How many kilowatts is a wire with a cross section of 2.5 designed for? How to select the cable cross-section according to power? Calculation

It is better not to skimp on wire insulation and choose the double option. After all, when the water breaks poor-quality insulation can lead to fire. And it is very easy to damage such a wire during operation.

If you live in a wooden house, you will have to install open supply lines. Can only be used here non-flammable copper options. It is best to lay the wire in. Such plastic boxes are now produced in a variety of modifications and colors.

In conclusion, we invite you to watch a video in which the master will tell you which wires are best for wiring in an apartment:

You can choose electrical cables that correctly support the supply voltage in the apartment yourself. But installation of electric mains should be entrusted to professionals. Working with electricity for an untrained person is life-threatening.

Calculation of wire and cable cross-section

Material of manufacture and wire cross-section(it would be more correct wire cross-sectional area) is perhaps the main criteria that should be followed when choosing wires and power cables.

Recall that the cross-sectional area (S) of the cable is calculated by the formula S = (Pi * D2)/4, where Pi is pi equal to 3.14 and D is the diameter.

Why is it so important correct choice of wire cross-section. First of all, because the wires and cables used are the main elements of the electrical wiring of your home or apartment. And it must meet all standards and requirements for reliability and electrical safety.

The main regulatory document regulating the cross-sectional area of ​​electrical wires and cables is the Rules for the Construction of Electrical Installations (PUE). The main indicators that determine the wire cross-section:

Metal from which the conductors are made Operating voltage, V Power consumption, kW and current load, A

Thus, incorrectly selected wires that do not correspond to the consumption load can heat up or even burn out, simply not being able to withstand the current load, which cannot but affect the electrical and fire safety of your home. The case is very frequent when, for the sake of economy or for some other reasons, a wire of a smaller cross-section than necessary is used.

When choosing a wire cross-section, you should also not be guided by the saying “you can’t spoil porridge with butter.” The use of wires with a larger cross-section than what is actually needed will only lead to greater material costs (after all, for obvious reasons, their cost will be higher) and will create additional difficulties during installation.

Calculation of cross-sectional area of ​​copper conductors of wires and cables

So, speaking about the electrical wiring of a house or apartment, the optimal use would be: for “outlet” - power groups of copper cable or wire with a core cross-section of 2.5 mm2 and for lighting groups - with a core cross-section of 1.5 mm2. If there are high power appliances in the house, for example. email stoves, ovens, electric hobs, then to power them you should use cables and wires with a cross-section of 4-6 mm2.

The proposed option for choosing cross-sections for wires and cables is probably the most common and popular when installing electrical wiring in apartments and houses. Which, in general, is understandable: copper wires with a cross-section of 1.5 mm2 are capable of “holding” a load of 4.1 kW (current - 19 A), 2.5 mm2 - 5.9 kW (27 A), 4 and 6 mm2 – over 8 and 10 kW. This is quite enough to power outlets, lighting devices or electric stoves. Moreover, such a choice of cross-sections for wires will provide some “reserve” in the event of an increase in load power, for example, when adding new “electrical points”.

Calculation of cross-sectional area of ​​aluminum conductors of wires and cables

When using aluminum wires, it should be borne in mind that the values ​​of the long-term permissible current loads on them are much less than when using copper wires and cables of a similar cross-section. So, for conductors of aluminum wires with a cross-section of 2.mm2, the maximum load is slightly more than 4 kW (current is 22 A), for conductors with a cross-section of 4 mm2 - no more than 6 kW.

Not the last factor in calculating the cross-section of wires and cables is the operating voltage. Thus, with the same power consumption of electrical appliances, the current load on the cores of power cables or wires of electrical appliances designed for a single-phase voltage of 220 V will be higher than for devices operating on a voltage of 380 V.

In general, for a more accurate calculation of the required cross-sections of the cores of cables and wires, it is necessary to be guided not only by the load power and the material of manufacture of the cores, one should also take into account the method of laying them, length, type of insulation, number of cores in the cable, etc. All these factors are fully defined main regulatory document – Electrical Installation Rules .

Wire Size Selection Tables

Selecting wire cross-section

The rules for choosing a wire cross-section depending on the design current are described, and the corresponding tables of the dependence of current and cross-section are given.

Note 1. Current values ​​for 220/380V wires are given according to the standard range of automatic fuses; wire cross-sections are rounded up to the standard cross-sections of manufactured wires from the corresponding material.

