Methods for connecting aluminum and copper wires, how to connect the wires correctly, expert advice. Connecting aluminum and copper wires: consider ways to connect wires to each other Transition from aluminum to copper in an apartment
There are still quite a few apartments in which the electrical wiring is made with aluminum wires. And since manufacturers of lighting devices and electrical equipment have switched to copper power cables, the question of how to connect copper and aluminum wires is still relevant today. Due to the fact that copper and aluminum have different electrical potentials, voltage will certainly form between them. If this bundle of two metals were located in a vacuum, the connection would last forever. The same cannot be said about the air atmosphere where humidity is present. It is a catalyst for chemical processes within the contact between copper and aluminum.
Experts have long come to the conclusion that a potential difference greater than 0.6 mV is already dangerous for wire connections. Such contact cannot be called long-term. As for copper and aluminum, the electrical potential between them is 0.65 mV, which is higher than normal. The result is a galvanic couple, like in a battery. Therefore, connecting them in electrical wiring is not allowed. But what should those who have an aluminum wiring diagram in their apartment or house do? There are several ways out.
Twisting two wires
Most old version connections electrical wires– twist. It is also the simplest. Let's return to the electrical potentials of metals. For aluminum with lead-tin solder, the potential difference is 0.4 mV, for copper with solder it is only 0.25 mV. It turns out that if one of the connected wires is treated with this solder, then they can be connected safely. Usually solder is applied to copper wire.
You can also tinker solid wire, and stranded. In the second case, the cores must be twisted, and their number is taken into account. For large cross-section cables, three cores can be tinned; for small cross-sections (no more than 1 mm²), five wires can be tinned.
But even this connection option does not provide a 100% guarantee that the contact will work for a long time. There is such a thing as linear expansion of metals, that is, they expand under the influence of temperatures. When twisting, it is not always possible to tightly press the wires to each other. When expanding, gaps form between them, which reduce the joint density. And this leads to a decrease in the conductive value. This is why twisting is rarely used today.
Threaded contact
It is believed that threaded connections of copper with aluminum are the most reliable contacts that will last without problems for the entire life of the wires themselves. The ease of connection and the ability to connect several cables in one node make this type in demand today. True, it is usually used for joining large cross-section wires. Number of connected electrical lines will be limited only by the length of the bolt (screw).
Back to electric potential metals and determine that between aluminum and steel (all elements of the bolted connection are made from it) the potential difference is 0.2 mV, between copper and steel - 0.45 mV, which is again less than the standard. That is, all metals present in the bond are not at risk of oxidation. The strength of the connection between aluminum wires and copper wires in this case ensures good clamping of the nut. Steel washers are installed between the two cores as a limiter or contact breaker.
Attention! During operation threaded connection care must be taken to ensure that the nut does not unscrew spontaneously due to vibrations of the building. This will cause the contact to weaken. Therefore, a Grover washer must be placed under the flat washer.
How to make correct contact with a threaded connection
To properly connect aluminum and copper wires to each other, you must:
- Remove the insulating layer to a length equal to four bolt diameters. If an M6 bolt is used, then the length open area should be 24 mm.
- If the veins already have oxidation on the surface, then they need to be cleaned.
- The ends are rolled into rings with a diameter slightly larger than the diameter of the bolt.
- Now they are put on the bolt in sequence: a simple flat washer, any one wire, a flat washer, a second wire, another flat washer, a Grover washer and a nut that is screwed in until it stops.
Please note that to clamp wires with a cross-section of no more than 2 mm² in this way, you can use an M4 bolt. If the copper wire is treated with solder, then it is not necessary to place a washer between the two wires. The end of a multi-core copper cable must be treated with solder.
Permanent connection
This type of contact is similar to the previous one, only it is permanent. And if there is a need to add another wire to it, then you will have to break the connection and make it in a new way. Essentially, this contact is based on a rivet clamp. The process itself is carried out using a special tool called a riveter.
- The ends are cleared of insulation, as in the previous version.
- Rings are made slightly larger than the diameter of the rivet (maximum size 4 mm).
- The aluminum end is put on first.
- Then a flat washer.
- Copper end.
- Another puck.
- Insert the end of the rivet into the rivet gun and squeeze the tool handles until you hear a click, which indicates that the steel rod has been trimmed.
