Purpose and design of the potential equalization box

In accordance with modern standards, the building where electrical wiring is installed must have a potential equalization system. Moreover, in addition to the main one, an additional SUP is installed. The organization of the latter (connecting a potential equalization box, etc.) will be discussed in this article. Let's start with the theory, namely, what SUPs are.

An example of organizing the main and additional SUP

Third party conductive part

A conductor that is not part of the electrical installation is called an extraneous conductive part.
A formal example is a metal door handle or hinge. You can focus on 2 principles according to which parts are selected for connecting to the additional potential equalization bus. The goal is not to make the system overloaded.

• The actual or potential possibility of communication with the “earth”.
• Possibility of potential appearance on a third-party conductive part in the event of an electrical equipment failure during operation.

The table below shows examples of third-party conductive parts that should or should not be connected to the additional potential equalization bus:

Issues related to potential equalization in bathrooms and shower rooms are regulated by Circular No. 23/2009.

One of the common questions: can tap water supplied through plastic pipes be a third-party conductive part? The said circular gives the following answer: “...Tap water of normal quality...is not considered as a third-party conductive part.” This means that such a possibility exists, at least due to the significant presence of various ferrous compounds in water. The circular recommends using conductive inserts on taps from water supply risers, connecting them to an additional potential equalization bus.

What is OSUP, what is it for?

This can be clearly explained in the picture of the equalization system in the house. For the safety of residents and staff, it is necessary to build such a system. All conductive parts of equipment, household appliances, metal communications must be connected to separate grounding buses; they are connected to the main grounding bus (GZSh). The GZSh is connected to the ground loop.

Important! The buses must have as many connection points as there are objects. Each object is grounded with a separate conductor. Serial connection is not allowed. All busbars must be accessible for inspection, conductors must have a sufficient cross-section to withstand short-circuit current.

Potential equalization system in the house

Additional potential equalization system (DSUP)

An additional potential equalization system is necessary to provide additional electrical safety in areas with increased danger, for example, a bathroom or shower room.

P. 7.1.88. The PUE establishes that all touchable elements must be connected to the additional potential equalization system:

1. exposed conductive parts of stationary electrical installations,
2. third-party conductive parts (i.e. not part of the electrical installation) and
3. neutral protective conductors of all electrical equipment (including plug sockets).

For bathrooms and shower rooms, an additional potential equalization system is mandatory and must include, among other things, the connection of third-party conductive parts extending outside the premises. If there is no electrical equipment with neutral protective conductors connected to the potential equalization system (i.e. with PE conductors, not to be confused with the working zero!), then the potential equalization system should be connected to the PE bus (clamp) at the input.

Heating elements embedded in the floor must be covered with a grounded metal mesh or a grounded metal shell connected to a potential equalization system. As additional protection for heating elements, it is recommended to use an RCD with a current of up to 30 mA.

It is not allowed to use local potential equalization systems for saunas, baths and shower rooms.

• exposed conductive parts of stationary electrical equipment;
• third-party conductive parts, including touchable metal parts of building structures;
• neutral protective conductors in the TN system and protective earth conductors in the IT and TT systems, including the protective conductors of socket outlets.

This system consists of the following elements:

1. potential equalization boxes (PEC);
2. potential equalization conductors.

The potential equalization box contains a PE bus, which is connected with a copper wire with a cross-section of 6 sq. mm to the PE bus of the input electrical panel (apartment, house). After this, by connecting to the PCC, all metal structures of the bathroom are grounded:

• heating;
• cold and hot water supply;
• bath (or shower).

Thus, the protective potential equalization conductors from grounded structures are laid with copper wire with a cross-section of 2.5-6 sq. mm and connected to the PE bus in the potential equalization box. The protective potential equalization conductors can be secured to the pipes using metal clamps.

All sockets installed in the bathroom are also subject to additional grounding.

The issue of ensuring electrical safety and implementing a system of additional potential equalization in bathrooms, showers and sanitary ware is discussed in detail in No. 23/2009, approved by the Deputy Head of the Federal Service for Environmental, Technological and Nuclear Supervision N.A. Fadeev. (letter dated 07/08/2009 No. NF - 45/2007) and approved by the President of the Roselectromontazh Association E.F. Khomitsky.

The purpose of the circular is to provide clarification on the implementation of a number of provisions of Chapters 7.1 and 1.7 of the PUE and specific recommendations for the implementation of individual elements of the system of additional potential equalization in bathrooms, showers and sanitary facilities and bringing them into compliance with new international requirements regulated by the IEC 60364-5-54 standard.

Requirements for conductors of potential equalization systems are specified in chapters 7.1 and 1.7 of the “Rules for Electrical Installations” (PUE) of the seventh edition.

However, at present, during the construction of buildings, plastic pipes in water supply systems have become widespread, and therefore additional questions have arisen regarding ensuring electrical safety in installations related to the likelihood of electric shock from a stream of water, water taps, faucets, heated towel rails and other metal elements of water fittings .

Note

Tap water of normal quality in terms of volumetric electrical resistance (conductivity) is classified as a semiconducting substance and, from the point of view of the possibility of electric shock, is not considered as a third-party conductive part.

The difference between equalization and leveling

The rules for the construction of electrical installations (PUE), section 1.7 discusses methods for arranging BPCS. It describes how to correctly connect and interconnect the conductors of protective grounding and equalization systems.

The difference between the concepts is as follows:

• Equalization is a connection method that makes the potentials that arise on all accessible metal parts of structures approximately equal to reduce voltage and make it safe;
• Equalization is the elimination of voltage that arises between all easily accessible metal surfaces by connecting them together with wires and grounding the resulting circuit.

