- Specificity of laying on combustible surfaces
- Electrical input and grouping
- Open or hidden gasket
- Fire safety measures
- Cable localization methods
- Wiring inside the blockhouse and installation of fittings
Electrical installation in wooden houses is difficult from the point of view of both fire safety and aesthetics, because interior decoration is not always done along a log frame. We will share with you the most relevant technical solutions for installing electrical wiring in a wooden house with our own hands.
Specificity of laying on combustible surfaces
The danger of electrical wiring is due to possible damage to the insulation and the occurrence of a short circuit. The arc temperature reaches several thousand degrees, which is more than enough to initiate wood smoldering. Fortunately, such phenomena occurring on the surface are not too dangerous: heat dissipates into the external environment and the wood does not have time to catch fire..
However, we will see a completely different picture if the closure occurs in a closed space. Almost all the heat will be absorbed by the flammable material, and even the slightest influx of oxygen will lead to the development of a sufficiently strong focus of smoldering. The situation is aggravated by the almost guaranteed presence of wood dust and shavings at the fire site..
For this and other reasons, electrical wiring laid over combustible (wood, plastic) and highly flammable (expanded polystyrene) substrates must be carried out either superficially or inside a special network of channels isolated from the external environment..
Electrical input and grouping
Getting acquainted with the electrical network of a wooden house should start from the connection point on the accounting device. Since the meters have a risk of fire due to overvoltage, their installation on the facade is allowed only in metal boxes with a mounting panel..
The entry of the electric cable into the house is carried out inside a conventional steel pipe, laid from the gable in the attic to the input-distribution device of the house. Naturally, the route is indirect, and the pipe will have to be extended. In this case, the connection is made with threaded elbows and corners..
Since it is the laying of cable lines that is the main difficulty in wooden buildings, it would be reasonable to reduce the length of the channels to a minimum. This is achieved by a well-structured cable system that has a tree-like type..
Large cross-section cables are routed from the ASU, feeding the group shields of several consumers at once. The main switchboard does not have a full range of protection equipment, only a general house one and a differential automatic for each line. In the group shields, on the contrary, there is a selective protection circuit: automatic switches for lighting and socket lines, RCDs and other equipment.
Open or hidden gasket
If you are not confused by the decorative component, electrical installation is performed with standard open wiring, implemented in two ways: on ceramic insulators and in a metal corrugated sleeve. Both methods are designed to distance the conductor from a flammable surface..
But hidden wiring in a wooden house is exactly the very subject of constant disputes on which electricians focus their attention. The implementation of such projects requires not only high financial costs, but also represents a highly complex installation..
First, the required degree of localization is achieved only inside a thick shell made of a material with a high heat capacity, for example, a steel pipe. Moreover, the shell must be airtight so that the development of combustion does not lead to the release of hot gases into the environment. Because of this, the duct system forms a fancy network of pipes and junction boxes with sealed entries. The most suitable place for such a system is inside the interfloor or attic floor, or in the floor.
Secondly, the PUE dictates the requirements for the replaceability of electrical wiring, therefore, in addition to junction boxes, transitional boxes are also installed, the task of which is to provide access to the cable at turns of the track and long sections. According to the standard, no more than two pipe bends between boxes with a total sum of angles of no more than 180 ° are allowed. In addition, it is not allowed to lay more than one cable in one channel, which imposes its own limitations.
Fire safety measures
Even laying in metal pipes cannot guarantee the safety of the wiring. Under certain conditions, such as failure of protective devices, arc burning can be very long and no shell can contain such an amount of heat..
The problem is solved in two ways. First of all, during installation, any damage to the cable, both visible and implicit, is excluded. For example, the permissible bending radius of a copper conductor is at least 6 of its own diameters, and this is the limit value. There is not enough space inside the plumbing elbow to turn, so often the pipes have to be bent.
The second stage is the device of a special protection system. The correct selection of tripping characteristics for automatic machines, the use of fire-prevention RCDs and fuses are just a short list of those measures that can be applied. In principle, with proper laying and well-supplied protection, any abnormal operation of the network that lasts more than 0.02 s is excluded, and this is a guaranteed absence of fires. It is up to you to decide what to spend your own funds: on cable localization or on expensive stuffing of modular shields.
Cable localization methods
The temperature generated by a short circuit is energy. It can be spent on ignition, or on heating a heat-consuming material such as the wall of a steel pipe. In Russia and in the West, this approach has been practiced since the first half of the last century: traditional water pipes and iron boxes with thick walls are an invariable attribute of old buildings. The entire channel system was connected to the main ground electrodes, so that in case of insulation failure and arc burning, a more sensitive differential protection would work.
On this score, there is something to say to modern manufacturers of electrical equipment and installation equipment. Large manufacturers have entire systems of covert cable channels with a high degree of localization. Their difference is that they are not metal, which means they are lightweight. Their installation is undoubtedly easier: such pipes can be easily bent with bare hands, and a wide range of fittings and piece products makes it easier to connect, insert into junction boxes and fasten.
Wiring inside the blockhouse and installation of fittings
The question remained unresolved: how to conduct vertical wiring in conditions where gating is impossible? First of all, it is assumed that the connection points are spacing along the outer and load-bearing walls, made of a double frame. Gasket is also carried out in a protective shell.
If the wall does not have any cavities, the channel is made during the assembly of the frame. Here, it is most beneficial to carry out wiring on the floor, raising the vertical sections of cable lines to a small height. A hole is drilled in each log to be laid with a thick crown, into which a pipe with a cable is then passed.
Sockets and switches can be surface mounted. It is also quite simple to drown them into the wall; for this it is enough to use special installation boxes for wooden walls with a metal case. The most difficult places for vertical wiring are the connection of cable channels to each other. If in the ceiling it is still possible to arrange a sealed pipe entry into the box, then on the socket boxes, most likely, you will have to seal the transition with fiberglass tape.