How to connect two cables together. Reliable ways to connect electrical wires

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Contact connections of conductors are a very important element of the electrical circuit, therefore, when performing electrical work, you should always remember that the reliability of any electrical system is largely determined by the quality of electrical connections.

Certain technical requirements are imposed on all contact connections. But first of all, these connections must be resistant to mechanical factors, be reliable and safe.

With a small area of contact in the contact zone, a fairly significant resistance can arise for the passage of current. The resistance at the point where the current passes from one contact surface to another is called the contact resistance, which is always greater than the resistance of a solid conductor of the same size and shape. During operation, the properties of a contact connection under the influence of various external and internal factors can deteriorate so much that an increase in its contact resistance can cause overheating of the wires and create an emergency. The transient contact resistance largely depends on the temperature, with an increase in which (as a result of the passage of current) an increase in the transient resistance of the contact occurs. Contact heating is of particular importance in connection with its effect on the oxidation process of contact surfaces. In this case, the oxidation of the contact surface is the more intense, the higher the contact temperature. The appearance of an oxide film, in turn, causes a very strong increase in the transfer resistance.

A contact connection is an element of an electrical circuit where two or more separate conductors are electrically and mechanically connected. At the point of contact of the conductors, an electrical contact is formed - a conductive connection through which current flows from one part to another.

Simple overlapping or slight twisting of the contact surfaces of the conductors to be connected does not provide good contact, since due to microroughnesses, actual contact does not occur over the entire surface of the conductors, but only at a few points, which leads to a significant increase in the contact resistance.

At the point of contact of two conductors, there is always a transient resistance of the electrical contact, the value of which depends on the physical properties of the contacting materials, their state, the compressive force at the point of contact, temperature and the actual area of contact.

From the point of view of the reliability of electrical contact, aluminum wire does not compete with copper. After a few seconds of exposure to air, the pre-cleaned aluminum surface is covered with a thin hard and refractory oxide film with high electrical resistance, which leads to an increased contact resistance and strong heating of the contact zone, as a result of which the electrical resistance increases even more. Another feature of aluminum is its low yield strength. A tightly tightened connection of aluminum wires weakens over time, which leads to a decrease in contact reliability. In addition, aluminum has the worst conductivity. That is why the use of aluminum wires in household electrical systems is not only inconvenient, but also dangerous.

Copper oxidizes in air at normal residential temperatures (about 20 ° C). The resulting oxide film does not have great strength and is easily destroyed by compression. Particularly intense copper oxidation begins at temperatures above 70 ° C. An oxide film on a copper surface itself has little resistance and has little effect on the value of the contact resistance.

The state of the contact surfaces has a decisive influence on the growth of the contact resistance. To obtain a stable and durable contact connection, high-quality stripping and surface treatment of the connected conductors must be performed. The insulation from the cores is removed to the required length with a specialized tool or knife. Then the bare parts of the veins are cleaned with emery cloth and treated with acetone or white spirit. The length of the groove depends on the characteristics of the particular method of connection, branching or termination.

The transient contact resistance decreases to a large extent with an increase in the compressive force of the two conductors, since the actual contact area depends on it. Thus, in order to reduce the transient resistance in the connection of two conductors, it is necessary to ensure their sufficient compression, but without destructive plastic deformations.

There are several ways to install the electrical connection. The highest quality of them will always be the one that provides, under specific conditions, the lowest value of the transient contact resistance for as long as possible.

According to the "Rules for Electrical Installations" (clause 2.1.21), the connection, branching and termination of the conductors of wires and cables must be carried out by welding, soldering, crimping or compressing (screw, bolt, etc.) in accordance with the current instructions. In such connections, it is always possible to achieve a consistently low contact resistance. In this case, it is necessary to connect the wires in compliance with the technology and using the appropriate materials and tools.

Connection of wires in the junction box is an important and responsible operation. It can be performed in various ways: using terminal blocks, by soldering and welding, crimping, and often by ordinary twisting. All of these methods have certain advantages and disadvantages. It is necessary to choose a connection method before starting installation, as this also involves the selection of appropriate materials, tools and equipment.

When connecting the wires, the same color of neutral, phase and ground wires should be observed. Usually the phase wire is brown or red, the neutral working wire is blue, the protective ground wire is yellow-green.

Very often, electricians have to connect a wire to an existing line. In other words, you need to create a branch of the wires. Such connections are made using special branch clamps, terminal blocks and piercing clamps.

When copper and aluminum wires are directly connected, copper and aluminum form a galvanic pair, and an electrochemical process occurs at the point of contact, as a result of which aluminum is destroyed. Therefore, to connect copper and aluminum wires, you need to use special terminal or bolted connections.

Wires connected to various devices often require special ferrules to ensure reliable contact and reduce contact resistance. These lugs can be soldered or crimped to the wire.

There are many different types of tips. For example, for copper stranded conductors, lugs are produced from a solid-drawn copper tube, flattened and drilled for a bolt on one side.

The connection of conductors by welding gives a monolithic and reliable contact, therefore it is widely used in electrical work

Welding is performed at the ends of pre-stripped and twisted conductors with a carbon electrode using welding machines with a power of about 500 W (for a cross-section of twists up to 25 mm2). The current on the welding machine is set from 60 to 120 A, depending on the section and the number of wires to be welded.

Due to relatively low currents and a low (compared to steel) melting temperature, the process occurs without a large blinding arc, without deep heating and metal splashing, which makes it possible to use protective goggles instead of a mask. At the same time, other security measures can be simplified. At the end of welding and cooling of the wire, the bare end is insulated with electrical tape or heat shrink tubing. After a little training using welding, you can quickly and efficiently make the connections of electrical wires and cables in the power supply system.

When welding, the electrode is brought to the wire to be welded until it touches, then it is retracted a short distance (0.5-1mm). The resulting welding arc melts the twist of the wires to form a characteristic ball. The contact with the electrode should be short-term to create the desired reflow zone without damaging the wire insulation. It is impossible to make a long arc length, since the welding place turns out to be porous due to oxidation in the air.

Nowadays, welding work on connecting electrical wires is convenient to perform inverter welding machine, since it has a small volume and weight, which allows the electrician to work on a stepladder, for example, under the ceiling, hanging the inverter welding machine on his shoulder. A copper-plated graphite electrode is used to weld electrical wires.