Note 2. The data is given for a temperature of 30 C. For higher temperatures, move to the next (larger) section for every 20 C.

Note 3. When laying several wires in a bundle, the wire cross-section should be increased: for 2-9 wires in a bundle by 80%, for 10-20 wires by 160%.

Note 4. The AWG value is a wire marking according to the American Wire Gauge System; these designations are especially often used for speaker cables.

Practical advice on how to select a cable/wire for a house, apartment or summer cottage

Reports of fires caused by faulty electrical wiring have become so frequent lately that we have begun to view such a disaster as a necessary evil. And completely in vain. Although the number of electrical appliances in homes and their power have increased sharply, choosing the right brand of wires and cables can help us avoid many troubles.

Equipping your apartment with numerous electrical appliances requires many different wires and cables, the selection and placement of which must be thought about in advance.

It is known that you need to dance from the stove. So, first of all, let’s determine what needs to be electrified. It is important. For, if you have a two-story stone cottage standing on a hillock that is never flooded with water, and all work on the site is limited to mowing the lawns, there will be one solution. If, for example, the place is swampy, with close groundwater, and you want to supply electricity to a wooden bathhouse where an electric sauna heater is installed, and on the site you plow the land using a tractor, then the solution will be completely different. However, in both cases you cannot do without a cable. Let's look at the cable selection process step by step. We deliberately leave the question of the cost of the resulting solution outside the scope of the article; here everything depends only on the thickness of your wallet.

Just don’t forget that good and cheap at the same time does not exist.

Wires and cables vary in the number of cores (from 1 to 37), cross-section (from 0.75 to 800 mm) and rated operating voltage.

Wires are manufactured with insulation for voltages of 380, 660 and 3000 V AC, cables - for any voltage. In an insulated wire, the conductor is enclosed in a sheath made of rubber, polyvinyl chloride or vinyl plastic. To protect against mechanical damage and environmental influences, the insulation of some brands of wires is covered on the outside with a cotton braid impregnated with an anti-rot compound.

Wires intended for laying in places where there is an increased risk of mechanical damage are protected by an additional braid of galvanized steel wire.

A little about the terms

The core is, in general, a separate conductor.

Wires are products containing one or more insulated strands or stranded wires, over which there is a light protective sheath (for example, metal winding, winding or braiding of fibrous materials).

Installation wire - wire for low voltage electrical distribution networks.

Electrical cord - wire with a cross-section of up to 1.5 mm with insulated cores of increased flexibility. Used to connect mobile devices. The cores in this case are necessarily multi-wire. In addition, they are connected to each other by twisting or a common braid.

A cable is several insulated wires enclosed in one or more protective sheaths.

So, if you have something in your hands that is very flexible, has single insulation and is no thicker than your little finger, it is most likely a cord. If we are talking about a product as thick as your arm and about the same rigidity, consisting of single conductors and equipped with double insulation, it is a cable. In the case when you need to supply electricity to a cottage or electrify an area, and besides, you don’t want to spoil the view with hanging wires, you will need a cable. How to choose it?

Selection of conductor material

Copper is preferable to aluminum. It has greater conductivity and is less susceptible to corrosion. In addition, compared to copper, aluminum is fragile and can simply break if subjected to several bends. A negative property of aluminum is its rapid oxidation in case of contact with air, which results in the formation of a refractory oxide film on the surface. It conducts electricity poorly, which means it prevents the creation of good contact. A place with poor contact will heat up, spark, oxidize even more, heat up even more, and then it’s not far from a fire. And if you don’t want to call 01, you will have to periodically check the attachment points of aluminum conductors to electrical appliances. When fastened in screw clamps, aluminum exhibits another disadvantage - low yield strength. As a result, the aluminum slips out from under the clamp (flows), weakening the contact. Thus, aluminum wires located in junction boxes and other devices where clamps are used for connection also require periodic checking and tightening.

In addition, when aluminum comes into contact with copper, a galvanic couple is formed, in which the aluminum, subject to electrocorrosion, is destroyed. Which leads to further deterioration of the connection. And we just talked about the results of this phenomenon.

Selection of cable cross-section

The cable usually consists of 2-4 cores. The cross-section (more precisely, the cross-sectional area) of the core is determined by its diameter.

Recall: the area of ​​a circle is S = 0.78d, where d is the diameter of the circle. Based on practical considerations, at low current values, the cross-section of the copper core is taken to be at least 1 mm, and the aluminum core - 2 mm.

At sufficiently high currents, the wire cross-section is selected according to the connected power.

Usually, based on power calculations, it is assumed that a load of 1 kW requires a 1.57 mm core cross-section. From this follow the approximate values ​​of the wire cross-sections, which should be followed when choosing its diameter. For aluminum wires this is 5 A per 1 mm. for copper - 8 A per 1 mm. Simply put, if you have a 5 kW instantaneous water heater, then you need to connect it with a wire rated at least 25 A, and for a copper wire the cross-section should be at least 3.2 mm. Please note that from a number of preferred cross-sectional values ​​(0.75 1 1.5 2.5 4 6 mm, etc.) for aluminum wires, the cross-section is chosen one step higher than for copper, since their conductivity is approximately 62% of the conductivity copper

For example, if, according to load calculations, a cross-sectional value of 2.5 mm is required for copper, then 4 mm should be taken for aluminum, if 4 mm is needed for copper, then 6 mm for aluminum, etc.

In general, it is better to choose a cable with a larger cross-section than required - what if you want to connect something else? In addition, it is necessary to check whether the cross-section of the wires is consistent with the maximum actual load, as well as with the current of the protective fuses or circuit breaker, which are usually located next to the meter.

The tables show the dependence of the cross-section of cables, wires and automotive flexible stranded conductors depending on the current strength and load power.

Table for selecting cable cross-section when laying wires openly and in a pipe

Calculation of cable cross-section by load

Both the uninterrupted operation of electrical appliances and the safety of property and people’s lives depend on how correctly the cross-section of the conductors of the electrical wiring cables being laid is selected. It's no secret that recently cases of fires due to poor-quality wiring have become more frequent. To avoid this, a correct calculation of the cross-section of the cable (wire) for the load is necessary.

Just as a theater begins with a hanger, so wiring in a country house, apartment or garage begins with an input cable. It bears the heaviest load, and if for any reason it fails, then there is a high probability of fire. To find out the optimal cross-section of the cable (wire), it is necessary and sufficient to estimate the total power consumption of all electrical appliances in a given area. The power of electrical appliances can be gleaned from the device datasheets, from labels located directly on them, or estimated approximately.

So, on average, a TV consumes 300 W, a coffee maker - 1000 W, a microwave oven 1500 W, an electric stove 3000 W, a washing machine 2200 W, a computer 500 W, a vacuum cleaner 1600 W, an iron - 1700 W, and so on. But you should use the sufficiently averaged data presented here only if you do not have a passport for the electrical device or a label on it. It is advisable to calculate the cross-section of the cable (wire) for the load using known specific data on the power consumption of electrical receivers.

Adding up all the power of electrical appliances and lighting, we get the total power consumption, even though all our devices most likely will not work at the same time, at least for a relatively long time. According to the tables, depending on the method of wiring (hidden or open), we select the nearest ascending value of the cable cross-section.

For outgoing lines (socket and lighting) we perform the same calculations. However, it is advisable to choose a cable with a cross-section of at least 2.5 mm2 for the socket group, and 1.5 mm2 for the lighting network. That's the whole calculation of the cable cross-section for the load.

The total power of all consumers is equal to 10 kW. Taking into account the simultaneity factor, we get 10,000 * 0.7 = 7 kW. We look at the table and see that 7 kW corresponds to a cross section of 6 mm2. Dividing the power by the voltage, we get the current value.

7,000 / 220 = 31.8 (A), that is, at the entrance to the apartment, garage or cottage it is necessary to install a 32 A input machine.

Calculation of cable cross-section along the length

Electrical wiring must be safe, economical and reliable. Therefore, correct calculation of the cable cross-section along its length is important.

If there is an installation diagram, the calculation of the cross-section of the cable (wire) along the length can be done by measuring the corresponding distances between the locations of panels, sockets, switches, junction boxes, and so on. Knowing the scale of the diagram, it will not be difficult to calculate the lengths of the corresponding sections of cable (wire), not forgetting to add at least 10 cm to each cable section for twists. If there is no diagram, then the length of the cable can be estimated visually by measuring the lengths of the lines along which the wiring will be laid in the future.

Any cable (wire) “loses voltage” as its length increases. These voltage losses are caused by the voltage drop in the cables that connect the electrical receiver to the power “source”. Calculation of the cable cross-section along the length, taking into account voltage losses, is carried out when designing industrial electrical networks.

In “home” conditions, or when designing electrical wiring for small rooms, voltage losses can be safely neglected due to their negligible magnitude. The main thing in this case is to correctly calculate the cable cross-section for power or calculate the cable cross-section for current. And then, using special tables, select the required cross-section of the cable cores.

Calculation of cable cross-section by voltage

Calculating the cable cross-section by voltage is quite important and requires attention. When calculating the cable cross-section by voltage, it should be borne in mind that the electrical network can be either single-phase (operating voltage 220 V) or three-phase (3 * 220 / 380 V). That is, the power consumed can come to a home or large power receiver as a single-phase load or as a three-phase load.

For example, the total power consumption of our garage is, for example, 20 kW. In single-phase wiring, the entire load of 20 kW will be carried per phase, and in three-phase wiring - only 6.6 kW. Accordingly, with a higher load on the core, we will need larger cross-sections of the cable (wire), and with lower loads, correspondingly smaller ones. The only point: for single-phase wiring we need a three-core cable, and for three-phase wiring we need a five-core cable. Therefore, reducing the cable cross-section simultaneously increases the number of cores.

Also, when calculating the cross-section of a cable (wire) based on voltage, it is worth remembering that some electrical appliances and engines operate only on a 380 V network.

Calculation of cable cross-section for current

For high-quality installation of electrical wiring, in order to avoid unnecessary troubles and troubles, and simply to sleep peacefully, it is vitally important to carefully calculate the current cross-section of the cable. To calculate the cable cross-section for current, you will need to calculate the current that will flow through our wiring. The rated current is calculated using the total load power. The total load power is calculated accordingly by adding the powers of all electrical appliances that will take electricity from our line. It is necessary to take into account all the capacities located in the desired area.

For example, on our site we have 3 lamps of 100 W, an Atlant refrigerator of 200 W, a Samsung microwave of 1100 W, and a Bosch electric kettle of 2200 W. Our wiring will be single-phase and will be laid hidden. Our total power will be equal to P=100*3+200+1100+2200=3800 W.

From the total power we find the required current using the formula familiar from school:

where P is our total power, I is the rated current, U is the voltage, cos? - Power factor. Сos? in our case it is practically equal to 1, so it can be neglected.

According to the formula, I = 3800/220*1 = 17.3 A. Looking at the table, a cable capable of holding 17.3 A for a long time in hidden wiring is a copper cable with a minimum cross-section of 2 mm2. For reserve, we use copper cable for wiring, with a cross section of 3 * 2.5 mm2. The calculation of the cable cross-section for current is completed.

Calculation of cable cross-section by power

Let's imagine that, for example, we need to choose a cable for the electrical wiring of an apartment. In the apartment we have single-phase wiring, with an operating voltage of 220 V. To select the necessary cable, we need to calculate the cable cross-section by power. To do this, you just need to calculate the total power of possible consumers of electrical energy. All electrical appliances, as a rule, have a manufacturer's label indicating power consumption. In addition to electrical appliances, it is necessary to sum up the power of all lighting fixtures. Let's say that as a result of adding the power of all irons, refrigerators, televisions, microwaves, washing machines, kettles and other electrical appliances, together with lighting, you get 7 kW. It turns out that we need to calculate the cross-section of the cable (wire) for a power of 7 kW. Although all electrical appliances usually do not turn on at the same time, we will count to the maximum. For large industrial facilities, simultaneity coefficients, demand coefficients, and so on are used to accurately calculate the load, but in our “home” conditions we can do without these difficulties.

Thus, we will calculate the cable cross-section for a power of 7 kW. According to the PUE tables, we find out that a 3x6 copper cable or a 3x10 aluminum cable can withstand such power. Remembering that the stingy pays twice, do not skimp on the cable cross-section!

