Which wiring is better to use - copper or aluminum?

Copper or aluminum wire - which is better?

Previously, they installed one socket at a time.
Nowadays they even install 5 or more sockets in one place. This is due to the huge number of electrical appliances in a modern home. In this case, the sockets are connected with a cable, which is quite difficult to do with aluminum wire. Modern chandeliers also have copper lead-in ends, and they cannot be connected to aluminum.

Thirdly, aluminum is prone to oxidation. A film of high resistance appears on its surface. As a result, the contacts heat up and possibly burn out. Over time, aluminum becomes very brittle. Sometimes, after disassembling an old electrical box for repairs and taking out the wires, you can see how they simply crumble in your hands.

Moreover, although aluminum wiring laid in the USSR has been in service for 30 years, modern aluminum is no longer the same as it used to be. Today's aluminum wire can be broken during installation, especially Chinese wire. It’s hard to even imagine what will happen to him in ten years.

Chemical properties

In terms of chemical properties, aluminum is one of the highly active metals with amphoteric properties. In the activity series it ranks behind the alkaline earth metals. But in its pure form, both in air and in water, it can be stored for a very long time, since its surface is eventually covered with a thin and very durable layer of oxide, which protects it from oxidation.

In order to observe the oxidation of aluminum in air, you must first remove the protective film.

To do this, aluminum is first rubbed with sandpaper and then boiled in alkali. Aluminum oxide, like the metal itself, exhibits amphoteric properties and therefore dissolves in alkali. After this, the aluminum is dipped into a solution of some mercury salt, for example, mercuric nitrate Hg(NO3)2. Aluminum, as a more active metal, displaces mercury from its salt:

2Al + 3Hg(NO3)2 = 2Al(NO3)3 + 3Hg

Mercury is deposited on the surface of aluminum, forming an alloy of aluminum with mercury - aluminum “amalgam” (alloys of mercury with metals are called amalgams). Such an alloy is not capable of forming a protective oxide film, and the aluminum in the amalgam is gradually oxidized to aluminum oxide according to the equation:

4Al + 3O2 = 2Al2O3

But since the amalgam covers the aluminum unevenly, oxidation occurs in places and aluminum oxide is noticeable on the surface of the metal in the form of a fluffy brush (Fig. 3).

The interaction of aluminum with halogens - with bromine and iodine - is interesting. For the reaction, powdered aluminum and liquid bromine are used, and for the reaction with iodine, a mixture of iodine powder and aluminum is used.

In all cases, aluminum behaves as a reducing agent.

Rice. 3. Formation of aluminum oxide on the amalgamated metal surface.

At high temperatures, aluminum displaces some metals from their oxides. This property has found application. If you mix iron oxide with aluminum powder and set it on fire using a magnesium flash, the reaction will occur:

Fe2O3 + 2Al = Al2O3 + 2Fe

which is accompanied by the release of a large amount of heat. Due to this heat, the resulting free iron melts and can be released from the crucible in which the reaction takes place through the hole located below. This smelting of metals is called aluminothermy; in technology it is used very widely. Some metals can only be produced by aluminothermic processes. This process was first carried out by N. N. Beketov.

Aluminum is an amphoteric metal. It behaves differently in different conditions. In an alkali solution, aluminum displaces hydrogen from water, forming a salt of aluminum acid - sodium (or potassium) aluminate, in which it plays the role of an acid-forming element:

Aluminum displaces hydrogen from acid:

In this case, it exhibits metallic properties. Concentrated nitric and sulfuric acids do not affect aluminum, since a protective film is formed on its surface, protecting the metal from further oxidation. In diluted form, nitric acid also has no effect on aluminum, and sulfuric acid has a weak effect.

