructions belong to open electroconductings. Wires and cables lay at the same time directly on the surface of walls, ceilings, on rollers, insulators, on ropes, on brackets, in pipes, in flexible metal sleeves or directly gluing to the surface.
The open electrical wiring can be stationary, mobile and figurative. The conductings laid in structural elements of buildings and constructions (in walls, floors, overlappings) and also in zashtukaturivayemy furrows, without furrows under the layer of wet plaster, in the closed channels and emptiness of building constructions, etc. belong to open electroconductings.
Wires and cables are laid or in pipes, flexible metal sleeves, boxes, or without them.
The buried electrical wiring completely protects wires and cables from mechanical damages and influences of the external environment.
Replaced and constant the electrical wiring
The buried electrical wiring can be replaced and constant.
Replaced call such wiring which allows to carry out in use replacement of wires without destruction of building constructions. At the same time wires lay in pipes or channels of building constructions.
Constant wiring cannot be dismantled without destruction of designs or plaster.
- design of the electrical wiring in the garden lodge, the cottage or the house is begun with drawing of the circuitry of connections tied to the floor-by-floor design of the house in scale 1:100 (1:200);
- the electrical wiring on the plan is put in unilinear execution. Lamps, switches, plug adapters, protection devices on drawings of plans designate conventional signs.
In different climatic zones of the country at construction of garden lodges, cottages and dachas apply various construction materials and designs. All built structures are subdivided into three categories:
- on degree of inflammability of construction materials and designs;
- under the terms of the environment;
- on extent of defeat electric current.
According to requirements of "Construction norms and rules" all construction materials and designs are subdivided into three groups: combustible, fire-resistant and fireproof.
- all natural and artificial inorganic materials applied in construction belong to fireproof; metals, plaster and gypsum-fiber plates at the content of organic substance up to 8% on weight; mineral-cotton plates on the synthetic, starched or bituminous sheaf at contents it up to 6% on weight;
- the materials consisting of fireproof and combustible components, for example, the asphalt concrete, plaster and concrete materials containing more than 8% on the mass of organic filler belong to fire-resistant; mineral-cotton plates on the bituminous sheaf at the maintenance of its 7-15%; glino-straw materials with a density not less than 900 kg/m ³; the wood subjected to deep impregnation by fire-retarding agents fibrolit, textolite, other polymeric materials;
- all other organic materials belong to combustible.
"Regulations for electrical installation" (REI) accepted the following classification of rooms under the terms of the environment:
- Dry: the relative humidity in them does not exceed 60%. It the inhabited heated rooms.
- Wet: here the relative humidity does not exceed 75%, vapors or the condensing moisture are emitted only temporarily and besides in small amounts (not heated rooms, outer entrance hall of houses, warehouses, sheds, utility rooms, kitchens, etc.).
- Crude: in them the relative humidity it is long exceeds 75%.
- Especially crude: here the relative humidity is close to 100%. The ceiling, walls, the floor and objects are indoors covered with moisture (bathing, shower rooms, toilets, cellars, vegetable storehouses, greenhouses, etc.).
- Hot: temperature it is long exceeds 30 °C (steam rooms, baths, attics, etc.).
- Dusty: in them perhaps abundant release of technology dust in such quantity that it can accumulate on wires and get in electric equipment.
- Rooms with chemically active environment: here under the terms of production it is constant or long couples contain or the deposits operating destructively on isolation and current carrying parts of electric equipment are formed (the room for the livestock and the bird, etc.).
- Explosive rooms and outside installations: in them explosive mixes of combustible gases or vapors with air or other gases-oxidizers and also combustible pyly and fibers with air can be formed (garages, gas storages and oil products, etc.).
Wires and cables
For the purpose of economy of scarce wires with copper veins apply wires and cables to electroconductings mainly with aluminum veins now.
Copper wires and cables lay only in the cases stipulated by "Rules of the device and operation of electric units", for example, in pozharo-and explosive rooms in buildings with combustible overlappings.
Laying of wires and cables with aluminum veins in principle does not differ from laying of wires and cables with copper veins, but is carried out with bigger care, in order to avoid injury of veins in view of their smaller mechanical durability in comparison with copper. Working with aluminum wires, it is not necessary to allow repeated excesses in the same place, cuts of veins when cleaning isolation.
Wire call one uninsulated or one and more isolated metal conducting vein over which depending on conditions of laying and operation there can be the nonmetallic cover, the winding or the braid fibroids.
Wires can be naked and isolated.
Wires which over conducting veins have no protecting or insulating covers are called naked. Naked wires of the PSO, PS, A, EXPERT brands, etc. are applied, as a rule, to overhead power transmission lines.
Wires at which conducting veins are covered with isolation are called isolated, and over isolation there is the braid from cotton yarn or the cover from rubber, plastic or the metal tape. Insulated conductors are subdivided on protected and unprotected.
The insulated conductors having the cover intended for sealing and protection against external climatic influences over electric isolation are called protected. Wires of the APRN, PRVD, APRF brands, etc. concern them.
Unprotected call the insulated conductors which do not have over electric isolation of the protective cover (wires of the APRTO, PRD, APPR, APPV, PPV brands, etc.)
Cord call the wire consisting of two and more isolated flexible or especially flexible veins with a section up to 1,5 mm ² twisted or laid in parallel covered with the protective isolating cover.
Is called the cable one or several the isolated veins twisted together concluded in the general rubber, plastic, metal cover (NVG, KG, AVVG and др).
The isolated adjusting wires and unarmoured power cables with rubber or molded insulation in the metal, rubber or plastic cover with the section of phase veins to 16 mm ² are applied to electroconductings of the power and lighting networks which are carried out in garden lodges and dachas and also in the territory of garden sites.
Conducting veins of adjusting wires have standard sections in mm: 0,35; 0,5; 0,75; 1,0; 1,5; 2,5; 4,0; 6,0; 10,0; 16,0, etc. Section of the wire is calculated by the following formula:
S =? D2: 4
where S - the section of the wire, mm ²;
п - number equal 3,14;
D - diameter of the wire, mm.
Diameter of the current carrying vein (without isolation) is measured by the caliper or the micrometer. Section of veins of multi-wire wires is determined by the sum of sections of all pro-reducing dies entering the vein.
Isolation of adjusting wires is expected the certain operating voltage. Therefore at the choice of brand of the wire it is necessary to consider that the operating voltage which isolation of the wire is expected has to be more than tension of the feeding network circuit. Mains voltage is standardized: linear stress - 380 V, phase - 220 V, and adjusting wires are issued on the rated voltage of 380 V and above therefore, as a rule, they are suitable for the device of electroconductings.
Adjusting wires have to correspond to the connected loading. For the same brand and the same section of the wire loadings, different in size, which depend on laying conditions are allowed. For example, the wires or cables laid openly are better cooled, than laid in pipes or hidden under plaster. Wires with rubber isolation allow the long heating temperature of their veins which is not exceeding 65 °C, and the wire with molded insulation - 70 °C.
Section of conducting veins is chosen proceeding from limit admissible heating of veins at which isolation of wires is not damaged.Top