Contact in terminal block
This type of connection between copper and aluminum wire most often used in lighting fixtures. The blocks come complete with the lamps. In terms of connection reliability, they are inferior to threaded contacts, but this is one of the most simple options. There is no need to twist rings, or tin the ends, or insulate. It is necessary to strip the wires to a length of 5-10 mm and insert them into the terminal slots of the device. The clamp is made with a screw. You will have to make an effort, especially for aluminum wire.
If copper and aluminum are connected to each other using a terminal block, then the device cannot be laid under plaster. It can only be used in closed boxes: in a distribution box or in a lamp hood.
Terminal block
Wago
There is no way to bypass the Wago adapter. This is a German-made device with which you can connect aluminum and copper together without effort and without tools. The only thing you need to do is clean the ends of the conductors.
Wago terminal block – spring device, into which the cable cores are inserted and it automatically clamps them. Today the manufacturer offers two versions of the pad: disposable (series 773) and reusable (series 222). In the first case, the wires are inserted into the terminal block and can only be pulled out by breaking the device. The second option is a device that includes levers. By raising or lowering them, you can pinch the end of the core or release it. Each connector socket has its own lever.
You can install wires with a cross-section of no more than 2.5 mm² in a disposable terminal block (it can withstand current up to 10 A), in a reusable terminal block no more than 4 mm² (current up to 34 A).
Nuts
Another design with which you can join aluminum and copper. The device consists of a metal plate-type connecting element and plastic case, somewhat similar to a nut. Hence the name.
The principle of fastening is the same as that of the threaded version. Just by design, these are two plates that are pressed against each other with four screws. In one of the plates, a thread is cut into the holes, onto which screws are screwed, compressing the plates together. Aluminum is connected to copper using a nut like this:
- Protects the ends of conductors.
- One is inserted on one side into a specially formed groove between the plates.
- On the other hand, a second one is inserted. It is important here that the two wires (aluminum and copper) do not touch inside the connecting device. Therefore, the nut includes an additional steel plate, which is located between clamping elements. So one wire must be placed on top of this plate, the second under it. This will ensure that there is no contact between the copper and aluminum wires.
- The screws are tightened until they stop, which ensures reliable contact.
- The structure is closed by a spring-loaded housing.
Today, manufacturers offer a wide variety of nuts, both in power and size. There are options in which the case itself does not open, and all the filling is hidden in it and is inaccessible. The connection is made by inserting the end of the wire into the socket, where it is clamped with a screw. There are nuts with a toothed connection; you just need to insert the conductor into the groove, where compression will occur with the help of teeth, which will ensure reliable contact.
Returning to the questions of whether it is possible to connect and how to correctly connect copper and aluminum wires, we need to make a generalization that there are many options. Each has its own pros and cons, but according to the necessary requirements, you can choose the right one, which will create conditions for long-term operation electrical diagram wiring.
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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.
Almost everyone already knows that aluminum wiring is a legacy of the last century, and it must be changed when renovating an apartment. Few people carry out major repairs and forget about it.
However, there are situations when the repair is carried out partially, and there is an urgent need to connect an aluminum wire with a copper one or simply extend them by adding a few extra centimeters of wire.
Electrochemical corrosion
However, aluminum and copper are not galvanically compatible. If you connect them directly, it will be something like a mini battery.
When current passes through such a connection, even with minimal humidity, electrolysis occurs. chemical reaction. Problems will definitely show themselves sooner or later. 
Oxidation, weakening of the contact, its further heating with melting of the insulation. Transition to a short circuit or burnout of the core.
What such contact can ultimately lead to, look at the photo. 
How to make such a connection competently and reliably to avoid problems in the future.
Here are some common methods that electricians use. True, not all of them are convenient for working in installation boxes.
Let's take a closer look at each of them and choose the most reliable one, which does not require subsequent maintenance or revisions.
Connection via bolt and steel washers
Here a steel washer and bolt are used for connection. This is one of the most proven and simple methods. The truth is that it turns out to be a very large design.
For installation, twist the ends of the wires into rings. Next, select the washers. 
They must be of such a diameter that the entire eye of the wire is hidden behind them and cannot come into contact with another conductor.
The most important thing is how to position the ring. It must be put on so that when tightening the nut, the eye does not unfold, but rather is pulled inward.
Steel washers between conductors made of different materials prevent oxidation processes. In this case, do not forget about installing the engraver or spring washer. 
Without it, contact will weaken over time.
The fact is that metals whose electrochemical potential of the connection does not exceed 0.6 mV can be safely connected to each other.
Here is a table of such potentials. 
As you can see, copper and zinc have as much as 0.85 mV here! This connection is even worse than direct contact between aluminum and copper conductors (0.65 mV). This means the connection will not be reliable.
