Table of section of aluminum wires. Current load over the cable section

Wire power table it is required to correctly calculate the wire cross-section, if the power of the equipment is large, and the wire cross-section is small, then it will be heated, which will lead to the destruction of the insulation and the loss of its properties.

For the transmission and distribution of electric current, wires are the main means, they ensure the normal operation of everything connected with electric current, and how high-quality this work will be depends on the right choice. wire sectionby power. A convenient table will help you make the necessary selection:

Current- conductive lived. mm
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

cross section Current conductive lived. mm	Aluminum core cables and wires
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

But in order to use the table, it is necessary to calculate the total power consumption of appliances and equipment that are used in the house, apartment or other place where the wire will be laid.

An example of power calculation.

Let's say, installation of closed electrical wiring of BB wires is carried out in the house. On a piece of paper, you need to rewrite the list of equipment used.

But how now find out the power? You can find it on the equipment itself, where there is usually a tag with the main characteristics recorded.

Power is measured in Watts (W, W) or Kilowatts (kW, KW). Now you need to write the data, and then add them.

The resulting number is, for example, 20,000 W, which would be 20 kW. This figure shows how much all electrical receivers together consume energy. Next, you should consider how many devices will be used simultaneously for a long period of time. Let's say it turned out 80%, in this case, the simultaneity coefficient will be equal to 0.8. We calculate the wire cross section by power:

20 x 0.8 = 16 (kW)

To select the cross section, you need a wire power table:

Current- conductive lived. mm	Copper conductors of cables and wires
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt
10		15.4

If the three-phase circuit is 380 Volts, then the table will look like this:

Current- conductive lived. mm	Copper conductors of cables and wires
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt
				16.5
10		15.4

These calculations are not particularly difficult, but it is recommended to choose a wire or cable with the largest cross-section of the wires, because it may be that it will be necessary to connect some other device.

Additional wire power table.

The cross section of the cable at the cut is standardized in all countries. This applies to both the CIS countries and Europe. This issue is regulated in our country by the document "Electrical Installation Rules", which are called PUE. The calculation of the cable cross-section by power is selected using special tables. Of course, many calculate the necessary parameters of the conductor "by eye", but this is not entirely correct. For each apartment, this figure may be different. This is due to the number of electrical consumers and their power. Without proper calculation, many unpleasant situations can occur, costly repairs of both wiring and the apartment.

Cable device

To determine the cable cross-section by power, one should understand its principle and structure. It can be compared, for example, with a water or gas pipeline. In the same way as through these communications, a stream flows through the electrical conductor. Its power limits the cross section of the conductor.

The cable cross-section using the power indicator can be incorrect in two cases:

1. The current-carrying channel will be too narrow. This will lead to an increase in current density and, consequently, to overheating of the insulation. Such a state of the conductor over time will be characterized by the presence of weak points where leakage is possible. This condition of the channel can cause a fire.
2. Conductor too wide. This, of course, is not the worst option. The space for transporting the electrical flow will allow more functional and durable use of the conductor. However, as the cross section increases, so does the cost of the cable.

The first option is a danger to life, health and property. The second method is safe, but the materials are quite expensive to purchase.

The easy way

The calculation of the cable cross-section by power is based on the well-known law developed by Ohm. He says that the current flow times the voltage equals the power. Voltage in everyday life is considered a constant value. In a single-phase network, it is equal to 220 V. Therefore, to determine the cable cross-section in terms of current, as well as power, only two variables remain.

Next, the current values ​​\u200b\u200band the expected load are calculated. Moreover, the size of the cable according to its power can be selected according to the PUE table. This indicator is calculated for a wire suitable for sockets. Traditionally, for lighting lines, a wire with a cross section of 1.5 mm 2 is laid.

However, it happens that devices such as a hair dryer, microwave oven, electric kettle, etc. are connected to the outlet group. It is necessary to distribute the load and correctly calculate the cable cross-section in terms of power, correlating the diameter and load.

If it is not possible to break up the socket groups, then many electricians will recommend immediately installing a cable with a copper core up to 6 mm 2.

Cross-sectional area and diameter

Calculation of the cable cross-section by power, diameter and load are not equivalent concepts. The first indicator is calculated in mm 2, and the second is simply in mm. You can choose the power and allowable current according to the table both by the cable cross section and by its diameter.

If the table takes into account only the size of the cross-sectional area in mm 2, and there is data only on the diameter of the cable, the missing indicator can be found using the following formula:

S \u003d 3.14D 2 / 4 \u003d 0.785D 2,

where: S is the cross section of the wire and D is the diameter.

If the wire in the section is not round, but rectangular, its cross-sectional area is calculated by multiplying the length by the width (just like the area of ​​a rectangle).

Load Based Calculation

The easiest way to calculate the cable wire cross section is by summing up the capacities of all units that will be connected to the line. To do this, you will need to perform a certain sequence of actions.

First, it is determined which electrical appliances will be used in the home, which of them are likely to function simultaneously. Next, you need to look into the data sheets of each of these units. It will be necessary to calculate the sum of the capacities of those electrical consumers that must work simultaneously.

Then the indicator obtained as a result of the calculations performed is rounded up. This will provide a safe supply of electrical wiring power. The cross section of the wire or cable is calculated further using the PUE tables.