If everything is connected to each other and connected to protective grounding, this is equalization.

Situations that arise in practice

The same thing happens in everyday life. A phase may occur on an electrical device due to damage to the insulation, the presence of moisture in the contact group, or failure of the power supply. If you touch a live device and at the same time touch a metal object in the room connected to the ground (for example, a pipeline), you may receive an electric shock.

When an electrical device is properly connected to grounding, a short circuit occurs on the housing, and automatic protection is triggered, disconnecting the circuit. In this case, there is no danger of electric shock, therefore the room is equipped with an energy supply system in accordance with the standards of the Electrical Installation Rules (PUE).

Another situation like this may arise. One of the neighbors in the building connected the neutral wire to the radiator (perhaps out of illiteracy, or perhaps in order to rewind the readings on the electric meter). A dangerous potential of 50 to 220 volts has arisen on the heating system. According to theory, the tension should remain in the ground where the steel pipes are laid. But if between any apartment and the basement part of the pipeline was replaced with plastic, the conductor will open.

The heated towel rail in the bathroom acquired a potential of, for example, 150 volts. When you touch it and a grounded washing machine, the same potential difference will occur, which is life-threatening. The problem is not with the electrical appliance, but with the heated towel rail, which is energized.

Here's another example. There is a power wire running through the wall of the apartment, and a water supply is laid nearby. Under load (when the boiler or electric oven is turned on), an EMF (electromotive force) may occur in the pipeline. The water flow is charged with a potential of up to 50 volts. This may not be a life-threatening voltage, but when you touch a faucet in the kitchen, you can feel electric shocks.

Purpose of the system and its types

At any residential property there are many metal objects and structures that are good conductors of electricity.

This:

• Heating pipes laid in the apartment.
• Steel boxes for ventilation shafts.
• Auxiliary equipment for bathrooms.
• Water supply and sewerage pipes.

Important!

Due to the peculiarities of their location within an apartment or house, most often all these elements do not have a reliable electrical connection.

Due to different transition resistances in the grounding contacts, the connection points (and, consequently, the housing) may have different potentials. Under certain conditions, the magnitude of this difference reaches values ​​that are dangerous for humans (25-50 Volts). This can be clearly seen from the following figure.

To eliminate this difference and eliminate the possibility of electric shock to the residents of the house, a potential equalization system is organized in it. To do this, within the apartment, all equipment housings, pipes, as well as steel doors and heating system elements are combined into a single circuit.

This is done for the purpose of subsequently connecting to the existing ground loop. This is the only way to equalize the potentials that appear on various elements of household equipment (photo below).

Types of equalization systems

There are two types of equalization systems, one of which is called the main one (OSUP), and the second - additional (DSU).

The latter will not be able to function without a properly functioning main system, which must meet the following requirements:

• Starting the GZSh in a distribution cabinet, when arranging it, it is forbidden to combine PE and N conductors.
• For all structures that are supposed to be grounded, only a radial connection scheme to the ground loop is selected.
• It is not allowed to install separate switching devices in protective grounding circuits.

Unlike OSUP, DCS combines conductive parts of electrical equipment, the distance between which is so large that a dangerous potential difference can form in them. There is also a possibility that they can be accidentally touched at the same time (with both hands, for example). These same elements include steel parts of underground and above-ground structures, as well as neutral protective conductors (photo below).

The most common case is when different potentials arise on the sewer and water pipes . It is worth noting that if a current leak occurs in the water supply pipes, then the likelihood of an electric shock while swimming will be extremely high. The main reason is the simultaneous touch of the faucet and the force of the water. By installing a potential equalization circuit in a timely manner, you will protect yourself and your loved ones from electric shock.

We carry out installation

Installation of an additional SUP (also called local) is not difficult. It is advisable to do such work at the stage of major repairs, because... the wire from the box (KUP) to the panel must be routed in the floor screed. So, first you must prepare the following materials:

1. Terminal box with a special copper bus - SHDUP, as in the photo below.
2. Single-core copper wire, cross-section 2.5; 4 and 6 mm2. It is recommended to use wire PV-1 and PV-3.
3. Fastening systems – clamps, bolts, contact tabs. Needed to connect conductors of potential equalization systems to pipes and metal cases.

Having prepared such a small set of DSUP, you can proceed to installation. First of all, it is recommended to draw up a potential equalization diagram, according to which you will connect all the elements. You can also sketch on the diagram where the wire will pass from the terminal box to the grounding bus in the panel. You can see examples of projects for an apartment in the plans below:

After this, you must prepare the communications for connection - clean the small area under the clamp on the pipes to a metallic shine. This is necessary so that the contact is reliable and the potential equalization system works in a dangerous situation.

Next, you need to connect each element with a separate wire. If there is no possibility of mechanical damage to the wire in areas, you can use a conductor with a cross section of 2.5 mm2 for equalization. When there is a possibility of damage, albeit insignificant, it is better to play it safe and use a wire with a cross-section of 4 squares. All wires are inserted into the PMC and securely fixed to the bus. By the way, it is recommended to choose a terminal box for installation in a bathroom with a protection degree of IP 54 or higher. A wire with a cross section of 6 mm2 is output from the bus, which must be laid to the apartment panel. There is also a specific requirement here - this conductor should not cross other cable lines, for example, if you decide to conduct electrical wiring in the floor.

Finally, the wire is connected to the grounding bus in the panel, which completes the installation of the additional potential equalization system. We recommend playing it safe and calling an electrician to check the functionality of the system with a tester and visual inspection!

