There are many rumors about the connection of copper and aluminum wire. Some say that there is nothing wrong with this and give examples where such connections last for decades, while others say that they know from practice how quickly they break down. We will discuss who to believe and how to correctly connect such wires in our article.
First of all, let's figure out why you can't connect these wires together, and what you need to ensure that such a connection lasts for many years. To do this, we will have to dive a little into the theory and understand the structure of these metals.
Why you can’t connect copper and aluminum wire
To understand how to connect copper and aluminum wire, let's figure out what's wrong with such a connection. After all, there are several theories about the inadmissibility of such a connection, and almost all of them have a rational grain.
Like any other metal, copper and aluminum oxidize when exposed to oxygen. As a result, an oxide film forms on their surface. The copper oxide film practically does not interfere with the passage of electric current, but the aluminum oxide film has a fairly high resistance.
If we connect copper and aluminum wires, no matter how much we want, the metals will interact. Aluminum is a more active metal, therefore, when moisture appears between the connection, which is in any case present in the air, the process of electrolysis begins, that is, aluminum ions are transferred to copper.
As a result, the aluminum conductor loses its mass. Voids and cavities form in it. They, in turn, also oxidize and further accelerate the electrolysis process. And the more moisture in the compound, the faster this process occurs.
As a result, we have an almost destroyed aluminum conductor. Its cross section is reduced, which means the current density increases. The current density increases, the metal begins to heat up more, and as a result, this will either lead to burnout of the aluminum at the junction, or, in the worst case, to a fire.
How to connect copper and aluminum conductor
But you can connect a copper wire to an aluminum one. To do this, it is enough to place a third material between these two conductors or completely eliminate the possibility of moisture penetrating to the point of contact of the metals.
- Let's look at both of these options. Let's start with the simplest one - placing a third metal between the conductors. Usually, an inactive metal is also chosen for this, so that we again do not have the electrolysis process. And usually the instructions recommend using brass for this.
- This is due to the fact that this material has fairly good electrical properties. It is chemically stable and interferes with the electrolysis process.
- Some suggest using regular steel or stainless steel for this. But you shouldn't do this. The fact is that these materials do not have very good conductivity. Therefore, when large currents pass through them, they will become very hot. As a result, we may get a fire again.
When making repairs (even cosmetic ones), we are often faced with the need to put the electrical wiring in order. In old houses, it happens that the wires are almost the same age as the owners of the apartment, and therefore it is simply necessary to replace entire sections of the wiring.
But this is where the main problem lies: very often old wires are made of aluminum, and you only have a piece to replace. Let’s immediately say that according to all the rules, joining them is strictly prohibited, but there are all sorts of situations.
So in this article we will discuss aluminum and copper ones, so as not to become the culprit of a short circuit and fire?
Why can't you do this?
In order for you to fully understand the danger of such actions, you should talk about why you should not twist copper and aluminum wires. We have to remember physics and chemistry.
Do you remember what Roughly speaking, this can be called a battery in which the current arises as a result of the interaction between two metals in the electrolyte. Accordingly, the twist between aluminum and copper is such a battery.
Of course, in dry air the formation of galvanic currents, which quickly destroy the material, is practically impossible. Yes, even the twist to the socket, which is constantly used to connect a kettle or other powerful appliance, will not fall apart after a couple of hours, but troubles await you for sure.
Judge for yourself: over time, the wire materials gradually deteriorate, and the resistance constantly increases. Accordingly, the twisting area begins to heat up very much when a powerful current consumer is connected to the outlet. If this happens regularly, then the likelihood of a fire becomes extremely high.
That is why it is not recommended to join aluminum and copper wires for a long time. How to connect them if an emergency arises? Agree, in the countryside it is not always possible to visit an electrical goods store!
Let us repeat once again that it is not always possible to do everything “according to science,” but we still strongly recommend using terminal blocks to connect wires. This is the easiest, fastest and safest way in which even the most inexperienced electrician can connect wires. Let's look at the most common structural types.
"Nuts"
The oldest and most proven method is called nuts. As you can understand, they received the nickname because of their specific shape. Structurally, they consist of three plates, between which the wires are fixed.
A special advantage of this method is the fact that it is not at all necessary to cut the central line to insert the second wire. To do this, you just need to peel off the insulation in the right place, and then clamp this area between two “nut” plates. A branch wire is inserted between them, after which the plates are securely twisted together.
WAGO
No less common are the methods of connecting wires, which are united under one abbreviation WAGO. These are very simple and reliable devices with which you can dock everything in a couple of seconds. This is done as simply as possible: the ends of the wires are stripped of insulation, after which they are inserted into the connectors.
The trick here is that the internal space of this connection is filled with a special lubricant, which prevents oxidation and galvanic reaction between different types of metals. But! We could recommend the use of this kind of devices only in those networks to which powerful devices will not be connected.
The fact is that under heavy load, connections of this type will become very hot, as a result of which the terminal materials will begin to deteriorate. It is not surprising that WAGO is most often used when working with lighting fixtures.
Terminal blocks
They are also quite common and popular. They look most like a small strip with terminals. As in the case described above, to use them you need to strip one end of the wire, then insert it into the adapter hole and tighten the bolts. On the other hand, everything is done exactly the same.
Here again lies the rub. How will aluminum and copper wires behave in this case? How to connect them if you need to connect really powerful devices to the network?
Fortunately, pads are quite suitable for this purpose. If the thickness of the insulating plate is normal, then it will withstand even very high loads without problems. But remember that it is highly not recommended to install it in a room with high humidity. There is no insulating lubricant in them, so the formation of a galvanic couple cannot be ruled out.
What other ways to connect wires are there? Let's figure it out.
Bolt-on mounting
This installation method is also great when you need to join copper and aluminum. The wires are clamped with a bolt, and between the two metals it is necessary to place a washer made of high-quality anodized steel. Remember that this type of connection must be checked for strength at least twice a year. If such a joint is used in a network that experiences high loads, then this needs to be done even more often!
Soldering iron
Is it possible to solder wires that are made of different metals? Yes, this is quite possible, but some important conditions will need to be met.
We won’t talk about copper for a long time, since there shouldn’t be any difficulties in this matter. But there will be problems with aluminum. Their cause is amalgam, which instantly forms on the surface of this metal when it enters an oxygen environment. It is surprisingly chemically resistant, and therefore solder does not stick to it at all. This is something that novice electricians constantly encounter, for whom any soldering of aluminum wires is a novelty.
How to remove this annoying film? First you will have to prepare a saturated solution of copper sulfate, a Krona battery and a piece of normal copper wire (not Chinese). On the aluminum wire, you need to carefully clean the place of future soldering, and then drop a couple of drops of copper sulfate solution onto it.
Attach aluminum to the negative terminal of the battery, and a piece of copper wire to the positive terminal. Lower its end into After some time, a fairly decent layer of copper will settle on the aluminum, onto which you can easily solder the wire you need.
As you can see, soldering wires, even in this case, can provide a reliable and high-quality connection.
Important!
In almost all the cases that we have discussed above, rigid fixation of wires stripped of insulation is used. Somewhere terminals are used for this, somewhere bolts... But few people take into account one important point when twisting aluminum and copper wires. We already know how to connect them, but it’s also worth talking about the safety of this process.
The fact is that aluminum under load becomes quite plastic and begins to “flow”. All (!) connections of this kind must be checked regularly and the bolts must be tightened. Otherwise, the day will come when a terminal that is kept on its word of honor will simply burst into flames, unable to withstand the strong heat.
- Stranded copper wires should never be clamped. The fact is that when clamping, a whole range of conditions are formed that this wire really does not like. So, part of the veins may well come out of the connection. The remaining part of the wire will be subject to a very high load, which may result in a fire.
- It is very important to select the terminal exactly for the cross-section of the wire you are using. From a channel that is too narrow or wide, the wire will simply fall out, and this is fraught with unpleasant consequences.
- Don't overdo it! In most cases, brass is used in terminals and sleeves, and this material is characterized by increased fragility.
- Look carefully at the markings, which indicate the maximum permissible current. As a rule, it is exaggerated: it is better to divide the indicated value by two.
We strongly advise against buying the so-called NoName from China. You won't go broke by spending a couple of rubles more, but buy a really high-quality terminal from a normal manufacturer! Manufacturers Tridonik, ABB, and Verit have proven themselves to be excellent.
What about the multi-core option?
If you have carefully read the article, then you already know very well that stranded wires should not be clamped. But what to do in the case when you need to connect them to a thick aluminum outlet, but you don’t have a soldering iron, copper sulfate and batteries, and you don’t want to bother with them?
It's time to tell you that there are special types of wire connections that are specifically designed to solve this kind of problem.
Sleeve connections
In specialized stores for electricians, you can easily find sleeves specially designed for normal connections. They look like miniature tournament spears of knights: behind a protective plastic cap there is a hollow metal tip.
How to work with them? It's simple: carefully remove the insulation from the end of the wire, twist the strands into one “pigtail”, and then insert it into the hollow tip. Afterwards it is crimped (you can use the most ordinary pliers). The resulting tip is inserted into the terminal.
This way you can easily connect the wires without soldering. Of course, no one forbids the above-mentioned “pigtail”, provided that you have a soldering iron, to tin it with solder and weld it with aluminum in the way that we described above.
Twist
Of course, making twists among professional electricians is considered bad manners and almost a violation of professional ethics, but in life anything can happen, and therefore no one is immune from the need to make such a connection.
What advice can be given in this case? Let's start with the fact that twisting aluminum and copper wires is allowed only after thoroughly cleaning the aluminum section. If the copper wire is presented in a multi-core version, it must not only be twisted into one “pigtail”, but also covered with solder for better contact.
Twisting should be done as carefully as possible, avoiding breaking off the wires. It is recommended to close its ends with a special insulating cap, which can be purchased at almost every hardware store.
Finally, we have already written more than once that twisting should under no circumstances be placed in a room with high air humidity. Under such conditions, the connection is destroyed almost instantly.
In a word, although it is not recommended by professional electricians to connect copper and aluminum wires, using the simplest means you can easily do it without exposing your home to the risk of fire.
When installing electrical wiring, sometimes the question arises about connecting copper and aluminum wires. This issue is especially relevant during electrical work in old housing stock, where the main part of the electrical networks is made of aluminum wire. How to connect aluminum and copper wires to avoid problems with electrical wiring will be discussed later in this review.
What is the difficulty of connecting copper and aluminum wiring directly
As is known, the cause of problems in the direct connection of copper and aluminum is electrocorrosion processes. In a dry environment, nothing will happen even with direct contact, but with increased humidity, a short-circuited galvanic cell is formed at the junction, in which the metals begin to play the role of a battery with a “plus” and a “minus”. The metal itself practically melts, resulting in a network rupture with a possible short circuit and insulation fire. Which in turn can lead to a fire.
In order to avoid this, various types of contact devices are used to indirectly connect copper and aluminum wiring.
All connection methods can be divided into 2 groups based on the presence of wire contact:
- There is direct contact between the wires: twisting, crimping, connection with rivets, strips.
- There is no direct contact between the wires: threaded fixation, connection with various types of terminal blocks.
Important! To connect aluminum and copper wires, it is recommended to use methods from the second group. It is allowed to use connections from group 1 provided that the copper wire is processed. For example, it can be tinned with solder.
Twist
The main method of connecting wires at home, it is quite convenient in that it does not require special tools and equipment. But in the case of connecting aluminum and copper wires, this method must be used extremely carefully, observing the following conditions:
- A twisted connection is made by mutually twisting both ends of the wire with each other; wrapping the end of one wire around the other is not allowed;
- It is recommended to tin the copper cable with tin or solder before twisting; this point is especially important for stranded copper wire;
- A protective moisture-resistant coating must be applied to the connection between aluminum and copper wires.
There are three main types of twist: simple, bandage and groove twist. It should be noted that bandage twisting will give the best results. When performing twisting, it is worth considering that the number of turns directly depends on the diameter of the wiring, so for a wire up to 1 mm in diameter it is necessary to make at least 5 turns, for large sections at least three turns. In addition to moisture insulation, one should not forget about the electrical insulation of the twist; for this you can use special tips.
High-quality twisting will last quite a long time, but only the use of an indirect connection can provide a true guarantee.
How to make a twist correctly
First you need to prepare the ends of the wires. To do this, remove the insulation at a distance of 3–5 cm from the edge of the cable. It should be noted that the heat-shrink tube is placed on one of the wires, before twisting, upon completion of all operations, the tube is moved to an open place and fixed there. After cleaning the ends, you need to twist the wires according to the proposed diagram. In this case, it is necessary to ensure that the cores are wrapped around each other, and that one cable core does not overlap another.
To make it easier to twist a multi-core copper cable, its cores can and should be tinned. It should also be noted that tinning copper in any case increases the reliability of the twisted connection. After twisting, the connection point must be coated with moisture-resistant varnish. Electrical insulation can be done using heat shrink tubing or cap caps with a soft clamp or cone spring.
Insulation of wire ends with caps with a cone spring
Important! Unless absolutely necessary, it is not recommended to use twisting to connect copper and aluminum cables. Currently, there are many safer and more reliable ways to combine copper and aluminum into one network.
In this case, a metal or plastic sleeve or tip is placed on the twisted connection, which is fixed to the connection with press pliers, a special crimping tool. Fixation in this case is carried out by crimping the connection with the sleeve material. The sleeves are a metal tube with insulation made of PVC materials. The nozzles are usually plastic caps into which the compound is inserted, after which the cap is crimped with press jaws.
Separately, it is necessary to note the connection using cap attachments with a clamping ring or cone spring. In this case, after twisting the wires, a cap is put on the twist, after which it is screwed onto the connection with rotational movements, after which it is simply crimped with pliers. In this case, a ring of soft metal inside the cap tightly compresses the junction. This crimping option is quite accessible for household use.
Threaded fixation
A reliable, although somewhat cumbersome, way of connecting copper and aluminum wiring is a threaded connection; in this case, the cores are clamped with a nut on a threaded base. In order to avoid direct contact, a washer is placed between the exposed ends of the cores.
The advantages of this connection method are simplicity and versatility. In this way, you can connect several electrical wires of different cross-sections. But at the same time, this type of connection is quite cumbersome, and it is also very inconvenient to isolate. But, at the same time, this type of connection requires only a bolt and nut.
First of all, the ends of the wire are prepared. The insulation is removed at a distance of 1–1.5 cm from the cut, after which rings with a diameter slightly larger than the diameter of the bolt or rivet are made from the exposed wires. These rings are used to attach the wire to the rivet or threaded part of the bolt. A spring washer is placed between the aluminum and copper cable; this is necessary to ensure that there is no direct contact between these metals. After which the connection is fixed by tightening the nut or a riveter.
It is worth noting that this option is suitable for splicing wires of sufficient length; when saving length, which is often found when connecting lighting electrical equipment to the short ends of an aluminum wire, as is often the case in old apartments, it is better to use terminal boxes.
Connecting copper and aluminum wires with rivets
The clamping of the wires in this case is carried out by a wedged rivet, consisting of a tube and a core, fixed with a rivet gun. To connect, prepared conductors with wound rings are placed on a rivet tube with a gasket - a steel washer. After which the rivet is crimped with a rivet tool, the core wedges the rivet tube, thereby compressing the metal cores among themselves, thereby fixing the cable cores.
The contact in this case is permanent, but at the same time strong and reliable. For this type of connection, you need a special tool - a riveter, and skills to work with it. This method is used mainly for working with wire breaks and splicing wire ends in hard-to-reach places.
Connection with two steel strips
You can connect copper and aluminum wires in this tricky way, which also requires pre-treatment of the copper wire with tinning: clamp the wires with two steel strips with bolts at the edges. Advantages of the method: the ability to connect several branches of wiring at once, without increasing the length of the bolt. In this case, the bare ends of the cores are placed between the slats. The method is applicable for wires of the same cross-section.
Important! The connection with two steel strips requires mandatory external insulation, as well as preparation of the copper wire by tinning.
Terminal blocks and terminal boxes
Convenient and reliable connection method. The terminal block is a strip of insulating material in which sockets for wires are located. The wires are fixed in the sockets using clamping bolts. An important feature in our case is the absence of contact between the wires. To connect copper and aluminum wires, you only need a screwdriver.
The terminal box is a system of several separately located terminal blocks, combined into one structure and having several terminals.
The advantages of this connection method are:
- Easy to install, all you need is an electrician's knife to strip the ends of the wire and a screwdriver to tighten the screws;
- Reliability of insulation, very often when using a terminal block or terminal box, additional insulation is not required;
- Undemanding to the length of the wire; 1–2 cm of wire is enough to fix the wire in the terminal box.
At the same time, to install hidden wiring in the wall, the terminal block requires the installation of a distribution box. Without a distribution box, installation of hidden wiring is unacceptable. But in this case, you can use a terminal box for flush mounting.
When working with the terminal box, it is important to carefully fix the ends of the wire in the socket, especially for aluminum wires. This is especially important when installing the box outdoors or indoors where temperature fluctuations are possible.
Connection with spring and self-clamping terminal blocks
Currently, both reusable and single-use terminal blocks and terminal blocks are produced.
- spring terminal blocks and reusable terminal blocks have a retaining spring that can be loosened by lifting a lever located on the device body. This allows you to remove or insert the wire without any effort. Lowering the lever securely fixes the cable cores;
- Single-use terminal blocks automatically clamp the wire when inserting it into the socket; removing the wire will require physical force, which can damage the clamping spring, so their single use is recommended.
Both reusable and single-use terminal blocks are produced in a wide range, including with a different number of connected wiring branches, designed to fix wires with a cross-section from 0.08 mm² to 6 mm². Including in the form of ready-to-install terminal boxes. This method of connecting aluminum and copper wires is currently the most optimal in terms of reliability and ease of use.
Section of the spring terminal block and placement of the connection in the junction box
Terminal boxes with spring clamps were first produced by the German company Wago, from which they got their name, but currently there are a large number of analogues, including counterfeit ones. For this reason, it is necessary to purchase spring terminal boxes only from electrical stores. When purchasing terminal boxes on the market, there is a high probability of purchasing low-quality products that do not meet the stated requirements.
To fix the wires in the terminal box, it is necessary to prepare the wires; to do this, remove the insulation from their ends; the size of the exposed part must be at least 0.5 cm. After that, the open part of the cable core is inserted into the desired socket of the terminal box and fixed in it using a spring clamp or screw. It should be noted that mounting in a terminal box usually does not require additional insulation, but at the same time, when they are located in a wall, a distribution box is required. Thus, spring terminal blocks have a number of advantages over other types of connections due to ease of connection.
conclusions
In this way, it is quite possible to connect copper and aluminum wire, but it is necessary to take into account the location of the cable and the environment. Copper and aluminum can only be connected by twisting in a dry room. If the humidity in the room increases, this connection may become unusable and, moreover, cause a fire. The most optimal method today is to connect electrical wiring using spring terminal blocks.
The main advantage of this method is stable fixation in any environmental conditions. Despite all the advantages of a screw terminal block, threaded or rivet connection, when operating under conditions of sudden temperature changes, the contact under the screw may weaken. Due to the difference in temperature expansion of the metals of the wires. These changes may result in loss of contact or short circuit. Thus, with all the variety of methods for connecting copper and aluminum wiring, the safest method at the moment is the use of self-clamping terminal blocks.
Video on the topic
I know what the topic is among themselves is as old as the hills, but I would like to touch on this topic and consider ways to connect wires from different materials.
When renovations begin in an apartment, the question arises of repairing or replacing (full or partial) electrical wiring. Someone wants to move sockets or switches, or add new ones. In this case, you cannot do without connecting the wires. This is where the fun begins.
As you know, in old houses built in the Soviet Union, all electrical wiring was made with aluminum wire. Why? Aluminum is a cheap material, has good conductivity, is chemically resistant, and lightweight, so there were no difficulties with installation. True, the load in the apartments was small. With the development of technology, various powerful devices appeared, and the use of aluminum wires became impractical. Therefore, copper wires began to be used in apartments.
When repairing or replacing electrical wiring, it is necessary to use copper wire. It’s good if the wires are completely replaced. But what if we only partially change the wires? After all, then we need to connect the aluminum wire with the copper wire to each other.
Previously, aluminum wires were connected using conventional twisting. Then they began to connect copper wires as well. But you can’t connect copper and aluminum wires by twisting them,
Although many electricians used to do this (and still do it now). Moreover, at present, twisting is generally prohibited by the rules (PUE). Someone will say that this paragraph of the rules does not directly prohibit twisting, but twisting is not specified. as one of the ways to connect wires, therefore it is considered that twisting is PROHIBITED!!!
Why can't you connect wires by twisting?
Each material has such a property as linear expansion - a change in linear dimensions with temperature changes. Copper and aluminum have different coefficients of linear expansion, therefore, when current flows through the twist, over time the contact between the wires weakens, the gap between the wires increases, the resistance at the contact point increases, the contact point heats up, which in the future can lead to destruction of the contact and burning of the insulation wires In the photo on the left you can see how the electrical tape on the aluminum-copper twist has been burnt. And on the right is the same twist after removing the burnt electrical tape.
And now it’s not far from disaster – a fire. Therefore, if an electrician offers you connect aluminum and copper wires using a twist and wrapping it with electrical tape, then drive him out of your apartment by the neck.
How to properly connect aluminum and copper wires to each other?
There are several ways to connect wires made of different materials:
Each of these methods has pros and cons. Let's consider each of them separately.
Bolted connection
For such a connection you will need a bolt and nut, several steel washers that will need to be placed between the wires, and electrical tape to insulate the connection. To make a bolted connection, you need to make rings at the ends of the wires of such a size that they will accommodate the bolt with which the connection will be made. Then we assemble our structure, placing washers between the wires, and using wrenches we tighten the nut and get an excellent connection, which is also very reliable. One drawback: the connection is bulky and very difficult to push into the junction box.
Screw connection
This type of connection is made using screw terminals (terminal blocks),
which are isolated from each other. Screw connections of wires are usually found in lamps and chandeliers. Screw terminals are brass tubes with a plastic housing. The tubes have two screws for fastening the wire. In this way, you can connect wires not only from different materials, but also homogeneous ones.
Disadvantages of this connection:
— the plastic housing of the terminal block may burst, and the insulation will accordingly be damaged;
— the brass tube itself may burst. This happens. When you tighten the screws too hard;
— the screw can crush the wire when tightening, and it will subsequently break off. Moreover, this applies not only to aluminum, but also to copper wires;
- You can break the screw when tightening. Then there is no need to talk about good contact;
- if you apply insufficient force, you may not tighten the screw and get poor contact.
Screw terminal blocks are convenient to use as a temporary connection or for connecting lamps. They also help out if you need to repair a broken wire whose tip is sticking out of the wall.
Connection using WAGO terminal blocks
WAGO terminal blocks appeared in Russia not so long ago, although the first screwless terminal blocks were developed in Germany in 1951. There are many self-clamping WAGO terminal blocks, but we are only interested in those that are suitable for connections of aluminum and copper wires.
These are special terminals of gray or black color, inside of which there is conductive paste. This paste prevents oxidation of aluminum wires. These terminal blocks are disposable, although they can be reused if desired. However, the quality of the connection deteriorates.
WAGO self-clamping terminal blocks have many advantages:
- fast and accurate installation;
- the connection does not need to be isolated;
- you can connect wires of different materials and different sections;
- the connection can easily be redone if necessary;
- connection with WAGO terminal blocks is less than twisting.Therefore, it is easier to fit in the distribution box (see photo);
- can be used to connect multiple wires (from 2 to 8)
The only drawback of these terminals is their cost. Therefore, many electricians use screw terminal blocks and even twist them. But I believe that this disadvantage is compensated by the advantages, and there are significantly more of them.
My colleagues and I, who carry out electrical installation work in Syzran, use exactly WAGO terminal blocks for connecting aluminum and copper wires.
If you need someone who will do everything correctly and accurately, then you can contact me using the information on. You can also ask questions in the comments to this article. I will be happy to answer them.
Modern electrical wiring in an apartment or house is carried out only with copper wires, as the PUE says. But in old houses, wiring was most often done with aluminum wire, and a situation arises in which it is necessary to connect 2 wires of different materials. And in this article you will learn how to connect copper and aluminum wire in different ways.
Is it possible to twist copper wire with aluminum
Let's start with the fact that is it possible to connect aluminum wires with copper wires, and will such a connection not lead to a fire? The answer is yes, you can. But let's first get acquainted with these materials.
If you ask yourself which wiring is better, copper or aluminum, then the choice is, of course, copper. This comes out of the technical characteristics of copper; the cross-section of aluminum wire under the same conditions has to be taken larger. There are also disadvantages: copper is more expensive. It is easier to distinguish copper wire from aluminum by color; copper has a reddish tint, aluminum is gray and white.
Having looked at the electrical performance of metals, the question of which conducts current better disappears. Here's some information:
- Resistivity: copper – 0.017 Ohm mm²/m, aluminum – 0.028 Ohm mm²/m.
- Heat capacity: copper - 0.385 J/gK, aluminum - 0.9 J/gK.
- Elasticity of the material: copper – 0.8%, aluminum – 0.6%.
So why can’t you twist copper and aluminum wires, because twisting, especially with a small cross-section, is the cheapest option in terms of both money and time? The thing is that these materials, when connected, create a galvanic couple.
Galvanic pair - 2 metals of different kinds, the connection of which will lead to increased corrosion. Copper and aluminum are just such a galvanic pair. The electrochemical potentials of the two metals are too different, so rapid corrosion will increase the resistance at the junction and subsequent heating. More details about the compatibility of metals are indicated in GOST 9.005-72. Below is a table with some data on metals:
Galvanic compatibility of meltals
You can achieve high-quality contact between two conductors in different ways (soldering, using a simple terminal block, more expensive WAGO terminals, or an ordinary bolt and nut).
Connecting wires
Connecting aluminum and copper wires to each other requires technological solutions; simple twisting is not enough.
Methods for connecting conductors with different electrochemical potentials:
- By soldering. But not simple soldering.
- Using simple terminal blocks or expensive WAGO. There is no point in saving money here, and if the question is how to properly connect copper and aluminum wires, then it is better to take WAGO. The advantages of this manufacturer will be described below.
- Using a bolted connection, which has many advantages: low cost, simplicity and the ability to work with large cross-section wires.
- Crimping with sleeves. Requires specialized tools.
WAGO
WAGO clamps for joining aluminum and copper are very popular, as they are very convenient to use:
- Click the pressure plates to the side.
- Insert wires into holes.
- Place the plates in their places and clamp them.
WAGO terminals for connecting copper wire to aluminum are an excellent solution
But now WAGO is casting doubt on its reputation. According to numerous reviews, the spring contact weakens, which leads to burning of the terminal block and its rapid replacement.
Twisting wires
Twisting aluminum and copper wires was previously mentioned as a very unreliable connection method, but sometimes this is the only way to quickly restore power supply.
A couple of tips before twisting:
- Before twisting, the copper wire should be well tinned.
- The amount of twist must be at least 5 turns.
- After work, the joint must be protected with several layers of insulating tape or heat shrink tubing.
Soldering copper to the terminal block
You can solder copper and aluminum together. If everything is clear with copper, then for soldering aluminum you need a special flux. Some electricians simply solder copper wire to the terminal block.
Flux for aluminum
Terminal blocks
The list of electrician tools and consumables includes terminal blocks. Terminal blocks are copper or brass coated with a layer of nickel, designed for wires of a certain cross-section and covered with a layer of insulating plastic. The wires are secured with 2 small screws.
When connecting copper and aluminum terminal blocks, the locking screws must be properly tightened. If you tighten them, you can damage the aluminum conductors, which will not have a very good effect on the further operation of the electrical wiring. Therefore, it is necessary to find a middle ground: not tighten too tightly, but achieve high-quality contact.
Bolted connection
If you don’t have a terminal block, soldering iron or WAGO at hand, and the cross-section of the wires is large enough, then you can achieve high quality with an ordinary bolt.
To connect two wires you will need: a bolt, a nut, 3 washers. Sequencing:
- Make rings at the ends of the wires, the same diameter as the bolt. For convenience, it is better to use round nose pliers.
- Place the rings on the bolt in such an order that they are between the three washers.
- Tighten the nut and check the quality of the connection.
- Apply several layers of insulating tape.
Bolted connection of aluminum and copper
Nut connection
"Nut" is another type of terminal block, most often used for branching large-gauge wires. It consists of 2 copper plates placed in a plastic case.
Copper and aluminum wire, as well as a branch wire, are placed between the plates. But you can simply use the “nut” as a connecting element. After laying the conductors, the plates are tightened with bolts. As insulation, a plastic case is placed over the entire structure, consisting of two halves, for fastening which standard screws are used.
Walnut connection is suitable for all types of street connections and branches
Crimping
For this method you will need special crimping pliers and sleeves. The principle of connecting wires with a sleeve is very simple: an aluminum wire is inserted into the sleeve on one side, a copper wire on the other, and the sleeve is crimped on both sides with pliers. There are sleeves for wires with a large cross-section - from 16 mm 2 to 300 mm 2, but in this case a special hydraulic press will be required. The only drawback of crimping is the high cost of the tool.
Special sleeve for connecting aluminum and copper
Lubrication
To improve the quality of contact, you can use a special lubricant or paste. Usually this is quartz vaseline paste. It is usually used to improve the connection of aluminum wires.
But this paste can be used for all types of connections (threaded, using terminal blocks, crimping), especially if the connection takes place outdoors. Then the contact is affected by additional factors that significantly reduce the durability of the connection. Although the use of lubricant without insulation raises doubts.
Bottom line
Based on all of the above, select the method that is suitable for you, depending on the location of the connection (street, house) and material capabilities.