In a similar way, you can summarize the current strength, which is indicated in the data sheets of electrical equipment. Rounding and searching in the power calculation table is performed.

Table of power, current and section of copper wires

According to the PUE, in residential buildings it is necessary to use only copper conductors for arranging wiring. The power supply of some electrical equipment, which belongs to the engineering types of receivers, can be connected to the network with aluminum conductors with a cross section of at least 2.5 mm 2.

Table of power, current and section of aluminum wires

The specialist will also be able to make correction factors for the type of wire location, ambient temperature, for a cable in the ground, etc. The table for calculating cable power, cross-section or current strength refers to conductors in plastic or rubber insulation. These include such common brands as VVP, PVS, PPV, VPP, AVVG, VVG, APPV, etc. Uninsulated or paper-screened cables should be calculated according to the table related to them.

Length and section

The calculation of the cable cross-section by power simply needs to be used to determine its length. This data is important when creating long extensions. The obtained exact values ​​​​must be increased by 10-15 cm. This margin is necessary for switching by soldering, welding or crimping.

In construction, the cable cross-section is calculated in terms of power and length at the design stage of electrical wiring. This is very important, especially for those communications that will be subject to significant or additional loads.

In everyday life, the calculation of the length of the wire is carried out according to the following formula:

I=P/U*cosφ, where:

• P - power (W);
• I - current strength (A);
• U - voltage (V);
• cosφ - coefficient, which is equal to 1.

The cable cross section must first be found in the table. The formula will help determine the correct wire length.

current density

The current strength varies in the range of 6-10 A, which was derived empirically. This value is calculated for the current flowing through 1 mm 2 of the copper core.

This statement means that the calculation of the cable cross-section in terms of power and current is based on a copper cable with a cross section of 1 mm 2, through which current from 6 to 10 A can flow to waiting household appliances without melting and overheating.

According to the PUE code, for each wire a margin of 40% is allocated for overheating that is safe for the sheath. If the value of 6 A characterizes the operation of the presented conductor for an infinitely long term without time limits, then the indicator of 10 A is suitable for the short-term flow of current through the core.

If a current of 12 A flows through a 1 mm 2 copper conductor, it will be cramped in such a core. This will increase the current density. The core will begin to heat up and will melt the insulation.

Therefore, such calculations are mandatory when choosing a cable section for each type of wiring.

Having familiarized yourself with the methods that allow you to calculate the cable cross-section by power and current strength, you can lay or repair old wiring that will last a long time and be completely safe for people living in the house. A lot of fairly simple, but effective ways will help you accurately determine the required cross-sectional size for the power grid.

The right choice of electrical cable for powering electrical equipment is the key to long-term and stable operation of installations. Using the wrong wire has serious negative consequences.

The physics of the process of damage to an electric line due to the use of an unsuitable wire is as follows: due to the lack of space in the cable core for the free movement of electrons, the current density increases; this leads to an excess release of energy and an increase in the temperature of the metal. When the temperature gets too high, the insulating sheath of the line melts, which can cause a fire.

To avoid trouble, it is necessary to use a cable with conductors of suitable thickness. One way to determine the cross-sectional area of ​​​​a cable is to start from the diameter of its cores.

Calculator for calculating the section by diameter

For ease of calculation, a calculator for calculating the cable cross-section by diameter has been developed. It is based on formulas by which you can find the cross-sectional area of ​​single-core and stranded wires.

It is necessary to measure the cross section by measuring the core without insulation, otherwise nothing will work.

When it comes to calculating tens and hundreds of values, an online calculator can significantly simplify the life of electricians and electrical network designers due to the convenience and speed of calculations. It is enough to enter the value of the core diameter, and if necessary, specify the number of wires, if the cable is stranded, and the service will show the required wire section.

Calculation formula

You can calculate the cross-sectional area of ​​​​an electric wire in different ways, depending on its type. For all cases, a single formula for calculating the cable cross-section by diameter is used. It looks like this:

D is the core diameter.

The core diameter is usually indicated on the wire sheath or on a general label with other technical specifications. If necessary, this value can be determined in two ways: using a caliper and manually.

The first way to measure the diameter of the core is very simple. To do this, it must be cleaned of the insulating sheath, and then use a caliper. The value that he will show is the diameter of the core.

If the wire is stranded, it is necessary to dissolve the bundle, count the wires and measure only one of them with a caliper. It makes no sense to determine the beam diameter as a whole - such a result will be incorrect due to the presence of voids. In this case, the formula for calculating the cross section will look like:

D is the core diameter;

a is the number of wires in the core.

If a caliper is not available, the core diameter can be determined manually. To do this, its small segment must be freed from the insulating sheath and wound around a thin cylindrical object, for example, a pencil. The coils should fit snugly against each other. In this case, the formula for calculating the diameter of the wire core looks like this:

L is the length of the wire winding;

N is the number of complete turns.

The longer the winding of the core, the more accurate the result will be.

Table selection

Knowing the diameter of the wire, you can determine its cross section from the finished dependency table. The table for calculating the cable cross-section by the diameter of the core looks like this:

Conductor diameter, mm	Conductor cross section, mm2
0.8	0.5
1	0.75
1.1	1
1.2	1.2
1.4	1.5
1.6	2
1.8	2.5
2	3
2.3	4
2.5	5
2.8	6
3.2	8
3.6	10
4.5	16

When the cross section is known, it is possible to determine the values ​​​​of permissible power and current for a copper or aluminum wire. Thus, it will be possible to find out what load parameters the conductive core is designed for. To do this, you need a table of the dependence of the cross section on the maximum current and power.

