Features of the installation of electrical wiring. General provisions. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Features of the installation of electrical wiring. General provisions. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric installation work

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Open laying of wires directly on combustible structures and surfaces is done when sheet asbestos about 3 mm thick is placed under the wire, protruding on both sides of the wire or pipe by at least 1 cm, or wires and cables are used in a sheath of fireproof or fire-retardant materials. It is possible to lay wires of any brand on rollers or in steel pipes.

Open laying of wires directly on combustible surfaces, for example, on wooden walls and ceilings, is allowed to be carried out with wires of the APPR (flat), APRN, PRN (single-core), ANRG, NRG brands in dry and damp rooms, APRF, PRFL in dry rooms. Marks of wires and cables for specific conditions are given in table. 5. If the laying of wires is carried out in a continuous layer of non-combustible materials (plaster, alabaster, cement mortar or concrete), then the thickness of the layer must be at least 1 cm. should be carried out in a plastered furrow, in a continuous alabaster layer with a thickness of at least 0,5 cm or under a layer of sheet asbestos 3 mm thick. If the wires are laid in dry or wet plaster, then the layer of wet plaster must be at least 0,5 cm. Hidden laying of wires within the attic or roof over the ceiling of the upper floor is allowed only under a layer of cement or alabaster mortar with a thickness of at least 1 cm. Hidden laying wires under plaster on combustible structures and surfaces is carried out on an asbestos sheet with a thickness of at least 3 mm or on plaster with a thickness of at least 5 mm. In this case, the wires must be laid on top of the shingles, or the shingles must be cut to the width of the asbestos gasket.

Asbestos or plaster must protrude at least 1 cm on each side of the wire.

On wooden walls and partitions covered with dry gypsum plaster, wires should be laid in the gap between two asbestos sheets with a thickness of at least 3 mm. Asbestos or alabaster must protrude from each side of the wire by at least 1 cm. Laying wires in vinyl plastic pipes is permissible only if the pipes are laid on an asbestos sheet with a thickness of at least 3 mm or on plaster with a thickness of at least 5 mm, protruding from each side of the pipe is not less than 1 cm, followed by plastering the pipe with a layer of at least 1 cm. , PRKA, PRKS). In such places, open electrical wiring in plastic pipes is mainly used. Open wires can be laid where the possibility of mechanical damage is excluded, or if they have appropriate protection. Open laying of unprotected wires with combustible insulation is prohibited.

Open laying of unprotected insulated wires is allowed to be carried out:

- at voltages above 42 V in rooms without increased danger and at voltages up to 42 V in any rooms at a height of at least 2 m from the floor level;

- at a voltage above 42 V in rooms with increased danger and especially dangerous at a height of at least 2,5 m from the floor level. These requirements do not apply to descents to switches, socket outlets, starting devices, shields, wall-mounted lamps. In industrial premises, the descents of unprotected wires to switches, socket outlets, devices, shields must be protected from mechanical influences up to a height of at least 1,5 m from the floor level or service platform.

In domestic premises, in residential and public buildings, these slopes may not be protected from mechanical influences. Flat wires are allowed to be laid in dry, damp and damp rooms.

Flat wires must not be used in the following cases:

- for hidden and open laying in explosive zones of all classes, in especially damp rooms, in rooms with a chemically active environment, directly on combustible bases, for charging pendant lamps;

- with open laying in fire hazardous areas of all classes, in attics.

During open laying of protected wires and cables with sheaths of combustible materials and unprotected wires, the distance from the wire or cable to the surface of bases, structures, parts made of combustible materials must be at least 1 cm. When attaching wires and cables to insulators, rollers, clips, exactly such a distance. In indoor and outdoor installations where a chemically active environment is present, all electrical wiring elements should be made resistant to such an environment. Wires and cables with outer insulation that is not resistant to light should be protected from direct sunlight. To power portable and mobile electrical receivers, it is necessary to use cords and flexible cables with copper conductors. All conductors of wires, including grounding (zeroing), must have a common sheath or common insulation, that is, they are laid together.

Author: Korshevr N.G.

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