■ 77. List the chemical properties of aluminum and justify your answer with reaction equations. (See Answer) 78. Why is mercury called “aluminum poison”? 79. Why do household aluminum products last a long time and are not subject to oxidation? 80. What is aluminothermy? 81. The dry mixture consists of aluminum, iron and coal powders. When 6 g of this mixture was treated with hydrochloric acid, 4.48 liters of hydrogen were released, and when the same amount of the mixture was treated with potassium hydroxide solution, 3.36 liters of hydrogen were released. Determine the composition of the mixture in grams. 82. There are 200 g of pyrolusite containing 87% manganese dioxide. How much aluminum will be required to recover manganese from it by aluminothermic means. 83. How should aluminum be treated so that it oxidizes in air? 84. Three test tubes contain dilute acids - hydrochloric, sulfuric and nitric. How, given pieces of aluminum, can you determine which test tube contains which acid? 85. How much sodium aluminate will be obtained when 27 g of aluminum reacts with alkali? (See answer)

How to combine copper with aluminum - the better and more reliable

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.

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, an electrolytic chemical reaction occurs. 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.

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 contact another conductor.

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.

Another method is to use a nut-type connecting clamp.

It is often used to branch off a supply cable with a much larger cross-section than a tap.

Moreover, it does not even require cutting the main wire. It is enough to remove the top layer of insulation from it. 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:

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. When installed in a 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.

Here is a very clear video that explains this problem without further ado.

This method has one significant disadvantage. Most of the pads sold are of very poor 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.

Copper or aluminum wire - which is better?

The most common types of cable for electrical wiring (apartments and industrial premises) are aluminum and copper wires. It should be noted that they are sold nearby on the shelves of our stores. YES, sometimes we can find copper and sometimes aluminum in wiring. So what is the difference and which is better between these two materials? Today I invite you to think about this...

If you studied physics, then of course you know that copper cable has the best electrical conductive properties. Also, this type, unlike aluminum, has an increased service life (aluminum is up to 20 years, but copper is already from 30 and above).

So if you are laying electrical networks in an apartment, then it is preferable to choose copper. And now in detail for each type.

Aluminum cable

Pros:

The big advantage is that the cost of this option is about half cheaper than its opponent (and sometimes even more). That is why all old houses (“STALINKI” and “KHRUSHCHEVKI”) have just such wiring. You know guys, this is probably the only plus, there are many more minuses.

Minuses:

This type of wire can withstand smaller loads compared to its competitor - remember, every millimeter of cross-section can withstand only 1 kW of power.

As I wrote above, the service life of an aluminum cable is only 20 years, so it is not recommended to install it in the wall, otherwise, after this period has expired, you will need to pick at the walls.

Another disadvantage (for me personally) is the inconvenience of installation. Such wires (as a rule) are single-core rigid, so if you use a cross-section of 3.5 mm, connecting them to sockets is quite problematic.

Copper cable

Pros:

This type can withstand high loads - 1 millimeter of cross-section can withstand 2 kW of load, which is twice as much as that of the enemy.

The service life is much longer; according to electricians, they can last 50 years.

There are plenty of types and designs of such wires, these include single-core and multi-core versions, having a practically non-melting braid (NYM cable), etc. Installation of a multi-core cable is much easier, it can be easily connected to a standard outlet, and it bends perfectly.

Minuses:

It's just the price. Technological wires (those with many cores and high-tech braiding) can cost up to two times more than a competitor.

A short comparison video - you can see the price and flexibility.

Useful tips

1) If you design the wiring yourself, then definitely choose copper. After all, with a smaller cross-section, it can withstand a fairly high voltage. That is, it will take up exactly half as much space. So a simple example - if I connected my hob with aluminum (let me remind you that its power is about 7.5 kW), then I would need a core cross-section of about 8 mm, and there are three of them in the cable, and even a braid - that is, the thickness would be about 4 – 5 cm, not a weak wiring! But copper can withstand a cross-section of 4 mm (total diameter about 2 cm), which is also quite a lot, but tolerable.

2) When designing sockets, the first thing you need to remember is that the wire must have three cores (grounding is required). Make the distance between them 2 meters, and the distance from the floor 30 cm, this is the EUROPEAN STANDARD. For lighting, you can use a two-wire version, since the load is minimal and there is practically no need for grounding.