Difference between cable and wire

The question, by the way, is not simple. In particular, in accordance with SN, from the times of the USSR to the present day, work with cables is more expensive than with wires. However, there was no very clear classification in this regard, either in past times or today. Different sources provide a variety of perspectives. In practice, the characteristic “cable” or “wire” is assigned by GOST/TU for the production of a specific brand. In particular, the GDP brand cable from Odeskabel OJSC differs from the PVS brand wire only in the configuration of the sheath: the GDP cable is flat, and the PVS wire is round. And in no reference book about cables is the shape of the cable/wire sheath indicated as an insignificant factor. Therefore, you need to look at the certificate - it will certainly be stated there: this is a cable or wire.

Calculation of cable cross-section

There are reference plates indicating what cross-section of aluminum/copper conductor is needed for the assigned load. However, most electricians use a simple formula (consider a load of 8 kW): a copper cable cross-section of 1 mm2 can pass through 10A or 2.2 kW (power = 10A x 220V).

Therefore, the load in 8 kW in A will be equal to 36 A(load = 8 kW/220V), and for such a volume of current a cable with a cross-section of equals 4mm2.

This calculation is more or less suitable for cables with a cross-section of no more than 6 mm2. For large cross-sections, tables of “Permissible current loads” are needed.

With an equal load, the cross-section of the aluminum cable should be almost 30% larger than that of copper. The cable cross-section is the cross-sectional area of ​​the core that conducts current.

The cross-section of a round current-carrying cable core is obtained according to the formula for the area of ​​a circle S = π × r2, where the number π=3.14, and r is the radius.

When there are a couple of wires in the core, then the cross-section of the core will be equal to the sum of the cross-sections of all the wires. The radius of the wire is measured with a caliper, and for very thin wires with a micrometer. How much cross-sectional margin is required? The reserve will undoubtedly not be superfluous. However, you need to know the limit.

For example, the limit of ordinary household socket-switches is 16A (3.2 kW = 16A x 220V) and connecting the socket using a 4 mm2 cable, with a throughput of 8 kW, is an inappropriate expenditure of finances.

And also, a cable with a cross-section of 4 mm2 will not fit into every socket.

Rational cross-sections in household electrical networks for copper: 1.5-2.5 mm2 for sockets and 0.75-1.5 mm2 for lighting.

Which cable to choose: copper or aluminum?

Many “experts” will say with absolute certainty - copper. Why? For the consumer, copper, compared to aluminum, is advantageous in that sooner or later copper does not deteriorate so quickly, and this is very significant when replacing lamps, etc. Whether it is necessary to pay three times more for this is a decision for the consumer.

You only need to connect copper and aluminum cables using a terminal block so that the aluminum does not come into contact with the copper.

Because due to some physical phenomena at the point of contact between aluminum and copper, the current resistance increases after some time. As a result, the connection point heats up extremely intensely, the cable breaks, a short circuit occurs, and in extreme cases, a fire. By the way, the connection of any heterogeneous materials with different resistance leads to a similar result.

As a result, there is no need to sharpen the wiring with the first wire you come across by twisting it.

Depending on the area of ​​use of the cable, the conductor is made from a variety of materials: first copper and aluminum, then nichrome, steel, etc. When you are not assured of the uniformity of the material of the cables being connected, use a terminal block.

Which cable is optimal: flexible or rigid?

A rigid cable is usually a single-core cable, and a flexible cable is usually a multi-core cable. The greater the number of wires in the core and how thinner each wire is, the more elastic the cable.

Based on flexibility, the cable is divided into 7 classes: monocore is class 1, and class 7 is the most flexible.

As the flexibility class of the cable increases, its price increases. A rigid cable is used for inserting into walls and laying in the ground, and a flexible cable is used for connecting maneuverable devices or electrical appliances. From an operational point of view, it doesn’t matter which cable to choose - rigid or flexible. From an installation point of view, every electrician has his own wishes. By the way: the ends of the flexible cable, which are embedded in sockets (switches), must certainly be soldered or crimped using special ends. For a rigid cable, a similar procedure is not necessary. To connect lighting equipment, it is better to purchase a flexible cable, because lighting devices are often replaced, and a rigid cable is more likely to break when connecting new electrical equipment.

How to independently determine the quality of the cable?

Many manufacturers do not always comply with cable manufacturing standards. Their main “trick” is to underestimate the cross-section of the conductor. And sometimes significantly. Of course, it is difficult to examine the cross section at the point of purchase. In the store you can measure any wire with a caliper and a micrometer.

You can also come across cables with a reduced sheath thickness or with a sheath made of low-quality material, and this reduces the service life of the cable.

