All wiring in Soviet-built houses is made of aluminum wires. Then it was quite justified, because the load on the network was much less. Therefore, during the repair process, the question often arises: Is it possible to connect these two wires with a conventional twist?
Answering the question about the possibility of connecting aluminum and copper wires with ordinary twist, you can confidently answer “no” and here's why.
Aluminum and copper are not galvanically compatible. When they are in direct contact with the passage of an electric current, a chemical reaction begins under the influence of water vapor, always present in the atmosphere. And the so-called galvanic bath is formed, which leads to an increase in the resistance between the wires and, as a result, to corrosion. As a result, the twist will begin to heat up, and in the future it can lead to a fire.
This is perhaps the most main reason on which twisting of aluminum and copper wires is not allowed. But there are other factors that negatively affect this species wire connections. 
Aluminum and copper have different coefficients of expansion when heated. When operating under load and without it, the wires will expand and contract differently, which will eventually lead to a weakening of their connection. And this is again overheating and a possible cause of a fire. 
Another negative factor is the oxidation of aluminum. Over time, the surface of aluminum is covered with an oxide film with a low conductivity coefficient. In this case, a large resistance arises, which leads to a weakening of the contact and heating. And it's not far from the fire.
Having examined in detail all the reasons for the ban on direct twisting of aluminum and copper wire, it is obvious that it is not worth risking your home. But this does not mean that there are no ways to connect these wires to each other. Now there are special adapters with which you can make a reliable and secure connection.
The easiest and most convenient way to connect aluminum and copper wires, in my opinion, are self-clamping terminals. 
The connection and disconnection of the wire is carried out using a special lever. To fix the wire, you just need to lift the lever and insert the cleaned core into the vacant hole. Then lower the lever back, thereby fixing the wire in the terminal. Installation speed and repeated use are excellent characteristics that make you opt for them.
But this is far from the only way safe connection of aluminum and copper wire, there are others.
Which is better - copper or aluminum wiring? This question is often raised among specialists and ordinary people planning to change old wires in a house, apartment or office. But to accept the right decision, it is important to know the advantages and disadvantages, operating rules, as well as the main differences between copper and aluminum switching.
Pros and cons
Aluminum wiring has the following advantages:
- Small mass. This feature is important when installing power lines, the length of which can reach tens or even hundreds of kilometers.
- Affordability. When choosing a material for wiring, many are guided by the cost of the metal. Aluminum has a correspondingly smaller one, which explains more low price products from this metal.
- Resistance to oxidative processes (relevant in the absence of contact with open air).
- The presence of a protective film. During operation, a thin coating is formed on aluminum wiring, which protects the metal from oxidative processes.
Aluminum has a number of disadvantages that you need to be aware of:
- High resistivity metal and tendency to heat. For this reason, the use of wire less than 16 sq. Mm is not allowed (taking into account PUE requirements, 7th edition).
- Weakening of contact connections due to frequent heating during the passage of a large load and subsequent cooling.
- The film that appears on the aluminum wire when in contact with air has poor current conductivity, which creates additional problems at the junctions of cable products.
- Fragility. Aluminum wires break easily, which is especially important with frequent overheating of the metal. In practice, the resource of aluminum wiring does not exceed 30 years, after which it must be changed.
Rules for joining copper and aluminum
There are situations when you need to replace only part of the wiring or add (relocate) several outlets in the apartment. In such a situation, the question arises. To avoid increased heating at the junction of copper and aluminum wiring, you should use the following switching methods:
The considered connection methods can be used to combine wires made of various metals (not only copper and aluminum). This design guarantees a high level of safety and the possibility of avoiding potentially dangerous twisting. But it is worth remembering the importance of periodically checking and pulling bolted connections and terminal blocks, because they tend to weaken.
What is the best wiring material?
Now let's take a closer look at which wire is better copper or aluminum. In this regard, there are many stereotypes and misconceptions, which we will discuss below:
- Durability. It is believed that the life of copper wire is longer than that of aluminum. This is an erroneous opinion. If you look in a special reference book, you can make sure that the resource of cables from both types of metal is identical. For products with single insulation, it is 15 years, and with double insulation - 30.
- tendency to oxidize. When using an aluminum cable, it is worth remembering its tendency to oxidative processes. Even at school, we were told that Al (aluminum) is a metal that actively interacts with oxygen, which is why a thin film appears on its surface. The latter protects the metal from further decay, but worsens its conductivity. If you isolate the wire from environment, the risk of oxidative processes is minimized. The best option- the use of special terminal blocks with conductive paste. The peculiarity of the latter is to improve the quality contact connection between two wires and removing the oxide film from the metal. In addition, a special lubricant prevents contact of aluminum with the surrounding air.
- Strength. Copper wiring is considered more durable and able to withstand repeated bending. The GOST states that a wire made of copper must withstand 80 kinks, and aluminum - 12. If the wiring runs in the wall, floor or is hidden under the ceiling, this feature is not so important.
