What is the best way to connect aluminum wires to each other. How to connect aluminum and copper wires

When installing electrical wiring, it is quite often necessary to connect different current conductors, namely, aluminum and copper wires. From the point of view of electrical and fire safety, this type of connection is more risky and must be carried out with strict adherence to a number of rules.

What is the essence of the problem of connecting aluminum and copper wires, and what are the options for solving it? Let's try to figure it out.

Difficulties connecting aluminum and copper wires

Over the past decades, there has been a rapid increase in energy consumption by the population. This has led to an increase in the load on the electrical networks and, accordingly, on the connection of wires in the wiring.

Therefore, today there are serious requirements for the installation of electrical wiring, aimed at improving electrical and fire safety.

Indicators of a reliable wire connection:

1. The density of the contracted contact.
2. Electrochemical compatibility of contact wires.

The first requirement of high-quality electrical wiring is quite simple to fulfill. The second requirement is often ignored in practice and incompatible current conductors are connected in a direct way (twisting). It is because of the electrochemical incompatibility of metals that difficulties arise when connecting copper and aluminum wires.

Aluminum is a metal with a high degree of oxidation. The oxide film formed on the surface of the aluminum wire in contact with moisture has a high resistance. This negatively affects the electrical conductivity of the connections.

Copper is a rather inert metal and the oxide film on copper wires has less resistance.

In a pair, copper and aluminum form a short-circuited galvanic connection - when moisture enters the contact, the aluminum wire begins to actively oxidize. A thin film with high resistance is formed between the current conductors, as a result, the current conduction becomes difficult, the electrolysis process takes place, shells, heating, and sparking of the contacts form at the contact point. This situation may cause a fire.

The electrochemical potential between copper and aluminum is 0.65 mV, while the allowable value of this indicator is 0.60 mV

The solution to this problem is the elimination of direct contact between aluminum and copper wires. There are several options for connecting different conductors, ensuring the reliability and safety of electrical wiring.

The main methods of connecting different current conductors

application of terminal blocks

The most common way is to connect wires through terminal blocks.

In essence, a terminal block is an insulating plate with contacts. Fastening wires in the terminal block is of two types:

• screw tightening (there is a risk of damage to the wire by the screw itself);
• pressing with plates (more reliable mounting option).

Among the advantages of the "terminal" method of connecting wires include:

• ease of connection;
• the connection does not need to be further isolated;
• affordable cost of adapters.

The sequence of connecting copper electrical wires with aluminum:

The terminal block is convenient to use when connecting a chandelier, when the conductor length is too short, or for connecting copper and aluminum wires that have been broken off and broken in the wall.

The terminal block, before being hidden under the finish, must be placed in a junction box

spring terminals for connecting wires

One of the varieties of terminal blocks are Wago spring clamp blocks.

Spring terminal blocks are the most efficient and fastest way to connect wires. The main difference from conventional terminal blocks is the method of fixing the wire - a spring clip is used. It is enough to remove the insulating layer from the conductor and insert the wire into the terminal block.

In order to connect copper and aluminum wire, it is better to use special Wago terminal blocks. The contacts in such a terminal block are made of a bimetallic plate and coated with a special paste that prevents oxidation of the wires.

Spring terminal blocks are of two types:

The disadvantage of spring terminal blocks is their cost, they are an order of magnitude more expensive than conventional adapters.

connection through the "nut"

To connect wires with a large cross section (4 mm² or more), you can use a branch clamp, known in everyday life as a "nut". It is an oval-shaped plastic case, inside which there is a block of metal plates. Aluminum and copper wires are clamped between the plates with screws.

This connection option is not entirely convenient due to the large dimensions of the adapter itself, which is difficult to hide under the decoration of the room: skirting boards and boxes.

permanent connection

A permanent connection is made using a special tool - a riveter.

The principle of operation of the riveter is simple - retraction and subsequent cutting of the rod, which passes through the tubular rivet with a cap.

