Installation of electrical wiring with protected wires. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Installation of electrical wiring with protected wires. 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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When installing both open and hidden electrical wiring on fireproof and slow-burning bases, all brands of protected wires and cables are laid directly on the bases. On wooden walls, partitions, ceilings and other combustible structures, electrical wiring can be carried out directly on the bases with a lining for wires and cables of fireproof materials or in a continuous layer of fireproof materials.

The method of laying on combustible bases is determined by the material of the sheath of wires and cables.

Direct laying of wires and cables on combustible substrates is permitted subject to the following conditions:

1) when laying protected wires and cables openly, their sheath must be made of hard-to- or non-combustible materials (wires PUNP, APUNP, APRN, PRN, APRF, PRF, PRFl; cables ANRG, NNG, AVVG, VVG, etc.);

2) in the case of hidden laying of protected wires and cables, their sheath must be made only of fireproof materials (APRN, PRN wires; ANRG, PRG cables, etc.).

Cables in PVC and rubber sheaths must be protected from exposure to sunlight and damage by rodents at the points of exit to the outside.

It is not allowed to leave unprotected cable ends that have been brought out and cut, as cracks may form on them due to the susceptibility of insulating rubbers to aging under the influence of sunlight.

Protected wires and cables are laid strictly parallel to the interface lines of walls, partitions, ceilings, door and window openings. Fasten the wiring to the bases of walls and ceilings with metal or nylon brackets. Single wires and cables in horizontal sections are fastened with brackets with one foot, in vertical sections - two or one, on ceilings, corners, at inputs - only two.

With horizontal laying, the distance between the brackets should be no more than 500 mm, with vertical laying - no more than 700-1000 mm (depending on the cross section of the current-carrying conductors). Staples at switches, sockets, junction boxes, walkways, etc. are installed at a distance of 50-70 mm and 10-15 mm from the beginning of the bend.

Connection and branching of wires and cables is carried out in junction boxes. Before entering the box, the ends of the wires and cables are cut and prepared for connecting branches inside the box. The length of the cut is chosen so that after fixing the wire or cable, their sheath goes inside the box by 1,5-3,0 mm.

Cable termination such as AVRG and VRG do so. Annular and longitudinal cuts of the sheath are made with a knife, then the sheath is unbent, starting from the end of the cable, and removed. Cutting a cable with a lead sheath (ASRG, SRG) is carried out by making annular and longitudinal cuts of the sheath with a knife by about half its thickness. When cutting the sheath, care must be taken not to damage the insulation, therefore it is forbidden to cut through the sheath.

After making cuts, starting from the end of the cable, unbend the sheath to one side and remove it to the annular cut. At a distance of 4-5 mm from the cut of the shell, a bandage of harsh threads is applied to the belt insulation, which is covered with an adhesive varnish or enamel.

It is forbidden to perform the cutting of ASRG, SRG type cable in a way in which the sheath is notched with a ring, and then broken and pulled together.

The laying of wires PRF, APRF, PRFl with a folded seam has specific features arising from the rigidity of the outer metal sheath. When attaching the wire, the foot of the bracket is always installed under it. When laying wires horizontally along the walls, the seam of the metal sheath should be directed downwards and, if possible, facing the supporting surface, which prevents accidental ingress of moisture into it. When laying wires vertically along the walls, as well as along the ceiling, the seam of the sheath must be adjacent to the supporting surface.

The wire should be bent in compliance with the permissible bending radii, using special tongs of the KT-2 type. The punch and die are selected according to the diameter of the wire. The first few indentations are made by incomplete compression of the tongs, then by compression to failure. Places of indentations are located close to each other so that the subsequent indentation does not overlap the previous one. The wires are bent carefully.

Wires with a folded seam are cut as follows. A seam incision is made and an annular incision is made around the shell from the incision site. In order not to damage the insulation, it is impossible to cut through the shell through. Then the entire shell is deployed with a knife, starting from the incision site. A bandage of harsh threads is applied similarly to the cutting of the ASRG cable. The paper is torn off by hand (not with a knife!) along the entire length of the cut up to the bandage in the direction opposite to winding. The operation is completed by cutting the paper filler. The remaining installation operations are performed similarly to the laying of unarmored cables.

To avoid corrosion, it is forbidden to lay wires in an aluminum sheath (AMC alloy), on freshly plastered and freshly painted surfaces. Before laying on such surfaces, the wire is pre-painted with quick-drying oil paints, varnishes or enamel.

Author: Bannikov E.A.

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