In a joint obtained by welding, an electric current flows through a monolithic metal of the same type. Of course, the resistance of such connections turns out to be record low. In addition, such a connection has excellent mechanical strength.

Of all the known methods of connecting wires, none of them can compare with welding in terms of durability and conductivity of the contact. Even soldering collapses over time, since a third, more fusible and loose metal (solder) is present in the joint, and at the interface between different materials there is always additional transition resistance and destructive chemical reactions are possible.

Soldering is a method of joining metals with another, more low-melting metal. Compared to welding, brazing is simpler and more affordable. It does not require expensive equipment, is less fire hazardous, and skills to perform a good quality soldering will require more modest ones than when making a welded joint. It should be noted that the metal surface in air usually quickly becomes covered with an oxide film, therefore, it must be cleaned before soldering. But the cleaned surface can quickly oxidize again. To avoid this, chemicals are applied to the treated areas - fluxes, which increase the fluidity of the molten solder. Thanks to this, the soldering is stronger.

Soldering is also the best way to terminate stranded copper strands into a ring - the soldered ring is evenly covered with solder. In this case, all wires must completely enter the monolithic part of the ring, and its diameter must correspond to the diameter of the screw clamp.

The process of soldering wires and cable cores consists in covering the heated ends of the connected cores with molten tin-lead solder, which after hardening provides mechanical strength and high electrical conductivity of the permanent connection. Soldering should be smooth, without pores, dirt, sagging, sharp bulges of solder, foreign inclusions.

For soldering copper conductors of small sections, use solder tubes filled with rosin, or a solution of rosin in alcohol, which is applied to the junction before soldering.

To create a high-quality soldered contact connection, the conductors of the wires (cables) must be carefully irradiated, and then twisted and crimped. The quality of the soldered contact largely depends on the correct twisting.

After soldering, the contact joint is protected with several layers of insulating tape or heat shrink tubing. Instead of insulating tape, the soldered contact joint can be protected with an insulating cap (PPE). Before that, it is desirable to cover the finished compound with a moisture-resistant varnish.

Parts and solder are heated with a special tool called a soldering iron. A prerequisite for creating a reliable connection by soldering is the same temperature of the surfaces to be soldered. The ratio of the temperature of the soldering iron tip to the melting temperature is of great importance for the quality of soldering. Naturally, this can only be achieved with the right tool.

Soldering irons vary in design and power. To perform household electrical work, an ordinary 20-40 W electric rod soldering iron is quite enough. It is desirable that it be equipped with a temperature regulator (with a temperature sensor) or at least a power regulator.

Experienced electricians often use the original soldering method. A hole with a diameter of 6-7 mm and a depth of 25-30 mm is drilled in the working rod of a powerful soldering iron (at least 100 W) and filled with solder. In a heated state, such a soldering iron is a small tinning bath, which allows you to quickly and efficiently solder several multi-core connections. Before soldering, a small amount of rosin is thrown into the bath, which prevents the appearance of an oxide film on the surface of the conductor. The further soldering process consists in lowering the twisted joint into such an impromptu bath.

Screw terminal blocks

One of the common ways to create a contact is to use screw terminal blocks. In them, reliable contact is ensured by tightening the screw or bolt. In this case, it is recommended to connect no more than two conductors to each screw or bolt. When using stranded conductors in such connections, the ends of the wires require preliminary tinning or the use of special ferrules. The advantage of such connections is their reliability and collapsibility.

By designation, terminal blocks can be bushing and connecting.

Designed to connect wires to each other. They are usually used for switching wires in junction boxes and distribution boards.

They are used, as a rule, to connect various devices (chandeliers, lamps, etc.) to the network, as well as when splicing wires.

When connecting with screw terminal blocks wires with stranded conductors, their ends need preliminary soldering or crimping with special ferrules.

When working with aluminum wires, the use of screw terminal blocks is not recommended, since aluminum conductors, when tightened with screws, are prone to plastic deformation, which leads to a decrease in the reliability of the connection.

Recently, self-clamping terminal blocks of the WAGO type have become a very popular device for connecting wires and cable cores. They are designed to connect wires with a cross-section of up to 2.5 mm2 and are designed for an operating current of up to 24 A, which allows you to connect a load of up to 5 kW to the wires connected by them. In such terminal blocks, up to eight wires can be connected, which significantly speeds up the wiring in general. True, in comparison with twisting, they take up more space in unsoldered boxes, which is not always convenient.

It is fundamentally different in that its installation does not require any tools and skills. A wire stripped to a certain length is inserted into its place with little effort and reliably pressed by a spring. The design of the screwless terminal connection was developed in the German company WAGO back in 1951. There are other manufacturers of this type of electrical products.

In spring-loaded self-clamping terminal blocks as a rule, the effective contact surface area is too small. At high currents, this leads to heating and release of the springs, as a result of which there is a loss of their elasticity. Therefore, such devices should only be used on connections that are not subject to heavy loads.

WAGO produces terminal blocks both for installation on a DIN rail and for fastening with screws to a flat surface, but construction terminal blocks are used for installation as part of household wiring. These terminal blocks are available in three types: for junction boxes, for luminaire fittings and universal.

WAGO terminal blocks for junction boxes allow you to connect from one to eight conductors with a cross section of 1.0-2.5 mm2 or three conductors with a cross section of 2.5-4.0 mm2. And terminal blocks for lamps connect 2-3 conductors with a cross section of 0.5-2.5 mm2.

The technology of connecting wires using self-clamping terminal blocks is very simple and does not require special tools and special skills.

Connecting insulating clamps

One of the most popular connecting products among electricians is connecting insulating clamp (PPE)... This clamp is a plastic housing with an anodized conical spring inside. To connect the wires, they are stripped to a length of about 10-15 mm and folded into a common bundle. After that, PPE is screwed onto it, rotating clockwise until it stops. In this case, the spring compresses the wires, creating the necessary contact. Of course, all this happens only when the PPE cap is selected correctly for its face value. With the help of such a clamp, it is possible to connect several single wires with a total area of 2.5-20 mm2. Naturally, the caps in these cases are of different standard sizes.