In the air (trays, boxes, voids, channels)						Section, sq. mm	in the ground
Copper conductors			Aluminum conductors				Copper conductors			Aluminum conductors
Current. A	power, kWt		Tone. A	power, kWt			Current, A	power, kWt		Current. A	Power, kWt
	220 (V)	380 (V)		220(V)	380 (V)			220(V)	380 (V)		220(V)
19	4.1	17.5				1,5	77	5.9	17.7
35	5.5	16.4	19	4.1	17.5	7,5	38	8.3	75	79	6.3
35	7.7	73	77	5.9	17.7	4	49	10.7	33.S	38	8.4
*2	9.7	77.6	37	7	71	6	60	13.3	39.5	46	10.1
55	17.1	36.7	47	9.7	77.6	10	90	19.8	S9.7	70	15.4
75	16.5	49.3	60	13.7	39.5	16	115	753	75.7	90	19,8
95	70,9	67.5	75	16.5	49.3	75	150	33	98.7	115	75.3
170	76.4	78.9	90	19.8	59.7	35	180	39.6	118.5	140	30.8
145	31.9	95.4	110	74.7	77.4	50	775	493	148	175	38.5
ISO	39.6	118.4	140	30.8	97.1	70	775	60.5	181	710	46.7
770	48.4	144.8	170	37.4	111.9	95	310	77.6	717.7	755	56.1
760	57,7	171.1	700	44	131,6	170	385	84.7	753.4	795	6S
305	67.1	700.7	735	51.7	154.6	150	435	95.7	786.3	335	73.7
350	77	730.3	770	59.4	177.7	185	500	110	379	385	84.7

Convert watts to kilowatts

In order to correctly use the table of wire cross-section versus power, it is important to correctly convert watts to kilowatts.

1 kilowatt = 1000 watts. Accordingly, to get the value in kilowatts, the power in watts must be divided by 1000. For example, 4300 W \u003d 4.3 kW.

Examples

Example 1 It is necessary to determine the values ​​​​of permissible current and power for a copper wire with a core diameter of 2.3 mm. Supply voltage - 220 V.

First of all, the cross-sectional area of ​​\u200b\u200bthe core should be determined. This can be done using a table or a formula. In the first case, a value of 4 mm 2 is obtained, in the second - 4.15 mm 2.

The calculated value is always more accurate than the table value.

Using the table of dependence of the cable cross-section on power and current, it can be found out that for a cross-section of a copper core with an area of ​​​​4.15 mm 2, a power of 7.7 kW and a current of 35 A is permissible.

Example 2 It is necessary to calculate the current and power values ​​for an aluminum stranded wire. Core diameter - 0.2 mm, number of wires - 36, voltage - 220 V.

In the case of a stranded wire, it is not advisable to use tabular values; it is better to apply the formula for calculating the cross-sectional area:

Now you can determine the power and current values ​​​​for a stranded aluminum wire with a cross section of 2.26 mm 2. Power - 4.1 kW, current - 19 A.

In order for the wiring to function flawlessly, it is important to choose the right cross-section of wires and make a competent calculation of power, because other characteristics depend on these indicators. Current flows through wires just like water flows through pipes.

The safety of the entire premises depends on the quality of the electrical installation work carried out. Here it is especially important to choose the right parameter such as cable cross-section. In order to calculate the cable cross-section by power, it is necessary to know the technical characteristics of all electricity consumers that will be connected to it. You should also consider the length of the wiring and how it will be installed.

The choice of cable for electrical wiring

Current flows through wires just like water flows through a pipe. Just as a larger volume of liquid cannot be placed in a water pipe, so it is impossible to pass more than a certain amount of current through a cable. In addition, the cost of the cable directly depends on its cross section. The larger the cross section, the higher the price of the cable.

A water pipe that is larger than necessary, costs more, and one that is too narrow will not allow the required amount of water to pass through. The same thing happens with the current, with the only difference that the choice of a cable with a cross section less than a given value is much more dangerous. Such a wire overheats all the time, the current power in it increases. Because of this, the light in the room will be arbitrarily cut down, and in the worst case, a short circuit will occur, a fire will start.

There is nothing wrong with the fact that the selected cable section will be more than necessary. On the contrary, wiring, where the power and cross section exceed the required value, will last much longer, but the cost of all electrical work will immediately increase by at least 2-3 times, because the main costs for power supply are precisely the cost of wires.
A properly selected section will allow:

• avoid overheating of wires;
• prevent short circuit;
• save on repair costs.

Formula calculation

A sufficient cross-sectional area will make it possible to pass the maximum current through the wires without overheating. Therefore, when designing electrical wiring, first of all, they find the optimal wire cross-section depending on the power consumption. To calculate this value, the total current must be calculated. It is determined based on the power of all devices connected to the cable.

To choose the optimal wire cross-section, knowing the power, one should remember Ohm's law, as well as the rules of electrodynamics and other electromechanical formulas. So, the current strength (I) for a section of a network with a voltage of 220 Volts, namely this voltage is used for a home network, is calculated by the formula:

I=(P1+P2+…+Pn)/220, where:

(P1 + P2 + ... + Pn) - the total power of each used electrical appliance.

