- Concealed or exposed wiring
- Paths of wires
- Protecting and fixing conductors
- Sleeves and pipes
- Cable channels
- Cable trays
- Cables and strings
- Joint wiring
- Basic rules for wiring
We invite you to discuss topical issues related to the laying of cables and wires. In the article, we will consider the basic requirements that apply to the installation of electrical wiring, we will try to highlight the various methods of sewerage electricity, we will give practical advice.
When creating electrical networks inside the premises, the wiring of cables and wires is considered a rough and routine work, which in specialized organizations and teams is often performed by auxiliary workers. However, this stage is standardized no less rigidly than, for example, the switching of electrical circuits, which we talked about in the last article. It is almost impossible to correct the mistakes made here, they are usually very difficult to identify, due to the fact that the layout usually refers to hidden work. Chains with improperly routed wires cannot reliably withstand the mechanical stresses that occur during operation. Such wiring does not cope with the tasks assigned to it and gives malfunctions, which cause the protection devices to operate, overheat and ignite the wires.
Electrical safety and fire safety are the main requirements for wiring. Electricians must prepare cable support systems for assembly with exceptionally high quality and lay wires in them in strict accordance with the plan. It is necessary to be guided by the current regulatory documents, among which are:
- PUE “Rules for Electrical Installations”
- GOST R 50571-15-97 Electrical installations of buildings. Part 5. Selection and installation of electrical equipment “(Chapter 52)
- SNiP 3.05.06–85 “Electrical devices”
One or another method of wiring installation (a set of cables, wires, as well as their protection elements and fasteners is called wiring) is used depending on:
- from the purpose of the premises;
- the type of conductors used;
- operating conditions;
- structural features of the building.
Sometimes it is possible to choose from several acceptable options, then preference is given to less time consuming and more economical.
Concealed or exposed wiring
Open wiring is inferior to hidden wiring in design and ergonomics, but it is much simpler and cleaner to install (there is no need to groove and seal channels), and is also easy to maintain, diagnose and modernize. In addition, open wiring is a safer option for buildings constructed with combustible materials. In this regard, the use of open wiring is more rational in the implementation of power supply for offices, retail outlets, wooden houses.
The open method of mounting wires is carried out on top of finished walls, floors, supports, trusses and other building elements, as well as on special load-bearing cables and cable racks. Cables, wires and their bundles can be laid:
- in cable ducts;
- on roller insulators (twisted “retrocable”);
- on polymer brackets (both for cables – round and flat, and for protective sleeves);
- in box skirting boards, cornices and platbands;
- free suspension on cables and strings (usually this is powering the lamps);
- on electrical trays.
Open wiring conductors can be protected with pipes or flexible sleeves, but they can also be installed without them. In most cases, installation options for open wiring have to be combined, for example, in a chopped wooden house, a straight section of the route fits into a plastic channel, and the vertical branch, which runs across the logs, is carried out on insulators, or in a corrugation with clips.
Hidden wiring is now used much more often, especially in residential premises, since it is safer and does not spoil the appearance of rooms. Hidden wiring should be considered an installation option in which wires are laid inside building structures – walls, ceilings, floors. As a rule, grooves are cut for the conductors, or the routes are monolithized during concrete work. Sometimes for wiring, channels are used in building elements (for example, drilled in walls from a bar, or in hollow concrete slabs). To be considered hidden, it is not necessary for communications to be located in building blocks, this type of electrical wiring includes wires laid behind the cladding of frame sheathing (walls and ceilings made of gypsum plasterboard, floors on logs).
Concealed wiring cables are always protected by pipes, corrugations or plastic channels made of non-combustible, hardly combustible materials, which, in addition to preventing mechanical damage, allows you to create an air gap for cooling and achieve conductor replacement. Changeability is one of the most important requirements for hidden wiring, its essence lies in the fact that we must be able to pull the wire out of the sleeve or channel at any time and stretch a new one.
Paths of wires
Sewerage of power supply consists in connecting the main elements of the system with conductors. The starting point is always the switchboard, the end point is junction boxes or individual consumers that are directly connected. There are several ways to lead wires.
On the ceiling in a hidden way, cables can be mounted only if it is hemmed using a frame (gypsum board, lining), or if the ceiling sheet is stretched. It is impossible to cut the floor, and the channels of the hollow-core slabs do not leave room for maneuver, since they have only one direction. There are no such restrictions for open wiring..
In the floor, the wires can be placed both in a monolith (electrical installation is carried out in strong corrugated sleeves or rigid pipes before pouring the screed), and in the voids of frame structures. Some builders and installers prefer to use this particular path, since it is much easier to work below, in many cases there is a significant savings in cable.