Depending on the size, PPEs have certain numbers and are selected according to the total cross-sectional area of the twisted cores, which is always indicated on the package. When choosing PPE caps, one should be guided not only by their number, but also by the total cross-section of wires for which they are designed. The color of the product has no practical meaning, but it can be used to mark phase and neutral conductors and grounding conductors.

PPE clamps significantly speed up the installation, and due to the insulated case, they do not require additional insulation. True, the quality of their connection is somewhat lower than that of the screw terminal blocks. Therefore, other things being equal, preference should still be given to the latter.

Twisting of bare wires as a connection method is not included in the Electrical Installation Code (PUE). But despite this, many experienced electricians consider a correctly performed twisting as a completely reliable and high-quality connection, arguing that the transition resistance in it practically does not differ from the resistance in the whole conductor. Be that as it may, good twisting can be considered one of the stages of connecting wires by soldering, welding or PPE caps. Therefore, high-quality twisting is the key to the reliability of all electrical wiring.

If the wires are connected according to the "how it happened" principle, a large transition resistance with all negative consequences can arise at the place of their contact.

Depending on the type of connection, twisting can be performed in several ways, which, with a small transition resistance, can provide a completely reliable connection.

First, the insulation is carefully removed without damaging the wire core. Sections of veins exposed to a length of at least 3-4 cm are treated with acetone or white spirit, cleaned with sandpaper to a metallic sheen and tightly twisted with pliers.

The crimping method is widely used to make reliable connections in junction boxes. In this case, the ends of the wires are stripped, combined into appropriate bundles and crimped. After crimping, the connection is protected with electrical tape or heat shrink tubing. It is one-piece and does not need maintenance.

Crimping is considered one of the most reliable ways to connect wires. Such connections are made using sleeves by continuous compression or local indentation with special tools (press tongs), into which replaceable dies and punches are inserted. In this case, the wall of the sleeve is pressed (or squeezed) into the cores of the cable with the formation of a reliable electrical contact. Crimping can be done by local indentation or continuous crimping. Solid crimps are usually hexagonal.

It is recommended to treat copper wires with a thick grease containing technical petroleum jelly before crimping. This lubrication reduces friction and reduces the risk of core damage. A non-conductive lubricant does not increase the transition resistance of the connection, since, if the technology is observed, the lubricant is completely displaced from the contact point, remaining only in the voids.

For crimping, manual pressing tongs are most often used.

In the most common case, the working bodies of these tools are matrices and punches. In the general case, the punch is a movable element that produces local indentation on the sleeve, and the matrix is a curly fixed bracket that perceives the pressure of the sleeve. Dies and punches can be replaceable or adjustable (designed for different sections).

When installing ordinary household wiring, as a rule, small crimping pliers with curly jaws are used.

As a sleeve for crimping, you can, of course, use any copper tube, but it is better to use special sleeves made of electrical copper, the length of which corresponds to the conditions for the reliability of the connection.

When crimping, the wires can be inserted into the sleeve both from opposite sides until they touch each other strictly in the middle, or from one side. But in any case, the total cross-section of the wires must correspond to the inner diameter of the sleeve.

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How to connect the wires? Soldering or welding? Long and uncomfortable. We need to look for a soldering iron or a welding machine. But I'll tell you a secret that the best connection is welding, then soldering goes. Twisting wires? It's a good thing, but not aesthetically pleasing. And according to the new rules, it is forbidden to use it, except perhaps on the sly in the country. Currently, special connectors for wires have been invented, which greatly facilitate the life of electricians and electricians. We will just talk about them in this article.

How to connect wires correctly and quickly

Connecting screw terminal block

It is used very widely in manufacturing, as well as in households to connect two wires to each other. Sold as a cassette of 10 or more. How much is required, we cut and use as needed. It is mainly used for connecting copper wires. For aluminum, it is undesirable. Aluminum wires have the property of flowability. This means that after some time the clamped aluminum wire will “spread” from under the clamping bolt and the connection will weaken.

The advantage of connecting terminal blocks is that they are very cheap and allow you to connect two wires together without any problems in a matter of seconds. The main thing is to find a suitable flat head screwdriver.

PPE caps

PPE - this is a connecting insulating clamp. Used to connect single-wire cores of wires, followed by screwing them clockwise. PPE caps are very comfortable, but still not very reliable. Therefore, if you have a critical part of the wiring, then it is better to give preference to cooler competitors of PPE caps.

As you may have noticed, there is a spiral inside the cap, which, when the cap is screwed on, compresses the wires to be connected.

In practice, it all happens like this: we strip two wires, and then screw the PPE cap onto them

Terminal blocks WAGO (WAGO)

Vago terminal blocks are currently the most top-end connectors for wires. Although they also have their disadvantages - high cost and weak switched current. The photo below shows the principle of operation of the Vago terminal blocks.

Conclusion

Currently, blue duct tape can already be put on the back burner. If earlier the Soviet Union was built with the help of it, now there is no longer a need for it. It is much easier to go to the nearest store and buy connectors for wires. It won't hit your pocket hard. As a result, your wiring will be much stronger and safer.

Also, do not forget about the amperage for which these connectors are designed. For example, you should not use VAGO terminal blocks for various electric boilers and powerful energy consumers. In this case, they may not withstand a heavy load, which will lead to even worse consequences.

The answer seems to be simple, but nevertheless, often connecting wires, electricians and people who do electrical work on their own violate the basic requirements for electrical contacts. What does this lead to? In the best case, to burn the wires at the junction, at worst to ignition and extensive fire. To prevent this from happening, further in the article we will consider the main methods of connecting wires when conducting electrical work.

Connection methods: - by twisting; - through the terminal; - through the clamp; - bolted connection; - soldering; - through the lugs.

Twist Wire Splicing - This is the fastest and easiest way to connect one or more wires and is the most commonly used method. If the wires are twisted correctly, then when used in a home network with a small load, they will last a long time without being reminded of themselves. Frequent mistakes when connecting wires using the twisting method.

The most common mistake that installers make is twisting the veins of different metals (copper with aluminum). With such a connection, a complex electrolysis process occurs in the twist, which leads to the destruction of the metal itself. It becomes covered with oxides and potholes. All this leads to poor contact at the junction, and subsequently heating.

At the end, fold the excess onto this twist.