3) Do not hang all electrical equipment on one wiring, the load will be very large! You need to make a branch, preferably for each room. The kitchen is especially worth highlighting. For the main cores for rooms, I advise you to take a cross-section from 4 mm, for the kitchen from 6 mm.

4) We bought an old apartment, it’s more than 20 years old, look at the wiring. Most likely, there is aluminum and it needs to be changed because after such a period it loses its elasticity and simply crumbles. This is often the cause of fires. “YES”, such a replacement will cost a pretty penny, but the game is worth the candle, because it’s your safety.

This is the choice, I think - now you will buy the right copper wire, aluminum is too difficult to install, and also short-lived.

I’ll finish here, read our construction blog.

remo-blog.ru

Cable laid over the air

The main type of installation of the input cable is its installation by air. Air input has its advantages:

• Minimum labor costs.
• It takes a short amount of time to connect your home. It is rare that such work takes more than two hours.
• Low cost of consumables: anchor bolts or clamps, special brackets, insulators.
• Possibility of quick troubleshooting, even if the entire cable needs to be replaced.

The following types of cables are used for aerial installation:

1. SIP cable is a self-supporting insulated wire.
2. Non-insulated, material - aluminum.
3. Bare aluminum with steel core.

What material for electrical wiring should you choose for your apartment?

In Soviet times, the use of aluminum electrical wiring in residential premises was common. This was due to the fact that in residential buildings there was no high load on the electrical network due to low power and a small number of electrical appliances. With the development of technology and the advent of a huge variety of powerful electrical appliances that are used at home, the requirements for the quality and materials for electrical cables have increased significantly. In modern realities, wiring made of aluminum material is practically not used, since according to the PUE, electrical wiring in residential premises must be made of copper!

Advantages and disadvantages of aluminum electrical wiring

The main advantages of aluminum electrical wiring are:

1. Low mass: the density of aluminum is lower and, accordingly, its mass is lower. When laying simple networks with many cables but light loads, this will be a convenient advantage.
2. Low price: aluminum is several times cheaper than copper, so products made from this material are also low in price.
3. Resistance to oxidation: in the absence of contact with the environment, it lasts a long time and is not destroyed by oxidation.

The disadvantages of this material include:

1. Low electrical conductivity - aluminum has a high resistivity and heats up when electric current passes through it. Therefore, the PUE prohibits the use of such a cable in home networks with a conductor cross-section of less than 16 mm².
2. Poor connection - due to oxidation processes and heating/cooling cycles, the connection points of the aluminum cable gradually deteriorate, which can lead to electrical wiring failure or short circuit.
3. Fragility of conductors - such cables easily break when heated, which also very often leads to malfunctions.

Advantages and disadvantages of copper electrical wiring

Copper is approved for use and is widely used for electrical wiring in residential and industrial buildings. In terms of electrical characteristics, it surpasses many materials and is second only to silver.

The advantages of copper cables are:

1. High electrical and thermal conductivity - copper has a relatively low resistance and effectively conducts electric current, has high efficiency, and does not heat up significantly with the correct cable cross-section.
2. Corrosion resistance - copper conductors can operate under any operating and environmental conditions, last a long time and are practically not subject to corrosion.
3. Resistance to mechanical stress - copper electrical wiring is strong, ductile and flexible.
4. Flexibility and ease of installation - copper conductors are very flexible and can be conveniently mounted at different angles and connected to sockets and switches.

The main disadvantage of copper is its high cost. But you need to understand that when performing such a responsible type of work as wiring installation, safety and durability are very important. Therefore, despite its cost, copper wiring quickly pays for itself and, if used correctly, lasts for a very long time without repairs or malfunctions.

Resistivity

this affects power loss

• Boards installed in computers are equipped with etched copper traces.
• Copper is also used to make a wide variety of components used in electronic devices.
• In transformers and electric motors it is represented by a winding, which is made of this material.

There is no doubt that the expansion of the scope of application of this material will occur with the further development of technological progress. Although there are other materials besides copper, designers still use copper when creating equipment and various installations. The main reason for the demand for this material is the good electrical and thermal conductivity of this metal, which it provides at room temperature.

Aluminum cable or copper? How to choose?

More and more owners of industrial premises are paying attention to which cable to choose for wiring. In this article we will try to give a complete answer to this question.

Aluminum power cable

Aluminum power cable is used more often for laying temporary wiring of three-phase current in a room - usually for 1-2 years, or even months. It is often used by builders during the construction of a building, and then replaced with copper. However, many industrial premises still have aluminum wiring, particularly in industrial buildings from the 1920s to the 1970s, where such wiring is used as regularly as copper wiring.

Today, aluminum power cables are produced with the following protective coatings:

• made of cross-linked polyethylene with a service life of up to 30 years;
• polymer - up to 25 years;
• with processing in the form of a special paste - up to 40 years.

You can buy these products on our website at a competitive price; just open the catalog and fill out an application.

Advantages

The advantages of the product include:

• light weight - this characteristic is important if electrical installation takes place in a dilapidated building or when installing power transmission lines stretching for tens of kilometers, since a large weight will simply pull the wires down, breaking them from their fastenings;
• low cost - the cost of an aluminum power cable is 3 times lower than that of copper;
• upon contact with air, a grayish-blackish film forms on the surface, protecting against oxidation.

Despite all the positive properties of aluminum wires, they have a significant drawback - destruction under the influence of time and relatively low throughput - per 1 square millimeter of aluminum cable area there is only 1 kW of load, while for copper analogues this figure is 2-2.25 kW .

To connect an electrical appliance to a network using an aluminum cable, you need to know the power of the electrical appliances that will be connected to the network. This will allow you to determine the cross-sectional area of ​​the aluminum wire. Having determined the exact cross-section, you need to add about 30-40% to it for overload or connection of other devices. The service life of the wiring is 20-25 years, after which it is destroyed at a rate of 3-8% per year of its original size, which leads to the inability to perform its function.

Copper power cable

Copper power cable today is used much more often for laying indoor wiring due to its low resistivity and the relatively short length of all indoor wiring. Many people claim that copper lasts longer, but this is not entirely true. Many reference books say that copper lasts as long as aluminum, but its problem is not time, but burnout. With a single winding, a copper wire will last about 20-25 years, with a double winding - up to 35 years.

Advantages

The advantages of the product include:

• the ability to withstand a large number of bends - up to 80 at one point;
• good level of current conductivity - 2 times higher than that of aluminum, which allows the use of cables with a less massive cross-section when laying;
• does not collapse over time.

You can order copper cable from our company, you just need to open the catalog, fill out an application or feedback form and our managers will contact you to confirm the order.

How to choose?

Aluminum power cable or copper, how to choose? Quite simple actually. Here you need to choose between an expensive and easy-to-install copper cable and a cheap, but sometimes difficult-to-install aluminum cable. To choose the right one, you need to remember the following:

• the cost of aluminum power wire is 2-4 times lower;
• copper wire is easier to install due to withstanding a large number of kinks;
• the service life is approximately the same and differs by 2-5 years, and sometimes a cheap aluminum cable in a special protective composition is more durable than copper;
• the throughput is better for copper - resistance is 0.018 Ohms per square millimeter versus 0.028 Ohms for aluminum;
• the cross-section of the aluminum cable is approximately 50-60% larger than that of copper if it is necessary to achieve the same level of throughput;
• aluminum wears out from current, and copper can quickly burn out.

Electrical conductivity and current carriers

The electrical conductivity of all substances is associated with the presence of current carriers (charge carriers) in them - mobile charged particles (electrons, ions) or quasiparticles (for example, holes in a semiconductor) capable of moving in a given substance over a long distance; in a simplified way, we can say what is meant that such a particle or quasiparticle should be able to travel an arbitrarily large, at least macroscopic, distance in a given substance, although in some particular cases carriers can change, being born and destroyed (generally speaking, sometimes, perhaps, through a very short distance), and carry current, replacing each other.

Since the current density is determined for one type of carrier by the formula:

j→=qnv→cp.,{\displaystyle {\vec {j}}=qn{\vec {v}}_{cp.},} where q{\displaystyle q} is the charge of one carrier, n{\displaystyle n} is the concentration of carriers, v→cp.{\displaystyle {\vec {v}}_{cp.}} is the average speed of their movement,

or j→=∑iqiniv→icp.{\displaystyle {\vec {j}}=\sum _{i}q_{i}n_{i}{\vec {v}}_{icp.}} for more than one type of carrier, numbered by the index i,{\displaystyle i,} taking a value from 1 to the number of types of carriers, each of which can have its own charge (possibly different in magnitude and sign), its own concentration, its own average speed of movement (summation in this formula is implied for all available types of carriers), then, given that the (steady-state) average speed of each type of particle when moving in a specific substance (medium) is proportional to the applied electric field (in the case when the movement is caused precisely by this field, which is what we are here we are considering):

v→cp.=μE→,{\displaystyle {\vec {v}}_{cp.}=\mu {\vec {E}},} where μ{\displaystyle \mu } is a proportionality coefficient called mobility and depending on the type of current carrier in a given specific environment.

It follows that the expression for electrical conductivity is valid:

σ=qnμ,{\displaystyle \sigma =qn\mu ,}

or:

σ=∑iqiniμi{\displaystyle \sigma =\sum _{i}q_{i}n_{i}\mu _{i}} - for more than one type of media.

The superiority of copper over aluminum for wiring

Electrical conductivity

Copper is superior to aluminum in electrical conductivity. The electrical resistivity of copper is 0.017 Ohm*mm 2 /m, while that of aluminum is 0.028 Ohm*mm 2 /m. That is, the electrical conductivity of aluminum is 65% of the electrical conductivity of copper, so for the same load, aluminum wire will have to be taken with a cross-section a “step” higher than copper.

For example, you need to power a load of 5 kW. For it you will need to take either a copper wire with a cross section of 2.5 mm 2, for example, NYM 3x2.5, or an aluminum wire with a cross section of 4 mm 2. Since aluminum wire is more voluminous, it will take up more space in the cable ducts, and it will require terminals for socket groups that are larger in size than for copper ones. Considering this, copper is more convenient to use for wiring in the house.

Oxidation

Both copper and aluminum oxidize during operation under the influence of air. However, with copper, oxidation occurs much more slowly, and the film itself (greenish coating) is quite easily destroyed, so it conducts current quite well (although the permeability deteriorates slightly). In aluminum, oxidation occurs much faster, and the oxide film itself is very dense and does not conduct current well. Oxidized connections on twists, clamps or terminals most often cause contact burning. You can remove the oxide film with quartz-vaseline lubricant, but it is not so easy to find it in stores, and this requires additional costs and maintenance time.

Mechanical strength

Copper wire is more flexible and durable than aluminum. During the installation process, the cores have to be bent, for example, for connection in distribution boxes and sockets. Copper conductors can withstand repeated bending without damage, but aluminum conductors can only withstand 5 to 10 bends, and then they break.

Aluminum wiring creates particular problems when it is necessary to repair connections in junction boxes - the old aluminum already has microcracks, so with one wrong move the wire may break off and you will have to remove part of the plaster in order to pull out at least a little of the wire.

Thermal conductivity

This parameter characterizes the ability of the conductor to dissipate heat. The higher the thermal conductivity coefficient, the better the metal dissipates heat. Copper has a thermal conductivity coefficient of 389.6 W/m* °C, and aluminum has a coefficient of thermal conductivity of 209.3 W/m* °C. That is, copper is almost twice as good at dissipating heat than aluminum.

This is especially important at connections where the wire gets hottest. At the same load, copper will remove heat twice as fast (or rather, not heat up)

Specific electrical conductivity of some substances (table)

Specific conductivity is given at +20 °C: