Wire for grounding, how to choose a cross-section and connect, color in a three-core wire, popular brands – ElektrikExpert.ru

A ground wire is an invariable attribute of wiring in houses and apartments, designed to protect a person from falling under the influence of electric current.

Failure to use ground electrodes carries serious risks. In the event of an insulation breakdown and phase contact with metal elements, a person may be energized. Serious injury or even death can result.

Below we will consider how to wisely choose the color, type and section of the ground wire. Let’s talk about the principles of selecting a product for installation in a private house, bathroom or apartment.

Basic terms

For a better understanding, let’s deal with the basic terms, because this is important for the correct choice and installation of a grounding conductor.

Consider the basic definitions:

1. Grounding – connection of metal parts of an electrical installation or equipment with a grounding device. In other words, this is a set of measures aimed at improving human safety when using electrical appliances.
2. A grounding device is a group of elements that ensure the removal of voltage (potential) to the ground to protect a person from the negative effects of electric current. It consists of a ground electrode and a wire or bar connecting to a non-current-carrying part.
3. Grounding – a structure that consists of several welded metal bars immersed in the ground to a certain depth to ensure rapid potential removal. The main characteristic of the ground electrode is the resistance, which should not exceed 4 ohms.
4. Ground wire – a product that connects a metal non-current-carrying part of the equipment to the ground electrode. Fixed by welding or bolting. The degree of safety directly depends on the correct choice of this part of the structure.
5. Ground bus is an element of switchboards designed to connect PE conductors, a neutral working wire and a ground electrode. The main difference from the wire is the design features that allow you to attach other ground wires to the busbar.

Today, a term such as a ground loop is often encountered. This is the name of the earth electrode used in everyday life. It also refers to the construction, the state of several electrodes or metal corners, located in the ground and mounted in the shape of a triangle. It is to this design that the grounding bar is connected.

Types and features of grounding

When buying a wire to connect to a grounding device, it is important to know the types of grounding and its purpose.

There are two types in total:

1. Working. Purpose – to ensure the normal operation of the electrical installation. Without fulfilling this condition, the functioning of the network would be impossible for various reasons. In other words, this is the normal mode of operation of the equipment. An example is the neutral grounding of power transformers in order to increase the short circuit current and increase the sensitivity of the relay protection.
2. Protective. The task is to guarantee the safety of people from falling under the influence of electric current in everyday life or when servicing equipment at overhead lines, substation or other electrical installations. Depending on the situation, it can be provided for protection against lightning, surge voltage and potential that may appear on the housing of household or other appliances.

In apartments and private cottages, protective type grounding is used, which we will discuss in more detail.

The principle of construction and purpose of protective grounding

In simple terms, protective grounding is formed as follows. The ground wire is connected to a non-current-carrying metal part.

At the next stage, the “ground” connected to the equipment is combined, and then goes by a separate wire or busbar to the grounding device.

In the event of a voltage breakdown on a metal case and a person touching it, the potential goes through the ground, and not through the body. Due to the low resistance, protections and RCDs operate faster.

For comparison, the R of a ground loop is only 4 ohms or less, and that of a human is over 1000 ohms. We know from Ohm’s law that current always takes the path of least resistance.

Thus, protective grounding is designed to solve such problems:

• reducing the potential difference between the grounded device and other objects and protecting human life;
• diversion of current to the ground and an increase in its values ​​​​for the operation of protective devices (RCD, automatic devices).

Therefore, when laying a conductor for grounding, it is important to take care of the presence of protective devices. The latter must quickly respond to leakage or high currents, cutting off the damaged area. The sooner this happens, the better.

Requirements for the cross section at the ground

Many owners of houses and apartments are faced with the need to do their own grounding. This is explained by the fact that in old buildings until 1998 there were no groundings and, accordingly, there were no busbars for connection at all.

Even if the house already has a grounding conductor, when choosing a wire, you need to find out the type of system.

Taking into account the PUE, four grounding schemes are distinguished:

1. TN-S – the use of a neutral and a separate conductor. The circuit is relevant for alternating voltage.
2. TN-C – combination of “0” and earth with a common wire. In such a scheme, the neutral goes separately, which is typical for old buildings.
3. TT – direct earth to electrical equipment.
4. IT – connection to the body with the use of resistance or insulation of current-carrying conductors.