For networks with a voltage of 380 Volts:

I=(P1+P2+…+Pn)/ √3/380.

Power ratings of some household electrical appliances

electrical appliance	Power, W	electrical appliance	Power, W
Blender	up to 500	Towel dryer	900-1700
Fan	750-1700	Dishwasher	2000
Video recorder	up to 500	Vacuum cleaner	400-2000
Storage water heater	1200-1500	Juicer	up to 1000
Instantaneous water heater	2000-5000	Washing machine	3000
Hood (ventilation)	500-1000	Washing machine with dryer	3500
Grill	1200-2000	Hand dryer	800
Oven	1000-2000	TV	100-400
Computer	400-750	Toaster	600-1500
Air conditioner	1000-3000	Humidifier	200
Coffee maker	800-1500	Iron	500-2000
Food processor	up to 100	Hair dryer	450-2000
Microwave	850	fryer	1500
Microwave combined	2650	Fridge	200-600
Mixer	up to 500	electric shaver	up to 100
Meat grinder	500-1000	Electric lamps	20-250
Heater	1000-2400	electric stove	8000-10000
Double boiler	500-1000	Electric kettle	1000-2000

But these are vague formulas and a simplified calculation. The detailed calculations take into account the value of the permissible loads, which for a copper cable will be 10A / mm², and for aluminum - 8 A / mm². The load determines how much current can pass through a unit area without hindrance.

Power correction

Also, when calculating, an amendment is added in the form of a demand coefficient (Kc). This coefficient shows which devices are used in the network constantly, and which for a certain time. A special calculator and tables showing the calculation of power simplify all these calculations.

Demand coefficients of auxiliary receivers (Ks)

But what to do if the characteristics indicate 2 types of power: active and reactive? Moreover, the first of them measures in the usual kV, and the second - in kVA. In our networks, an alternating current flows, the value of which varies with time. Therefore, for all consumers there is active power, which is calculated as the average of all instantaneous alternating currents and powers. Active power devices include incandescent lamps, electric heaters. For such energy consumers, the phases of current and voltage coincide. If, however, units that accumulate energy, for example, transformers or electric motors, are involved in the electrical circuit, then they may have deviations in amplitude. Due to this phenomenon, reactive power arises.

For networks where there is reactive and active power, one more correction must be taken into account - the power factor (cosφ) or the reactive component.

Thus, the formula is obtained:

S= Kc*(P1+P2+…+Pn)/(220*cosφ*Rd), where:

• S is the cross-sectional area,
• Rd - allowable load.

In addition, possible current losses that occur during passage through the wires are considered. When using a cable with several cores, you need to multiply the loss by the number of these cores.

Important! For all these calculations, you will need not just a calculator, but also deep knowledge in the field of physics. It is impossible to make an accurate calculation immediately without theoretical knowledge.

Finding area by diameter

Sometimes even a rigorous calculation does not help, a short circuit occurs in the circuit. This is due to the fact that the declared technical characteristics often do not correspond to the real value. Therefore, in order to find out how to make a power calculation, it is important to be sure that the store will offer a suitable electrical wire according to the cross section. To do this, we use a simple formula:

S=0.785d 2 where:

• d is the core diameter;
• S is the cross-sectional area.

Determine the exact diameter of the wire, you can calculate the cross section using a caliper or micrometer, which is more accurate.

If the cable consists of several thin wires, then first they look at the diameter of one of them, and then the obtained data is multiplied by their number:

Stot=n*0.785di 2 , where:

• di is the area of ​​a single wire;
• n is the number of wires;
• Stot is the total cross-sectional area.

Tables for calculations

Every time resorting to complex calculations for the calculation is not entirely correct. The industry produces wires of a certain section. If, after accurate calculations and calculations, a cable cross section of 3.2 square millimeters in size is obtained, then it will not be possible to find such a wire, because there are wires with a cross section of 2.5 mm 2, 3 or 4 mm 2.

Attention! In order to find out the cable cross-sections, a table is needed where all the data is regulated, and also drawn up in accordance with the PUE - the rules for electrical installations.

In order to determine the cable cross-section at a known load, it is necessary:

• calculate the current strength;
• round up to a larger value according to the data in the table;
• then find the nearest standard section value.

Permissible continuous current for wires and cords with rubber and PVC insulation with copper conductors

Current- wire- wire core, mm 2		Current, A, for wires laid
	Open- That		in one pipe
		two one- vein	three one- vein	four one- vein	one two- vein	one three vein
0,5	11	-	-	-	-	-
0,75	15	-	-	-	-	-
1	17	16	15	14	15	14
1,2	20	18	16	15	16	14,5
1,5	23	19	17	16	18	15
2	26	24	22	20	23	19
2,5	30	27	25	25	25	21
3	34	32	28	26	28	24
4	41	38	35	30	32	27
5	46	42	39	34	37	31
6	50	46	42	40	40	34
8	62	54	51	46	48	43
10	80	70	60	50	55	50
16	100	85	80	75	80	70
25	140	115	100	90	100	85
35	170	135	125	115	125	100
50	215	185	170	150	160	135
70	270	225	210	185	195	175
95	330	275	255	225	245	215
120	385	315	290	260	295	250
150	440	360	330	-	-	-
185	510	-	-	-	-	-
240	605	-	-	-	-	-
300	695	-	-	-	-	-
400	830	-	-	-	-	-

It is easy to make such a calculation. First you need to determine the total power of all electrical appliances used in the network. For this, a table will be needed, and the missing data for each electrical appliance can be taken from the product passport. The resulting amount must be multiplied by 0.8 - the demand coefficient, if electrical appliances are not used all at once, or left unchanged during constant operation. Now the resulting value must be divided by the voltage in the network and add a constant value of 5. This will be the required current indicator. Let's say the current is 20A.

Note! In residential premises, a three-wire electrical wire and closed wiring are used. This must be remembered when the calculation is done according to the table.

Next, you need a table from the PUE. We take a column where the current values ​​\u200b\u200bare given for a three-core core, and select the closest ones: 17 and 22. It is better to take the section with a margin, therefore, in this example, the desired value will be 22. As you can see, this value corresponds to a three-core cable with a cross section of 2 mm 2 .

You can additionally consider how this calculation is made for an aluminum cable according to the PUE, although for safety reasons such wires cannot be used in residential buildings. Aluminum wiring is still preserved in old houses, but it is recommended to replace it during a major overhaul. In addition, aluminum electrical wire crumbles at the bends and has less conductivity at the joints. Bare parts of aluminum quickly oxidize in air, which leads to significant losses of electricity at the junctions.

Calculator

Today, specialists use not only a table, but also a special calculator to determine the cross section. This calculation greatly simplifies the calculations. The calculator is easy to find on the Internet. To calculate the size by section, you need to know the following parameters:

• alternating or direct current is used;
• wire material;
• power of all used devices;
• network voltage;
• power supply system (one or three-phase);
• wiring type.

These indicators are loaded into the calculator and the required wire cross-sectional value is obtained.

Length calculation

It is important to calculate the cross-section along the length in the construction of industrial-scale networks, when sections are subjected to constant heavy load, and the cable must be pulled over considerable distances. After all, during the passage of current through the wires, power losses occur due to electrical resistance in the circuit. The power loss (dU) is calculated as follows:

dU = I*p*L/S, where:

• I - current strength;
• p - resistivity (copper - 0.0175, aluminum - 0.0281);
• L is the cable length;
• S is the cross-sectional area already calculated by us.

According to the specifications, the maximum voltage drop along the length of the wire should not exceed 5 percent. Otherwise, you should choose a wire with a larger cross section.

Peculiarities

There are certain standards according to which the cable is calculated according to the cross section. If you are not sure which electrical wire is needed, then you can use these rules: electrical appliances in the apartment are divided into a lighting group and the rest; for powerful electrical appliances, for example, washing machines or electric ovens, a connection from separate wires is used; the standard wire section for the lighting group in the apartment is 1.5 mm 2, and for the rest of the wires - 2.5 mm 2. Such standards are used because the rated input power cannot be greater.

Three-phase current is required when high power production value appliances are used. Therefore, to determine the cable cross-section at enterprises, it is necessary to accurately calculate all additional factors, and it is also necessary to take into account power losses and voltage fluctuations. For electrical work in an apartment or a private house, such complex calculations are not carried out.

For the installation of acoustic equipment, wires with minimal resistance are used. This is necessary in order to remove distortion as much as possible and improve the quality of the transmitted signal. Therefore, cables 2x2.5 or 2x1.5 with a length of at least 3 meters are better suited for acoustic systems, and the subwoofer is connected with the shortest cable 2.5-4 mm 2.

Examples

Consider the general scheme for choosing the cable section in the apartment:

• First you need to determine the places where sockets and lighting fixtures will be located;
• Next, you need to determine which devices will be used at each output;
• Now you can draw up a general connection diagram and calculate the cable length, adding at least 2 cm to the wire connections;
• Based on the data obtained, we consider the size of the cable section according to the formulas given above.

I \u003d 2400W / 220V \u003d 10.91A, round up and get 11A.

As we already know, different coefficients are used to accurately determine the cross-sectional area, but almost all of this data refers to a network with a voltage of 380V. To increase the safety margin, add another 5A to our current value:

For apartments, three-core cables are used. The table will show a current value close to our 16A, it will be 19A. We get that to install one washing machine, a wire with a cross section of at least 2 mm 2 is required.

General theory

To determine the optimal cable cross-section for domestic needs, in the general case, the following rules are used:

• sockets require wires with a cross section of 2.5 mm²;
• for lighting - 1.5 mm²;
• for devices with increased power - 4-6 mm².

If there are doubts about the calculation of the cross section, then the PUE table is used. To determine the exact data on the cable cross-section, all factors affecting the passage of current through the circuit are taken into account. These include:

• type of wire insulation;
• the length of each section;
• laying method;
• temperature regime;
• humidity;
• permissible value of overheating;
• power difference of current receivers in one group.

All these indicators allow to increase the efficiency of energy use on an industrial scale, as well as to avoid overheating.

Section selection. Video

In this video, the master shares his experience in choosing the cable section and the nominal value of the machine. He points out possible mistakes and gives practical advice to beginners.

If after reading the article there are still some doubts, then the table or calculator described above will help you find the exact cross section of the wire in terms of power.

