In construction or repair, no object can do without the laying or replacement of electrical networks. And certainly the decisive value in this case is the cable brand. Cable products for internal wiring should not only meet the requirements for maximum current, insulation, permissible heating, but also fire safety requirements.
NYM Cable Design
The most popular cable product in recent years is the NYM-cable. Description and characteristics are given below. It consists of single-stranded or multi-wire copper conductor cores in the insulation made of a PVC filled plastic compound. Color marking of the conductors of the cable:
- 2-wire - black, blue;
- 3-core - green-yellow, black, blue;
- 4-core - green-yellow, black, blue, brown;
- 5-core - green-yellow, black, blue, brown, black.
The outer shell is made of a PVC filled plastic compound. The color of the shell is light gray. The common shell is filled with extruded, filled-in rubber.
The designation of the type of cable product consists of the letters NYM, denoting:
- N - standard cable (in the German classification);
- Y - PVC insulation (PVC in European interpretation);
- M - the presence of the outer shell.
In addition, the symbols J - the presence of green-yellow wire, or O - the product without a yellow-green vein are put through a hyphen. After that, the number and cross-section of the conductors, working voltage, are indicated.
For example, the marking NYM-J 3x2.5-0.66 denotes a standard cable with an outer sheath in PVC insulation with three cores of 2.5 mm² section for a voltage of 0.66 kV.
In the marking of domestic manufacturers that comply with the requirements of GOST R 53769-2010, this cable will be marked with NYM 3x2.5 ok (N, PE). Here, "o" - a single-wire vein (as an option "m" -multidable wire), "k" - a round vein, N and PE - zero and protective veins.
It's often not the cable, but the NYM wire. Cable - what is it? The definition given in the national standard reads: "A cable product containing one or more insulated sheaths encased". Therefore, it is correct to call NYM not a cable, but a cable.
Technical specifications are important for professionals and for home masters:
- The rated voltage is 0.66 kV.
- Operating temperatures range from -50 to +50 0 C.
- The minimum temperature of the gasket is -5 ° C.
- The minimum bend radius is not less than 4 cable diameters.
- The service life is 30 years.
- Number of cores - from 1 to 5.
- The range of conductor cross-sections is from 1.5 to 35 m2.
- Packing - coils on 25, 50 m or on a drum on 500 m.
And of course, the most important parameter of the cable is its permissible current. It is determined depending on the cross-section of the wires, the method of laying, the outside temperature. For an approximate evaluation it is necessary to use tabular data from the PUE:
|Section, mm.kv.||Current, A|
It should be noted that the cable can be manufactured according to European standards (German), GOST, or TU (technical specifications). The latter are developed by the manufacturer himself. Therefore, the cable parameters, such as the thickness of the insulation, the cross-section tolerance, can vary for different NYM manufacturers. Cable reviews, depending on the manufacturer, get both positive and not very.
Advantages and disadvantages
Like any product, NYM cable also has its own chips. A description of its features is given below:
- High quality insulating material. PVC-plastic heat-resistant, does not support combustion, is flexible enough.
- Ease of installation. Due to the soft aggregate, the outer protective cover is easily removed without the risk of damage to the insulation of current-carrying veins.
- Quality conductive wires of soft copper wire. Easy to twist, forming a quality connection.
- The light-gray color of the outer shell is very convenient for marking with a ballpoint pen or markers during installation.
- Long service life, normative 30 years.
- The cable is not recommended for external installation, it is not resistant to direct sunlight.
- Inconsistency of the cross-section of the conductors indicated in the marking. You often hear "bought a NYM-cable, what is this nonsense?" And everything is very simple: now the production of products under this brand is mastered both at domestic cable plants and in the near abroad. And not all of them comply with German standards or even our GOSTs.
NYM - cable, the description of which indicates that it is intended for a single fixed installation only indoors. A gasket in the beam without additional protection is not allowed. Also, it is not allowed to use this brand cable for direct connection of electrical appliances, in extension cords. Ways of laying are regulated by the manufacturer's recommendations and regulatory documents on electrical and fire safety. The cable allows the laying in the cavities and channels of wall panels, in wall strobes in the layer of plaster, in electrical pipes and boxes. There is an opinion that NYM cables can be laid open on wooden walls, but this is not so. The rules for the installation of electrical installations clearly indicate the possibility of open laying only in pipes or ducts, but hidden inside the wooden walls - in the metal pipes of any wire, including NYM. The cable, the photo of which is placed below, is mounted correctly.
On the domestic market, mainly cable products of domestic production or "nameless" plant are represented. When choosing to pay attention to the marking, any serious cable factory always applies its logo or name. This is at least a minimum, but still a guarantee of quality.
- Sometimes sellers recommend instead of NYM to use SHVVP, PVS. Do not succumb to this trick: SHVVP and PVS are cords, and NYM is the cable. The description regulates completely different areas of their application. Cords - for connection of household electrical appliances and extension cords, cable - for fixed wiring.
- Use cables with a third green-yellow core for protective earthing.
- When choosing the cable section, you can follow the simple recommendation: for lighting - 1.5 sq. Mm, for a rosette network - 2.5 sq. Mm, for an electric stove with an oven - 4-6 sq. M.
- If you doubt the quality of the cable-get a small piece, 1 meter is enough. Check the cable for flammability - insulation must not support self-combustion.
- It is also advisable to check the cross-section of cores. If there is no micrometer, you can simply tightly wind 10 turns of exposed veins on a pencil. And then measure the length of the winding of a conventional ruler. Dividing it by 10, we get the actual diameter of the wire.