NYM (cable): description and reviews

In the construction or repair, not a single object can do without laying or replacing electrical networks. And of course, the cable brand is of decisive importance. 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 recently is the NYM cable. Description and characteristics are given below. It consists of single or multi-wire copper current-carrying conductors in isolation from finely filled PVC compound. Color coding of cable cores:

• 2-core - 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 finely filled PVC compound. Shell color is light gray. The common shell is filled with extruded finely filled rubber.

Marking

The cable type designation is made up of NYM letters that indicate:

• N - standard cable (in German classification);
• Y - PVC insulation (PVC in the European interpretation);
• M - the presence of the outer shell.

Additionally, the hyphen characters J are applied - the presence of a green-yellow wire, or O - a product without a yellow-green core. After that, the number and cross-section of cores, operating voltage are indicated.
For example, the NYM-J mark 3x2.5-0.66 indicates a standard cable with an outer sheath in PVC insulation with three conductors with a cross-section of 2.5 square mm for a voltage of 0.66 kV.
In the marking of domestic manufacturers that comply with the requirements of GOST R 53769-2010, such a cable will be marked with NYM 3x2.5 ok (N, PE). Here “o” is a single-wire core (as an option “m” is multi-wire), “k” is a round core, N and PE are zero and protective conductors.
Often they say not a cable, but a NYM wire. Cable - what is it? The definition given in the state standard reads as follows: “A cable product containing one or more insulated cores enclosed in a sheath”. Therefore, it is correct to call NYM not a wire, but a cable.

main parameters

Technical specifications are important for both professionals and home masters:

• Rated voltage - 0.66 kV.
• Operating temperatures - from -50 to +50 ⁰ .
• The minimum gasket temperature is from -5 ⁰ .
• The minimum bending radius is at least 4 cable diameters.
• The service life is 30 years.
• Number of cores - from 1 to 5.
• The cross-sectional range of conductors is from 1.5 to 35 sq. Mm.
• Packing - bays of 25, 50 m or on a drum of 500 m.

And of course, the most important parameter of the cable is its allowable current. It is determined depending on the cross-section of the cores, the laying method, and the outside temperature. For an approximate assessment, you need to use the tabular data from the PUE:

It should be noted that the cable can be produced according to European standards (German), GOST, or TU (technical conditions). The latter are developed by the manufacturer. Therefore, cable parameters such as insulation thickness, core cross section tolerance may vary from NYM manufacturers. Cable reviews, depending on the manufacturer, receive both positive and not very good.

Advantages and disadvantages

Like any product, NYM cable has its own chips. A description of its features is given below:

• High quality insulating material. PVC plastic is heat-resistant, does not support combustion, is flexible enough.
• Convenience of installation. Due to the soft filler, the outer protective cover is easily removed without the risk of damage to the insulation of live conductors.
• Quality conductive wires made 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 marker during installation.
• Long service life, normative 30 years.
• The cable is not recommended for outdoor installation, unstable to direct sunlight.
• Inconsistency of the cross-section of the wires indicated in the marking. You often hear “bought a NYM cable, what the hell is this?” And everything is very simple: now the production of products under this brand has been mastered both at domestic cable factories and in neighboring countries. And not all of them comply with German standards or even our state standards.

Application

NYM is a cable, the description of which indicates that it is intended for single stationary installation only indoors. Laying in a bundle without additional protection is not allowed. It is also not allowed to use a cable of this brand for direct connection of electrical appliances in extension cords. Laying methods are governed by the manufacturer's recommendations and regulatory documents on electrical and fire safety. The cable allows laying in the cavities and channels of wall panels, in wall gates in a layer of plaster, in electrical pipes and ducts. It is believed that NYM cables can be laid openly on wooden walls, but this is not so. Electrical installation rules clearly indicate the possibility of open laying only in pipes or ducts, and hidden inside wooden walls - in metal pipes of any wire, including NYM. The cable, the photo of which is posted below, is mounted correctly.

Cable selection

The domestic market is mainly represented by cable products of domestic production or the “nameless” factory. When choosing, pay attention to the marking, any serious cable factory always puts its logo or name. This is at least minimal, but still a guarantee of quality.

• Sometimes sellers recommend instead of NYM to use ballscrew, PVA. Do not fall for this trick: ball screw and PVA are cords, and NYM are cables. The description governs completely different areas of their application. Cords - for connecting household electrical appliances and extension cords, cable - for stationary wiring.
• Use cables with a third green-yellow core for protective grounding.
• When choosing a cable section, you can be guided by a simple recommendation: for lighting - 1.5 sq. Mm, for a power outlet - 2.5 sq. Mm, for an electric stove with an oven - 4-6 sq. Mm.
• If in doubt about the quality of the cable, get a small length, 1 meter is enough. Check the cable for flammability - the insulation should not support spontaneous combustion.
• It is also advisable to check the cross section of the cores. If there is no micrometer, you can simply tightly wind 10 turns of bare core onto a pencil. And then measure the length of the winding with a regular ruler. Dividing it by 10, we get the actual diameter of the wire.