Exposed electrical wiring inside the premises

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 2. Sewerage of electricity

Wiring. Exposed electrical wiring inside the premises

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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2.1.52. Open laying of unprotected insulated wires directly on the bases, on rollers, insulators, on cables and trays should be carried out:

1. 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 or service platform.

2. At voltages above 42 V in areas with increased danger and especially dangerous - at a height of at least 2,5 m from the floor level or service platform.

These requirements do not apply to descents to switches, sockets, starting devices, shields, wall-mounted lamps.

In industrial premises, the descents of unprotected wires to switches, sockets, devices, shields, etc. 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 of industrial enterprises, in residential and public buildings, these slopes may not be protected from mechanical influences.

In rooms accessible only to specially trained personnel, the height of openly laid unprotected insulated wires is not standardized.

2.1.53. In crane spans, unprotected insulated wires should be laid at a height of at least 2,5 m from the level of the crane trolley platform (if the platform is located above the crane bridge deck) or from the crane bridge deck (if the deck is located above the trolley platform). If this is not possible, then protective devices must be provided to protect the personnel on the trolley and crane bridge from accidentally touching the wires. A protective device must be installed along the entire length of the wires or on the crane bridge itself within the location of the wires.

2.1.54. The height of the open laying of protected insulated wires, cables, as well as wires and cables in pipes, boxes with a degree of protection of at least 1P20, in flexible metal hoses from the floor level or service platform is not standardized.

2.1.55. If unprotected insulated wires intersect with unprotected or protected insulated wires with a distance between the wires of less than 10 mm, then additional insulation must be applied to each unprotected wire at the intersection.

2.1.56. When crossing unprotected and protected wires and cables with pipelines, the clear distances between them must be at least 50 mm, and with pipelines containing flammable or flammable liquids and gases, at least 100 mm. If the distance from wires and cables to pipelines is less than 250 mm, wires and cables must be additionally protected from mechanical damage at a length of at least 250 mm on each side of the pipeline.

When crossing with hot pipelines, wires and cables must be protected from exposure to high temperature or must have an appropriate design.

2.1.57. When laying in parallel, the distance from wires and cables to pipelines must be at least 100 mm, and to pipelines with flammable or flammable liquids and gases - at least 400 mm.

Wires and cables laid parallel to hot piping must be protected from high temperature or must be of the appropriate design.

2.1.58. In places where wires and cables pass through walls, interfloor ceilings or exit to the outside, it is necessary to provide the possibility of changing the electrical wiring. To do this, the passage must be made in a pipe, duct, opening, etc. In order to prevent the penetration and accumulation of water and the spread of fire in places of passage through walls, ceilings or exits to the outside, gaps between wires, cables and a pipe (duct, opening etc.), as well as reserve pipes (ducts, openings, etc.) with an easily removed mass from fireproof material. The seal must allow replacement, additional laying of new wires and cables and ensure the fire resistance of the opening is not less than the fire resistance of the wall (ceiling).

2.1.59. When laying unprotected wires on insulating supports, the wires must be additionally insulated (for example, with an insulating pipe) at the points of passage through walls or ceilings. When these wires pass from one dry or wet room to another dry or wet room, all wires of one line can be laid in one insulating pipe.

When passing wires from a dry or damp room to a damp one. from one damp room to another damp room, or when wires exit the room to the outside, each wire must be laid in a separate insulating pipe. When exiting a dry or damp room into a damp or outside building, wire connections must be made in a dry or damp room.

2.1.60. On trays, supporting surfaces, cables, strings, strips and other supporting structures, it is allowed to lay wires and line them close to one another in bundles (groups) of various shapes (for example, round, rectangular in several layers).

The wires and cables of each bundle must be fastened together.

2.1.61. In ducts, wires and cables are allowed to be laid in a multilayer orderly and arbitrary (in bulk) mutual arrangement. The sum of cross sections of wires and cables, calculated according to their outer diameters, including insulation and outer sheaths, should not exceed: for deaf ducts 35% of the duct cross section in the light; for boxes with opening lids 40%.

2.1.62. Permissible long-term currents for wires and cables laid in bundles (groups) or in multilayers should be taken into account with reduction factors that take into account the number and location of conductors (cores) in the bundle, the number and relative position of bundles (layers), as well as the presence of unloaded conductors.

2.1.63. Pipes, boxes and flexible metal sleeves of electrical wiring must be laid in such a way that moisture cannot accumulate in them, including from the condensation of vapors contained in the air.

2.1.64. In dry, dust-free rooms, in which there are no vapors and gases that adversely affect the insulation and sheath of wires and cables, it is allowed to connect pipes, ducts and flexible metal hoses without sealing.

The connection of pipes, ducts and flexible metal hoses with each other, as well as with ducts, electrical equipment cases, etc., must be performed:

in rooms that contain vapors or gases that adversely affect the insulation or sheaths of wires and cables, in outdoor installations and in places where oil, water or emulsion can get into pipes, boxes and sleeves - with a seal; the boxes in these cases should be with solid walls and sealed with solid covers or deaf, split boxes - with seals at the split points, and flexible metal sleeves - sealed;
in dusty rooms - with sealing of joints and branches of pipes, sleeves and ducts to protect against dust.

2.1.65. The connection of steel pipes and ducts used as grounding or zero protective conductors must comply with the requirements given in this chapter and Ch. 1.7.

See other articles Section Rules for the installation of electrical installations (PUE).

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