- Price. The price of aluminum wire is 3-4 times lower. But when choosing, it is important to remember that a copper wire with a cross section of 2.5 sq. mm is designed for a current of 27 amperes. If you prefer aluminum wiring, the thickness of the wire should be 4 square meters. mm (rated current 28 Amps).
- Resistance. When deciding what to choose - aluminum or copper wires, it is worth considering the different resistivity. For copper, this parameter is about 0.018 Ohm * sq. mm / m, and for aluminum - 0.028. But it is worth considering that the total resistance (R) of the conductor depends not only on the mentioned parameter, but also on the length and area of \u200b\u200bthe conductor. If we take into account that larger aluminum wires are used for the same load, the final R of copper and aluminum products will be approximately identical. The greatest resistance occurs at the junctions, but if you follow the tips discussed above, you can not be afraid of this.
- Ease of installation. It is believed that the connection of aluminum wires is more difficult task. This is relevant only with the usual combination of wiring, by twisting. In the case of using end caps, terminal blocks or bolts, this problem disappears.
Special attention deserves the situation, implying. When copper and aluminum are combined, various processes occur at the point of contact, due to which the resistance increases. As a result, the junction of two wires overheats, the insulation is destroyed and the risk of ignition increases.
The feature discussed above is characteristic of all metals having different resistivity. In addition, many manufacturers do not use "pure" metals, but their alloys, which also leads to a change in the resistance parameter. To avoid problems in the future, it is better to connect the wires correctly and refuse to twist them.
In conclusion, here are a few tips that should be taken into account when organizing the wiring:
- In the case of independent design of wiring in a house or apartment, it is better to choose copper wires. With a smaller cross section, they withstand more currents and are more resistant to frequent bending. Not less than important point- volume. Copper wires are compact, which simplifies the process of creating a strobe. For example, when connecting a receiver with a power of 7-8 kW, the aluminum wire should have a cross section of about 8 mm. The cable has three cores and a braid. As a result, the total diameter is about 1.5 centimeters. For comparison, copper can have a cross section of 4 sq. mm, and a total diameter of no more than a centimeter.
- When installing the socket, a three-core cable with a ground wire must be used. The distance of the socket from the floor is 30 cm. When organizing the lighting circuit, it is allowed to use cables with two cores (grounding is not needed here).
- It is forbidden to hang the entire load on one pair of wires (especially if they are aluminum). The best option is to divide the chain into several lines. For example, a bathroom is fed through one machine, lighting through another, a kitchen through a third, and so on. The cross section of the wire for the kitchen and bathroom should be 4 or 6 sq. mm, and for the lighting circuit - 1.5 or 2.5 mm.
The most difficult situation is in old apartments, where aluminum wires are installed, which have outlived their resource and need to be replaced. Wiring with a cross section of 2.5 sq. mm can withstand a load of no more than 20 amperes, which is not enough for modern electrical receivers. In addition, wire insulation loses elasticity over time and gradually breaks down. In such a situation, the only solution is to completely replace the wiring with copper wires.
For more information on why it is worth replacing aluminum wiring with copper in an old house, see this video:
Results
Which wire is better? From the position operational qualities more preferred is copper. Based on the cost, aluminum wires are cheaper. And here it is important to make a decision - to save on your safety or not.
:
I invited an electrician to update the electricity input to the house.
He began to insist that the connection to the house should be made only with copper wire,
proving that this is a mandatory requirement.
I've given up on his services for now.
Can you tell me if it's a requirement?
And one more thing: which wire is better: copper or aluminum?
Wistr
Such mandatory requirement there is no change from aluminum wires to copper wires yet.
There are only recommendations.
Most likely, this is a personal initiative of the electrician himself. Because copper wires are much more expensive
aluminum. Perhaps the electrician could have some personal benefit.
Now about which wire is better: copper or aluminum ...
Copper according to its electrical characteristics better than aluminum, i.e. her resistance is almost
one and a half times less than aluminum.
In other words: with the same wire diameter, a copper wire can pass one and a half
times more current without heating up.
But what is the significant difference for you if you use a slightly larger section of aluminum wire?
In addition, copper has a very bad quality: it oxidizes strongly over time.
Therefore, the reliability of contacts drops rapidly. This leads to heating of the wire about
contact node. Accordingly, the insulation begins to melt and a short circuit may occur.
If you still decide to use copper wires, then their ends must be well cleaned
and tinker. You also need to view all the fasteners of the contacts.
It is desirable that they be either brass or bronze.
liqerr
Today, professionals prefer copper. Why? On the outdoors aluminum quickly oxidizes, forming an oxide film that is practically non-conductive electricity. Aluminum is a fragile, fragile material - bent several times and it broke. With prolonged use, it literally crumbles into powder. Copper also oxidizes, but its oxide is conductive, thus. it does not lose its electrically conductive properties. Resistant to torsion, bending, etc. Yes, it is more expensive.
But it’s not worth saving here - remember, the miser pays twice!