On the walls, electrical wiring is bred either if the first two options are not suitable (as a rule, during small repairs), or if an open installation method is used. The main routes should be 100–150 mm from the finished ceiling and within 50–100 mm from beams and cornices. Vertical sections of electrical wiring, suitable for sockets and switches, are mounted strictly vertically, no closer than 100 mm from corners, openings, columns. Inside the frame partitions, through the racks, wires for several consumers located on it can pass, but it will not be possible to stretch the routes here. Note that it is forbidden to lay wires in the joints of several panels, for example, in the corner between the wall and the ceiling..
Protecting and fixing conductors
Sleeves and pipes
Pipes for the protection of wires and cables are used both for hidden wiring and for open installation. They serve several functions. First of all, they prevent mechanical damage to the electrical wiring, for example, when communications are filled with a screed or hidden in strobes. They also allow cables to be mounted without pinching them, so that individual sections of the wiring can be replaced, even if they are located inside an array of buildings. In critical situations, sleeves and pipes resist cable ignition and provide additional electrical protection in case of insulation damage.
Corrugated pipes (sleeves, corrugations) are favorably distinguished by their plasticity, while the edges of the sleeves can withstand mechanical stress well. Corrugated pipes are produced in coils of 25-100 meters, so they can be easily cut along the length of the cable, and do not require the use of additional angle and connecting fittings. The inner diameter of the sleeve is selected for a specific conductor or several conductors, corrugations of 16 and 20 mm are most common, but you can buy a product up to 5 cm in diameter. It is not difficult to bring the wire into the corrugation, since it has a broaching wire, and some sleeves have a smooth inner surface.
Smooth pipes are also used for cable routing, as a rule, they have a greater wall thickness than corrugations, therefore, they are more resistant to static and shock loads. Steel pipes are connected by threaded couplings, while polyethylene products are welded, and vinyl plastic products are glued. Some plastic pipes are turned under heat.
Metal pipes are much more expensive than their plastic competitors and less resistant to corrosion, it is much more difficult to work with them, therefore they are used only in the most difficult conditions (explosive atmosphere, corrosive liquids, wooden walls of a building, heavy monoliths).
Pipes and corrugations are attached individually to the enclosing structures using special clips, or in groups in one layer they are pressed to the base with perforated bracket plates. The optimal spacing for corrugated hoses is from 0.5 to 1 meter, rigid pipes can be fixed after 1.5-3 meters.
Cable ducts are made of thin galvanized steel or plastic, they have a rectangular cross-section with a removable cover (for exposed wiring), or can be solid – for hidden wiring. Plastic ducts are usually used in public and office premises as a cable bearing and at the same time a protective wiring element; they can accommodate power circuit conductors, as well as information and signal wires, for example, intended for a building management system. In residential premises, cable channels are used only if it is impossible to apply hidden installation, as well as in wooden houses with exposed wiring.
The design of polymer channels may vary depending on the purpose. So for the transit of conductors, simple U-shaped products are used, which perform only a protective and carrying function. To organize a workplace, for example, in an office, cable channels with internal partitions have been developed (for wiring conductors for various purposes). They are equipped with the necessary fittings (bends, corners, connectors, plugs, adapters), and also have places for mounting various wiring accessories (sockets, switches, automatic devices). For public premises, special floor boxes are produced, which have a rounded shape and are particularly durable and resistant to abrasion. To make exposed wiring more aesthetically pleasing, you can use skirting or ceiling molding channels..
The main advantage of the channels is the ability to easily get to the wiring, add or replace a conductor, and make diagnostics. It is very easy to assemble structures from plastic boxes, since the material is easily processed. Due to their low dead weight and removable cover, cable ducts can be conveniently mounted on surfaces using ordinary dowels or self-tapping screws. There are no special requirements for the route of cable channels – you can freely choose where to mount the structure. As a rule, plastic products are produced in white, but they are also tinted in bulk..
The routing of wires and cables in trays is considered open. Due to its industrial appearance, it is rarely used to organize the power supply of residential buildings, but in all other cases it is the most successful, especially if there are a lot of wires:
- The cable support system is economical as no protective pipes are required.
- Simplifies the installation of the route – fewer attachment points than for individual wires, there is no gating and furrow filling.
- Conductors are well cooled.
- Possibility to maintain wiring, easy to add and change wires.
Wire trays are made by welding from galvanized wire with a cross-section of 3-5 mm. They are U-shaped with the width of the main bottom shelf up to 500 mm. Partitions are often located inside the wire tray, which delimit power and low-current information conductors, excluding interference. A clear advantage of wire trays can be considered a low weight of the structure with high spatial rigidity, which allows them to be made quite wide.
Sheet trays are made of galvanized steel, stainless steel or aluminum. The sheet, as a rule, is perforated to ensure ventilation of the wires, from above the structure in the form of an inverted “P” can be covered with a solid cover. Sheet trays can be used both for laying a single cable and for a multi-component system – the width of such products is small (about 50–150 mm).
For the heaviest cables, ladder trays (“kabelrost”) are used, consisting of longitudinal load-bearing crossbars and jumpers. They are mounted not only in the horizontal plane, but also for inclined laying, and vertical. Ladder-type trays do not impede ventilation of conductors, leaving easy access to them.
Metal trays are assembled into a single system on threads by means of auxiliary elements – corners, bends, connectors, hangers. The sections have reliable electrical contact with each other, therefore the metal system of the trays can serve as a protection circuit (grounding element). Fastening of cable trays is carried out at a height of at least 2 meters from the floor, they are fixed either to the wall on consoles or to the ceilings using hangers and anchors. Conductors in trays can be arranged in one layer, bundles (packages) or multilayer.
Cables and strings
Such wiring is made by cables with built-in metal support cables. Also lightweight insulated wires (usually up to 16 mm2) can be rigidly or freely fixed on cables (2–6 mm in diameter) or strings – along one supporting element, or across several. Usually, cable wiring is used to organize group lighting lines in large open areas: trading floors, sports grounds, warehouses, workshops, courtyards. The advantage of cable wiring is the economy and low labor intensity of installation, the asset of this system can also include the high industrialization of the preparatory work and, as a result, the tight deadlines.
Often, when installing electrical wiring, situations arise when several cables for various purposes go in the same direction, so the question arises: can they be wired in one protective pipe, box, tray? Regulatory documents do not give an unambiguous answer, the only thing in the PUE (clause 2.1.15 and clause 2.1.16) states that it is impossible to lead together power cables and backup power supply of some consumers, as well as circuit conductors up to 42 V and over 42 V, if the former are not enclosed in an additional insulating pipe. It is also indicated that it is necessary to separately mount emergency and evacuation lighting, the phase and zero of one circuit are recommended to be laid in one pipe.
The experience of operating complex devices shows that power cables with electromagnetic fields and capacitive couplings affect measuring circuits, control systems, and alarms. In control systems, under the influence of interference, false circuits can occur, provoking false alarms of various devices. Therefore, low-current signal cables, communication lines, computer wires and conductors of measuring devices are recommended to be laid and switched separately from power ones. It should be noted that between the wires supplying currents of a close frequency, pickups are minimal..
If separate wiring is impossible for any reason, then it is necessary to use shielded cables or locate poorly compatible conductors at the maximum distance from each other. The optimal distance between parallel routes for various purposes is considered to be from 100 mm, therefore, you can make a wiring in one box or tray, divided by partitions.
Basic rules for wiring
Wiring should be started only after drawing up a detailed plan. We talked about planning power supply in the article “How to make the right wiring in the house: planning electrical work”.
- The wires must be fixed parallel to the main architectural structures.
- Cable turns are always carried out only at right angles with a moderate radius, although it is believed that if the conductors are not fixed, then they can be guided along the shortest path.
- It is not allowed to lay wires in ventilation ducts, however, they are allowed to be crossed by single conductors in a rigid metal pipe.
- Avoid crossing electrical wiring with heating pipes, chimneys, rough, lighting housings. In extreme cases, it is necessary to provide a barrier layer of thermal insulation, or use high-temperature-resistant wires.
- The wires should not touch metal structures, therefore, even behind the frames, they must be fixed to walls and ceilings.
- With parallel installation, the distance between the wires and any pipeline should not be less than 100 mm, if there are intersection points, then it is necessary to organize a gap of at least 50 mm. Leave a “gap” of at least 400 mm between the electric cable and the gas pipe.
- It is also better not to cross wiring cables with each other, therefore, it is necessary to consider the order of the lines, taking into account the direction of rotation of individual conductors relative to the main harness.
- To ensure the possibility of replacing the wires, the transitions of routes between walls and ceilings are carried out only in pipes or ducts. With open wiring, for example, on trays, it is possible to lay wires in layers and bundles through openings filled after wiring with easily removable compounds.
- Wall structures can be used for hidden wiring only if their thickness and bearing capacity are sufficient so that the sleeve with the cable, placed in the gate, is covered with a plaster layer with a thickness of at least 10 mm. Similar requirements for floor wiring – at least 20 mm of mortar must be above the protective sleeve.
- The step of fastening wires and placing supports / hangers is chosen so as to exclude damage to the equipped line under its own weight.
- Pipes, cable ducts and trays are fully assembled into a single system before laying wires and cables.
- When performing hidden wiring, it is recommended to ring out the conductors and measure the insulation resistance.
- After the end of the wiring, measurements should be taken and a wiring plan drawn up, where the main distances will be indicated according to the actual results. We recommend photographing complex knots against the background of a roulette wheel.
These are the basic provisions regarding wiring, they should be relied on in choosing one or another method of wiring. To implement the power supply of a specific object, you have to carefully study it, make difficult decisions, taking into account a lot of different factors. But, if the work is done carefully and in accordance with time-tested standards, then the wiring will be durable and absolutely safe..