The wire connection technology is as follows:

1. Remove the insulation from the conductors (the length of the cleaning is equal to 4 diameters of future rings). It is optimal if the diameter of the rings is slightly larger than the diameter of the rivet.
2. Twist rings from the cleaned ends of the wire.
3. Put all the elements on the rivet in the following order:
   • aluminum wire;
   • spring washer;
   • copper wire;
   • flat washer.
4. Insert the steel rod into the riveter and squeeze its handles until a characteristic click.
5. Bare areas of the connection must be isolated.

The reliability of the permanent connection is very high, the only drawback is that it is not possible to disconnect and re-fasten the wires.

Alternative ways to connect aluminum and copper wires

If there are no special adapters or a riveter at hand, you can use alternative methods for connecting different conductors.

Bolted connection considered quite durable and safe. Among its advantages are ease of installation and versatility (in this way, you can connect almost any type and brand of aluminum wires with copper).

Bolted connection technology:

For connecting conductors with a cross section of less than 2 mm², an M4 screw is suitable

A technologically more complex and time-consuming method is applying solder to a copper wire. You can use lead-tin solder.

When aluminum comes into contact with lead-tin solder, the electrochemical resistance index is 0.40 mV (the permissible rate is not more than 0.60 mV)

The wire connection sequence will be as follows:

This method can be used if there are no jumpers or the bolted connection does not fit into the box. However, for an electrical wire with significant loads, such a connection cannot be used.

Features of connecting wires indoors and outdoors

Outdoor wire connections are exposed to external factors and need additional protection.

The optimal solution for outdoor connections is the use of branch clamps for SIP. The material of the clamps is resistant to ultraviolet rays and low negative temperatures.

In addition, branch clamps nuts are also suitable for the street.

To connect the wires in the room, you can use different conductors. One of the most convenient is the Wago self-clamping terminal block.

Expert advice: how not to connect aluminum and copper wires

There are frequent cases of the use of dangerous, unacceptable methods for connecting aluminum and copper wires, which had very sad consequences. These methods include:

1. Stranding copper and aluminum wire. It should be noted that a number of experts do not recognize twisting, even if a layer of solder is applied to the copper wire.
2. Twisting of wires with subsequent protection of the junction from moisture. As a waterproofing, some "craftsmen" use paraffin, oil or varnish. This method is unacceptable and, to put it mildly, ineffective.

To date, the problem of connecting different current conductors is solved very simply and quickly - just purchase one of the special adapters. Therefore, it is completely inappropriate to waste time and test untested methods, endangering the safety of not only housing, but also the people living in it.

It's no secret to anyone that copper and aluminum wires are not recommended to be connected. But many, even knowing this, still neglect it, hoping for the Russian "maybe it will pass."

As a result, such a pair of copper-aluminum will live for a very short time. And if the connection is located on the street or in a room with high humidity, then the life of such a pair is several times shorter.

But quite often there are situations when we need to connect copper and aluminum wiring. Often this situation occurs when repairing electrical wiring in houses where aluminum wiring is laid.

Special terminal blocks and bolted connections will help us get out of this situation, through which we will connect copper and aluminum wires. Using terminal and bolted connections, we we do not allow direct contact of the copper-aluminum pair.

Without really going into the design features of the terminal clamps, we will consider the most used of them.

One of the old and proven ways to connect wires are nut type terminal connections. They got their name because of their resemblance to nuts.

Connections of this type consist of three plates, between which, in fact, the wires are clamped. One of the advantages of this type of connection is that there is no need to break the line to connect the outgoing wire. It is enough just to unscrew 2 bolts, insert a wire between the two plates, and tighten the bolts into place. The outgoing wire is inserted between the middle and remaining plate. Everything, the connection is ready.

The next most popular can be called. These connection terminals can be made from aluminum and copper. It is enough just to strip the wires by 10-15 mm, insert them into the terminal block hole, and that's it, the next connection is ready to go.

The inside of the terminal block is filled with a special lubricant that does not allow the wires to oxidize. We recommend using this type of connection in lighting circuits. The use of these connections in power circuits is not recommended, since a large load can lead to heating of the springy contacts, and as a result, to poor contact.

Another popular connection is. Outwardly, they are a bar with terminal strips. It is enough to strip the end of the wire, insert it into one hole and clamp it with a screw. The stripped end of the second wire is inserted into the other hole. These terminal blocks also allow you to connect wires from different metals.

Bolted wire connections. This type of connection can also be used if you need to connect copper and aluminum wires. When installing the connection, it is necessary to install an anodized metal washer between the copper and aluminum wires.

All installation work must be carried out by a specialist. All screw and bolt connections must be checked: for aluminum wires - once every half a year, for copper - once every two years is enough.

Sergey Seromashenko

When partially replacing the wiring, extending the conductor or replacing the burnt area, a wire is used. It happens that in their material they do not match. Then it becomes necessary to connect aluminum wires with copper. There are five ways to do this, and each has its own advantages and disadvantages. Some of them require preliminary preparation of the conductor.

Danger of bad wiring

The industry produces two types of wires for domestic purposes, copper and aluminum. The former have less resistance, which allows using a smaller section for the same load. They are more resistant to mechanical stress, this makes it possible to repeatedly twist, not to be afraid that they will break at the place of the incision. The latter have one advantage - comparative cheapness. But sometimes it plays a key role. What can happen if the junction is of poor quality?

Copper and aluminum have different characteristics, for example, a different coefficient of expansion when heated. When a large current passes through an aluminum conductor, it begins to "flow". If the cores move relative to each other during heating or cooling, this will lead to a gap between them. The gap, in turn, will lead to a discharge (spark). Sparks can cause a fire. Along with this, copper and aluminum begin to oxidize, the resistance between them increases, the voltage drops because of this or may completely disappear. Voltage fluctuations can adversely affect connected devices.

Methods for joining copper to aluminum

There are several connection methods. All of them have their pros and cons. Some require special equipment and skills, others are easy to use. Here are a few of them:

• twist;
• threaded;
• terminal;
• one-piece.

Wire twisting

It is strictly forbidden to use twisting in fire hazardous areas. This is the fastest and easiest way. Two or more wires are taken and wrapped around each other. One or more than one strand must not be left straight. There is a rule - thick cores must have at least three turns, thin ones (from 1 mm or less) - five. To reduce the oxidation of the conductor, the copper core is soldered for the length of the twist. The same rule applies to stranded copper cables.

After the twisting has been made, it must be protected from the environment by coating with any waterproof varnish. This is necessary to reduce further over-oxidation. Then it is isolated with electrical tape or special caps, which are sold in the store, and hidden in an insulating case. But even all this does not guarantee that the twist will work flawlessly.

Threaded method

More labor-intensive connection compared to twisting. Requires a tool and some skill. It has greater mechanical strength. On the electrical side, it is better than twisting. Allows you to immediately connect a large number of wires, and of different sections. You can connect both single-core and multi-core.

For connection, a bolt is used, on which conductors are put on in turn. They are pre-cleaned and wrapped in rings. Each core, if they are made of different materials, is laid with a washer. A washer and a spring washer are superimposed on the last conductor. The whole package is tightened with a nut until the spring washer straightens out. Further pressure may break the conductor.

To prevent the washer from cutting the wires, they must be put on in a checkerboard pattern (so that they do not lie on top of each other). If the copper wire is tinned, washers are not needed. The stranded copper wire also needs to be soldered, then it will not disintegrate during compression.

After assembly, measures must be taken to prevent short circuits with neighboring packages. Over time, it is necessary to check the condition of the spring washer, if it is weakened, tighten the nut. Such a connection prevents sparking, allows you to output wires in different directions. If necessary, it can be easily disassembled and assembled without damaging the conductor.

Terminal method

The terminal connection is made in factories. Has an extensive range. Two groups can be distinguished:

• pads;
• terminal blocks.

pads have different shapes and designs. The bottom line is to attach several wires to one conductor (plate, tetrahedron, etc.), which are inserted into special connectors and pressed with a screw. As a rule, the pads themselves are attached to the base, creating structural rigidity.

The advantage of pads is that no preliminary steps are needed, with the exception of stripping the cores. The connection is fast and does not require any skills. They are indispensable if the conductor is short (connecting a chandelier, restoring a broken wire). If they are located in switchboards, metering boards - they do not require insulation. Since each wire is connected separately, both copper and aluminum wires can be used.

The disadvantages include the following:

• less resistant to mechanical stress than a threaded connection;
• each block is designed for a conductor of a certain section;
• it is impossible to connect wires of large and small diameter at the same time;
• take up more space than before.

Terminal blocks have recently found wide application. According to their purpose, they are of two types:

• reusable;
• for one time use.

reusable the terminal block is a fully insulated block. Instead of screws, a spring plate is used, which is pressed out with a plastic lever. After that, a wire is inserted into the opening. In some embodiments, the plate has teeth, which allows the use of unstripped wires. To pull out the wire, you need to lift the lever again.

One-time have the same principle, but do not have a lever. Designed for single use. If the wire is still pulled out and reinserted, the quality of the connection will be poor.

Advantages:

• allows you to very quickly connect aluminum and copper wires to each other;
• minimal training required;
• ease of use;
• the necessary insulation is available.

Disadvantages:

• the method is the most sensitive to mechanical stress;
• compared to other compounds, it is the most expensive;
• sensitive to high current and, according to user comments, does not withstand the regulated load.

One-piece method

Probably the most laborious way. Requires special knowledge and skills. Special tools and fixtures are required. This method includes:

• riveted;
• soldering.

stave very similar to a threaded connection, with the only difference being that a rivet is used instead of a bolt. The ends of the wires are cleaned of insulation and cleaned with sandpaper. When combining aluminum and copper wires, the latter is tinned. This also applies to copper stranded wire. After that, rings are made a little larger in diameter than the rivet. Finally, when the entire structure is assembled (without intermediate washers), a washer is put on top. All this is compressed by the terminal block. It is insulated in the same way as a threaded one.

Soldering used where high reliability of the connection and its low resistance are needed. It looks like a twist, but the wires are soldered. This cannot be achieved in the usual way for aluminum, so the wires must be prepared.

To do this, you need a solution of copper sulfate, a small non-metallic container, a constant voltage source of 9-24 V. Pour a solution of copper sulfate into the container and lower the previously cleaned conductors to the length of the twist. We connect the copper wire to "+" so that the electrons go from it, and the aluminum wire to "-". Turn on the power source.

The voltage, of course, can be increased, the main thing is that the solution does not boil or there is no overload in the electrical circuit. You can also reduce the voltage, then the process will proceed more slowly. All this works until the aluminum wire is covered with a copper film.

After that, both wires are covered with a layer of tin. A twist is made in 3 turns for a thick wire and 5 for a thin one (less than 1 mm). All this is carefully soldered. It remains to cover them with waterproof varnish, insulate - and the connection is ready.

Advantages:

• has an aesthetic appearance;
• good mechanical strength;
• reliable connection.

Disadvantages:

• there is no way to disassemble;
• you can only work with removable wires;
• purchase of additional equipment;
• requires some skills.

Now, knowing all the ways to connect copper and aluminum wires without soldering, you can fix this problem when it occurs.

When it is required to connect 2 different sections of the wire together, it is necessary, in addition to high-quality contact, to obtain sufficient strength of the section where these wires are connected to each other.

If we take into account the regulatory documents that are in force on the territory of our country, then it is permissible to connect aluminum wires to each other using various methods:

1. Welding.
2. Crimping.
3. Soldering.
4. Connection using .

Despite the fact that all these connection methods specified in the regulatory documents are presented as universal, not every one of them will be suitable when working with aluminum wires.

First of all, this is due to the characteristics of such a material as aluminum, in particular, to its technical characteristics. As is known from the school chemistry course, there is always an oxide film on the surface of aluminum, formed as a result of direct contact with atmospheric oxygen.

It is unable to conduct electricity through itself. In addition, the oxide film has a rather high melting point - in the region of 2000 degrees. This figure is much higher than the melting point of aluminum itself.

If you remove this film mechanically, then it will very quickly reappear. It should be noted that the presence of this film when soldering aluminum greatly interferes with the process of connecting the aluminum core with solder. Also, it can cause difficulties when welding wires, because due to its presence, various inclusions occur, due to which the quality of the contact is greatly reduced.

Additional characteristics of a material such as aluminum include increased brittleness and fluidity. In this regard, when connecting aluminum wires, care should be taken in advance that they are located so that the possibility of mechanical impact on this area is completely excluded.

It is worth noting that when connecting wires using a standard bolt clamp, it will have to be tightened periodically, as the metal will gradually flow out from under the bolt. As a result, the connection will become weaker.

Twisting

Aluminum wires are often interconnected by twisting. This is the simplest, but also the most dangerous method of connecting wires to each other.

The sequence of actions when using this technology will be as follows:

1. At first, the insulation is removed from the wires approximately 4-5 cm on each side. It is most convenient here to use a special tool designed specifically for this purpose.
2. Now the contacts should be degreased. To do this, they will have to be wiped with a cloth previously moistened with acetone.
3. sandpaper remove the oxide film from the surface of the metal, that is, they clean it until a metallic sheen is obtained.
4. Wires cross each other, after which one of the cores is twisted as tightly as possible onto the other with the help of pliers.
5. Second wire in the same way it is wound on the first one.
6. The twist should now be insulated with insulating tape. Professional electricians also recommend using a special heat shrink tube or cambric. With it, you can qualitatively protect the bare area from the negative effects of the external environment.

In principle, the technology is quite simple. It is only necessary to remember that the cores need to be bared by at least 4-5 cm, and the twisting should not be done manually, but only with the help of pliers, so that the wires fit as close to each other as possible.

If this is not done, then the result will be a loose contact, due to which the area can become very hot. In turn, this effect causes a short circuit, and in some cases even a fire.

Threaded connection

This type of connection can be very reliable if done correctly. It should be noted that aluminum has the highest linear expansion, and therefore a gap appears between the connected wires over time, which worsens their contact with each other. To prevent a short circuit, you need to tighten these screws from time to time.

To get rid of this need, install special washers with cuts or grovers. They choose the resulting gaps and several times increase the reliability of the connection.

On the screw, the wires will need to be wound so that the area of ​​\u200b\u200bcontact with the contact pad is much higher. Professional electricians often do this: they flatten this ring on an anvil to increase the contact area.

The technology for making a high-quality threaded connection of wires begins with the removal of insulation from them at a distance equal to 4 screw diameters. Cleaned areas are degreased.

Then you need to bend their tips so that rings form.

The elements are put on the screw in the following sequence:

1. Spring washer.
2. Standard puck.
3. Ring of the first wire.
4. Another standard washer.
5. Ring of the second wire.
6. Screw.

This whole system is tightened until the spring washer is in a straightened state. In principle, if both wires are made of aluminum, then a standard washer can not be laid between them.

We use terminal blocks

If aluminum wires have a slight current load, then they can be interconnected using terminal blocks. Despite the fact that the appearance of such products may vary greatly, the principle of their work is the same.

The body of the pads is made of plastic or carbolite. It contains tubes with thick walls made of brass. There are threaded holes on the sides. Connected wires are inserted into opposite ends, which are fixed with screws. It should be noted that it is allowed to insert as many wires into one brass tube as will fit there.

This is not a very reliable connection compared to soldering, but several times less time is spent on installation work. In addition to connecting conductors made of the same material, it is permissible to use different wires in terminal blocks.

