Wood, despite the appearance of other building materials, firmly holds the leading position in suburban housing construction, at least in central Russia. With all its environmental advantages, it has such a disadvantage as flammability, the severity of which is greatly increased by the presence of developed electrical wiring in the house. This is confirmed by the statistics of the Ministry of Emergency Situations: more than half of the fires occurred due to wiring faults. Given this feature, when creating a power cable system, it is necessary to strictly observe certain rules, the most significant of which are discussed below.
1. Air inlet
A popular air inlet into a wooden house is implemented on the basis of SIP-4, the core of which is assembled on aluminum conductors. PUE, clause 2.1.49 contains a ban on open laying of such wires on wooden structures. This requires the transition to a cable with copper conductors as close as possible to the entry point, which is traditionally VVG-ng (LS), i.e. in a non-flammable and low-smoke version. It is permissible to refer to VVG-ng or its imported analogue, NYY-J.
2. Compliance with the rules of hidden wiring according to PUE
The linear part of the hidden wiring based on paragraph 7.1.38 of the PUE is carried out only on metal pipes, which provide reliable protection of cables from damage by nails. The ends of the pipes must be free of sharp edges and burrs that can damage the insulation when pulling. The cross-section of pipes and the location of the junction (broaching) boxes are selected taking into account the replacement of cables when such a need arises without excessive pulling forces.
3. Correct implementation of open wiring
An open transaction is created in two main variants.
For its implementation, mainly protective boxes are involved, Figure 1, which, similar to other plastic products for indoor use, must have a fire safety certificate
Retro wiring, which is quickly becoming fashionable lately and looks very appropriate in wooden houses, is created using roller insulators, Figure 2, i.e. without direct contact with the tree.
Corrugated pipes and conventional open cabling with triple insulated cables are rare due to poor aesthetics.
4. Minimizing the number of bends and splices
This recommendation is based on the known fact that any damage to the integrity of an electrical wire increases line losses. The reason for this phenomenon is the appearance of the so-called. contact resistance, which tends to increase during operation. At currents close to the limit, the splice point of the wires begins to heat up, which in severe cases can lead to a fire.
5. Application of fire protection RCDs
Article 7.1.84 of the PUE recommends installing a 300-millimeter fireproof RCD, Figure 3, at the entrance to the house, if possible combining it with an introductory machine. A number of experts express some skepticism about the usefulness of such an element, which is associated with the recommendatory nature of the PUE. Nevertheless, it cannot be denied that the introduction of another stage of protection into the wiring will increase the level of fire safety of the home.
6. Use of appropriate wiring accessories
Regardless of the version of the socket or switch (internal or external), their components that directly in contact with wood during installation, must be made of metal or non-combustible plastic, Figure 4. There is a requirement to use only metal products for this purpose.
For other elements, the use of plastic or other components is allowed. Non-flammable performance must be confirmed by a certificate.