Threaded fitting. Photo: OTP Equipment
Residents of city apartments are accustomed to the fact that electrical cables are hidden from view and reliably protected by concrete structures — they are practically not in danger of damage, and a short circuit due to overload and broken insulation will not lead to a fire. When building a country wooden house, the owners also tend to hide the wiring, but serious problems lie in wait here. Before discussing them with installers, you need to look at the regulatory documents.
Despite the desire to hide the wiring, it is easier and safer to lay it openly using overhead installation products. Photo: naBrevno
How to find hidden wiring in the wall with and without special devices
Twisted metal hose. Photo: Eleks
On construction sites and forums of electrical installation companies, you can find numerous references to standards (PUE, PPB and PTEEP) without links to specific pages and paragraphs of these documents. Let’s fix this situation.
In the PUE (“Rules for the Installation of Electrical Installations”) of the 7th edition of electrical wiring in wooden houses, paragraph 7.1.38 indirectly refers to: “Electrical networks laid behind impassable suspended ceilings and in partitions are considered as hidden electrical wiring, and they should be carried out: behind ceilings and in the voids of partitions made of combustible materials — in metal pipes with a localization ability (that is, the ability to withstand a short circuit of the cable cores without burning out. — Ed.), and in closed boxes ”(obviously, also metal. — Ed.). It is worth noting that PUE-7 are not complete and do not yet take into account many of the nuances of electrical installation.
Behind wooden ceilings and sheathing, it is impossible to lay a cable without protection, as well as in a PVC sleeve. Photo: ShutterStock/Fotodom.ru
A more detailed guide to laying wires and cables can be found in the 6th edition of the EMP, which practitioners are mainly guided by.
Hidden wiring is carried out in a steel pipe. Photo: naBrevno
An abridged version of the table from chapter 2.1 (“Electrical wiring”) of this standard, supplemented by information from some paragraphs of the same chapter, we provide in the article. It should also be mentioned that paragraph 2.1.23 prescribes to maintain access to the junctions and branches of the wires, that is, the junction boxes must be mounted openly.
Open — on insulators and in cable channels. Photo: naBrevno
In addition, GOST R53315-2009 “Cable products. Fire Safety Requirements”, section 6 of which contains the requirement to use a cable marked VVGNG-LS in residential premises (in non-combustible insulation, with low smoke emission).
Wiring in a private house: planning and installation
Today, in timber and log houses, cables are laid in three main ways — in hidden metal pipes, on open insulators and in overhead cable channels. They differ in the appearance of the wiring, as well as the cost of materials and labor.
With any method of laying cables, the circuits must be equipped with automatic devices and RCDs, carefully calculating the ratings of these devices.
Clamps. Photo: Stroysvyazdetal
Hidden wiring in steel and copper thick-walled pipes is performed, as a rule, at the stage of assembling a log house. This method greatly increases the volume of carpentry work, is carried out in stages by the joint efforts of builders and an electrical installation company. The task is complicated by the need to take into account the shrinkage of the walls and the possibility of rusting pipes in contact with wet wood. In addition, you have to use special mortise sockets and switches with metal cups, which are at least twice as expensive as usual and are often only available on request.
Wires on insulators and antique switches go well with wooden walls. Photo: Salvador
Open wiring on insulators goes well with chopped walls (especially when decorating an interior in a classic and country style). Twisted wires (there are several colors) and ceramic insulator glasses are by no means cheap, but the cost of them is offset by ease of installation. If you do without antique-style sockets and switches, the price of which starts from 1100 rubles, and use ordinary overhead products, then the cost of electrical installation will be 2-3 times lower than with hidden cabling. At the same time, an open network, if necessary, can easily be supplemented with new lines.
The disadvantage of wiring on insulators is that it is poorly protected from mechanical damage, so it should be mounted at a height of at least 2 m from the floor (clause 2.1.52 PUE-7) and equip all circuits in the house with residual current devices (RCD) with leakage current not more than 30 mA.
A corrugated pipe, unlike a twisted metal hose, can have a localization ability and be used in a wooden house. Its connection and fixation should be carried out using threaded fittings and clamps. Photo: Elektrogarant
Open laying in cable channels. This is the easiest and most affordable option. PVC boxes provide fast attenuation of the cable in case of a short circuit and protect it well from external influences. Today, many manufacturers produce a series of electrical installation products, cable channels and special accessories that allow you to aesthetically and safely perform open wiring in a log or timber house.
As for buildings made of SIP panels and other «frameworks» (which are often also classified as wooden houses), it is most safe to conduct wiring in the thickness of a three-layer inner wall cladding made of plasterboard sheets. At the same time, in the middle layer, grooves are made for cables, so that the latter are separated from the combustible structure by non-combustible material 10 mm thick — in full accordance with PUE-6. At the locations of mortise sockets and switches, at the same time, sampling should be made to an increased depth and combustible insulation should be covered, for example, with a thick layer of gypsum plaster.
Wireless switches and regulators will help to significantly simplify the wiring in a wooden house and make the wiring safer in terms of fire. Among them are single- and multi-channel radio remote controls and IR sensors powered by batteries (batteries need to be replaced every 5–10 years), devices that convert pressure energy into a radio signal, as well as mobile “devices” with special programs installed for home electrical control. Such solutions can be used to control specific devices or their groups (for example, blinds or lighting) or be part of a “smart home” system that controls all electrics in the premises and on the territory of the backyard.
Whom to entrust the electrical installation
It is imperative that the wiring in the house is not installed by handymen builders, but by professional electricians who are familiar with the requirements of the regulations. They will control the quality of components, calculate the rating of protective devices, assemble the shield, reliably isolate the connections and perform the installation of electrical installations in accordance with the project.
The proximity and contact of electrical wiring, even protected, with flammable vapor and waterproofing materials should be avoided.
Retro wiring. Photo: naBrevno
The choice of the method of laying wires and cables on bases and structures made of combustible materials according to fire safety conditions (according to PUE-6)
|Type of wire or cable||Type of wiring and laying method|
|Exposed electrical wiring||Unprotected wires; shielded wires* and cables sheathed with combustible materials||On casters, insulators** or lined with fireproof materials***|
|Sheathed wires and cables sheathed from non-combustible and slow-burning materials||directly on the surface|
|Unprotected and protected wires and cables sheathed from combustible, slow-burning materials||In pipes and boxes made of non-combustible materials|
|Hidden wiring||Unprotected wires; shielded wires and cables sheathed with combustible materials||With a lining of fireproof materials and subsequent plastering or protection on all sides with a continuous layer of other fireproof materials|
|Sheathed wires and cables sheathed with flame retardant materials||Lined with fireproof materials|
|The same from non-combustible||directly on the surface|
|Unprotected wires and cables sheathed with combustible, slow-burning and non-combustible materials||In pipes and ducts made of slow-burning materials — with a lining of fireproof materials and subsequent plastering; in pipes and boxes made of non-combustible materials — directly|
* Unprotected — wires that do not have a sheath over the electrical insulation of conductors (brands APRTO, PRD, etc.). Protected — wires that have a hermetic sheath over the insulation of the conductors (brands APRN, PRHD, etc.).
** At a distance of at least 10 mm from the combustible structure. At the same time, in the places where walls and ceilings pass, the wires must be additionally protected by an insulating pipe (clause 2.1. 59 PUE).
*** The lining of non-combustible materials must protrude from each side of the wire, cable, pipe or conduit by at least 10 mm. (When laying in closed niches and voids, for example, between a cladding and a wall, pipes and ducts should be separated on all sides from combustible structures with a layer of fireproof material at least 10 mm thick — clause 2.1.40.)
Source: Ideas for Your Home Magazine#229