For inspection, it’s a good idea to have a piece of the “correct” cable with you as a standard. In stores you can come across a Chinese cable made of aluminum covered with copper (sold as copper with markings in Cyrillic).

It is easy to inspect such a cable: the cut of the current-carrying core on the cable gleams white - it is aluminum.

There are manufacturers who use low-quality copper or aluminum to reduce costs. Such cables have a much lower service life and conductivity than those required by GOST. It is possible to test the quality of the metal of a current-conducting core as follows:

• try bending and straightening the cable a couple of times. In factories, such a test is performed on a special bending mechanism under a certain bending radius. Of course, your number of bends will be less than those provided for in GOST. However, in any case, aluminum should withstand at least 7-8 bends, and copper - 30-40. After this, deformation of the insulation and wire breakage are possible. It is better to carry out the experiment at the end of the cable, so that you can simply cut it off later.
• a cable made of high quality copper/aluminum should bend and not spring;
• the copper/aluminum core on the stripped cable should have a bright (glare) color. When the vein is heterogeneous in color and there are hopeless spots, this indicates large impurities in the metal and its low quality.

Nevertheless, an amateur will not be able to determine the quality of the cable 100% on his own. In this case, there is only one recommendation - rely on the brand and purchase it in large, trusted stores.

What kind of insulation and sheath should the cable have?

It is best when the insulation and sheath of the cable are double insulated. A single-insulated cable has a service life of up to 15 years, while a double-insulated cable usually lasts 2 times longer. Typically, “insulation” and “sheath” are 2 different materials. The insulation is the layer of dielectric material that goes immediately behind the conductive core, and the sheath is all the layers on top of the insulation. The sheath is intended to protect the cable from various mechanical influences. The cable may have a couple of layers of sheath made of different types of material. Certain types of shell that may be useful:

1. Heat-resistant cables are designed for installation in rooms with high temperatures (saunas). Typically, the material used is fluoroplastic, with fiberglass on top. There are no special designations for such cables, i.e. if necessary, you need to seek help from reference books or catalogs, where the value of the “operating temperature” is indicated precisely;
2. non-flammable, marked “ng” - indicates the ability to self-extinguish when the flame disappears, but cannot withstand high temperatures
3. when the cable brand contains “FR” (fire resistant) and then E30, E90 or E120, then this cable can “function” in an open fire for 30, 90 or 120 minutes;
4. cables with a polyethylene sheath can be pulled both in the soil and in an open way (for example, along the walls of houses);
5. cables with insulation and sheath made of PVC (polyvinyl chloride) are used for pulling inside buildings (under plaster) or in cable ducts.

The most famous cable brands

1. wire PPV (copper), APPV (aluminum) in single insulation - for pulling inside walls;
2. cable PVS (copper), GDP (copper) in double insulation - for pulling inside buildings;
3. heat-resistant cables RKGM (copper) - up to 180°C, BPVL (tinned copper) - up to 250°C;
4. cable VVG (copper), AVVG (aluminum) - for stretching along the walls of houses and in the ground;
5. runway cable (copper) water-submersible - for pulling in water;
6. TPP cable (copper) telephone pair - for pulling in the ground;
7. TRP wire (copper) telephone distribution for subscriber communications (switching on the telephone)
8. twisted pair cable UTP, FTP - for organizing computer networks, turning on intercoms, etc.;
9. “Alarm” signal wire for connecting intercoms, security and fire alarms, etc.;
10. coaxial cable RG-6 for connecting TVs, antennas, CCTV cameras.

Internet cable

The concept of “Internet cable” generalizes many types of cable products. A variety of information cables are used to broadcast information. If you mean connecting to the Internet, then you need to check with the operator which cable needs to be laid across the walls. In this case, it is necessary to find out both the brand of the cable and the manufacturer in order to accurately determine compatible cable products.

For example, for the Internet they use a regular television cable TM Finmark, a twisted pair cable or an existing subscriber cable (the so-called “noodles”) to which the telephone is connected.

Optical cables can be laid on dedicated Internet lines.

Computer cable

The term is also general.

As a rule, a twisted pair cable is used to connect PCs with each other and with the server, but other information cables can also be used.

