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 outdoors or indoors with high humidity, then the lifetime of such a pair is many times less.
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 going too far into design features terminal clamps, 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.
Everything 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
Although, by modern standards, wiring in residential apartments is made mainly of copper wires, it is not uncommon to find electrical wiring made of aluminum. If it is impossible to replace the old wiring with a new one, then you need to learn how to connect aluminum wires with your own hands. So, how, for example, to connect a chandelier, socket and other electrical appliances correctly? Is it possible to connect aluminum wires with others? How to make the connection reliable? How to firmly connect aluminum wires to each other? You can get answers to these questions in this article.
feature of aluminum wire
Due to its special characteristics, aluminum is difficult to work with. Also, in the process of oxidation of this metal, an oxide film is formed on the surface. It, in turn, prevents the good passage of current. This film melts at a temperature of two thousand degrees, and this figure is higher than the melting point of aluminum itself. If you peel off the film mechanically, then literally in a short period of time it appears again. As a result, the oxide film interferes with the quality contact of the connection.
Among other features of aluminum, an increased degree of brittleness and fluidity can be distinguished. Based on this, the contact should not be subjected to any mechanical stress. For example, if the connection is made with a bolt, then from time to time it must be constantly tightened. This is due to the fact that aluminum will leak out from under the contact over time.
Electrochemical corrosion
Can aluminum wire be connected to others? Yes! But here it is important to consider some important points. If there is no moisture, then such a connection will be eternal. However, moisture is present everywhere, it in turn contributes to the destruction of contacts. It is important to take into account the fact that each conductor of electric current has its own electrochemical potential. In this regard, accumulators and batteries were created, however, at the moment of water ingress at the junction of metals, a short-circuited galvanic cell is formed. As a result, one of the metals is destroyed. To find out which metals can be connected and which cannot, it is important to know the magnitude of the electrochemical potential of a particular current conductor.
So, for example, it is permissible to connect different wires when the level of the electrochemical potential between them does not exceed 0.6 mV. Based on this, it turns out that the connection of copper with stainless steel will be of high quality with a potential difference of 0.1 mV, in contrast to the connection with silver (0.25 mV) or gold (0.4 mV).
Note! If the copper wire is coated with tin-lead solder, then any mechanical connection to the aluminum wire is allowed.
Methods for joining aluminum with copper
Based on the foregoing, it may seem that connecting aluminum wires is not an easy task. However, it is not! In the process of connecting an aluminum wire to a copper wire, you just need to follow the technology. Consider several well-known methods for connecting aluminum wire to copper:
Twisting
This is one of the easy wire connection methods. It absolutely does not require any qualifications, as well as special knowledge. But the result is far from reliable connection. Why? Everything is due to the fact that during the period of temperature fluctuations, a linear expansion of the wires occurs and, as a result, a gap is formed between them, which in turn increases the resistance. After that, the contact is oxidized and after some time is destroyed.
Note! Such a phenomenon will not happen in the first year. But if you want to create a reliable and high-quality connection, then you should consider a more reliable alternative.
How is such a connection made? It is important here that one wire does not wrap around the other, but they both wrap around each other. In order for the connection to come out of high quality, the copper wire can be tinned with solder. There is no restriction on the diameter of the connected wires. If the copper wire is stranded, then in without fail it needs to be soldered. If the wire is thick, then three turns will be enough, and on a thin one up to Ø1 mm, five turns must be made.
Threaded connection
One of the most reliable options for connecting aluminum and copper wires with nuts and screws. Such a connection will provide high-quality contact for many years. Using this method, you can connect wires of different sections, stranded and single-core.
So, from the end of the wire, you first need to remove the insulation. After that, a spring washer, a regular washer, a ring of one conductor, a simple washer, a ring of another conductor, a washer and at the end a nut are put on the screw, which twists the entire structure.
Note! If the conductor has a core Ø2 mm, then the screw must be M4.
If the wire is stranded, then it must first be soldered.
Terminal block
The terminal block is another modern method connection of aluminum and copper wires. Although it is very popular, the screw and bolt method is much more reliable. However, the terminal block allows you to quickly and efficiently connect the wires. At the same time, there is no need to form rings at the end of the wire, as well as additional insulation. This design completely eliminates the possibility of contact between two bare wires.
Such a connection is made as follows: The end of the wire is stripped of insulation to a length of up to 5 mm. After that, a wire is inserted into the hole in the terminal block, which is tightened with a screw.
Note! Tighten the screw with feeling, especially aluminum wire.
Such a connection is very helpful in cases where a short piece of aluminum wire sticks out of the ceiling. If in this case you use the twisting method, then sooner or later the wire will simply break off. The same cannot be said for the use of the terminal block. Also, if aluminum wires were accidentally broken in the wall, this technology simplifies their connection. But there is one thing here! The terminal block must not be hidden in plaster or in a wall without a special junction box.
Terminal block and flat-spring clip
This method of connecting wires appeared relatively recently. There are two types: disposable and reusable. In the latter case, there is a special lever that allows you to remove and insert the wire several times. Such terminal blocks allow you to connect stranded wires different types aluminum with copper wires.
They are widely used for mounting chandeliers, as well as for connecting wires in junction boxes. The wire is inserted into the hole of the block with force and is securely fixed there. It will take a lot of effort to remove the wire. In practice, it is better to use reusable terminal blocks, which allow you to redo the connection in case of a miscalculation.
10 mm insulation is removed from the wire. The lever on the reusable terminal rises up and the wire is inserted. Then the lever returns to the opposite position. Connection is ready!
This type of connection has almost all the advantages of a threaded connection. You can highlight the speed of installation, strength, affordable price and ease of connection. The principle of its operation is simple. To connect the wire with a rivet, rings with a diameter of 4 mm are prepared. The aluminum wire is put on first, then the spring washer, the copper wire and the flat washer. A steel rod is inserted into the riveter and compressed until the handle clicks. As a result, the excess conductor is cut off and the connection is completely ready.
The reliability of such a connection is very high. It is used for splicing wires. The most important requirement when using it is the isolation of the connection section.
Twisting aluminum wires together
We spoke about the advantages and features of twisting above, but now we will consider this issue from a different angle, namely, connecting an aluminum wire with its own kind. In this case, the success of applying the twisting method will directly depend on the cross section, wire diameter and other important factors. Ideally, aluminum wires are best soldered, after twisting them with a groove.
However, it is important to be careful here, since an oxide film forms on the surface of aluminum wires. Even if it is cleaned, it will reappear very quickly, as noted above, so the ends of the wire can be cleaned with a file to a shine or sandpaper. The lowest coil is recommended to be compressed with pliers. Such a connection will be durable and strong.
Each wire connection must be properly insulated.
It is recommended to place them in junction boxes. If such a connection is simply plastered in the wall, then access to it is limited and, accordingly, it will be impossible to tighten the contacts. Although if you use the technology of spring clips, then this will not be necessary.
If you want to make such a connection with your own hands at home, then it is not recommended to use soldering or welding wires in the absence of experience in performing such work. The best option there will be a contact clamp or one of the methods described above for connecting aluminum wire to copper wire or to each other.
So, we have reviewed with you the most common methods for connecting aluminum wire. Of course, if you do not have experience or you are simply afraid to take on such work, then it is better not to take risks and contact a specialist. Otherwise, if you have experience with such work, proceed by following all the recommendations from this article.
Video
See a master class on connecting copper to aluminum:
Until now, there is a considerable number of premises where electrical wiring is made of aluminum. Wherein modern systems based on the use of copper as a conductor. That is why the problem of joining wires from these dissimilar materials is relevant. How to join copper and aluminum wires will be discussed below.
Electrochemical corrosion
It is often possible to meet statements that it is undesirable to combine copper and aluminum into one. From the point of view of material compatibility, these are fair statements. What about combining copper and zinc or steel and silver? There are many options for metal pairs, and remembering which ones are compatible with each other and which are not is difficult. To simplify the task, there are special tables, one of which is presented below.
Table of electrochemical potentials (mV) that occur between connected conductors.
To understand the issue, you need to know what processes occur when different conductors of electricity touch each other. If there is no humidity, the contacts will be reliable anyway. However, in practice, this situation is impossible, since moisture is always present in the atmosphere, which breaks the connections.
Each conductor of electricity has a certain electrochemical potential. This circumstance is used by a person for practical purposes, for example, batteries and batteries work on the basis of different potentials.
When moisture gets on the contacting metal surfaces, a short-circuited galvanic medium occurs, and one of the electrodes is deformed. In the same way, one of the two metals is destroyed. Thus, in order to determine the compatibility of metals, it is necessary to have information about the electrochemical potential of all materials involved in the reaction.
What happens if copper is connected directly to aluminum According to technical regulations, mechanical joining of metals is allowed if the electrochemical voltage between the two materials is not higher than 0.6 mV. For example, from the table above, it can be established that in the case of a combination of aluminum and copper, the electrochemical potential is 0.65 mV, which is much higher than when the same copper is joined with duralumin (0.20 mV).
And, nevertheless, if it is very necessary, then it is possible to combine such not quite compatible materials, which include copper and aluminum. How to connect copper and aluminum wires will be discussed below.
Overview of connection methods
There are several ways to connect aluminum and copper wires. Moreover, in each of the described cases, special devices will be needed. Let's consider each type of docking separately.
This type of connection is the most common, since it is simple and cheap. If done correctly, a wired connection with nuts and bolts will provide reliable contact for the life of the wiring and electrical appliances. In addition, you can always disassemble the connection, attach additional conductors, etc. Thanks to the threaded connection, the relevance of the electrochemical incompatibility of metals is lost, it becomes possible to join aluminum and copper, thick and thin wires, stranded and single-core. It is important to avoid direct contact between dissimilar materials by making gaskets from spring washers.
To do the job, you will need a bolt and nut, as well as a washer (it must be made of anodized steel).
The connection is made as follows:
- We remove the insulating layer from the wires for a short length (about four bolt diameters). We also perform stripping of the conductor, especially if its cores have undergone oxidation. We form rings from the veins.
- First, an aluminum conductor is screwed to the bolt in one girth.
- We put on the puck.
- Now it's the turn of the copper conductor. We also screw it in one turn.
- Next, screw the nut in such a way as to achieve a secure connection.
Note! If docking is carried out for operation in a room where, according to technical conditions, there is vibration, an additional nut will be required for a qualitative result.
Terminals
There are several options for terminal connections. One option is the so-called "nuts". Such an unusual name for terminal blocks comes from their external resemblance to nuts. There are several varieties of "nut" terminals available.
The model, which is the most primitive in its structure, has three delimiting plates inside. Conductors are located between the plates. Thus, it is possible to avoid direct contacts between dissimilar materials. At the same time, "nuts" allow you to save the supply circuit of the electrical circuit.
To achieve the integrity of the circuit, it is necessary to strip the supply conductor from the insulating layer, unscrew a couple of bolts, install a bare wire between the plates and tighten the bolts again. Remove the insulator from the outlet ends, and then direct the wires into holes located perpendicular to the inlet channel. Further, the conductors are fixed between other delimiting plates.
There is also a more complex model on the market, the design of which is designed in such a way that there is no need for cutting conductors. The fact is that the plates of the device contain teeth, which, when squeezed by bolts, simply break the insulating layer. The described docking option is considered very reliable.
There is another option for terminal blocks - ordinary pads. The device is a bar with terminals. To connect two dissimilar materials, you need to strip their ends and send the wires to the terminals. The ends are fixed with bolts that are located over the terminal holes.
Wago terminal blocks
The connection of copper and aluminum wires can be done using Wago terminal blocks. This device belongs to the aforementioned terminals, however, Wago pads should be described in a little more detail due to their popularity among buyers.
Wago is made in two versions: disposable with a non-removable wire and reusable - with a lever that allows you to repeatedly install and remove the conductor.
Wago is used for all types of solid wires, the cross section of which is between 1.5 and 2.5 square millimeters. The block can be used in distribution boxes with a current of up to 24 amperes. However, in practice, it is believed that 10 amperes is more than enough and large figures will lead to overheating.
To connect the conductors, it is necessary to force one of them into the shoe hole, as a result of which it will be securely fixed there. To remove the conductor from the hole, you will also need to apply force. Please note that removing the wire from the disposable terminal block may deform the contact, so a reliable contact is not guaranteed next time.
It is much more convenient to use the Wago reusable device. A characteristic feature of such a terminal block is the presence of an orange lever. With the help of such a device, it is possible to dock or disconnect all types of wires with a cross section from 0.08 to 4 square millimeters. Permissible current level - 34 amperes.
To create a connection, you need to remove the insulation from the wire by 8-12 millimeters, raise the lever up, direct the wire into the hole in the terminal block. Next, return the lever to the opposite position, thereby fixing the wire in the terminal.
The only significant drawback of Wago is the higher cost compared to traditional terminals.
Rivets
This method of joining dissimilar conductors resembles a bolted one. However, instead of a nut and a bolt, a rivet is used, which forms a permanent connection. In other words, after fixing, it is no longer possible to remove the rivet without damaging it.
To perform the docking, we clean both conductors from the insulating material, and also bend the wires into rings. Next, we string one of the rings onto the rivet, after that we put on a steel washer, then we string the ring again, but already the second conductor.
The rivet has a cap on one side. Now you need to flatten the second side, thus forming a second hat, which will act as a fastener. The deformation of the rivet is carried out either with a hammer or with a special tool similar to pliers. The method of joining with rivets allows you to get a very high-quality connection.
soldering iron
If desired, you can solder two dissimilar metals. However, this will require compliance with some technological nuances.
As for copper, there will be no problems with soldering, but with aluminum the situation is more complicated. The fact is that as a result of soldering and under the influence of oxygen, an amalgam appears on the metal surface. This alloy-film is incredibly chemically resistant, which means it does not adhere to solder. To eliminate the film, you will need a solution of copper sulfate, a Krona battery and a piece of copper wire.
On the aluminum wire, we clean the soldering area, and after that we apply a little vitriol there. We fix the aluminum wire on the negative pole of the battery, and we fix the copper wire with one end on the positive pole, and put the other end in copper sulfate. After some time, aluminum will be covered with a copper layer, on which you can solder a copper conductor.
Connection quality
In most of the cases considered earlier, rigid fastening of the conductors cleared of the insulating layer will be used. However, when joining copper and aluminum, one important technological nuance must be taken into account: aluminum under the influence of the load acquires plasticity, as experts say, it begins to "flow". As a result of this process, the connection is weakened, and therefore the bolts must be tightened regularly. If the bolts are not tightened in time, the terminal may simply catch fire due to severe overheating.
There are a number of rules, adhering to which, you can achieve a high-quality connection:
- Conductors with multiple strands must not be clamped too tightly. In such wires, the cores are too thin, they are easily torn under the influence of compression. The result of the gaps is an overload on the remaining cores, which may cause a fire.
- It is important to choose the right terminal, taking into account the cross section of the conductor. If the channel is too narrow, the conductor will not fit, and if it is too wide, it will fall out.
- Brass sleeves and terminals are very fragile, so do not overtighten them.
- You should carefully consider the marking, where the maximum possible current strength is suggested. Moreover, it is better not to achieve this indicator, limiting yourself to no more than 50% load.
Note! It is not recommended to buy nameless products made in China. Connectors are too important a detail to skimp on. It is best to give preference to products of well-known companies (for example, the Swiss company ABB).
stranded wires
As mentioned earlier, conductors with many strands should not be strongly pinched. To connect stranded wires, sleeves or ordinary twists are most often used. We will discuss these methods in more detail below.
Sleeves
The sleeve is a protective cap made of plastic, under which there is a hollow metal tip. First of all, it is necessary to remove the insulating layer from the conductor. Further, the veins are twisted into one whole, and the resulting "pigtail" is sent to the sleeve. Next, the sleeve is crimped (pliers are suitable for this operation). The tip of the sleeve is inserted into the terminal. To increase the reliability of the connection, the sleeve can be treated with solder.
Twisting
Among professional electricians, twisting is not revered. However, there are situations when twisting is the most convenient way way out (for example, to create a temporary connection or in the absence of the necessary materials).
So, twisting from copper and aluminum is allowed only after a thorough cleaning of the aluminum surface. If the copper conductor has many strands, all available strands must be assembled into one "pigtail". Also, copper must be coated with solder - this will improve contact.
When twisting, it is important to prevent the wires from breaking. The endings are best covered with insulating protective caps, which can be purchased at any hardware store.
Note! Twisting is unacceptable in rooms with humid air.
So, there is nothing complicated in connecting copper and aluminum conductors. You just need to remember the price of a mistake: incorrectly connected wires can cause not only the failure of electrical appliances, but also a fire.
In residential buildings that were built in Soviet times, electrical wiring was carried out with aluminum wires. Professional electricians prefer to make a modern household network with copper wires. Therefore, whether we like it or not, we often face such a problem as connecting copper and aluminum wire. Do not listen to those who will tell you that this cannot be done categorically. Of course, not all methods are suitable for this case, however, connecting electrical aluminum and copper wires is a completely solvable task. The main thing is to do everything right.
These two metals have different chemical properties, which affects the quality of their connection. But there were smart heads who figured out how to connect two conductors, while excluding direct contact between them.
We will consider everything existing options of how copper and aluminum wire can be connected, but first, let's figure out why this cannot be done with ordinary twisting and what is the reason for this incompatibility?
Reasons for incompatibility
The main reasons for the undesirable connection between these two metals lies in the aluminum wire.
the result of twisting copper and aluminum - overheating of the connection, melting of the insulation, the possibility of fire
There are three reasons, but they all lead to the same result - over time, the contact connection of the wires weakens, starts to overheat, the insulation melts and a short circuit occurs.
- Aluminum wire has the ability to oxidize under the influence of moisture in the air. When in contact with copper, this happens much faster. In the oxide layer, the resistivity value is greater than that of the aluminum metal itself, which leads to excessive heating of the conductor.
- Compared to copper conductor, aluminum is softer and has less electrical conductivity, due to which it heats up more. During operation, the conductors heat up and cool down many times, resulting in several cycles of expansion and contraction. But aluminum and copper have a big difference in the magnitude of linear expansion, so a change in temperature leads to a weakening of the contact connection, and weak contact is always the cause of strong heating.
- The third reason is that copper and aluminum are galvanically incompatible. If you twist them, then when an electric current passes through such a node, even with minimal humidity, a chemical electrolysis reaction will occur. It, in turn, causes corrosion, as a result of which the contact connection is again broken, and as a result, heating, melting of the insulation, short circuit, fire.
Bolted connection
Bolted connection of aluminum wires with copper is considered the most affordable, simple, fast and reliable. To work, you will need a bolt, nut, some steel washers and a wrench.
Of course, it is unlikely that you will be able to apply this method to connect wires in an apartment junction box, because now they are produced in miniature sizes, and the resulting electrical assembly will be very cumbersome. But if there are still Soviet-era boxes in your house or when you need to make a connection in a switchboard, then such a bolted method is best suited. Generally, it is considered ideal option when it is necessary to switch absolutely incompatible conductors - with different cross-sections, made of various materials, stranded with single-core.
It is important to know that using the bolt method you can connect more than two conductors (their number depends on how long the bolt is long enough).
You will need to do the following:
- Strip each connected wire or cable from the insulating layer by 2-2.5 cm.
- From the stripped tips, form rings according to the diameter of the bolt so that they can be easily put on it.
- Now take a bolt, put a washer on it, then a copper conductor ring, another washer, an aluminum conductor ring, a washer and securely tighten everything with a nut.
- Insulate the connection with electrical tape.
Most importantly, do not forget to place an intermediate washer between the aluminum and copper wires. If you connect several different conductors, then you can not put an intermediate washer between the cores of the same metal.
Another advantage of this connection is that it is detachable. At any time, you can unwind it and, if necessary, connect additional wires.
How to properly bolt the wires is shown in detail in this video:
Clamp "Nut"
Another good way to connect copper and aluminum wires is to use walnut clamps. It is more correct to call this device a branch clamp. It was already electricians who called him "nut" because of the resemblance.
It is a dielectric polycarbonate case, inside of which there is a metal core (or core). The core is two dies, each of which has a groove for a certain section of the conductor, and an intermediate plate, all this is interconnected by bolts.
Such clamps are sold in any electrical supply store, they have different types, which depend on the cross section of the connected wires. The disadvantage of such a device is its non-tightness, that is, there is the possibility of moisture, dust and even small litter. For the reliability and quality of the connection, it is better to wrap the “nut” with insulating tape on top.
The process of connecting wires using such a compression is as follows:
- Disassemble the clamp housing, to do this, pry and remove the retaining rings with a thin screwdriver.
- On the wires to be connected, strip the insulating layer to the length of the dies.
- Unscrew the fixing bolts and insert the bare conductors into the die slots.
- Tighten the bolts, position the plate in the compression housing.
- Close the housing and put on the retaining rings.
A practical example of using a walnut clamp is shown in this video:
Terminal block
Cheap and simple solution in the question of how to connect aluminum wires to copper, is the use of terminal blocks. Buying them now is not a problem at all, moreover, you can buy not a whole section, but ask the seller to cut off right amount cells. Terminal blocks for sale different sizes, depending on the cross section of the conductors connected in them.
What is such a block? This is a transparent polyethylene frame designed for several cells at once. Inside each cell there is a tubular brass sleeve. From opposite sides, it is necessary to insert the ends of the wires to be connected into this sleeve and clamp it with two screws.
The use of terminal blocks is very convenient because it is always possible to cut exactly as many cells from it as how many pairs of wires need to be connected, for example, in one junction box.
Using the terminal blocks is very simple:
- Unscrew one clamping screw, thereby freeing one side of the sleeve for the passage of the conductor into it.
- On the strands of aluminum wire, strip the insulation to a length of 5 mm. Insert it into the terminal, tighten the screw, thereby pressing the conductor to the sleeve. The screw should be tightened firmly, but do not be too zealous, so as not to break the core.
- Do the same operations with the copper wire, inserting it into the sleeve from the opposite side.
Why do you have to do everything in order? After all, you can immediately unscrew the two screws, insert the wires and tighten. This is to ensure that the copper and aluminum wires do not touch each other inside the brass sleeve.
As you can see, the advantages of terminal blocks are the simplicity and speed of their application. This connection method refers to detachable, if necessary, you can pull out one conductor and replace it with another.
Terminal blocks are not quite suitable for connecting stranded conductors in them. In order to do this, you must first use the end sleeves that will compress the bundle of cores.
There is another feature in the use of terminal blocks. Under the pressure of the screw at room temperature, aluminum can flow. Therefore, a periodic revision of the terminal and tightening of the contact connection, where the aluminum wire is fixed, will be required. If this is neglected, the aluminum conductor in the terminal block will loosen, the contact will weaken, it will start to heat up and spark, which may result in a fire.
How to connect the wires using the terminal block is shown in this video:
Self-clamping terminals
Even faster and easier to connect aluminum and copper conductors in self-clamping terminals.
The stripped conductors must be inserted into the terminal holes until they stop. There they will automatically be fixed with the help of pressure plates (it will firmly press the conductor to the tinned bar). Thanks to the transparent housing of the terminal block, it is possible to check whether the core has completely entered the terminal. The disadvantage of such devices is that they are disposable.
If you want a reusable clamp, use lever-type terminals. The lever rises and releases the entrance to the hole into which it is necessary to insert the stripped core. After that, the lever is lowered back, thereby fixing the conductor in the terminal. This connection is detachable, if necessary, the lever rises, and the wire is taken out of the terminal.
WAGO self-clamping terminals have proven themselves in the best way on the electrical goods market. The manufacturer produces a special series of terminals in which there is an Alu-plus contact paste. This substance protects the contact junction of aluminum and copper from the manifestation of electrolytic corrosion processes. These terminals can be distinguished by a special marking on the package "Al Cu".
Using these clamps is also extremely simple. The clamp itself indicates how long it is necessary to strip the insulating layer of the conductor.
The advantages and disadvantages of using WAGO terminal blocks are described in this video:
Twisted connection
Twisting copper and aluminum wires is not recommended. If you can’t do without this, then first you should tin the copper conductor, that is, cover it with lead-tin solder. So you exclude the possibility of direct interaction of aluminum and copper.
Do not forget that aluminum is very soft and brittle, it can break even under slight loads, so twist very carefully. Do not forget to insulate the connection properly, in this case it is best to use a heat-shrinkable tube.
We tried to tell you in detail whether it is possible to connect aluminum and copper wires together, as well as how to do it efficiently and reliably. Choose the most suitable method for yourself, depending on where this connection will be switched and operated.
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:
- Welding.
- Crimping.
- Soldering.
- 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, with its technical specifications. 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 quite heat melting - 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:
- 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.
- Now the contacts should be degreased. To do this, they will have to be wiped with a cloth previously moistened with acetone.
- sandpaper remove the oxide film from the surface of the metal, that is, they clean it until a metallic sheen is obtained.
- Wires cross each other, after which one of the cores is twisted as tightly as possible onto the other with the help of pliers.
- Second wire in the same way it is wound on the first one.
- 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:
- Spring washer.
- Standard puck.
- Ring of the first wire.
- Another standard washer.
- Ring of the second wire.
- 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. Though appearance such products can be very different, 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:
- Connected sections of wires treated with a special flux, which removes the oxide film from the surface.
- Solder is handled as carefully as possible so that it has the largest area of \u200b\u200bcontact with the wires.
- When the connection area cools down, it is desirable to process it with sandpaper to remove sharp edges that can damage the insulating layer.
- Wires must be insulated.
Soldering requires certain skills.
It should be said that this method has several negative points:
- He has to be isolated.
- The method itself is rather complicated., especially if you have to solder wires under the ceiling, standing on a stepladder.
- If an error was made in the course of work, then fixing it will be quite problematic.
- 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
flat spring clamp 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 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.
- Professional electricians do not recommend connecting aluminum and copper wires. 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.
- 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.