Standard apartment wiring is calculated for a maximum current consumption at a continuous load of 25 amperes (a circuit breaker is also selected for this current strength, which is installed at the input of wires to the apartment) is carried out with a copper wire with a cross section of 4.0 mm 2, which corresponds to a wire diameter of 2.26 mm and load power up to 6 kW.

According to the requirements of clause 7.1.35 of the PUE the cross section of the copper core for residential wiring must be at least 2.5 mm 2, which corresponds to a conductor diameter of 1.8 mm and a load current of 16 A. Electrical appliances with a total power of up to 3.5 kW can be connected to such wiring.

What is wire cross section and how to determine it

To see the cross section of the wire, it is enough to cut it across and look at the cut from the end. The cut area is the cross section of the wire. The larger it is, the more current the wire can transmit.

As can be seen from the formula, the cross section of the wire is light in its diameter. It is enough to multiply the diameter of the wire core by itself and by 0.785. For the cross section of a stranded wire, you need to calculate the cross section of one core and multiply by their number.

The conductor diameter can be determined with a vernier caliper to the nearest 0.1 mm or a micrometer to the nearest 0.01 mm. If there are no instruments at hand, then in this case an ordinary ruler will help out.

Section selection
copper wire electrical wiring by current strength

The magnitude of the electric current is indicated by the letter " A” and is measured in Amperes. When choosing, a simple rule applies, the larger the cross section of the wire, the better, so the result is rounded up.

Table for selecting the cross section and diameter of the copper wire depending on the current strength
Maximum current, A	1,0	2,0	3,0	4,0	5,0	6,0	10,0	16,0	20,0	25,0	32,0	40,0	50,0	63,0
Standard section, mm 2	0,35	0,35	0,50	0,75	1,0	1,2	2,0	2,5	3,0	4,0	5,0	6,0	8,0	10,0
Diameter, mm	0,67	0,67	0,80	0,98	1,1	1,2	1,6	1,8	2,0	2,3	2,5	2,7	3,2	3,6

The data I have given in the table are based on personal experience and guarantee the reliable operation of electrical wiring under the most unfavorable conditions for its installation and operation. When choosing a wire cross-section according to the magnitude of the current, it does not matter whether it is alternating current or direct current. The magnitude and frequency of the voltage in the electrical wiring also do not matter, it can be an on-board network of a DC car at 12 V or 24 V, an aircraft at 115 V at a frequency of 400 Hz, an electrical wiring at 220 V or 380 V at a frequency of 50 Hz, a high-voltage power line at 10,000 IN.

If the current consumption of an electrical appliance is unknown, but the supply voltage and power are known, then you can calculate the current using the online calculator below.

It should be noted that at frequencies above 100 Hz in the wires, when an electric current flows, the skin effect begins to appear, which means that as the frequency increases, the current begins to “press” against the outer surface of the wire and the actual cross section of the wire decreases. Therefore, the choice of wire cross-section for high-frequency circuits is performed according to other laws.

Determination of the load capacity of electrical wiring 220 V
made of aluminum wire

In older homes, electrical wiring is usually made of aluminum wires. If the connections in the junction boxes are made correctly, the service life of aluminum wiring can be up to a hundred years. After all, aluminum practically does not oxidize, and the life of the electrical wiring will be determined only by the life of the plastic insulation and the reliability of the contacts at the points of connection.

In the case of connecting additional energy-intensive electrical appliances in an apartment with aluminum wiring, it is necessary to determine the ability of it to withstand additional power by the cross section or diameter of the wire cores. The table below makes this easy.

If your wiring in your apartment is made of aluminum wires and it became necessary to connect the newly installed socket in the junction box with copper wires, then such a connection is made in accordance with the recommendations of the article Connecting aluminum wires.

Calculation of the cross section of the electrical wiring
by power of connected electrical appliances

To select the cross section of the cable wires when laying electrical wiring in an apartment or house, it is necessary to analyze the fleet of existing household appliances in terms of their simultaneous use. The table provides a list of popular household electrical appliances with an indication of the current consumption depending on the power. You can find out the power consumption of your models yourself from the labels on the products themselves or passports, often the parameters are indicated on the packaging.

If the strength of the current consumed by the electrical appliance is unknown, then it can be measured using an ammeter.

Table of power consumption and current strength of household electrical appliances
at supply voltage 220 V

Typically, the power consumption of electrical appliances is indicated on the case in watts (W or VA) or kilowatts (kW or kVA). 1 kW=1000 W.

Table of power consumption and current strength of household electrical appliances
household appliance	Power consumption, kW (kVA)	Consumed current, A	Current consumption mode
Incandescent light bulb	0,06 – 0,25	0,3 – 1,2	Constantly
Electric kettle	1,0 – 2,0	5 – 9	Up to 5 minutes
electric stove	1,0 – 6,0	5 – 60	Depends on operating mode
Microwave	1,5 – 2,2	7 – 10	Periodically
Electric meat grinder	1,5 – 2,2	7 – 10	Depends on operating mode
Toaster	0,5 – 1,5	2 – 7	Constantly
Grill	1,2 – 2,0	7 – 9	Constantly
coffee grinder	0,5 – 1,5	2 – 8	Depends on operating mode
Coffee maker	0,5 – 1,5	2 – 8	Constantly
Electric oven	1,0 – 2,0	5 – 9	Depends on operating mode
Dishwasher	1,0 – 2,0	5 – 9
Washing machine	1,2 – 2,0	6 – 9	Maximum from the moment of inclusion before heating of water
Dryer	2,0 – 3,0	9 – 13	Constantly
Iron	1,2 – 2,0	6 – 9	Periodically
Vacuum cleaner	0,8 – 2,0	4 – 9	Depends on operating mode
Heater	0,5 – 3,0	2 – 13	Depends on operating mode
Hair dryer	0,5 – 1,5	2 – 8	Depends on operating mode
Air conditioner	1,0 – 3,0	5 – 13	Depends on operating mode
Desktop computer	0,3 – 0,8	1 – 3	Depends on operating mode
Power tools (drill, jigsaw, etc.)	0,5 – 2,5	2 – 13	Depends on operating mode