It will be interesting to read:

• How to install electrical wiring in a bathroom
• How to deal with low voltage in the network
• How to make grounding in an apartment

Published: November 18, 2015 Updated: August 26, 2019

Performing installation

The PMC varies depending on how the building is constructed and where the box itself will be mounted:

• into a solid wall;
• into a hollow wall;
• on the wall surface (open installation method).

It is a housing made of plastic, inside of which the main element is located - the grounding bus. It is made of copper and has a cross-section of at least 10 mm2.

Copper wires from plumbing, heating and gas systems are connected to this bus through the connectors on it; from electrical appliances in the room, as well as from sockets and lighting fixtures installed in the bathroom.

Wires are connected to the listed elements using bolted connections or clamps. Sometimes special contact petals are used, in which case the metal connection between the protected element and the wire will be especially strong. For the potential equalization system to work in dangerous situations, reliable contact is needed. Therefore, the place on the pipes where the clamp will be installed must be cleaned to a metallic shine.

The internal bus is connected with a separate copper wire, called a protective PE conductor, to the input panel of the apartment, and through it it is connected directly to the main switchgear. The cross-section of the PE conductor must be at least 6 mm2. An important condition, if you decide to lay this wire in the floor, it should not intersect with other cables.

Such a box is like an intermediate link between all grounded elements and the input panel. It is very convenient that from each element it is enough to extend the wiring only to the control panel, and not to the general apartment panel.

When the wiring is made with plastic pipes, wires from water taps and mixers are connected to the control panel.

Before installing the SUP, you need to find out how the grounding is done in the house. If using the TN-C system (when the protective conductor PE and the working zero N are combined into one wire), equalization cannot be performed. This will cause danger to other neighbors if they do not have such a system.

Requirements

When installing the control unit, you must adhere to some requirements and rules:

1. Its installation in bathrooms and toilets is mandatory. Firstly, these rooms contain a lot of metal bodies and surfaces. Secondly, there are a considerable number of electrical appliances here. Thirdly, these rooms always have high humidity.
2. The box is installed in the place where the plumbing risers pass.
3. It is necessary to connect all electrical equipment to which there is open access (this is, first of all, the housings of water heating boilers, washing machines), as well as third-party conductive elements.
4. Access to the PMC must be free.
5. Installation of the PMC is prohibited when the grounding is installed in the house without a grounding conductor (using the grounding method).
6. The DSUP must not be connected via a cable.
7. The DSUP along the entire length, starting from the control panel in the bathroom and up to the entrance panel itself, cannot be torn. It is prohibited to install any switching devices in this circuit.

Finally, I would like to say, do not confuse the concepts of equalization and equalization of different potentials. To equalize means to connect conducting elements electrically to make their potentials equal. And to level is to reduce the potential difference on the floor or surface of the earth (step voltage).

If you have little experience in electricity, then do not take on such work yourself, entrust it to professionals. Among other things, after completing the installation work, the specialist must also measure the grounding resistance and check the presence of a circuit between the grounding elements.

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Purpose

The metal structures of the building, the engineering and communication networks laid in it, are conductors of electricity. Until they are closed into a single circuit, a potential difference may arise between these elements. Moreover, the reason for this may be either damage to the insulation of the power cable, or static, interference, atmospheric overvoltage, etc. This threatens that by touching, for example, the body of a household electrical appliance and the radiator of a heating circuit, you can receive not only a noticeable, but also a fatal electric shock.

Electric shock due to breakdown on the body

To avoid such troubles, all conductive structures in the building, as well as utility networks with similar properties, are combined into a single circuit connected to the PE terminal block. Grounding can be laid separately or supplied together with the incoming cable.

With a properly organized control system, in the event of a “breakdown” on current-carrying structural elements, a short circuit will occur or a large leakage current will occur, which will lead to the activation of devices that produce a shutdown. As a result, the damaged area will be disconnected and there will be no threat to human life.

Potential equalization system provides protection in case of breakdown

Now let's move on to the design of the main and additional systems.

Why is additional potential equalization necessary?

Hot and cold water risers, heating risers, all these parts in the past were made strictly of metal. But as you know, metal has been replaced by plastic - polypropylene pipes. If earlier, when absolutely all pipes were made of metal and dangerous potential, accidentally ending up on a metal part, could flow into the ground without obstacles, then plastic does not provide such an opportunity. For example, you have metal risers, but your neighbor on the floor below changed them to plastic. Now the dangerous potential has nowhere to go. Holding a pipe on which a dangerous potential has accumulated with one hand, and with the other a riser that is grounded, this is exactly the case that can turn out to be fatal.

Additional potential equalization circuit

Additional potential equalization circuit

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• What is the difference between grounding and grounding?

Exposure Hazard

The passage of current through the body when touching structural elements with different electrical voltage levels is dangerous to health and life. Here the body is a conductor of current from a point with a high potential to a point with a low voltage.

The dangerous characteristics of current are:

• frequency;
• force;
• path through the victim's body.

Alternating current is the most dangerous. It is noticeable already at a value of up to 0.6 mA. A current ranging from 0.6 mA to 0.025 mA has attractive properties due to its periodicity of pulses. A person cannot independently “unstick” from the points of contact. The limbs involuntarily contract, the body does not obey.

Current strength above 0.1 A causes fibrillation of internal organs and the heart and is fatal.

The direction in which electricity moves through the human body determines the level of harm to health.

Deadly routes of electric current:

• “hand - hand” - the bronchi, lungs and heart are affected;
• “arm – leg” – all internal organs suffer;
• “head - limbs” - both internal organs and the brain are affected.

Another path of harmful current movement is “leg-to-leg”. This is a “step voltage” that can occur when there is a current spreading across the surface in the event of a break in a live wire. In this case, the heart is not damaged if the person did not fall and did not change the points of contact with the source of danger.

Step voltage range

Danger

Remember from school? Any metal object conducts electric current. In our homes, similar items are everywhere. These are pipes of the central heating system, cold and hot water supply; batteries and heated towel rail; ventilation box and drain; metal body of any electrical appliance.

In general house communications, metal pipes are interconnected. Let's look at a simple example. We have a bathroom with a heating radiator and a shower stall nearby. If suddenly a potential difference arises between these two elements, and a person touches both the battery and the shower stall at the same time, it will be extremely dangerous in terms of electric shock. In this case, the human body will play the role of a jumper through which electric current will flow. The path of its flow is known to us from the laws of physics - from a potential with a large value to a smaller one.

Another typical example is if different potentials arise on water supply and sewerage pipes. When a current leak appears on a water pipe, there is a possibility of injury to a person while bathing in the bathtub. This will happen if a person stands in a bathtub with water, opens the drain and touches the water tap with his hand. To prevent such problems from arising, potential equalization is necessary.

The situation when there is voltage on the pipes in a residential building is shown in this video:

https://youtube.com/watch?v=Ume7hhDA5Zc

In order to equalize potentials, there are two systems, we will talk about each of them in more detail.

Basic adjustment

The main one is the basic potential equalization system; in its abbreviated form it is called OSUP. In essence, this system is a circuit that combines several elements:

• the most important is the main ground bus (GZB), it is on it that all other elements are connected;
• all metal fittings of a multi-storey residential building;
• lightning protection of the building;
• heating system;
• parts and elements of elevator facilities;
• ventilation box;
• metal pipes for water supply and drainage.

Each building has an input switchgear (IDU), and a main grounding bus (GZSH) is installed in it. It is connected to the ground loop using a steel strip.

Previously, there was no need to worry, all metal elements were combined, and there were no preconditions for different potentials. If any potential appeared on the pipe, it calmly went into the ground along the path of least resistance (we remember that metal is an excellent conductor).

Now the situation has changed; many residents, during renovation work in their apartments, are replacing metal water pipes with polypropylene or plastic ones. Due to this, the common chain is broken, batteries and heated towel rails are left without protection, because the plastic does not have conductive ability and is not connected to the grounding bus. Imagine that you still have metal pipes, and the neighbor below has changed everything to plastic. When potential appears on your pipes, it has nowhere to go; the path to the ground is interrupted by your neighbor’s plastic pipes. This is how a potential difference occurs.

The main system has a small problem. In multi-storey buildings, communication paths are very long, due to this the resistance of the conductive element increases. There will be a noticeable difference in the potential value on the pipes of the first and last floors, and this already poses a danger. Therefore, an additional potential equalization system is created and installed on each apartment individually.

Additional adjustment

An additional potential equalization system (abbreviated name DSUP) is installed in bathrooms and combines the following elements:

• metal body of a shower stall or bathtub;
• ventilation system, when its outlet to the bathroom is made of a metal box;
• heated towel rail;
• sewerage;
• metal pipes for water supply, heating and gas services.

And here you will need a potential equalization box. A separate wire (single-core, material made of copper) is connected to each of the above objects; its second end is brought out and connected to the PMC.

What is the danger

• Sections of the heating and water supply systems are being replaced with polypropylene pipes. The physical connection with the ground electrode is lost. You can't rely on water in the pipes. Today it is there, but tomorrow the pipe will be dry.
• The neighbor decided to rewind the meter readings and connected a zero to his heating battery. Potential appeared throughout the system: from 220 volts near the neighbor’s apartment, to zero in the area where the pipeline connects to the main grounding bus.
• Someone has a boiler installed without grounding, and it breaks a phase into the water tank. A couple of the nearest floors receive voltage up to 110 volts in the water taps.
• An “advanced” neighbor, an electrician, arranged for the electric stove to be grounded to a hot water riser (it actually has good contact with the ground, and is also structurally connected to the main fire). And after the accident, on the second floor they replaced a piece of steel riser with plastic. A neighbor's "electrician" suffered a short phase on the body of the electric furnace, and the entire entrance above the 2nd floor received a potential of more than 127 volts on the riser.

You say that this is all illegal and prohibited? Yes it is.

But this is the logic of a pedestrian who sees a car rushing towards him and continues to be at the crossing, relying on traffic rules. A pedestrian will be hit, and the driver will definitely be punished. Who will benefit from this?

You should not hope that everyone around you adheres to the Electrical Installation Rules. Therefore, we organize additional potential equalization.

About potential difference

If the potential values ​​of conductive objects in a room differ, then voltage (potential difference) arises between them, which poses a great danger of electric shock to humans

It is especially important to take this into account when connecting devices in rooms with high humidity (sanitary rooms, showers)

The difference in electrical potential between household appliances and pipes in an apartment may appear as a result of:

• current leakage due to damaged wire insulation;
• incorrect connection of electrical equipment;
• faulty electrical appliances;
• manifestations of static electricity;
• occurrence of stray currents in the grounding system.

In order to prevent potential differences from occurring in the room, a potential equalization system (PES) is implemented - a parallel connection of all metal structures located in the house. The basis of the control system is the integration of conductive objects into a single circuit.

The building provides for the installation of both a main grounding loop and additional potential equalization systems in accordance with the requirements of modern construction rules and regulations. The main system includes metal structures of the building: fittings, ventilation ducts, pipes, parts and elements of elevators and lightning protection.

Engineering communications have a fairly significant length, which increases the resistance of the conductors. In this case, the electrical potential of metal pipes on the top floors of a high-rise building is much greater than that of the pipeline on the first floors.

In addition, recently metal pipes have begun to be replaced with plastic ones. Thus, batteries and heated towel rails, which are made of metal, are deprived of protection, since plastic is not a conductor and has no connection with the grounding bus. Therefore, to solve such problems, an additional potential equalization system (DPES) is installed.

Lightning protection design

Lightning strikes cause the current to increase sharply and begin to increase rapidly. The potential difference that arises in this case is several times greater than the difference that occurs when electricity leaks from the network. To avoid negative consequences, this difference must be leveled out.

This can be achieved by combining electrical devices, metal parts, grounding and protective equipment. Connect the conductors to an equalizing bus, which is connected to the grounding structure.

A lightning protection equalizing system is installed at the entrance to the premises and in places where a safe distance cannot be ensured (on the ground surface, on the ground floor).

In buildings with a concrete or metal frame, or in places equipped with lightning protection, leveling is carried out at ground level. In high-rise buildings, the potentials are equalized every 20 meters.

When installing conductive elements, they must be located at a safe distance from the alignment system. Otherwise, dangerous connections will arise between the PMC, the lightning rod and the lightning rod.

Additional control unit device

An additional system is often used in domestic premises. It includes the following components:

• Potential equalization box. It is equipped with a special terminal block intended for switching additional elements with conductive properties. The size of the PMC depends on the number of such elements. Most often, the box has standard dimensions of 100x100x50 mm.
• Electrical cables. For their manufacture, copper wire with a cross-section of about 2.5-6 mm is used. Aluminum conductors are not suitable for these purposes, since the thin film formed on them breaks the contacts and the use of the equalization system becomes useless.

https://youtube.com/watch?v=Ume7hhDA5Zc

Main SUP

It is laid directly during the construction of the building or during its reconstruction or major repairs.

Main components of the SUP:

• Ground loop.
• PE wires
• Main grounding bus.

We will not go into details of the organization of the main management system, since this is the topic of a separate article, but we will present three tenets of its construction:

1. It is strictly prohibited to combine the wires used by the control system with the working zero (N).
2. Grounding should be carried out according to a radial scheme, that is, a separate conductor should be connected to each element.
3. No switching devices can be installed in the system, since one of the main requirements states that the conductors included in it must be continuous.

The need for additional EMS and its main elements

It would seem, why install an additional system if there is a main one, there are several good reasons for this, here are two of them:

1. Ensuring safety in wet areas where electrical equipment is installed (for example, bathrooms and kitchens).
2. There is no guarantee that the neighbor below did not replace metal pipes with plastic ones in the riser or heating circuit during the repair process, thereby violating the main control system.

As you can see, these two reasons are quite enough to create a potential threat to life.

Potential equalization box (PEC), equipped with a special terminal block (SHDUP) for additional connection of elements with conductive properties. It is advisable to choose a product from well-known brands, for example, DKC, Hegel or domestic models KUP2604, KUP2603, KUP1101, etc. The size of the box is selected depending on the number of connected elements. In most cases, standard 100x100x50 mm will be sufficient, for example, like the KUP version for open installation, shown in Figure 4.

In principle, you can also use boxes from unknown brands from the Middle Kingdom, just before installing, make sure that non-flammable material was used for their manufacture. In addition, check the quality of the internal terminal block. There were many cases where the fastening did not provide reliable contact.

Fig 4. Appearance of the potential equalization box

Wires used by DSUP. Their number must correspond to the number of connected elements. The basis is copper wire, whose cross-section is in the range of 2.5-6 mm. Let us immediately note that aluminum conductors are not suitable for this task, since the oxide film formed on it can disrupt the contact, negating the functional purpose of the system.

Typical use case

To better understand all the principles described above, let's look at an example of using the main function of the EMS and its components. Let's imagine the following situation. The neighbors below or above you have purchased a washing machine. After working for quite a long time, it expired and broke down. All the wires are frayed, and the machine begins to electrocute. And since it is directly connected to the sewer pipes and has contact with water, the impacts can be felt by neighbors below or above the riser. As a result, you will get at least unpleasant sensations.

It is precisely to prevent them and ensure electrical safety in the house that a potential equalization box is used. It connects to the risers, the busbar in the electrical panel and every outlet in the bath or kitchen (in the bathroom). In conclusion, it is worth saying that a potential equalization system should be created during the construction of the building. However, it happens that such a network is simply not available on premises. In this case, it is urgent to correct the situation. After all, this is a rather serious moment. The potential equalization system is responsible for the electrical safety of the room and your health. Its installation must be carried out competently and professionally

What else needs to be taken into account?

It is prohibited to install an additional system if the house uses TN-C type grounding, since this creates a real danger to the lives of other residents who have not installed DSUP.

The PMC must be connected to the panel terminals only after de-energizing the electrical wiring.

Let's pay attention! If a boiler is installed in the bathroom or kitchen, it must be connected to the instrumentation, and power must be supplied to it through a separate line protected by an RCD.

If water can get into the sockets installed in the bathroom, then it is necessary to use products with a class of at least IP54.

Installation of a potential equalization system for an apartment building (industrial premises)

Installation of system elements begins during the construction process. When creating the foundation, a metal bus is laid along the entire perimeter of the future structure. This is a closed conductor (steel strip or reinforcement) with welded branches for connection to grounding conductors, and for internal wiring of conductors. To ensure uniform spreading of potential into the physical ground, several groups of grounding conductors are installed along the contour of the building at an equal distance. If possible, equal distance is provided between them.