The copper is now in direct contact with the aluminum through the tinned wire. And this will prevent electrolysis from occurring on different conductors. Connection through a terminal. The presence of terminals can also facilitate this work and ensure a high-quality connection. There are many types of terminals, but the principle is the same. The photo shows two types of terminals, which can often be seen in different devices.

For example, in fluorescent lamps, at the junction of the supply wires. Also, these terminals are freely available on sale and can be 10 pcs. and more in length. Having bought such a block, you can simply cut off the required number of elements with a knife. It is not difficult to connect conductors made of different metals in the terminal. First, you need to remove the insulation from the ends of the wires by 3-4 mm so that the bare area does not greatly extend beyond the terminal.

We unscrew the screws until the free passage of the wires of the wires, and insert, clamp them.

Do not use too much force, otherwise the fragile thread will "break", which will require replacing the terminal. This connection is quite reliable. With a current of up to 1.5 kW, it can freely cope with its task. It all depends on which terminal to use. Here the weakest is considered, using a more powerful one, the flow current can be increased.

In addition to the option to connect wires from different materials, the terminals can be successfully used to extend the length. This can be useful in the case when the wire in the box is so short that it is not enough to make a twist. This is where the terminal will help. The same applies to the broken wire extending from the ceiling to the lamp.

Then the problem with the connection can be solved with its help. How to do this is clear from the photograph.

After the screws are securely tightened, this entire exposed area should be insulated with PVC adhesive tape. Bolted connection. Bolts, nuts and washers are always at hand. Therefore, in the absence of clamps and terminals, they will also fit. By the way, on bolts of large sizes, they make fairly high-quality connections of powerful cables of large cross-section, and this method is still successfully used in industrial enterprises. So, you will need: - a bolt of the required length; - a nut; - three wide washers.

You need to bend along the movement of the thread. That is, so that when the nut is tightened, the loop does not open to the sides. The washer between the two conductors will prevent them from touching, and will prevent the effect of electrolysis, which destroys metals.

Soldering The soldering connection is considered to be of the highest quality, since the resistance in this place becomes minimal. Some of them solder the strands in the boxes themselves, thus improving the connection. But it can be done with copper. And aluminum doesn't solder very well. Yes, different acids and additives can be used, but they tend to degrade the bond over time.

Tips - If you find these tips, it will be very good. This is one of the most reliable types of connection. We insert the wires into the terminals, and clamp them with pliers, and then press them with a hammer and a guide.

Terminals must be tinned, or an aluminum conductor is needed, wrap with tinned wire before inserting into the hole in the ferrule. After that, the lugs should be squeezed with a bolt and nut, and everything should be insulated with tape.Conclusion.Of course, now there are more advanced methods and devices for connecting wires, but they need to be bought and mastered, which takes extra money and time. The good old methods described above will be used for a long time, and will also serve faithfully for a long time. So why pay more ?!

Quite often, it is necessary to connect wires with different cross-sections, this can be seen in the distribution boards of residential buildings, when branches go from the supply conductor to each of the apartments.

The difference in cross-sections, and sometimes significant, primarily implies a very tight connection, in order to avoid heating in this place.

In this case, twisting becomes the most used connection method. Despite the apparent backwardness of this method, many experts can confirm that if the twisting is done with high quality, it can withstand a much higher load and temperature than the clamp.

It is advisable to do twisting when it is necessary to make a branch from the main line that does not have a gap. In this case, in the selected area, the insulation layer is simply removed, and the end of the connected wire is wrapped around the core of the line.

When, nevertheless, a wire break occurs, then mechanical clamps, or terminal blocks, and any other device, where it is structurally provided for the possibility of connecting such cross-sectional sizes, can be used.

If, for example, you need to connect wires of different cross-sections (for the same cross-section, they are also suitable) and the same material (copper or aluminum), then in this case the special connecting blocks presented below are well suited.

They have a different number of inputs: in the figure, respectively: 2, 4, 6.

That is, it is a "like" twist for 2, 3, 4, 5 or 6 wires.

You need to understand that after connecting the wires in this way, you cannot remove them back from the block. Therefore, if you have never tried to work with such devices, buy several of them in the store with a stock and practice at home. They cost a penny.

For a chandelier, the option of using wago-type terminals, especially if the wires coming from the ceiling are short, will not be very good, because, as already mentioned, in this case, the wires cannot be removed (for example, you will need to change the chandelier or wash it) and you will have to cut them off. In the case of terminals with screw connection, it will be enough to simply unscrew the fixing screws and release the wires.

Connecting wires of different sizes requires care. However, by twisting or soldering, it is possible to connect the veins of only an adjacent section, for example, 4 sq. mm and 5 sq. mm.

Connect conductors of different sizes using screw-type clamps (ZVI). Such a device allows you to bring a vein of one section into one entrance, and into the other - of a different section. A secure clamp will ensure perfect electrical contact. Each wire is clamped with a separate screw.
Universal self-clamping Wago. Such a tool has been used for a long time. Differs in ease of use. Designed not only to connect conductors with different cross-sections, but also create good contact between conductors from different raw materials.
A bolted connection can be made from an unlimited number of conductors. They use both different cross sections and not the same materials. The installation of washers in such a connection is required. It is also important to tighten the bolts tightly so that they do not loosen quickly.
There is also the use of tinned copper lugs in combination with a bolted connection. Tips alone are not enough, you also need to purchase a hydraulic press or special pliers. To achieve a tight connection, the insulation must be removed in accordance with the PUE. Similar to the previous method, flat metal washers are used.

All the types of wire connections described above are used when laying electrical wiring, but a specific type is selected based on several characteristics:

type and material of the core (copper / aluminum and single / stranded);
the number of wires to be connected;
operating conditions (indoors, outdoors).

Removing the insulating layer from the wires

I would like to dwell right away on a question that will be common to any method. Before connecting the wires to a common electrical unit, they must be stripped from the upper insulating layer.

This can be done with an assembly knife. This method is simple, but there is a high probability of damage to the conductive core. To do everything right, you must clearly follow the step-by-step instructions:

Place the wire on a flat surface (such as a table).
Press it down with your left index finger.
Take the knife with your right hand and lightly press it into the insulating sheath of the wire. To avoid snagging the metal strand, position it towards the cut at an angle. If the angle is right, there is a possibility of a circular cut in the vein, as a result of which it can subsequently break.
Holding the knife in this position. With the index finger of your left hand, slowly rotate the conductor one full turn, thus cutting the insulation around the entire circle.
It remains only to pull off the cut piece of insulation.