However, despite the simplicity of the threaded assembly, the end result is a large, awkward structure, shaped like a beehive. 
And it’s not always possible to stuff this whole thing into a shallow socket. Moreover, even in such a simple design, many manage to screw it up. 
The consequences will not keep you waiting in a very short time.
Squeeze - nut
Another method is to use a nut-type connecting clamp.
It is often used to tap off a supply cable with a much larger cross-section than a tap. 
Moreover, it does not even require cutting the main wire. It's enough to take it off upper layer isolation. Some have found a use for it to connect the input cable to the SIP.
However, you shouldn't do this. Why, read the article below. 
But again, nuts are not suitable for junction boxes. Moreover, sometimes such clamps burn out. Here is a real review from a user on one of the forums: 
Wago Clamps
There are a series of special clamps that can be used to join copper to aluminum.
Inside these terminals there is antioxidant paste. 
However, disputes about the 100% reliability of such clamps, especially for sockets and not lighting groups, have not subsided to this day. With a certain installation in limited space, the contact may weaken, which will inevitably lead to burnout. 
Moreover, this can happen even at a load below the minimum for which Vagos are designed. Why and when does this happen?
The fact is that when the connected conductors are compressed, a small gap appears between the pressure plate and the contact point. Hence all the heating problems.
That's very visual video, which explains this problem without further ado.
Terminal block
This method has one significant disadvantage. Most of the pads sold are of very low quality.
Some people get clever and, in order to avoid direct contact between copper and aluminum, the copper core is soldered to the side of such a clamp, rather than inserted inside. 
True, the terminal will have to be disassembled for this. In addition, reliable aluminum contact under the screw without revision does not last very long.
The screws will need to be tightened every six months to a year. The frequency of revision work will directly depend on the load and its fluctuations during periods of maximum and minimum. 
Forget to tighten up and expect trouble. And if this entire connection is hidden deep in the socket, then getting into it every time is not a very convenient task. 
Therefore, the most reliable of available ways– crimping. Here we will not consider the use of specialized copper-aluminum sleeves GAM, since they start from sections of 16mm2.
For home wiring, as a rule, you need to increase the wires by 1.5-2.5 mm2 no more.
Connecting copper and aluminum by crimping
Let's consider the most common case that occurs in panel houses. Let's say you need to power one or more additional outlets from an existing aluminum outlet in a through niche. 
For extensions, take a FLEXIBLE copper wire with a cross section of 2.5 mm2. This will reduce mechanical impact on an aluminum core when you lay the wires in the socket box.
For soldering, it is convenient to use a homemade crucible, which is a slightly modified soldering iron in the shape of a hatchet.
In this case, before soldering with flux, remove the oxide layer from the core. 
The tinning process itself involves dipping the wire into a special hole in the soldering iron filled with tin. 
After the core has cooled, the remaining flux is removed with a solvent.
Next, move on to the aluminum wires sticking out of the wall. Carefully clean their ends and also remove the oxide layer. 
To do this, you can use oxide conductive paste. The same paste is used when installing modular pin systems grounding. 
It is designed to work in any conditions and eliminates the further appearance of oxide on the surface of the wire. Keep in mind that the oxide film can subsequently have a resistance several times greater than the aluminum itself.
And without deleting it, all your further work will go down the drain. Moreover, the melting point of such a film reaches 2000 degrees (versus approximately 600C for Al).
After all preparatory work, insert the wires into the GML sleeve from both sides. All that remains is to crimp this connection. 
Some people will have a logical question: will the solder layer on the core be pressed through during crimping? Then it turns out that all tinning manipulations will be in vain.
The main thing here is to choose the correct cross-section of the sleeve and die of the tool for crimping. 
In this case, the soft solder will, as it were, seal the contact spot of the copper-aluminum connection. And without oxygen access to this point, contact erosion will not be observed.
Be careful; when working with aluminum conductors, you must act with extreme caution, as this is a very brittle material. One careless movement and you are guaranteed to have a broken wire. 
After crimping, it is necessary to insulate this connection with adhesive heat shrink. 
It is the adhesive type that will ensure 100% tightness and prevent the flow of oxygen to the contact areas. In order not to risk burning through the insulation, it is better to heat the heat shrink construction hairdryer, not a lighter or portable torch. 
The resulting bundle of wires must be placed in the electrical box with great care, since aluminum does not like sharp bends.