Permanent connection

If in the future it is not planned to disassemble the connection of wires, then the so-called one-piece methods can be used. These methods are among the most reliable. It is desirable to use them, first of all, in hard-to-reach places.

One of the easiest methods of permanent connections is crimping. To do this, an aluminum tube of a suitable diameter is taken, the wires are twisted together, inserted into this tube and clamped with press tongs. It is best here that the conductors enter as tightly as possible.

Only in this case the connection will be the most durable. It is worth noting: if the wires enter the tube quite tightly, then you don’t even have to twist them together. At the last stage, the connection is isolated.

Today on sale you can find special tips for the manufacture of this connection, which already have an insulating cap. It shrinks together with the tip and wraps around the wires, blocking any access to them.

To obtain a high-quality one-piece connection, you need to have special pliers that will not bite, but only squeeze. If they are not available, then standard pliers are quite suitable.

Soldering and welding

Soldering wires allows you to get a fairly high-quality and one-piece connection. However, when connecting aluminum wires, you should be aware of the presence of an oxide film on them, due to which the solder will not adhere too well.

To prevent the occurrence of such a defect, you need to follow a certain sequence of actions:

1. Connected sections of wires treated with a special flux, which removes the oxide film from the surface.
2. Solder is handled as carefully as possible so that it has the largest area of ​​\u200b\u200bcontact with the wires.
3. When the connection area cools down, it is desirable to process it with sandpaper to remove sharp edges that can damage the insulating layer.
4. Wires must be insulated.

Soldering requires certain skills.

It should be said that this method has several negative points:

1. He has to be isolated.
2. The method itself is rather complicated., especially if you have to solder wires under the ceiling, standing on a stepladder.
3. If an error was made in the course of work, then fixing it will be quite problematic.
4. It takes a lot of time to work.

Welding is somewhat similar to soldering wires, but it is performed much faster. In order to obtain a quality connection, the electrode is brought to the connection area for only 1-2 seconds. Both ends of the wire are pretreated with flux to remove the oxide film.

If there is no experience in this area, then initially you should practice on twists prepared in advance, but not connected to the system.

After the welding process is completed, the twists are passed with a special solvent and varnished. The result is a quality connection that can last for a long period of time, as this method allows you to prevent the occurrence of overheating. Accordingly, such an area will need to be isolated.

Alternatives

The wires can be connected to each other with a rivet. In principle, this technology is similar to screw technology, only here a rivet is taken instead of a screw. The end result is a non-separable connection.

This connection is quite simple: both conductors are put on the rivet through the spring washer, then it is inserted into the riveter and the handles are brought together until a click is heard.

Also, there is a special flat-spring clamp. Such products are disposable and reusable, when the wire can be both inserted and removed. However, it should be remembered that such clamps are made of plastic, so it is undesirable to use them for currents above 10 A.

Working with them is very simple: the wires are stripped and inserted into the clamp until it clicks. It is impossible to pull them out without using a special lever. It is also desirable to isolate this section of the wire.

Connection Features

Aluminum wires are best placed in special ones, to which they must fit in corrugated sleeves. This is especially important when laying outdoors or in the case of wiring in a damp room such as a bathroom.

In general, when connecting aluminum wires that will function outdoors, care must be taken to ensure that moisture does not approach the connection areas.

Otherwise, a short circuit cannot be avoided. It is very convenient in this case to use the technology of welding wires, since the subsequent use of a special varnish makes it possible to exclude the effect of water on the junction, and the insulating layer additionally protects against electric shock.

1. Professional electricians It is not recommended to connect aluminum and copper wires together. This is due to many reasons, the most important of which is the different resistance of metals. In addition, when interacting with each other, copper and aluminum oxidize very quickly, which causes heating of the wires, significantly worsens the contact. In addition, their rigidity is different, which greatly complicates the work.
2. You can, if necessary, combine certain methods of connecting wires. In particular, twisting goes well with soldering or welding. The result is a very reliable and one-piece contact that will last for a long time.