From the common bus, branches are made into each section (entrance), where the input power supply panel is installed. A grounding shield is formed, connected to a potential equalization system.

It is located in the panel room or in the basement. Access to the panel should be limited (unless it is a private house). Only representatives of the energy company, or state unitary enterprise, are allowed to perform maintenance.

Next, the wall reinforcement of the building is attached to the foundation bus.

The ceiling reinforcement is welded to the vertical elements of the system. If necessary, bus transitions are made from room to room.

After the walls are erected, a conductive busbar is laid along the outer wall for lightning protection installed on the roof. All these conductors are part of the potential equalization system.

Bends in the form of reinforcement or steel strips must be made into the shafts through which vertical pipelines (risers) are laid. After installing the water supply and sewerage systems, conductors are welded to the steel pipes to connect to the potential equalization system.

This means that the integrity of the potential equalization system has been compromised. It is recommended to duplicate the connection by simply connecting the grounding conductor to the grounding bus. This can be done using a contact clamp.

Types of installation

Boxes are distinguished by type of installation. The designs of different boxes are designed to accommodate:

• in wall cavities;
• directly into the wall;
• wall mount.

Installation of the structure in hollow and solid walls is possible during the construction stage. The mounting location is selected taking into account the previously drawn up diagram. The location is chosen in such a way as to provide easy access for monitoring and maintenance.

When the system is installed in a building or room that is in use, open-type boxes are installed. Before you begin fixing the box, it is necessary to bring the grounding conductor from the GZSh to the installation site.

Attention! The main condition for using a shdup box is the mandatory connection of accessible open areas of household electrical appliances and foreign conductive areas.

Leveling and Leveling

Let's look at the basic concepts and terms:

• Potential equalization is the leveling of the difference in electrical potential values ​​between the metal elements of an electrical installation in the room where the electrical installation is located, including the conductive elements of the building. In this case, a situation is considered dangerous when it becomes possible for a person to simultaneously touch conductive parts. It is achieved by non-disconnecting connection of all current-carrying parts to each other using conductors.
• Potential equalization is a system for reducing the relative difference in electrical potential between grounding, accessible conductive parts of electrical installations, the surface of the earth and all metal structures of the building. To do this, the potential equalization system must have an unbreakable connection with the working (protective) grounding conductor.

In addition, potential equalization includes reducing the electrical potential difference on the ground surface (floor, ceilings) to prevent the effect of step voltage.

What does the term "unbreakable" mean? All conductive lines are permanently connected to each other (contact blocks, screw connections, soldering, welding, etc.). It is not allowed to install disconnecting devices: fuses, switches, circuit breakers. That is, the entire potential equalization system is a single conductive circuit combined with a similar protective grounding circuit.

Thanks to these systems, in all points that a person can simultaneously touch, the electrical potential is equalized to the same value. The situation when, when touching at the same time, the voltage will be 220 volts at one point and 10 volts at another, is excluded.

Your home becomes absolutely safe.

Reasons for creating an adjustment scheme

Each conductor has its own non-hazardous electrical potential. The threat lies precisely in the potential difference between two metal products, and the greater the difference, the greater the likelihood of receiving an electric shock.

In order to explain clearly about potential equalization, you can use the following example. The metal surface of the refrigerator and the water pipe located nearby have their own potential indicators, one of which is greater than the other, and the potential difference, as is known, is voltage. If these objects accidentally touch each other at the same time, a dangerous situation may arise, since the person in this case is a conductor from greater to lesser potential. All pipes are interconnected by a common house communication system.

To be more convincing, we can give an example with an electrical appliance, for example, a 220-volt household outlet. The phase contact has a potential of 220 V, and the zero contact has a potential of 0 V, the difference is 220 V. When connecting the contacts with a piece of wire having a small resistance (about 1 ohm), a voltage of 220 amperes will appear in the conductor (wire), the insulation will ignite, and the wire will melt. Of course, this should not be done. If a person touches both contacts, then even with high body resistance under the influence of current, the outcome will be tragic.

Purpose and device of SHDU

Cause of electric shock

The additional electrical potential equalization system covers the following mandatory elements:

• Without exception, all devices located in rooms with high humidity - in bathrooms, kitchens, basements and attics of private buildings - and subject to grounding.
• Elements of metal structures directly adjacent to these premises and extending beyond their planning boundaries.
• Neutral conductors of the grounding system. All other equalizing bends are connected to them.

If there are no neutral N conductors on this branch, the entire system is connected to a PE bus installed in the distribution cabinet at the entrance to the building.

This procedure also applies to heating tires of the “warm floor” system, tightly embedded in concrete coverings. Before installing them, you will need to cover the set of steel tubes with a metal mesh, which is subsequently connected to the system in which the SHDU bus is provided. To provide additional protection in the power supply circuits of heating devices, it is recommended to install an RCD for a current of up to 30 mA (see clause 7.1.88 of the PUE).

Methods for connecting elements connected to U4 type SHDU buses are very different. The following typical schemes are widely practiced:

• radial connection method to potential equalization elements;
• connection with a loop that ensures continuity of the equalization circuit.

DSUP conductor parameters

DSUP

Only conductors specially designed for this purpose are suitable for the additional potential equalization system. According to the provisions of the PUE (see clause 1.7.138), their characteristic dimensions must satisfy the following requirements:

• when connecting two own conductive parts of the equipment, the cross-section of the smaller of the protective conductors connected to the grounded parts is selected as the main one;
• when connecting own and third-party conductive elements of equipment or devices, half the cross-section of the protective conductor connected to the open part of the ground loop is taken as a basis.

• it should be equal to 2.5 mm2, subject to reliable mechanical protection from deformation and other extraneous influences;
• its value reaches 4 mm2 in the absence of the necessary security.

The general scheme of the DSUP, in addition to all of the above, includes elements of protection against lightning and lightning discharges.

Types of soup

To ensure safety levels, the control system is divided into two types of equalization systems:

1. the main one is OSUP;
2. additional - DSUP.

Let's look at their differences.

Basic BPCS system

In modern conditions, during the construction of a building, it is included in the design of the house layout and is installed before the residents move in. It includes:

• ground loop;
• main ground loop bus (GZSH);
• distribution of a “grid” of PE conductors throughout the building connected to the main switchgear;
• system of potential equalization conductors.

The OSUP is entrusted with the function of ensuring the protection of the building from the penetration of electric current from the outside through any metal parts included in its building elements: water and gas pipelines, metal fire escapes, etc. A
high potential accidentally entering them from an extraneous source of enormous magnitude will instantly reach the building and thanks to BPCS design will be instantly redirected to the earth circuit, where its energy will be reliably extinguished without causing harm to building structures and internal equipment.

If lightning strikes the lightning protection of a building, then it is immediately directed through a lightning rod to the ground, bypassing the structure and equipment of the house along the shortest path.

The OSUP system is used according to different principles in existing building grounding schemes:

• It is prohibited to use it for TN-C. If the need arises for potential equalization, it is necessary to switch to one of the new grounding standards;

in TN-CS, a PEN conductor is connected to the BPCS circuit, coming along the electrical supply line from the transformer substation. Moreover, at the entrance to the house through the installed re-grounding, it is branched through the main grounding bus into PE and N. All third-party current-carrying parts of the building are electrically connected to the main grounding bus with PE conductors;

in the TN-S grounding circuit, the protective role of the OSUP is carried out through the main protection system connected to the elements of the building's building structures through PE conductors;

for the TT circuit, the house is individually grounded and PE conductors are connected to it.

Features of installation of OSUP

They can be boiled down to three important questions:

1. after the GZSh it is prohibited to combine the working zero N with the protective conductors PE anywhere in the circuit;
2. The only way to connect the components of the OSUP to the GZSh is the radial method, when each grounded element of the house is mounted with an individual conductor. The use of a cable in this situation is strictly prohibited;
3. It is prohibited to embed any switching devices into the BPCS circuit.

Why do you need to equalize potentials?

Before considering this system in detail, you should understand the concepts of electric potential and current. Their physical properties are clearly visible in the example of a conventional conductor. When it is at rest, all charged particles - positive and negative - evenly fill its internal structure.

Each current source has an insufficient number of electrons at one of its poles, and an excess number at the other. When a conductor is connected to it, all the electrons inside will move in a certain direction in order to equalize this deficiency and excess. This movement is called electric current, and the difference in electrons is known as positive and negative electric potential.

With a constant potential difference, the electrons will move in one direction, so the current is considered constant. If there is a frequent change of places of positive and negative potentials, then such a current will be called alternating. In a home network, such changes occur 50 times per second, that is, the AC frequency is 50 Hz.

All conductors through which electric current flows are protected by insulation, preventing any contact with surrounding objects. This applies to all metal elements, parts and structures that have zero electrical potential and through which no current should flow. Ideally, they all work autonomously and do not pose a danger to others.

However, quite often situations arise, in an apartment or in a private house, associated with current leaks. For example, as a result of an accident, a live wire and a battery came into contact. In this case, the current penetrates the entire heating system, which leads to a change in the electrical potential of the metal radiator.

Such a situation can lead to various options for further developments:

• A man stands on the floor wearing non-conductive shoes. In this case, nothing will happen and there will be no electric shock.
• When standing on a grounded floor, a person inevitably receives an electric shock. For such situations, an RCD is provided - a residual current device.
• A person stands on an insulated floor while simultaneously touching a metal pipe and a live battery. Each of these structures has a different electrical potential and current will begin to flow through the body. It is at this moment that a person receives an electrical injury. To combat this phenomenon, a potential equalization system is provided.

For this purpose, all types of metal elements and protection of devices and equipment that should not be energized are connected into a single circuit. In the event of an emergency, they will all have the same potential

Even if the voltage is 220 volts, no electric shock will occur; it is important that there is an insulated surface under the person’s feet

Causes and danger

Before eliminating the potential difference, you need to find out what are the main reasons for its appearance. Provoking factors:

• generation of static electricity;
• regular exposure of the object to stray currents;
• high atmospheric pressure (similar phenomena are often observed when there is a thunderstorm outside).
• structural changes in metal structures and parts.

A particular danger is posed by leakage of electric currents from wiring strands and short circuits on the housings of household appliances and other electrical devices. Most often, this phenomenon can be found in the bathroom - if you touch a wet faucet or pipe, you can get an electric shock. This happens most often due to the destruction of the insulating layer or violation of the integrity of the wires. This and similar situations can lead to negative consequences, for example:

• A person stands on the floor and at this moment touches a battery or pipe, which, as it turns out later, is energized. Each surface that a person touches has a different potential, hence the current begins to flow through his body. The result is electrical injuries of varying severity.
• If the floor surface was not insulated, but grounded, the person would also inevitably receive an electric shock.

In order to prevent the occurrence of dangerous situations in the future, all equipment and devices that should not be energized should be connected into a single circuit. In this case, when emergency situations develop, all surfaces will have the same electrical potential.

Basic potential equalization system

The main potential equalization system (BPES) combines all large current-carrying parts of the building, which normally do not have electrical potential, into a single circuit with the main grounding bus. Let's consider a graphic example of implementing a control system in an electrical installation of a residential building.

Potential equalization system in a residential building

According to the above diagram, the BPCS consists of the following elements:

• grounding loop (grounding device);
• main grounding bus (GZSh);
• zero protective conductors;
• potential equalization conductors.

The list of conductive parts in electrical installations up to 1 kV, subject to connection in the OSUP, is defined in clause 1.7.82 of the PUE. The main grounding bus can be installed inside the input distribution device or separately, subject to the following conditions: location near the protected object, provision of access for its maintenance and mandatory protection from possible contact. Inside the input distribution device, a PE neutral protective conductor bus is used as a main shield, which ensures not only the connection of the protective zero of the incoming supply line with the neutral conductors of the building's distribution network, but also performs the function of connecting individual conductive parts and grounding devices. A separately located bus connects only the current-carrying structures and grounding conductors included in the OSUP. The cross-sectional area of ​​such a main shield must be no less than the cross-sectional area of ​​the neutral protective conductor of the incoming supply line. The main grounding bus is made of copper, steel can also be used. A grounding loop and neutral protective conductors (PEN or PE, depending on the selected grounding system) are connected to it. The metal parts and structures of the building, as well as the communications and ventilation system related to it, are mounted to the main building in a radial pattern, connecting each conductive element with a separate potential equalization conductor, with the possibility of disconnecting any of them. Conductive parts of communications entering the building from the outside must be connected to the main building as close as possible to their entry point. The connecting conductors of the OSUP are subject to increased requirements, the main one of which is their continuity. Therefore, the installation of various switching devices in circuits is strictly prohibited. The conductors are yellow-green in color and must have a tag with the name of the connected element. They are secured to the busbar with bolted connections, they are also attached to conductive structures by welding, and clamps are used for communication pipes. The cross-section of potential equalization conductors must be at least: 6 mm 2 for copper, 16 mm 2 for aluminum and 50 mm 2 for steel. see clause 1.7.137 PUE.

What is GZSH?

To take a closer look at the purpose, types and structure of the MUP, let’s find out in more detail what the Main Grounding Bus (GGB) is. After all, it is the GZSh that is the basis of the entire safety system in any electrical installation. The connection to the GZSh is made by protective PE conductors, which are connected to the GZSh, the role of which is usually played by the PE bus (PUE, 1.7.119) .

GZSh and PE bus are in fact the same thing if it is located inside the input switchgear (IDU). And only if the GZSh is located somewhere outside the ASU (somewhere at the entrance to the building, in the basement), can there be two buses - GZSh and PE. Moreover, there is usually one GZSh (according to the number of inputs into the building), and several PE busbars (according to the number of electrical panels).

Simplified, it might look like this:

Grounding system and buses N and PE

This system ensures that all connected parts have the same potential. The voltage between any individual points in such a system is guaranteed to be zero.

The definition of GZSh is given in clause 1.7.37 of the PUE and in GOST 30331.1-2013, article 20.5 :

The main grounding bus is a bus that is part of the grounding device of an electrical installation up to 1 kV and is intended for connecting several conductors for the purpose of grounding and potential equalization.

Requirements for GZSh are reflected in paragraph 1.7.119 of the PUE:

The main grounding bus can be made inside the input device of an electrical installation with voltage up to 1 kV or separately from it. Inside the input device, a PE bus should be used as the main grounding bus.

When installed separately, the main grounding bus must be located in an accessible, convenient place for maintenance near the input device.

The cross-section of a separately installed main grounding bus must be no less than the cross-section of the PE (PEN) conductor of the supply line.

The main grounding bus should, as a rule, be copper. It is allowed to use a main grounding bus made of steel. The use of aluminum tires is not permitted.

The design of the bus must provide for the possibility of individual disconnection of the conductors connected to it. Disconnection must only be possible using a tool.

In places accessible only to qualified personnel (for example, switchboard rooms of residential buildings), the main grounding bus should be installed openly. In places accessible to unauthorized persons (for example, entrances or basements of houses), it must have a protective shell - a cabinet or drawer with a key-locked door. There must be a “Grounding” sign on the door or on the wall above the busbar.

A description of the term “Grounding device” can be found in SP 437.1325800.2018 clause 3.14 and in GOST 30331.1-2013, article 20.14:

Grounding device : A set of grounding conductors, grounding conductors and the main grounding bus.

The GZSh is usually connected to the ground loop by a steel strip or copper conductor. The PEN conductor of the input cable (when using the TN-CS grounding system) or the PE conductor of the input cable (if using the TN-S grounding system) is connected to it. Or - a grounding conductor from a ground electrode in the TT system.

Inside the ASU, PE conductors of outgoing group lines and PE conductors serving for potential equalization are connected to the main switch.

To ensure safety, there is a rule: one PE wire - one connection (screw or bolt).

A radial connection diagram should be used - that is, the protective conductor cannot be “circulated”, connecting it in series to various protected structures. The main requirement for PE conductors is to ensure their continuity throughout. Therefore, the installation of any switches, switches, fuses and connections that can be disassembled without the help of a tool is prohibited.

The GZSh at the entrance to a building or other electrical installation can be like this:

GZSh at the entrance to the electrical installation

In the photo above there is a GZSh at the power input to the production line. I published an article about the reasons and process for replacing the input machine in this line.

Question for experts: What grounding system is shown in the diagram?

Power supply of the technological line, input circuits