Since the extended copper wires are flexible, you put insulated NShVI lugs on the ends of these conductors.
Only after this can they be safely inserted into the terminal blocks of the sockets and the screws tightened. 
Of course, this is not the only way to extend aluminum wires, but it is one of the simplest (as opposed to welding or soldering) and reliable (as opposed to twisting). 
If you have the slightest opportunity to change the entire aluminum wiring, be sure to do it, do not skimp on your safety.
Greetings! Today I will tell you how to connect copper and aluminum wires to each other so that they do not oxidize and the connection is as reliable as possible.
In general, in theory, it was always explained to us that connecting conductors with different resistivities, in this case copper and aluminum, is strictly prohibited, but no one said that this prohibition could be circumvented without breaking any rules.
Although theory tells us that such crafts are categorically excluded, even in everyday practice we increasingly have to build up (extend) aluminum with copper wire. For example, when, when replacing an outlet, a wire breaks off at the root. This happens everywhere, since the shelf life of aluminum electrical wiring has long expired, and aluminum wires are becoming increasingly difficult to find on the electrical goods market.
Now let’s look at several options for combining copper with aluminum:
The first option there will be a connection using bolt terminal blocks, this is one of the simplest and safe ways connections. And it is simple because you just need to insert the wires, stripped of insulation, into the terminal block sleeve and tighten them tightly with bolts. For two conductors with a cross section of 2 * 2.5 mm, 16 Ampere terminal blocks are suitable.
After the work done, everything looks quite neat and reliable.
This connection method has been practiced for quite some time and has not caused any particular complaints. But nevertheless, there are disadvantages here:
- When the bolts are tightened tightly, notches appear on the cores, which can later lead to the wires breaking off when bent. The serifs are very visible in the photo.
- and the second problem is that if the wire that needs to be extended is too short, then the ability to use a terminal block immediately disappears, since you simply cannot crawl into the problem area.
Second option we are associated with a certain innovation called Wago. These are self-clamping terminal blocks designed for connecting wires in distribution boxes, and also for extending wires, including aluminum and copper. There are a large variety of such terminal blocks.
But for extending aluminum wire with copper, this type of Wago is most suitable
All we need is to simply pull the clamps up, at a right angle, and insert the wires we need into the opened contacts, then snap the clamps back. We are guaranteed a tight connection. Today this is the most popular connection due to its speed and reliability. But unfortunately, if the break is in an inconvenient place, you again will not be able to use this terminal block.
If the situation is a little more serious,
than a broken wire in a socket... For example, if there is a fire in your switchboard, and you need to efficiently build up the input (supply wires) wires, then we will need special connecting clamps
Compressions will ensure a tight connection and make it possible to withstand heavy loads. But if it is not possible to buy clamps, then for such loads, the correct bolted connection is quite suitable.
To increase the contact area, both wires must be bent into rings. The cores must be covered with washers on all sides so that when the wires are pulled together they are not forced out. Be sure to tighten it at the end so that the screw does not unscrew over time.
Without connecting the wiring, you cannot connect even the simplest electrical devices. The slightest deviation from the connection rules can cause huge troubles. Electrical wiring in a private house or apartment there are even in the most remote and small settlements.
Energy consumption is constantly increasing, and as a result, the load on wire connections increases. Requests to them intensify and become stricter, because any negligence or imperfection can turn into a disaster.
Nowadays everyone knows that it is necessary to properly stretch the sections of wiring connections, but not everyone knows about electrochemical compatibility.
Application area of connections
The increase in electricity consumption is causing stricter requirements for wire connections aimed at improving the quality of fire and electrical safety.
What determines the reliability of connections:
- Contact alignment density.
- Compatibility of wires according to electrochemical parameters.
Almost every person can twist wires tightly; the second requirement is often ignored when connecting two wires (even incompatible ones) in a direct way. It is for this reason that problems arise during the operation of organized wiring of aluminum and copper wires.
Electrochemical corrosion
Aluminum – chemical element with high oxidation capacity. The oxide film that appears on an aluminum wire under the influence of dampness has increased resistance. This has a negative impact on the ability to carry out electricity at connection areas.
Copper– a substance with low chemical activity on which the oxide film is formed worse and, moreover, it has less resistance.
Aluminum and copper conductors together create a short-circuited galvanic circuit - when such a contact is moistened, rapid oxidation of the aluminum contact begins.