The current is also consumed by a refrigerator, lighting devices, a radiotelephone, chargers, and a TV in standby condition. But in total, this power is no more than 100 W and can be ignored in calculations.

If you turn on all the electrical appliances in the house at the same time, then you will need to select a wire section that can pass a current of 160 A. You will need a wire as thick as a finger! But such a case is unlikely. It is hard to imagine that someone is able to grind meat, iron, vacuum and dry hair at the same time.

Calculation example. You got up in the morning, turned on the electric kettle, microwave, toaster and coffee maker. The current consumption, respectively, will be 7 A + 8 A + 3 A + 4 A = 22 A. Taking into account the included lighting, refrigerator and in addition, for example, a TV, the current consumption can reach 25 A.

for 220 V network

You can choose the wire section not only by the current strength, but also by the amount of power consumption. To do this, you need to compile a list of all electrical appliances planned for connection to this section of electrical wiring, determine how much power each of them consumes separately. Then add the data obtained and use the table below.

for 220 V network
Appliance power, kW (kBA)	0,1	0,3	0,5	0,7	0,9	1,0	1,2	1,5	1,8	2,0	2,5	3,0	3,5	4,0	4,5	5,0	6,0
Standard section, mm 2	0,35	0,35	0,35	0,5	0,75	0,75	1,0	1,2	1,5	1,5	2,0	2,5	2,5	3,0	4,0	4,0	5,0
Diameter, mm	0,67	0,67	0,67	0,5	0,98	0,98	1,13	1,24	1,38	1,38	1,6	1,78	1,78	1,95	2,26	2,26	2,52

If there are several electrical appliances and for some the current consumption is known, and for others the power, then you need to determine the wire cross-section for each of them from the tables, and then add the results.

Selection of the copper wire cross-section by power
for 12 V vehicle electrical system

If, when connecting additional equipment to the vehicle's on-board network, only its power consumption is known, then you can determine the cross-section of additional electrical wiring using the table below.

Table for selecting the cross section and diameter of copper wire by power for on-board vehicle network 12 V
Appliance power, watt (BA)	10	30	50	80	100	200	300	400	500	600	700	800	900	1000	1100	1200
Standard section, mm 2	0,35	0,5	0,75	1,2	1,5	3,0	4,0	6,0	8,0	8,0	10	10	10	16	16	16
Diameter, mm	0,67	0,5	0,8	1,24	1,38	1,95	2,26	2,76	3,19	3,19	3,57	3,57	3,57	4,51	4,51	4,51

The choice of wire cross-section for connecting electrical appliances
to a three-phase network 380 V

During the operation of electrical appliances, for example, an electric motor connected to a three-phase network, the consumed current no longer flows through two wires, but through three, and, therefore, the amount of current flowing in each individual wire is somewhat less. This allows you to use a smaller wire for connecting electrical appliances to a three-phase network.

To connect electrical appliances to a three-phase network with a voltage of 380 V, for example, an electric motor, the wire cross-section for each phase is taken 1.75 times less than for connecting to a single-phase network of 220 V.

Attention, when choosing the wire section for connecting the electric motor in terms of power, it should be taken into account that the maximum mechanical power that the motor can create on the shaft, and not the consumed electric power, is indicated on the nameplate of the electric motor. The electric power consumed by the electric motor, taking into account the efficiency and cos φ, is approximately two times greater than that generated on the shaft, which must be taken into account when choosing the wire section based on the motor power indicated on the plate.

For example, you need to connect an electric motor that consumes power from a network of 2.0 kW. The total current consumption by an electric motor of such power in three phases is 5.2 A. According to the table, it turns out that a wire with a cross section of 1.0 mm 2 is needed, taking into account the above 1.0 / 1.75 = 0.5 mm 2. Therefore, to connect a 2.0 kW electric motor to a 380 V three-phase network, you will need a three-core copper cable with a cross section of each core of 0.5 mm 2.

It is much easier to choose the wire cross-section for connecting a three-phase motor, based on the amount of current it consumes, which is always indicated on the nameplate. For example, in the nameplate shown in the photograph, the current consumption of a motor with a power of 0.25 kW for each phase at a supply voltage of 220 V (motor windings are connected according to the "triangle" scheme) is 1.2 A, and at a voltage of 380 V (motor windings are connected according to “star” scheme) is only 0.7 A. Taking the current strength indicated on the nameplate, according to the table for selecting the wire cross section for apartment wiring, we select a wire with a cross section of 0.35 mm 2 when connecting the motor windings according to the “triangle” scheme or 0.15 mm 2 when connected according to the "star" scheme.

About choosing a brand of cable for home wiring

At first glance, it seems cheaper to make residential electrical wiring from aluminum wires, but operating costs due to the low reliability of contacts over time will many times exceed the costs of electrical wiring from copper. I recommend doing wiring exclusively from copper wires! Aluminum wires are indispensable for overhead wiring, as they are light and cheap, and when properly connected, they last reliably for a long time.

And which wire is better to use when installing electrical wiring, single-core or multi-core? From the point of view of the ability to conduct current per unit section and installation, single-core is better. So for home wiring, you need to use only single-core wire. Stranded allows multiple bends, and the thinner the conductors in it, the more flexible and durable it is. Therefore, a stranded wire is used to connect non-stationary electrical appliances to the mains, such as an electric hair dryer, an electric razor, an electric iron and all the others.

After making a decision on the cross section of the wire, the question arises about the brand of cable for electrical wiring. Here the choice is not great and is represented by only a few brands of cables: PUNP, VVGng and NYM.

PUNP cable since 1990, in accordance with the decision of the Glavgosenergonadzor “On the prohibition of the use of wires of the type APVN, PPBN, PEN, PUNP, etc., produced according to TU 16-505. 610-74 instead of APV, APPV, PV and PPV wires in accordance with GOST 6323-79 * "is prohibited for use.

Cable VVG and VVGng - copper wires in double PVC insulation, flat shape. Designed for operation at ambient temperature from -50°C to +50°C, for wiring inside buildings, outdoors, in the ground when laying in tubes. Service life up to 30 years. The letters "ng" in the brand designation indicate the incombustibility of the wire insulation. Two-, three- and four-core are produced with a cross-section of cores from 1.5 to 35.0 mm 2. If in the designation of the cable before VVG there is the letter A (AVVG), then the conductors in the wire are aluminum.

The NYM cable (its Russian analogue is the VVG cable), with copper conductors, round shape, with non-combustible insulation, complies with the German standard VDE 0250. Technical characteristics and scope are almost the same as the VVG cable. Two-, three- and four-core are produced with a cross-section of cores from 1.5 to 4.0 mm 2.

As you can see, the choice for wiring is not great and is determined depending on which shape of the cable is more suitable for installation, round or flat. A round-shaped cable is more convenient to lay through walls, especially if input is made from the street into the room. You will need to drill a hole slightly larger than the diameter of the cable, and with a larger wall thickness this becomes relevant. For internal wiring, it is more convenient to use a VVG flat cable.

Parallel connection of electrical wiring

There are hopeless situations when you urgently need to lay the wiring, but the wires of the required section are not available. In this case, if there is a wire of a smaller section than necessary, then the wiring can be made from two or more wires by connecting them in parallel. The main thing is that the sum of the sections of each of them should not be less than the calculated one.

For example, there are three wires with a cross section of 2, 3 and 5 mm 2, but according to calculations, 10 mm 2 is needed. Connect them all in parallel, and the wiring will withstand current up to 50 amperes. Yes, you yourself have repeatedly seen the parallel connection of a larger number of thin conductors for the transmission of large currents. For example, a current of up to 150 A is used for welding, and in order for the welder to control the electrode, a flexible wire is needed. It is made from hundreds of thin copper wires connected in parallel. In a car, the battery is also connected to the on-board network using the same flexible stranded wire, since during the engine start, the starter consumes up to 100 A from the battery. And when installing and removing the battery, it is necessary to take the wires to the side, that is, the wire must be flexible enough .

The method of increasing the cross section of an electrical wire by connecting several wires of different diameters in parallel can only be used as a last resort. When laying home electrical wiring, it is permissible to connect in parallel only wires of the same cross section, taken from one bay.

Online calculators for calculating the cross section and diameter of the wire

Using the online calculator below, you can solve the inverse problem - determine the diameter of the conductor from the cross section.

How to calculate the cross section of a stranded wire

Stranded wire, or as it is also called stranded or flexible, is a single-core wire twisted together. To calculate the cross section of a stranded wire, you must first calculate the cross section of one wire, and then multiply the result by their number.

Consider an example. There is a stranded flexible wire, in which there are 15 cores with a diameter of 0.5 mm. The cross section of one core is 0.5 mm × 0.5 mm × 0.785 \u003d 0.19625 mm 2, after rounding we get 0.2 mm 2. Since we have 15 wires in the wire, to determine the cross section of the cable, we need to multiply these numbers. 0.2 mm 2 ×15=3 mm 2 . It remains to determine from the table that such a stranded wire can withstand a current of 20 A.

It is possible to evaluate the load capacity of a stranded wire without measuring the diameter of an individual conductor by measuring the total diameter of all stranded wires. But since the wires are round, there are air gaps between them. To exclude the area of ​​​​the gaps, the result of the wire section obtained by the formula should be multiplied by a factor of 0.91. When measuring the diameter, make sure that the stranded wire is not flattened.

Let's look at an example. As a result of measurements, the stranded wire has a diameter of 2.0 mm. Let's calculate its cross section: 2.0 mm × 2.0 mm × 0.785 × 0.91 = 2.9 mm 2. According to the table (see below), we determine that this stranded wire will withstand a current of up to 20 A.