More about grounding systems https://elektrikexpert.ru/sistemy-zazemlenij.html, their advantages and disadvantages.

To choose the correct section, it is important to take into account one more thing – the type of grounding.

It can be:

• stationary (done without the need to move, on an ongoing basis);
• portable (can be removed if necessary, moved to another object).

For domestic purposes, as a rule, the first option is used. It is on him that we will focus when choosing a section (S).

To avoid mistakes, follow these simple rules:

1. For phase S up to 16 sq. mm grounding conductor is selected of the same size.
2. At S, the phase is from 16 to 35 square meters. mm cross section of the “ground” conductor is selected for 16 square meters. mm.
3. If S of the phase wire is over 35 sq. mm, the grounding conductor must have a thickness of at least half of this indicator.

Most often, copper wires with S equal to 4 square meters are tried on in a house or apartment. mm. Under such circumstances, the S of the ground wire is selected with the same parameter.

If, for example, the thickness of the phase suitable for the cabinet is 25 sq. mm, the optimal parameter S is 16 sq. mm. Everything is simple here, so there should be no confusion.

It is important to remember a number of rules:

1. For TN-C and TN-CS, the lower cross-sectional threshold is 10 sq. mm for copper and 16 sq. mm for aluminum conductor.
2. In an apartment or house, a wire with one residential is enough.
3. Color requirements – yellow-green.

Sometimes a special formula is used when calculating the grounding cross section. It takes into account the short-circuit current, protection response time, type of insulation, type of gasket and other features. In practice, this method is rarely used.

Ground wire color and connection features

To avoid confusion, it is important to understand what designations need to be provided for such wires.

The following types of markings are currently used:

1. PE – 0-th protective wires and shank, having a color in the form of intertwining yellow-green shades.
2. N – 0-th wires, indicated in blue (neutral).
3. PEN – the union of zero and ground. The main part is blue, at the edges a combination of yellow-green.

In our case, a designation with the corresponding color design (yellow and green) is used. In the same way, it is also indicated in a three-wire wire.

If there is no wire with the required color at hand, you can use ordinary yellow and green electrical tape. All that is required is to make marks on the ends of the wire.

Grounding (PE) is brought out and connected to the grounding bus, the housing or the metal door of the shield. The neutral wire (N) is connected to the neutral bar.

More about grounding and zeroing https://elektrikexpert.ru/zazemlenie-i-zanulenie.html, what is the difference between them.

Marking

For a better understanding, let’s raise the issue of marking the insulation of the conductors used.

The following designations can be used in the wire name:

• A – aluminum core (in the absence of a letter – copper);
• AC – the presence of a braid of lead;
• AA – stranded wire having an aluminum core and a braid of the same material;
• B – corrosion protection, made of two-layer steel;
• G – without a shell;
• Bn – protection against moisture and resistance to fire;
• NP – non-combustible material;
• P – rubber sheath;
• B – sheath made of polyvinyl chloride;
• K – control cable, etc.

It is necessary to pay attention to the above marking when choosing a wire for grounding in relation to its cross section (this was mentioned above).

Brands and requirements

When buying a cable for grounding, it is necessary to thoroughly study it for the possibility of using it in a house, apartment or a special room (for example, a bathroom, sauna, etc.).

The grounding conductor can be single-core or stranded. Here you need to focus on the place of installation and ease of use.

Here are some examples:

1. When connecting the housing to the cabinet door, it is necessary to maintain mobility, so it is better to use a stranded product. If you install a single-core conductor, it will quickly be damaged due to frequent bending.
2. For connecting the body of an electric motor, where mobility is not needed, rigid cores are useful. There are no special requirements for flexibility here.
3. When arranging grounding in an apartment or house, you can use any of the types of wires, taking into account the risk of damage and ease of installation.

Depending on the type, the grounding conductor can be made of aluminum and copper, come as a separate product or as part of a cable coil, be with or without insulation.

Today, there are several main brands of wires.

NYM

A product with a copper core, an intermediate sheath of green-yellow color. Differs in convenience of installation, it is applied to voltage up to 660 V. Operating frequency is 50 Hz.

The number of conductors can be from one to five with a cross section of 1,5 to 6 square meters. mm. The rated current is determined by the working section of the conductor.

Operating temperature from -50 to +50 degrees Celsius. The bending radius is not more than four cable diameters.

Pros – resistance to moisture and fire, flexibility and a large selection of options.

Cons – high price and fear of direct sunlight.

VVG

Cable with PVC insulation, outer PVC sheath and without a special protective layer (armor). It can be single or multi-core.

In 3, 4 and 5-core cables, grounding and neutral can be provided.

It is allowed to use as a grounding conductor at voltages up to 600 V.

Some types of cable are designed to operate at 1000-2500 V. Temperature range from -50 to +50 degrees Celsius.

PV3

Copper wire with PVC insulation. It is highly flexible, which allows it to be used for grounding various devices and mechanisms (including in everyday life).

The product is resistant to moisture and can operate in temperatures from +60 to -70 degrees Celsius. Therefore, it can be used even in extreme conditions – baths, bathrooms and on the street.

PV3 is not afraid of mold and is not subject to fire. When exposed to high temperature, the usual melting of the shell occurs.

PV6

A reliable product used for laying current-carrying parts and grounding. During use, it is important to avoid direct sunlight and high temperatures.

The cores of the product consist of copper, they are monowire or stranded. Operating voltage up to 1000 V.

Thanks to the use of transparent plastic, it is more convenient to control the health of the device.

Colors may vary, so color coding is required. To do this, you can use the approach mentioned above – marking with yellow and green electrical tape.

ESUY

Copper grounding cable with a high degree of flexibility. The core is made of thin wires. The top has a high strength braid. Silicone rubber is not used in the manufacture.

The product has high resistance to frost, a transparent shell and operating temperature from -40 to +70 degrees Celsius.

The most popular brands of wires / cables for grounding are discussed above, but other options can be used. The main thing is that the conductor meets the requirements of flexibility and section.

Wires for grounding 380 Volts

When choosing a 380 V ground wire, it is important to adhere to the same requirements as discussed above. Pay attention to the type of insulation, section, flexibility, operating temperature and other parameters. There are no special differences in requirements between grounding at 220 or 380 V.

If we talk about the type of wires used, it is recommended to use the brands already discussed above.

To them, you can add a PVA 5×6 wire in double round insulation with five cores. Suitable for powering and grounding equipment up to 660V.

Despite the general approaches to choosing a conductor, there are some differences in grounding between 220 and 380 V networks.

In the first case, a single-phase network is used, and in the second, a three-phase network. Therefore, for a 220 V network, a cable with three wires (ground, phase and zero) is suitable, and for 380 V – with five (three phases, zero and ground).

What is better to buy for a private house and bathroom

Now let’s look at how to choose a wire for grounding in relation to a specific installation site.

For home

When installing a grounding structure in a private house, consider the cross section of the wiring and the presence of a ground loop. If the grounding conductor is dug into the ground, and the bar is removed, it remains to choose the right cable.

Pay attention to the following points:

1. Section. Should be selected taking into account the operating conditions. In most cases, for a house, you can use a wire from 4 square meters. mm and thicker.
2. If a wire with a cross section of 6 square meters is used. mm without insulation, it is necessary to give preference to a stranded conductor.
3. As grounding conductors, it is recommended to use steel reinforcement having a diameter of 16 sq. mm. It is allowed to use a steel angle of 50 mm or more.
4. After finishing work, it is important to measure the resistance, which should not exceed 4 ohms.

When choosing a cable, you can use any of those proposed above – VVG, PV-6, NYM, ESUY, PPV and others.

Read – how to make grounding in a private house.

For bathroom

When it comes to the bathroom, it is important to ground all metal elements. This category includes the body of a metal bath, pipelines for hot and cold water supply and other metal elements.

The cross section of the ground wire must be at least 2,5 square meters. mm, but when using a thicker phase wire, it is necessary to use the “ground” for 4 square meters. mm.

Wires that are connected to metal elements can be brought out to a common busbar, and from there, send the wire to the shield or to the machines (there must be a ground wire for a bolted connection).

The conductor used may be flexible or solid, depending on the particular installation. Here the decision is made on the spot.

An important point is the requirement for cable resistance to temperature and moisture. The above brands of wires fully comply with the required characteristics.

Results

Now you know almost everything about ground wires, what they are used for, how to select them and which cables to prefer.

Remember that health and even life depend on the correct choice of the earth conductor. Mistakes in selection can lead to damage to the “ground” wire and its inability to perform its functions of dissipating current.