Vlad128
The electrician is right. The direct connection of parts made of copper (brass) with aluminum causes the rapid destruction of the latter due to contact corrosion. Therefore, in old plugs, sockets and switches, the contacts for aluminum wire were made of galvanized iron. Now such electrical products are practically not used. There is only one option: a cable with a copper core.
Oleg40
My aluminum wiring has been serving for 30 years without any complaints, and even despite the repairs, I did not change it to copper. Minus only in fragility. During this period of time, I had to change switches and sockets a couple of times. The wire sometimes broke, but since the stock is left in the box, this is not a problem. This is more of a fashion trend and some advantages in installation. If aluminum is installed, it will not be a big problem, it is more important not to make a mistake with the section.
Jack
In fact, there are rules and regulations that must be followed. Input to the house is regulated by the PUE, chapter 2.1 tells us about the input and wiring in houses, chapter 2.4 - there is about overhead lines and inputs to the house, table 2.4.2 - here are the norms of cables and their cross sections that can be used for input, for aluminum has its own standards for copper, it also depends on the distance from the support to the house.
vladislavus
Copper has really less resistance than aluminum and it can withstand heavy loads well. Aluminum, on the other hand, is a more fragile material, and I myself “burned” on this.
Electric cables differ in the type of insulation, cross-sectional diameter, material conductive cores, scope and operating conditions. Copper wire is widely used to transmit electricity.
Copper cable: what it consists of and what are the advantages
The working element of the cable is a conductive conductor made of electrical copper. Inside the cable there are several insulated cores enclosed in a common inner sheath. Depending on the operating conditions, the product is additionally covered protective screen or armor.
Advantages:
High thermal and current conductivity. This means that for electrical installation tasks, you can choose a copper cable with a smaller cross-sectional diameter than a cable with an aluminum core. Losses during heating of the conductor will be less. The property of the cable remains unchanged even when the metal is oxidized.
Plasticity and flexibility. The copper cable is resistant to kinks during bending and twisting, and this facilitates installation and further operation.
Resistance to corrosion and, as a result, a long service life. Complete replacement wiring requires overhaul. If a copper cable is chosen, then in the next 30-35 years you can not worry about replacing it.
Minimal risk of wire fire. In a fire, combustion does not spread, and insulating material emits a minimum of smoke and gas.
Applications for copper cables
Cables with a copper core are used in power lines that serve to transfer and distribute electricity in stationary installations. The use of copper cables is justified in industrial enterprises where there is a risk of fire or explosion. Use them to install internal wiring in residential and office space, industrial complexes, production and public buildings.
The main types of copper cable
1. Power. They are used to transmit electricity from a power station to substations, utility and transport facilities, and industrial enterprises. The insulation of power cables is rubber, plastic and paper. Inside contains up to 5 conductive cores. In an armored copper cable, the coating is made of aluminum or lead. According to the marking elements, it is possible to distinguish the purpose of the cable.
VVG, VVGE without marks - the cable is used for laying single lines indoors and in cable installations.
Mark ng-LS (does not spread combustion, low degree of gas and smoke emission) - high level fire safety allows the exploitation of copper power cable of this type in concert halls, at stadiums, in subway buildings. Allowed laying in the soil, can be used at nuclear power plants.
Marking ng-FRLS (fire-resistant, flame retardant, low degree of smoke and gas emission) - power cable with copper conductors is suitable for power supply fire alarm and pumps, evacuation elevators, lamps on emergency exits and evacuation routes. In case of fire, cables of this type continue to conduct current for 2-3 hours. Note (a) - the cable does not spread combustion in a group laying due to the use of insulating materials with a reduced degree of flammability.
2. Control. Used to connect electrical appliances, distribution devices and mechanisms. A control cable with copper conductors is installed in tunnels and channels if protection against mechanical damage. Can be installed outdoors and indoors.
3. Household. May contain one or more copper conductors. Single-core types are used to connect welding machines. The stranded type of cable is used for the manufacture of outdoor carriers.
4. Special (signal cables). Serve for signal transmission (high-frequency cables - for long-distance communication, low-frequency cables - locally).
Operation features
Power products of the VVG brand and their modifications are in demand among installers. This type of wire is characterized by double PVC insulation. The permissible load on the cable ranges from 60 V to 600 V (depending on the diameter of the section).
The flexible copper cable (control) is insulated with a layer of rubber. It can be used even when laying power lines for construction sites in harsh climatic conditions. To improve the characteristics, special components are added to the insulating material of the cable.
For laying in tunnels, routes, in the air and in the ground, it is advised to choose an armored cable with double insulation. Part outer coating includes graphite chips, which maximizes the resistance of the cable to fire and mechanical damage.
MTD "Energoregionkomplekt" is the official dealer of the plant "Energokabel" and offers for sale high-quality cable products from the enterprise. Here you can buy copper cable, power wires, lighting cords and wires, as well as other types of products that meet Russian standards and quality standards.