The technology of twisting two wires into a pair has been used in telephony since the last century. Due to the correctly calculated twisting pitch and the quality of the material, a maximum information transfer speed was achieved than that of a standard paired telephone cable. There are quite a few types of twisted pair cables, depending on the number of cores, the diameter of each core, installation locations, etc. Depending on the data transfer speed, twisted pair cables are divided into groups:

• 3rd category (standard telephone cable),
• 5th category (office networks),
• 6th category (new generation cable for changing category 5).

“Twisted pair”, which has gained the greatest popularity in our time, is a category 5 cable made of 8 twisted pairs of cores, the diameter of the core is at least 0.45mm and maximum 0.51mm.

TV cable

This is the common name for coaxial cable with a resistance of 75 ohms.

And " satellite cable" is a coaxial cable. Any 75 Ohm coaxial cable can be used to connect a satellite and any other antenna, and to connect to cable television. The only thing that matters is whether the cable is good or not.

Important characteristics of coaxial cable are signal attenuation and noise immunity.

All other characteristics of the cable are aimed at improving these two indicators themselves and are of secondary importance. In particular, our RK cable is made only from copper wire (sometimes even silver-plated), but the attenuation of the RK cable will be almost four times worse than that of any current RG cable made from inexpensive materials: steel and aluminum. This is achieved through special cable production technology.

It would be unnecessary to repeat that the correct and competent selection of components can protect a house or apartment from many troubles. Guided by a wise rule, instead of abstract statements, the article provides practical advice on calculating the cross-section of wires for wiring in an apartment or house.

The simplest, but not the most correct way to select wire cross-sections

Very often, when installing wiring in a house or apartment, they do not resort to formulas and calculations, guided by a primitive pattern:

• socket lines - 2.5 sq. mm,
• – 1.5 sq. mm,
• powerful consumers (hobs, electric fireplaces, electric stoves) – 4-6 sq. mm.

This simple method cannot be called fundamentally incorrect. It assumes a “reserve” that will not allow the electrical wiring to burn out under minor overloads and, in principle, does not contradict the PUE. At the same time, this method has a number of disadvantages:

• the lack of precise selection does not make it possible to ensure the efficiency of the electrical wiring system,
• this method does not include the calculation of the submarine cable,
• The method is not applicable for rooms with more powerful and specific energy consumers, that is, it cannot be used to calculate the cross-section of wires for a home workshop in which the welding machine will operate; it is not suitable for a house with a powerful one.

Submarine cable calculation

The submarine cable “carries” the entire load. In addition, if it fails, the entire house will be de-energized, so it is important to calculate its cross-section and select the type of cable in such a way as to minimize the likelihood of unpleasant situations.

We sum up the power of all energy consumers

The power of consumers is the main quantity on the basis of which the cross-section of wires is calculated, therefore, summing the powers of all consumers available in a house or apartment is the first stage of calculating an underwater cable. In most cases, this characteristic is indicated not only in the instructions included with any household appliance or electrical appliance, but also on consumer housings. If it is impossible to accurately determine this value, approximate values ​​should be used.

It should be remembered: when calculating the total power, one should not forget about electrical appliances that are connected for a short time. So, when looking around your home, they often do not take into account an iron, hair dryer, electric razor, mixer or blender, etc. Realizing that this probability is extremely low, for safety reasons the wiring at this stage is designed so that it can withstand the simultaneous switching on of all electricity consumers in the house.

Approximate power values ​​for household appliances:

• TV – 300 W,
• computer with printer – 1000 W,
• microwave oven – 1400 W,
• refrigerator – 600 W,
• washing machine – 2500 W,
• vacuum cleaner – 1600 W,
• iron 1700 W,
• hair dryer – 1200 W.

When calculating wiring in a private house or cottage, the power of special equipment should be taken into account:

• instantaneous water heater – 5000 W,
• water pump – 1000 W,
• – 1500 W,
• circular saw – 2000 W,
• compressor – 2000 W,
• – 1500 W.

Electricity consumed in the workshop is:

• electric sharpener – 900 W,
• drill – 800 W,
• electric planer – 900 W,
• hammer drill – 1200 W,
• jigsaw – 700 W,
• grinder – 1700 W,
• – 2300 W.

Using the Wire Sizing Chart

To determine the cross-section of the input cable, a standard table is used, in which it is necessary to find the resulting total power and determine the cable cross-section corresponding to this value.
When calculating the total power, we assumed the simultaneous inclusion of all consumers, remembering that such a situation is impossible. Therefore, we multiply the figure obtained by summing by 0.7. Turning on 70% of electrical appliances is also unlikely, so even taking into account the “reserve” factor, it will be sufficient.