A layer of metal oxide with high resistance appears between the 2 conductors, as a result, the conduction of electric current is hampered, the process of electrolysis occurs, sparks appear at the contact junction area, the metal heats up, and cavities are formed, all this can cause a fire:
- The coefficient of thermal expansion of these substances is significantly different. When an electric current is passed through them, they change their dimensions differently; after the current is turned off, they cool down differently. As a result, the contraction and expansion of metals changes their geometry, which worsens contact. And as a result, in areas with poor contact, the metal heats up, which further worsens the contact;
- There is a non-conducting oxide film on the surface of aluminum, which also worsens the quality of contact and contributes to the destruction of the metal;
- Copper and aluminum produce a “galvanic couple,” which also heats the metal and promotes its oxidation.
These shortcomings can be eliminated if direct contact of these metals is avoided. There are several options for connecting copper and aluminum conductors to create reliable and safe contact.
Let us note that with an increase in air humidity, all the above processes increase significantly. A layer of aluminum oxide that is poorly conductive to electrons and significantly different thermal expansion– these are factors aggravating the situation.
Most common connection options
Twist
This connection method is suitable for a short time; indoors it will last for a certain period, with high humidity or outdoors, the service life of this pair is reduced significantly.
But often it is necessary to connect several cables made of copper and aluminum. This happens during restoration or repair of the electrical system in buildings where aluminum wiring is used.
Crimping- this is a type of twisting, with this method, the twisting is crimped with a specially prepared sleeve made of copper or aluminum with internal section equal to the twist section. I would like to say that this option is simple and quick to implement and at the same time very reliable. The finished connection is insulated in the usual way - using insulating tape or using heat shrink paste.
Bolted connection and terminal blocks
Combining two wires will help correct some twisting defects. different metals using one of these methods. Using bolted or, we eliminate direct contact of the copper-aluminum pair.
There are several types of terminal blocks:
- A proven and long-used method is to use “nuts,” they are called so because they look like nuts. Such products are made of three plates, with the help of which copper or aluminum cables are clamped. Positive quality The "nuts" is that to create a branch from the main wire there is no need to cut it. You just need to unscrew the two bolts, place the stripped cable core between the two plates, and tighten the bolts again. The core for creating a branch is placed between the middle and one of the outer plates;
- WAGO type terminal blocks are also often used. With this method, you only need to remove 10-15 mm of insulation, insert the cleaned areas into special holes and the contact is ready for service. Inside the terminal block there is a special lubricant that protects the wire from oxidative processes. This option is best used only when installing lighting. They should not be used for power circuits; a high load can cause the springy contacts to heat up, and as a result, cause deterioration of the contact;
- In addition, terminal blocks are often used; they look like a strip with special terminal strips. You just need to prepare the ends as described above, insert one of them into the hole, and fix it with a bot. The prepared end of the second wire is placed in another hole and fixed.
Wires made of copper and aluminum are joined together using the bolt method if it is necessary to obtain reliable and safe contact. The two cable cores are twisted with a bolt, placing an anodized steel washer between them. All installation work must be performed by an experienced professional.
Bolted and screw connections must be inspected after a certain period of time: for aluminum wires, the inspection is carried out once every six months, for copper wires, the frequency of inspections is every two years.
Soldering
The most durable and reliable option for joining copper and aluminum wires. Its disadvantages are technological complexity, increased installation time and labor intensity. When an electrician does electrical wiring, he most often de-energizes the room and there is no way to heat the soldering iron.
Homemade adapter
You can independently make an adapter that will allow you to mount an electrical network without a soldering iron using the soldering method.
Before installation begins, two pieces of wire are soldered on the table - aluminum and copper, leaving two free ends. It turns out to be a kind of homemade adapter for connecting wires.
It is best to make several of them, after which the power supply is de-energized and the necessary installation is carried out, connecting the aluminum tip to an aluminum wire, and copper to copper, insulating in the usual way.
Welding
The method is similar to soldering, but it will require special equipment and when connecting copper and aluminum wire it is practically not used, since the melting points of these metals are different.
When performing it, copper and aluminum cable twist tightly, and the end of the resulting flagellum is carefully welded resistance welding, as a result, a small ball of metal should appear at the end of the twist. The contacts are connected almost tightly and there is perfect contact between them.
- All connections must be reliably insulated.
- It is advisable to place them in special ones. By laying a copper-aluminum connection into the wall, you block access to it if necessary; it will be impossible to inspect the connections without damaging the wall.
- If you have no experience with soldering, then the best option will become a terminal box.
Of course, without having the necessary experience in electrical installation work, it is better not to risk your life and property and contact a specialist.