Professional electricians now necessarily have such a device as a stripper in their arsenal. It is a multifunctional tool that can be used to strip a wire or strip a cable. It can be simple, semi-automatic and automatic. The most important thing is that when the insulation is removed with a stripper, the conductive core is not damaged. For each standard core diameter, such a tool has a calibrated hole with a cutting edge.

The length for which it is necessary to strip the conductors of the wires is different for each connection method.

Twisting

Let's start with the simplest and most well-known method - twisting. It can also be called the most ancient, it is not for nothing that electricians call twisting among themselves the “old-fashioned method”.

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Grandfather's methods of primitive twisting of wires with obligatory insulation with the notorious blue tape are long gone. requires a professional approach, which means you need to use materials and devices that meet not only the highest safety requirements, but also simplicity, reliability and attractive appearance. One such device is wire connection terminals. Today we will talk about how to choose and use them correctly.

Small terminal - the solution to many problems in electrical wiring

How the two wires are connected depends on many factors. Consider the metal of the conductor, the thickness of the wiring, the number of cores and the type of insulating material. An important factor is the conditions in which the connection will be operated.

There are several main types of connections:

Let's consider in detail the main characteristics of all these compounds.

Features of professional twisting

Twisting is the simplest method of connecting wiring. No special tools are required for work, a knife and pliers are enough. To make the connection strong, experts recommend stripping the cores by at least 5 cm. To make the contact tight, the wires are clamped with pliers and twisted with a rotational motion. After the resulting connection is wrapped in one direction and tightly wrapped with electrical tape. This is the simplest version of such a connection.

Professional electricians have other ways to twist wires together:

Important! If you are using electrical tape, do not skimp on the winding. The insulation should cover not only the twist itself, but also go over the wires by at least a couple of centimeters.

Instead of electrical tape, you can use modern material - heat shrink tubing. Before connecting the conductors, the heat shrinkage of the required length is put on one of the wires and then pulled over the twist. It remains only for a moment to bring a match or a lighter to the tube, it will shrink and tightly fix and insulate the veins.

With reliable insulation, such a connection will last long enough. Its advantage is good vibration resistance, which is good for moving machinery. Electricians do not recommend using this method when connecting wires of different sizes. During operation, excessive resistance heats up the contact point so that the insulating layer can melt. Professionals do not advise twisting wires with conductors of different metals and cables with a large number of conductors.

Soldering for perfect conductivity

Not only the perfect operation of the mechanism, but also the safety of its user depends on the reliability and strength of the connection of the conductors. Soldering is one of the most reliable types of connection.

There is a soldering iron in almost every home, and the procedure itself does not take much time

Rosin is used for tinning, and tin or other fluxes are used as solder. Copper wires are recommended to be soldered with tin or lead, aluminum - with zinc-tin, aluminum or copper compounds. Before soldering, the wires are stripped and twisted using one of the above methods. After that, rosin and flux are applied to the twisting place with a soldering iron.

Important! The heated solder should fill in all the irregularities and holes in the twist.

After soldering, the connection is insulated with tape or heat shrink. The hardest part is soldering aluminum wiring. It oxidizes rapidly at high temperatures and does not form a strong bond with the solder material. For a strong connection, tinning must be used.

If the soldering is done correctly, the contact should be good. The only drawback is the fragility of the connection; under vibration and mechanical loads, it will not last long.

For professionals: welding

Welding allows the metal of the conductors to fuse and provide optimal resistance. This contact is strong and durable.

Arc, spot, torsion, plasma, ultrasonic and beam welding can be used.

Such work requires experience and dexterity, so the welding method is the tool of professional electricians. They use graphite and carbon electrodes, are stationary, and use high precision voltage controlled inverters. This technique is not suitable for domestic conditions, only experienced welders know how to correctly connect the wires to each other in such a complex way.

Important! All welding work must be carried out in a protective helmet. It will be very difficult for a beginner to achieve a high-quality connection of conductors.

After welding, the contact point is also insulated with tape or heat shrinkage.

Crimping with sleeves

Returning to the ways of connecting wiring more accessible for domestic use, it should be noted that crimping is a simple and affordable method that can be used without special skills.

The technique is very simple - conductors of wires are inserted into a metal sleeve and then the soft metal is crimped using pliers or a vice. It is best to use special pliers for this purpose. They can manually crimp sleeves up to 120 mm². If a larger liner is required, use hydraulics. The disadvantage of a sleeve connection is that it is final, and, if necessary, it will not work to fix the contact without cutting the wire.

For your information! For crimping, select sleeves of the correct material to ensure optimal contact. There are sleeves made of aluminum, copper and alloys. The cross-sectional diameter of the conductor is also taken into account, the cores must fit tightly into the sleeve.

The use of terminal blocks for connecting wires

The easiest to use and at the same time reliable is installation using terminal blocks.

Terminal clamps for wires can be used when mounting conductors from different metals. At the same time, the design of the terminals avoids direct contact between aluminum and copper and the formation of corrosion inevitable for such a connection.

Terminal blocks are divided into three main types: knife, screw and spring. As a rule, a brass alloy is used as the base material. Some models are filled with a gel that protects the contacts from corrosion.

Standard requirements for terminal strips

Like any electrical component, the terminal block has developed standards of reliability and quality:

Requirement	Description
Heat resistance	The terminal body material must be able to withstand high temperatures and be free from any risk of ignition. The body must not deform when heated, and the protective cover is not made of flammable material.
Strong hold	The terminal blocks must be secured without undue effort and, at the same time, securely hold the wire strands. In this case, the conductors do not need to be additionally processed or twisted.
Corrosion resistant	The contact plates in the terminals are of such a length that direct contact between the conductors is excluded. In this case, even if the wires are made of different metals, there will be no electrochemical corrosion.
Informativeness	Each connector for electrical wires contains information about the diameter of the conductors and the permissible voltage in the mains.

Pros and cons of terminal switching

As with any device, terminal connections have their advantages and disadvantages. First about the benefits:

Easy to connect. The terminals can connect two or more wires with different cross-sections and metal, while each core is placed in a separate socket and, if necessary, can be easily separated. If welding, jacket or soldering were used for switching, you would have to remove the insulation, break or untwist the contacts and then repeat the switching procedure again.
Safety. The terminals are made of insulating material. Even if you accidentally touch the switching point, you will not receive an electric shock.
There is no need to use a special tool. For the screw connection, you only need a suitable screwdriver.
Reliability of fastening. The junction of the wires is resistant to mechanical and temperature stress, vibration and stretching.
Aesthetics. Connecting wires with clamps looks much more neat than winding electrical tape.

Disadvantages of clamping connections:

Price. The price of a high-quality terminal is 10 ÷ 12 rubles per piece. If you just need to connect a pair of wires in the chandelier, this is not essential. But with a set of terminal contacts, it can cost a lot. But this drawback is a matter of time. A lot of competition in this market and the development of new technologies will soon make these devices cheap.
Some difficulties in installation in hard-to-reach places. If you need to install the terminal block in a place where it is difficult to reach your hand or fingers, the task may seem too difficult. On the other hand, it is not easy to perform any other switching in such a place.

How to choose terminals for connecting wires

To choose the right terminal, first of all, you should study the cable that you plan to connect. You need to find out, it is usually indicated in the marking of the wire.

The second selection criterion is high-quality terminal material. It must be sufficiently rigid and have reliable insulation. It is better if the screw and bracket of the device are made of steel. The terminals must be compact. It is possible that you will have to place the contact group in a limited space, so the size of the connections will matter.

Another criterion for making the right choice is ease of installation and maintenance. The terminals with a guide cone and a flag marking the place of conductor entry are especially convenient in operation.

Important! For terminals with a small cross-section up to 16 mm², the insulation is installed on one side, so you need to be very careful when installing them, otherwise a short circuit may occur.

Convenient if the surface of the terminal is suitable for marking. Sometimes it is necessary for the further operation of the connection.

Types of terminal contacts

Modern manufacturers offer a wide range of switches for performing connections of various purposes. Each model meets certain tasks and requirements, we will consider them in more detail.

Screw switches

These simple and reliable devices are ideal for installation in wall outlets and similar locations. The cores are fixed in the terminal with screws.

For your information! Lead and copper switches can be used to connect the car battery. Auto mechanics recommend giving preference to lead fasteners. They do not oxidize as much as copper ones when exposed to acid.

Screw terminal blocks are not used for aluminum wiring. This is due to the fact that the aluminum conductor collapses under the pressure of the screw fastening. If provided in the switch, the head of the screw is marked with green paint.

Terminal clamps for wires

The design of such switches provides for the use of a small spring that fixes the core in the desired position.

These terminal blocks are installed in an instant: the stripped wiring is simply inserted and the fixation is carried out in one click.

Junction Box Switches

Such terminals are used to connect wires in junction boxes. The switch body is made of polycarbonate and the contact point is made of copper. Springs are used to fix the cores.

For reliability, the terminals are treated with a special paste that protects the contacts from overheating.

Video on how to properly connect wires in a junction box using terminals

Fuse Terminals

A separate type of switches is with a built-in fuse. Such contact groups additionally protect the wiring from short circuits.

Such wagons for connecting wires take up more space than conventional terminal blocks and are used in cases where electrical appliances do not have built-in fuses in their design.

Connecting pads

Pads are a handy gadget for connecting multiple wires. Brass tubes with threaded holes are placed in the body of such a device. With the help of such small devices, it is possible to connect copper and aluminum wires to each other, as well as conductors of different cross-sections.

Switching in the block occurs in such a way that the conductors do not contact directly. The only thing that you should pay attention to is the indicator of the rated current on the block itself.

Blade terminals

These switches are also called wire crimp terminals. They are used for power conductors with a small cross-section up to 2.5 mm. The maximum voltage for such a connection is 5 kV. Such a connection will not withstand a more powerful current, so knife terminal blocks are not used in large power plants.

Which terminal blocks are better

In fact, choosing the right terminal should be taken very seriously. Especially if there is a need to connect wires with conductors of different metals. During operation, such contacts get very hot and deformed. This can lead to a complete loss of circuit integrity and even a short circuit. It is worth remembering that spring and screw terminal blocks are not suitable for fastening aluminum and copper wiring.

A few words about switch manufacturers

Products from European, Chinese and domestic manufacturers are presented on the shelves of electrical goods stores. As a rule, few ordinary buyers are puzzled by the origin of switches. And in vain. These tiny, fingertip-sized devices can directly affect the safety of your property. You should not blindly trust Chinese consumer goods. In most cases, China's products do not meet the requirements of domestic standards.

Domestic products are more reliable, but less aesthetic and technological. European goods are more expensive, but I bought such a terminal and forgot it. Manufacturers guarantee long-term and reliable performance of their products. Here are some of them:

LEGRAND

Screw switches from this manufacturer are the most popular product in this category. Brass products are nickel plated and can reliably withstand extreme temperature changes. Such terminals are characterized by high strength and a wide range of sizes.

WAGO

The products of the French company guarantee a strong connection of wiring of different types and cross-sections. The devices perfectly resist possible vibration and stretching and are installed without special tools. The main material of French terminal blocks is tin-plated copper, which gives good contact with low resistance. Some models are filled with anti-corrosion gel.

PHOENIX CONTACT

The German manufacturer is distinguished by excellent product quality. It offers over 200 kinds of different switches for different types of connections. Among the models presented there are those that are resistant to high humidity and explosion hazard.

WIEDMULLER

Another European brand offers one and a half hundred terminal models. The basis of the assortment is made up of screw connections made according to DIN technology.

Common problem: how to connect aluminum and copper wire

Residents of Soviet-built houses often face such a task. At that time, almost all wiring was done with aluminum conductors. Modern electricians mostly use copper wire. How to connect aluminum to copper wire? There are skeptics who argue that such a connection is impossible. You shouldn't believe them. If you correctly use the techniques that we will give below, the switching will be reliable and durable.

As already mentioned, ordinary twisting will not work for such a connection. The contact between copper and aluminum is very hot and can damage the insulation layer.

Option 1 - bolted

This is a simple and affordable method using a steel nut, bolt and washer. Due to the impressive dimensions of such fasteners, it is unlikely that it will be possible to place it in a modern small junction box. But on the other hand, such switching allows you to combine wiring not only from different metals, but also with different sections. These connections are easy to disassemble and reassemble if necessary.

Option 2 - nut connection

The name of such a connection was invented by electricians because of the external similarity. For fasteners, a special crimp is used, which is sold in electrical stores. The device consists of two dies with grooves for conductors. After fixing the veins, the dies are wrapped with electrical tape.

It would seem that what could be simpler than connecting wires? After all, there are several ways to connect wires. These are wire twisting, wire soldering, wire welding, crimping and connecting wires using a terminal block. Even a schoolboy knows the simplest way of twisting conductors. It is necessary to attach together the ends of metal wires, called veins, and twist into one "pigtail", then wrap with electrical tape. No need for a soldering iron, terminal block, connecting caps and other "unnecessary".
Any “his own electrician” has mastered such an operation. And, if necessary, he applies this method in his daily practice. For example, it splices the wires of a power cord of a household appliance, a tablet adapter or a computer after a break.
Russian "techies" use this technology of fastening wires everywhere. But in the rules for the construction of electrical installations PES "twists", all kinds of "bends" and "rivets" are not provided. There are no such methods of wiring in other regulatory documents. Why?

We often do not think about the consequences of such a "simplification". Meanwhile, an unreliable contact will fail at the most inopportune moment, the power supply to consumers / electrical consumers can always be cut off. From "surges" of voltage there is a breakdown of the elements of power cascades of complex household appliances SBT. Even special protection devices used in the most "sophisticated" models of foreign manufacturers do not save from breakdown.

The induction of short electromagnetic pulses with a voltage of several thousand volts on the electronic filling causes "harmless" sparking at the joints. At the same time, the standard protection equipment with which apartments are now equipped (RCDs, circuit breakers, fuses) do not "see" such short low-current impulses, therefore they simply do not work, and we do not customize to install special devices for this. Uninterruptible power supplies for computers also did not become a panacea for transient impulses. The appearance of "poking" causes malfunctions in the operation of electronic equipment and computer equipment, leads to the failure of electrical components and expensive functional modules.
Overheating in the place of a bad connection leads to even more catastrophic consequences; when current passes, the weakened connecting node becomes red-hot. Often from this occur fires and fires, causing enormous damage to the owners of premises. Statistics show that 90% of all wiring faults occur due to twists and poor contact connections of conductors. In turn, the very malfunction of electrical wiring and equipment, according to the Ministry of Emergency Situations, is the cause of one third of the fires occurring in Russia.

However, it so happened historically that several decades ago, in the face of a shortage of electrical accessories / copper conductors, twisting of aluminum wires was considered the main method used in electrical work. Twisting as a connection can be used in electrical engineering when carrying out repair and restoration work.

How to connect wires correctly

How to connect the wires: start by stripping the insulation off. Correct connection of conductors must satisfy three basic requirements:

Provide reliable contact with a minimum contact resistance between each other close to the resistance of a single piece of wire.
Maintain tensile strength, fracture and vibration resistance.
Connect only homogeneous metals (copper to copper, aluminum to aluminum).

There are several connection methods that satisfy these requirements. Depending on the requirements for wiring and the possibilities of practical application, the following types of wire connections are used:

All these methods require preliminary preparation of the wire or cable - stripping the insulation to expose the wires to be connected. Traditionally, the material of the insulating shell is rubber, polystyrene, fluoroplastic. Additionally, polyethylene, silk and varnish serve as insulation inside. Depending on the structure of the conductive part, the wire can be single-core or stranded.
A single-core wire means a wire, the cross-section of which is formed by an insulating sheath with a metal core or a wire inside.

In a stranded wire, the metal core is formed by several thin wires. They are usually intertwined and present as a bundle surrounded by an insulator on the outside. Often, individual veins are covered with polyurethane varnish, and nylon threads are added to the structure between them to increase the strength of the wire. These materials, like the fabric braid on the outside, complicate the stripping process.

Depending on the type of connection, 0.2 - 5.0 cm of insulation is removed from each end of the wire. For this, several types of tools are used.
According to a 5-point system, it is possible to assess the quality of stripping and the degree of protection against notching - damage to the cores by each device:

Insulation / core damage

Monter's (kitchen) knife - 3/3
Side cutters (nippers) - 4/3
Stripper - 5/4
Soldering iron or loop burner - 4/4

In low-current television / computer networks, coaxial cables are used. During the cutting process, it is important to carefully cut and remove the insulating jacket without damaging the braided shield. To access the central vein, it is fluffed up and removed, exposing the trunk. After that, the polyethylene insulation is cut with a knife or a special device, the cut is removed from the core.
The bifilar in the screen consists of a pair of wires in the screen, which is also preliminarily fluffed into wires to access the conductors, opening access to each core.

Important! To remove the insulating material of the enameled wire with a cross-section of less than 0.2 mm², a soldering iron should be used. The enamel is carefully removed using an emery "zero" by moving the paper along the wires.

How to twist wires correctly

Most often, twisting is used to repair electrical wiring, cords and adapters (including low-current ones) of household appliances and equipment. If we are talking about a home electrical network, then the norms provide for the use of wires in houses with a current-carrying conductor cross-section of 1.5–2.0 mm made of copper and 2.5–4.0 mm made of aluminum. Usually, wires of the VVG and PV brands in a PVC sheath are used for wiring. Power cords of the ShVL and SHTB brands with rubber or PVC insulation have a cross section of 0.5 - 0.75 mm.
Step-by-step splicing of wires together can be done as follows:

Degrease the bare ends of the wires by wiping with acetone / alcohol.
Remove the varnish or oxide layer by sanding the conductors with sandpaper.
We apply the tips so that they cross. We wind at least 5 turns of one core to another in a clockwise direction. To make the twist tight, use pliers.
We isolate the open current-carrying parts of the wires with electrical tape, or screw on an insulating cap. They should go behind the insulation for 1.5–2.0 s to cover the bare sections of the conductors.

For splicing a stranded stripped wire with a single-core wire, another winding technique is used:

A single wire is twisted with a stranded wire, leaving a free end without winding.
The end of the single-core wire is bent 180 ° so that it presses the twist, then pressed with pliers.
The connection point must be firmly fixed with electrical tape. For best performance, an insulating heat pipe should be used. For this, a piece of cambric of the required length is pulled over the joint. In order for it to grip the wiring more tightly, the tube should be warmed up, for example, with a hairdryer or a lighter.

With a bandage connection, the free ends are placed next to each other and wrapped from above with an existing piece of wire (bandage) made of a homogeneous material.
Coupling with a groove provides that before mutual twisting, small hooks from the ends of the wire are configured, they are interlocked with each other, then the edges are wrapped.
There are more complex types of parallel / serial connections. The connection of wires by the twisting method is used by professional electrical repairers when carrying out restoration work.

Important! Copper and aluminum have different ohmic resistance, they actively oxidize when interacting, the connection is fragile due to different hardness, therefore, the connection of these metals is undesirable. In case of emergency, the ends to be connected should be prepared - irradiated with tin-lead solder (POS) using a soldering iron.

Why is it better to crimp (crimp) the wires

Crimping of wires is one of the most reliable and high-quality methods of mechanical connections that are currently used. With this technology, the cables and wires are crimped in the connecting sleeve using press tongs, ensuring tight contact along the entire length.

The sleeve is a hollow tube and can be manufactured independently. For sleeve sizes up to 120 mm², mechanical pliers are used. For large cross-sections, products with a hydraulic punch are used.

When crimped, the sleeve usually takes the shape of a hexagon, sometimes local indentation is made in certain parts of the tube. In crimping, sleeves made of electrical copper GM and aluminum tubes GA are used. This method allows crimping conductors made of different metals. In many respects, this is facilitated by the treatment of the constituent components with quartz-vaseline lubricant, which prevents subsequent oxidation. For joint use, there are combined aluminum-copper sleeves or tinned copper sleeves GAM and GML. The crimp connection is used for wire bundles with a total cross-sectional diameter between 10 mm² and 3 cm².

Soldering as a reliable alternative to twisting

The closest alternative to twisting, prohibited for wiring, is the connection of wires using the soldering method. It requires special tools and consumables, but provides absolute electrical contact.

Advice! Overlapping wire splicing is considered the most unreliable in technology. During operation, the solder crumbles and the connection opens. Therefore, before soldering, apply a bandage, wrap a piece of wire of a smaller diameter around the parts to be connected, or twist the conductors together.

You will need a 60-100 W electric soldering iron, stand and tweezers (thin nose pliers). The soldering iron tip should be cleaned of scale, sharpened by selecting the most suitable tip shape in the form of a spatula, and connect the device case to the ground wire. From "consumables" you will need POS-40 solder, POS-60 from tin and lead, rosin as a flux. Solder wire with rosin placed inside the structure can be used.

If you need to solder steel, brass or aluminum, you need a special soldering acid.

Important! Do not overheat the junction points. In order not to melt the insulation when soldering, be sure to use a heat sink. To do this, hold the bare wire between the heating area and the insulation with tweezers or pliers.

The conductors stripped of insulation should be irradiated, for which the tips heated with a soldering iron are placed in a piece of rosin, they should be covered with a brown-transparent layer of flux.
We place the tip of the soldering iron tip in the solder, grab a drop of the melted one and evenly process the wires alternately, turning and moving along the blade of the tip.
Attach or twist the wires together, fixing them firmly. Warm up with a sting for 2–5 s. Treat the areas to be soldered with a layer of solder, allowing the drop to spread over the surfaces. Turn over the wires to be connected and repeat the operation on the reverse side.
After cooling, the soldering points are insulated by analogy with twisting. In some compounds, they are pre-treated with a brush dipped in alcohol and varnished on top.

Advice! During and after soldering within 5–8 s. the wires must not be tugged or wiggled; they must be stationary. The signal that the structure has hardened is the acquisition of a matte shade by the surface of the solder (in the molten state, it shines).

Still, welding is preferable

Welding surpasses all other technologies in connection strength and contact quality. Recently, portable welding inverters have appeared that can be carried to the most inaccessible places. Such devices are easily held on the welder's shoulder using a strap. This allows working in hard-to-reach places, such as welding from a ladder in a junction box. For welding metal wires, carbon pencils or copper-plated electrodes are inserted into the holder of the welding machine.

The main disadvantage of welding technology - overheating of the parts to be welded and melting of the insulation is eliminated by:

Correct adjustment of the welding current 70-120 A without overheating (depending on the number of welded wires with a cross-section of 1.5 to 2.0 mm).
The short duration of the welding process is no more than 1-2 seconds.
Tight preliminary twisting of wires and installation of a copper heat sink clamp.

When connecting wires by welding, the twisted cores should be bent and be sure to turn upwards with a cut. An electrode is brought to the end of the wires connected to the ground and an electric arc is ignited. The molten copper flows down into a ball and covers the wire strand. In the process of cooling, an insulating belt made of a piece of cambric or other insulating material is put on the warm structure. Varnish cloth is also suitable as an insulating material.

Terminal blocks - the most ergonomic wiring products

The rules of the PUE, clause 2.1.21 provide for the type of connections using clamps (screws, bolts). There is a connection directly with the help of fasteners "on the weight", when a screw, a washer is threaded through the loops of each of the wires and is fixed with a nut from the back side.

Such an installation is wrapped in several turns of electrical tape and is considered quite practical and reliable.
More ergonomic wiring products, called screw terminal blocks. They represent a contact group located in a housing made of insulating material (plastic, porcelain). The most common connection of wires by the method using terminal blocks is found in junction boxes and electrical panels. To connect the wire, you need to push it into the socket and tighten the screw, the clamping bar will securely fix the core in the seat. Another wire to be connected is connected to the mating socket, shorted to the first.

In self-clamping terminal blocks of the WAGO type, the wire is snapped into the socket, for better contact, a special paste or gel is used.

Tap-off clamps represent the capital version of the screw terminal block with several short-circuited taps, used mainly on the street and in places with unfavorable environmental conditions.

The connecting clamps represent an insulating cap with a thread inside, it is screwed onto a twist, at the same time squeezing and protecting from mechanical stress.