The cross-section of wires for lighting fixtures and socket groups is carried out in a similar way. After calculations, it is most often determined that a sufficient cross-section for lighting is 0.5-0.7 square meters. mm, and for - 1.5 sq. mm.

In most cases, wires with a obviously large cross-section are used: 1.5 square meters. mm for lighting and 2.5 sq. mm for ordinary household socket groups. Socket groups in the workshop may require a thicker cable.

The increase in the thickness of the wires from the design cross-section is due to the possible damage to the cable from corrosion and mechanical loads during long-term operation.

Taking into account the length of the line when calculating the wire cross-section

This point is often not fulfilled in calculations, since in most cases it turns out that losses along the length of the conductor are within acceptable limits. At the same time, an additional check will not hurt, especially since it will not take much time.

The resistance of the conductor (wire) is calculated by the formula R=p L/S, in which L is the length of the wire, expressed in meters, S is the required cross-sectional area we previously obtained, and p is the resistivity of the material, which for copper is 0.0175 Ohm mm2/m.

For a two-core cable, the resulting value is multiplied by two. For a three-core one, it’s also two, since one of the three cores is “ground”.

By determining the resistance of a conductor, we can calculate how much it can reduce the voltage. Voltage drop is defined as the product of current and conductor resistance.

The final step will be to determine the percentage of voltage loss to the whole number (initial voltage 220 Volts). If the losses are less than 5%, you can install the wiring using a wire with a cross-section calculated by us. If the losses are 5% or more, the wire cross-section should be increased.

Selecting a wire for wiring

At the beginning of the article, we said that aluminum wires are used much less frequently than copper wires. Indeed, the advantage is its low cost, but in terms of operational characteristics it is significantly inferior.
Benefits of copper:

• strength, higher compared to aluminum,
• softness and plasticity, which does not allow wires to break at bends,
• ability to withstand high current loads compared to aluminum.

Please note: when purchasing cables or wires in a store, you should keep in mind that the actual cross-section may not coincide with the nominal one, and this is not a defect or violation. We quote GOST 22483-77 clause 1.4.a: “The actual cross-section of the cores may differ from the nominal cross-section if the electrical resistance meets the requirements of this standard.” That is, if, by improving the quality of the material (copper), the required wire parameters are maintained, its diameter (cross-section) can be reduced.

Every master wants to know... how to calculate the cable cross-section for a particular load. You have to deal with this when wiring in a house or garage, even when connecting machines - you need to be sure that the selected power cord will not smoke when you turn on the machine...

I decided to create a calculator for calculating cable cross-section by power, i.e. The calculator calculates the current consumed, and then determines the required wire cross-section, and also recommends the closest circuit breaker.

Power cables GOST 31996-2012

Calculation of the cable cross-section by power is carried out in accordance with the tables of the normative document GOST 31996-2012 “Power cables with plastic insulation”. In this case, the cross-section is indicated with a current reserve to avoid heating and fire of the wire operating at the maximum current. I also introduced a coefficient of 10%, i.e. another 10% is added to the maximum current for smooth operation of the cable :)

For example, we take a load power of 7000 W at a voltage of 250 Volts, we get a current of 30.8 Amps (adding 10% in reserve), we will use a single-core copper wire laid through the air, as a result we get a cross-section: 4 sq. mm., i.e. cable with a maximum current of 39 Amps. Cable with a cross section of 2.5 sq. mm. It is not recommended to use it for a current of 30 Amps, because the wire will be operated at the maximum permissible current values, which can lead to heating of the wire with subsequent destruction of the electrical insulation.

Table of cable cross-section by current and power for copper wire

Also check out these articles

The data in the tables is given for OPEN wiring!!!

Table of aluminum wire cross-section by power consumption and current

Cable cross section calculator

The online calculator is designed to calculate the cable cross-section by power.

You can select the required electrical appliances by ticking them to automatically determine their power, or enter the power in watts (not kilowatts!) in the field below, then select the remaining data: network voltage, conductor metal, cable type, where it is laid and the calculator will calculate the wire cross-section by power and tell you which circuit breaker to install.

I hope my calculator will help many craftsmen.

Calculation of cable cross-section by power: