Electrical wiring in modern apartments provides for a maximum operating current in the network of up to 25 Amperes. The circuit breakers installed in the apartment's distribution board are also designed for this parameter. The cross-section of the wire at the entrance to the room must be at least 4 mm2. When installing internal wiring, it is permissible to use cables with a cross-section of 2.5 mm2, which are designed for a current of 16 Amps.
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Wire diameter measurement
According to the standard, the diameter of the wire must correspond to the declared parameters, which are described in the marking. But the actual size may differ from the declared one by 10-15 percent. This is especially true for cables that are manufactured by small companies, but large manufacturers can also have problems. Before purchasing an electrical wire for transmitting large currents, it is recommended to measure the diameter of the conductor. For this purpose, various methods can be used, differing in error. Before performing measurements, it is necessary to remove insulation from the cable cores.
Measurements can be made directly in the store if the seller allows you to remove the insulation from a small section of the wire. Otherwise, you will have to purchase a small piece of cable and take measurements on it.
Micrometer
Maximum accuracy can be achieved using micrometers that have a mechanical and electronic circuit. On the shaft of the instrument there is a scale with a division value of 0.5 mm, and on the circle of the drum there are 50 marks with a division value of 0.01 mm. The characteristics are the same for all micrometer models.
When working with a mechanical device, the following sequence of actions should be followed:
- By rotating the drum, the gap between the screw and the heel is set close to the measured size.
- Use a ratchet to bring the screw closer to the surface of the part being measured. The eyeliner is performed by rotating the hand without effort until the ratchet operates.
- Calculate the transverse diameter of the part according to the readings on the scales located on the stem and drum. The diameter of the product is equal to the sum of the values on the rod and the drum.
Mechanical micrometer measurement
Working with an electronic micrometer does not require rotation of the units; it displays the diameter value on the liquid crystal screen. It is recommended to check the settings before using the device as electronic devices measure in millimeters and inches.
Vernier caliper
The device has reduced accuracy compared to a micrometer, which is quite sufficient for measuring a conductor. Vernier calipers are equipped with a flat scale (vernier), a circular dial or a digital display on a liquid crystal display.
To measure the transverse diameter, you must:
- Clamp the conductor to be measured between the jaws of the caliper.
- Calculate the value on the scale or view it on the display.
An example of calculating size on a vernier
Ruler
Measuring with a ruler gives a rough result. To perform measurements, it is recommended to use tool rulers, which have greater accuracy. Using wooden and plastic school products will give a very approximate diameter value.
To measure with a ruler you need:
- Remove insulation from a piece of wire up to 100 mm long.
- Wind the resulting piece tightly around a cylindrical object. The turns must be complete, that is, the beginning and end of the wire in the winding are directed in one direction.
- Measure the length of the resulting winding and divide by the number of turns.
Measuring the diameter with a ruler by the number of turns
In the example above there are 11 turns of wire which are about 7.5mm in length. By dividing the length by the number of turns, you can determine the approximate value of the diameter, which in this case is 0.68 mm.
On the websites of stores selling electrical wires, there are online calculators that allow you to calculate the cross-section based on the number of turns and the length of the resulting spiral.
Determination of cross-section by diameter
After determining the diameter of the wire, you can begin to calculate the cross-sectional area in squares (mm2). For cables of the VVG type, consisting of three single-core conductors, calculation methods are used using a formula or a ready-made table of diameters and areas. The methods are also applicable to products with other markings.
According to the formula
The main method is to calculate using a formula of the form - S=(n/4)*D2, where π=3.14, and D is the measured diameter. For example, to calculate the area with a diameter of 1 mm, you will need to calculate the value: S=(3.14/4)*1²=0.785 mm2.
Online calculators are available on the Internet that allow you to calculate the area of a circle by diameter. Before purchasing a cable, it is recommended to calculate the values in advance, put them in a table and use it in the store.
The video from user Alexander Kvasha demonstrates checking the cross-section of wire cores.
According to the table with common diameters
To simplify the calculation, it is convenient to use a ready-made table.
The order of using numbers from the table:
- Select the type of wire that you intend to purchase, for example, VVG 3*4.
- Determine the diameter from the table - a section of 4 mm2 corresponds to a diameter of 2.26 mm.
- Check the actual wire diameter. If there is a match, the products can be purchased.
Below is a table of the ratio of cross-sections of the main types of copper wiring to diameters and current (at a voltage of 220 V).
An additional criterion for matching the cross-section to the diameter is the weight of the wire. The method of determining diameter by weight is used when testing thin wire for winding transformers. The thickness of the product starts from 0.1 mm, and it is difficult to measure it with a micrometer.
A brief table of correspondence between vein diameters and weight is given below. Detailed data is available in stores specializing in the sale of electronic components.
| Diameter, mm | Section, mm2 | Weight, g/km |
| 0,1 | 0,0079 | 70 |
| 0,15 | 0,0177 | 158 |
| 0,2 | 0,0314 | 281 |
| 0,25 | 0,0491 | 438 |
| 0,3 | 0,0707 | 631 |
| 0,35 | 0,0962 | 859 |
| 0,4 | 0,1257 | 1,122 |
When calculating the wire diameter for fuses, the conductor material should be taken into account. A brief table of cable diameters from common types of material and current strength is given below.
| Break current, A | Copper | Aluminum | Nikelin | Iron | Tin | Lead |
| 0,5 | 0,03 | 0,04 | 0,05 | 0,06 | 0,11 | 0,13 |
| 1 | 0,05 | 0,07 | 0,08 | 0,12 | 0,18 | 0,21 |
| 5 | 0,16 | 0,19 | 0,25 | 0,35 | 0,53 | 0,60 |
| 10 | 0,25 | 0,31 | 0,39 | 0,55 | 0,85 | 0,95 |
| 15 | 0,32 | 0,40 | 0,52 | 0,72 | 1,12 | 1,25 |
| 25 | 0,46 | 0,56 | 0,73 | 1,00 | 1,56 | 1,75 |
| 50 | 0,73 | 0,89 | 1,15 | 1,60 | 2,45 | 2,78 |
| 100 | 1,15 | 1,42 | 1,82 | 2,55 | 3,90 | 4,40 |
| 200 | 1,84 | 2,25 | 2,89 | 4,05 | 6,20 | 7,00 |
| 300 | 2,40 | 2,95 | 3,78 | 5,30 | 8,20 | 9,20 |
For multi-core cable
The diameter of a multi-core cable is determined by the cross-sectional size of one conductor multiplied by their number. The main problem is measuring the diameter of a thin wire.
An example is a cable consisting of 25 cores with a diameter of 0.2 mm. According to the above formula, the cross-section is equal to: S=(3.14/4)*0.2²=0.0314 mm2. With 25 cores it will be: S=0.0314*25=0.8 mm2. Then, using the correspondence tables, it is determined whether it is suitable for transmitting the current of the required strength or not.
Another way to approximately calculate the current strength is to multiply the diameter of a multi-core cable by an adjustment factor of 0.91. The coefficient provides for a non-monolithic wire structure and air gaps between the turns. The outer diameter is measured with little effort, since the surface is easily deformed and the cross-section becomes oval.
When calculating the segment part of the cable, formulas or table values are used. The table shows the standard values for segment width and height.
Photo gallery
Segment cable (far right) 
Cable segment
Table of power consumption of electrical appliances
A common way to determine the required wire cross-section is the peak power calculation method. In order to find out the load, you can use a standard table that summarizes the parameters of power and peak current consumption for household appliances.
| Device type | power, kWt | Peak current, A | Consumption mode |
| Standard incandescent lamp | 0,25 | 1,2 | Constant |
| Kettle with electric heater | 2,0 | 9,0 | Short-term up to 5 minutes |
| Electric stove with 2-4 burners | 6,0 | 60,0 | |
| Microwave | 2,2 | 10,0 | Periodic |
| Electric meat grinder | Likewise | Likewise | Depends on intensity of use |
| Toaster | 1,5 | 7,0 | Constant |
| Electric coffee grinder | 1,5 | 8,0 | Depends on intensity of use |
| Grill | 2,0 | 9,0 | Constant |
| Coffee maker | 1,5 | 8,0 | Constant |
| Separate electric oven | 2,0 | 9,0 | Depends on intensity of use |
| Dishwashing machine | 2,0 | 9,0 | Periodic (for the period of heater operation) |
| Washing machine | 2,0 | 9,0 | Likewise |
| Dryer | 3,0 | 13,0 | Constant |
| Iron | 2,0 | 9,0 | Periodic (for the period of operation of the heating coil) |
| Vacuum cleaner | Likewise | Likewise | Depends on intensity of use |
| Oil heater | 3,0 | 13,0 | Likewise |
| Hairdryer | 1,5 | 8,0 | Likewise |
| Air conditioner | 3,0 | 13,0 | Likewise |
| Computer system unit | 0,8 | 3,0 | Likewise |
| Electric Motor Driven Tools | 2,5 | 13,0 | Likewise |
The current will be consumed by the refrigerator, electrical appliances in standby condition (TVs, radiotelephones), chargers. The total value of power consumption by devices is considered to be within 0.1 kW.
When connecting all available household appliances, the current can reach 100-120 A. This connection option is unlikely, therefore, when calculating the load, common connection combinations are taken into account.
For example, in the morning the following can be used:
- electric kettle - 9.0 A;
- microwave oven - 10.0 A;
- toaster - 7 A;
- coffee grinder or coffee maker - 8 A;
- other household appliances and lighting - 3 A.
The total consumption of devices can reach: 9+10+7+8+3=37 A. There are also calculators that allow you to calculate the current based on power consumption and voltage.
Cable selection according to tables of maximum current in the network
Two types of data from the table above are used for the calculation:
- by total power;
- by the amount of current consumed by the devices.
There are tables of standard values that allow you to determine the required diameter and cross-section, which are then checked on the purchased wire. The found indicator is rounded up until it matches the actual cable diameter.
In residential premises, wires with excessive cross-section should not be used, as they have high resistance, which leads to a voltage drop.
For copper cable
To calculate a copper conductor, a table compiled for a voltage of 230 V is used.
| power, kWt | Current, A | ||||
| 0,1 | 0,43 | 0,09 | 0,33 | 0,11 | 0,37 |
| 0,5 | 2,17 | 0,43 | 0,74 | 0,54 | 0,83 |
| 1,0 | 4,35 | 0,87 | 1,05 | 1,09 | 1,18 |
| 2,0 | 8,70 | 1,74 | 1,49 | 2,17 | 1,66 |
| 3,0 | 13,04 | 2,61 | 1,82 | 3,26 | 2,04 |
| 4,0 | 17,39 | 3,48 | 2,10 | 4,35 | 2,35 |
| 5,0 | 21,74 | 4,35 | 2,35 | 5,43 | 2,63 |
| 8,0 | 34,78 | 6,96 | 3,16 | 9,78 | 3,53 |
| 10,0 | 43,48 | 8,7 | 3,33 | 10,87 | 3,72 |
For aluminum cable
To calculate aluminum wire, the table below can be used (data taken for a voltage of 230 V).
| power, kWt | Current, A | Area (with external wiring), mm2 | Diameter (for external wiring), mm | Area (with hidden wiring), mm2 | Diameter (with hidden wiring), mm |
| 0,1 | 0,43 | 0,12 | 0,40 | 0,14 | 0,43 |
| 0,5 | 2,17 | 0,62 | 0,89 | 0,72 | 0,96 |
| 1,0 | 4,35 | 1,24 | 1,26 | 1,45 | 1,36 |
| 2,0 | 8,70 | 2,48 | 1,78 | 2,90 | 1,92 |
| 3,0 | 13,04 | 3,73 | 2,18 | 4,35 | 2,35 |
| 4,0 | 17,39 | 4,97 | 2,52 | 5,80 | 2,72 |
| 5,0 | 21,74 | 6,21 | 2,81 | 7,25 | 3,04 |
| 8,0 | 34,78 | 9,94 | 3,56 | 11,59 | 3,84 |
| 10,0 | 43,48 | 12,42 | 3,98 | 14,49 | 4,30 |
Cable selection according to PUE and GOST tables
When purchasing a wire, it is recommended to look at the GOST standard or the technical specifications according to which the product is manufactured. GOST requirements are higher than similar parameters of technical specifications, so you should prefer products made according to the standard.
Tables from the rules for electrical installations (PUE) represent the dependence of the strength of the current transmitted through the conductor on the cross-section of the conductor and the method of installation in the main pipe. The permissible current decreases as the individual cores increase in size or as multi-core cable insulation is used. The phenomenon is associated with a separate clause in the PUE, which stipulates the parameters of the maximum permissible heating of the wires. The main pipe is understood as a box, including a plastic one or when laying wiring in a bundle on a cable tray.
Types of solid wires.
Electric wire- a cable product containing one or more twisted wires or one or more insulated cores, on top of which, depending on the installation and operating conditions, there may be a light non-metallic sheath, winding and (or) braid made of fibrous materials or wire, and is not generally intended for , for laying in the ground.
As a rule, copper or aluminum wire is used as a conductor. The core may consist of several wires (usually twisted) - multi-wire core.
Not to be confused with stranded wire, where each core is an independent wire.
The wire consists of the following elements:
1. A conductor that conducts electric current (copper or aluminum).
2. Insulating shell.
Single core solid wire.
Solid Stranded Wire
A cable is a structure of one or more conductors (cores) insulated from each other, or optical fibers enclosed in a sheath.
Wire classification:
1. winding wires:
copper wires (grades PEV, PEL, PETV-2, PET-155, LELO, LENK, etc.);
high resistance wires (constantan, manganin, nichrome);
2. installation wires (brands MGTF, MGTFE, etc.);
3. connecting wires (brands PVS, PRS, Ball Screw, etc.);
4. output wires (brands PVKV, RKGM, VPP, etc.);
5. wires for rolling stock (brands PPSV, PPSRN, PS, etc.);
6. automobile wires (brands PGVA, PGVAE, PVAM, etc.);
7. aviation wires (brands BPVL, BIF, BIN);
8. installation wires (grades APV, PV1, PV2, PV3, etc.);
9. communication wires (brands PVZh, PPZh, PKSV, etc.);
10. insulated wires for overhead lines (grades SIP-1, SIP-2, SIP-3, etc.);
11. bare wires (grades M, A, AC, etc.);
12. wires for geophysical work (grades GSP, GPMP, etc.);
13. heat-resistant wires (brands PVKV, PAL, PVKF);
Table: wire diameter - wire cross-section
thermoelectrode wires (grades SFK-KhK, PTV-KhK, PTP-KhK, etc.);
15. warm-up wires (brands PNSV, PNPZh, NO-1, etc.).
Parameters of single-core wires
The wires include the following parameters: cross-sectional area, operating voltage and frequency, core material, type of insulation, flexibility, heat resistance, operating temperature range, relative air humidity during operation, wire bending radius, wire color, etc.
Calculation of cable cross-section
The cross-section of the wire can be determined by the diameter of the core. In practice, the diameter of the core without insulation is most often measured with a caliper or micrometer. Knowing the diameter of the core, it is quite easy to determine the cross-section of the wire. To do this, you need to use the wire cross-section formula, which coincides with the usual school formula for calculating the circle area, which is given below.
Calculation example
The warehouse received a single-core single-wire wire PV-1 without markings with a core diameter of 3.57 mm. Let's determine the cross-section of the wire by diameter:
Skr=3.14*3.57^2/4=10 mm2
The nearest standard section is 10mm2. Thus, the PV1 10 wire was delivered to the warehouse.
If the wire is multi-wire, then you need to fluff it up and count the number of wires in the bundle. Determine the diameter of one wire, calculate its cross-sectional area s, then determine the cross-sectional area of the entire wire by adding up the areas of all the wires.
For example: the number of wires in a bundle is 37 pieces; diameter of each wire d = 0.3 mm.
Let us determine the cross-sectional area of one wire.
s = 0.785*d² = 0.785 *0.3*0.3 = 0.070 mm2
Cross-sectional area of the entire stranded wire
S = 37*s = 37*0.070 = 2.59 mm2
Read also:
How to determine the cross-section of a stranded wire by its diameter?
| Sectional area, mm2 | Diameter, mm |
| 0.75 | 1.0 |
| 1 | 1.1 |
| 1.5 | 1.4 |
| 2 | 1.5 |
| 2.5 | 1.8 |
| 4 | 2.3 |
| 6 | 2.8 |
| 10 | 3.6 |
| 16 | 4.5 |
| 25 | 5.6 |
| 35 | 6.7 |
| 50 | 8.0 |
| 70 | 9.5 |
| 95 | 11.0 |
| 120 | 12.4 |
| 150 | 13.8 |
| 185 | 15.4 |
| 240 | 17.5 |
| 300 | 19.5 |
| 400 | 22.6 |
| 500 | 25.2 |
| 630 | 28.3 |
| 800 | 31.9 |
| 1000 | 35.7 |
| 1200 | 39.1 |
| 2000 | 50.5 |
| Sectional area, mm2 | Diameter, mm |
How can you find out the cable cross-section by the diameter of the core?
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When purchasing, you should always pay attention to its actual cross-section, since you can often find cable products in stores with a cross-section that does not correspond to its marking, and significantly so. And this, as you understand, can lead to overheating of the cable and ultimately to a short circuit.
To independently calculate the actual wire cross-section, several simple methods will help us. The most convenient way is to calculate the cross-section of the wire based on its diameter. To do this you will need a micrometer or caliper.
Having measured the diameter of the core, we recall the formula for the area of a circle:
For example, let’s take a wire whose insulation is marked VVGng 3×2.5. We measure the diameter of the core with a caliper - we get 1.7 mm. Next, we substitute this value into the formula:
Skr = 0.785 x 1.7 x 1.7 = 2.27 mm2.
It turns out that the actual cross-section of the wire is 2.27 mm2 instead of the stated 2.5.
Everything is clear with a single-core wire, but what about multi-core?
Everything is about the same here. We take one core from a stranded wire and measure it with a caliper. For example, the diameter turned out to be 0.4 mm.
Skr = 0.785 x 0.4 x 0.4 = 0.125 mm2.
Then we count the total number of veins in the wire, suppose 12.
Now we find out the total cross-section of the wire by multiplying the value of one core 0.125 mm2 by the number of cores - 12.
S = 0.125 x 12 = 1.5mm2- this is the actual cross-section of the wire.
Of course, not everyone has a caliper, much less a micrometer, in which case you will have to go another way.
To do this, we will need a ruler and a pencil, or some kind of round rod, from available means. We remove the insulation from the wire and wind about 10 turns onto the rod. The main thing is that the turns fit tightly to each other, without gaps.
Using a ruler, measure the length of the winding and divide by the number of turns. We get the diameter of the core. And then, using the same formula, we find the cross-section of the core. The method is quite accurate, but not very convenient - and you can’t measure it in a store this way and you can’t wind thick wires.
In order not to calculate the cross-section each time on a calculator, below I will post a table of the correspondence of diameters and cross-sections of wires, which contains the most common sizes. You can rewrite it or print it out and take it with you to the store. All that remains is to measure the diameter of the core and compare it with the value from the table. If the measured value differs significantly from the table, then it is better not to buy such a cable.
The most important thing when installing electrical wiring is to choose a high-quality cable, because you can always easily replace a socket or switch, but replacing a burnt-out cable will be difficult, not to mention what consequences this may have. Very often, the cable cross-section differs from that declared by the manufacturer, because reducing the cross-section allows unscrupulous manufacturers to save on the most expensive component - copper. To avoid becoming a victim of deception, it is advisable to measure its cross-section yourself before purchasing a cable, and we will tell you how to determine the cable cross-section by diameter in three simple ways in this article.
Method No. 1 - using a caliper or micrometer
Using a caliper or micrometer, measure the diameter of the conductive cable core stripped of insulation. It is advisable to take measurements on several sections of the core, as well as on all cable cores, and record the lowest values. If you take measurements using a micrometer, then the measurement must be made on a flat section of the core, so the indicators will be more accurate.
As you know from a school mathematics course, the area of a circle (and in our case it will be the cross-sectional area of the cable) is calculated by the formula S = πR² and if this formula is simplified by dividing the number π by 4, the result is a formula by which you can determine the cross-section of the cable by diameter:
Method number 2 - using a ruler
What to do if you don’t have a caliper at hand, or even a micrometer, how can you determine the cable cross-section by diameter without these tools? The old and proven method of measuring using a ruler and pencil will come to the rescue.
The principle of measurement using this method is as follows: the cleaned core is wound around a pencil, as shown in the figure below. The minimum number of turns should be 15-20, but here you also need to take into account the thickness of the conductor; if it is too thin, it is advisable to wind more turns.
To reduce measurement error, the turns need to be wound as tightly as possible. Next, using a ruler, measure the length of the wound wire and divide it by the number of turns, we get the diameter of the core, everything is simple.
Using the formula we already know, we determine the cable cross-section by diameter. For clarity, let's give an example: let's say we wound 20 turns of wire, and got a result of 19.6 mm, divide this number by the number of turns of 20, and get a diameter of 0.98 mm. Using the formula, we calculate: 0.785*0.98*0.98=0.753914 mm², round it up, and get 0.75 squares.
The disadvantage of this method of determining the cross-section of a cable by diameter is that it will be difficult to wind a wire with a large cross-section, but for small cross-sections this method, on the contrary, will give a more accurate result. In addition, you will probably need to buy a piece of wire for testing, because no seller will allow such experiments to be carried out at their place.
Method number 3 - using a table
The easiest way to determine the cable cross-section is by diameter, but you will still need a measuring tool - a caliper or micrometer. We measure the thickness of the diameter of the core, and using the table we determine the cross-section.
| Conductor diameter, mm | Cable cross-section, mm.sq. |
| 0,80 | 0,5 |
| 0,98 | 0,75 |
| 1,13 | 1,0 |
| 1,38 | 1,5 |
| 1,60 | 2,0 |
| 1,78 | 2,5 |
| 2,26 | 4,0 |
| 2,76 | 6,0 |
| 3,57 | 10,0 |
| 4,51 | 16,0 |
| 5,64 | 25,0 |
| 6,68 | 35,0 |
| 7,98 | 50,0 |
| 9,44 | 70,0 |
| 11,00 | 95,0 |
| 12,36 | 120,0 |
| 13,82 | 150,0 |
| 15,35 | 185,0 |
| 17,48 | 240,0 |
| 19,54 | 300,0 |
| 22,57 | 400,0 |
In conclusion, it must be said that it is also important to pay attention to the composition of the current-carrying core; most often, wires and cables with a copper core are counterfeited. Buy cable products from a trusted seller. Our store sells only high-quality, certified products from trusted domestic manufacturers. If you want to ask a question related to the choice of cable products, then you can always consult with our consultants, just contact us via
Standard apartment wiring is calculated for a maximum current consumption at a continuous load of 25 amperes (the circuit breaker that is installed at the entrance of wires into the apartment is also selected for this current strength) and is carried out with 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 electrical 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 electrical wiring.
What is wire cross-section and how to determine it
To see the cross-section of the wire, just 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 according to 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 diameter of the conductor can be determined using a caliper with an accuracy of 0.1 mm or a micrometer with an accuracy of 0.01 mm. If there are no instruments at hand, then 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 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 provided in the table is based on personal experience and guarantees reliable operation of electrical wiring under the most unfavorable conditions of its installation and operation. When choosing a wire cross-section based on the current value, it does not matter whether it is alternating current or direct current. The magnitude and frequency of the voltage in the electrical wiring also does not matter; it can be the on-board network of a DC car at 12 V or 24 V, an aircraft at 115 V with a frequency of 400 Hz, electrical wiring 220 V or 380 V with 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 the current can be calculated using the online calculator below.
It should be noted that at frequencies above 100 Hz, a skin effect begins to appear in wires when electric current flows, which means that with increasing frequency, 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 carried out according to different laws.
Determining the load capacity of 220 V electrical wiring
made of aluminum wire
In houses built a long time ago, electrical wiring is usually made of aluminum wires. If connections in junction boxes are made correctly, the service life of aluminum wiring can be one hundred years. After all, aluminum practically does not oxidize, and the service life of electrical wiring will be determined only by the service life of the plastic insulation and the reliability of the contacts at the connection points.
In the case of connecting additional energy-intensive electrical appliances in an apartment with aluminum wiring, it is necessary to determine by the cross-section or diameter of the wire cores its ability to withstand additional power. Using the table below, this is easy to do.
If your apartment wiring is made of aluminum wires and there is a need to connect a newly installed socket in a junction box with copper wires, then such a connection is made in accordance with the recommendations of the article Connecting aluminum wires.
Calculation of electrical wire cross-section
according to the power of connected electrical appliances
To select the cross-section of cable wire cores when laying electrical wiring in an apartment or house, you need to analyze the fleet of existing electrical household appliances from the point of view of their simultaneous use. The table provides a list of popular household electrical appliances indicating 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 data sheets; often the parameters are indicated on the packaging.
If the current consumed by an electrical appliance is unknown, it can be measured using an ammeter.
Table of power consumption and current for household electrical appliances
at supply voltage 220 V
Typically, the power consumption of electrical appliances is indicated on the housing in watts (W or VA) or kilowatts (kW or kVA). 1 kW=1000 W.
| Table of power consumption and current for household electrical appliances | |||
|---|---|---|---|
| Household electrical appliance | Power consumption, kW (kVA) | Current consumption, 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 switching on until the water is heated |
| 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 |
Current is also consumed by the refrigerator, lighting fixtures, radiotelephone, chargers, and TV in standby mode. 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, you will need to select a wire cross-section capable of passing a current of 160 A. You will need a finger-thick wire! But such a case is unlikely. It’s hard to imagine that someone is capable of grinding meat, ironing, vacuuming and drying 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 will accordingly be 7 A + 8 A + 3 A + 4 A = 22 A. Taking into account the switched on lighting, refrigerator and, in addition, for example, a TV, the current consumption can reach 25 A.
for 220 V network
You can select the wire cross-section not only by the current strength, but also by the amount of power consumed. To do this, you need to make a list of all electrical appliances planned to be connected to a given section of electrical wiring, and determine how much power each of them consumes separately. Next, add up the data obtained and use the table below.
for 220 V network |
|||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Electrical 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 up the results.
Selecting the cross-section of copper wire according to power
for the car's on-board network 12 V
If, when connecting additional equipment to the vehicle’s on-board network, only its power consumption is known, then the cross-section of the additional electrical wiring can be determined using the table below.
| Table for choosing the cross-section and diameter of copper wire according to power for vehicle on-board network 12 V |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Electrical 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 |
Selecting the wire cross-section for connecting electrical appliances
to a three-phase network 380 V
When operating 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 cross-section wire to connect 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 smaller than for connecting to a single-phase 220 V network.
Attention, when choosing a wire cross-section for connecting an electric motor based on power, it should be taken into account that the nameplate of the electric motor indicates the maximum mechanical power that the motor can create on the shaft, and not the electrical power consumed. The electrical power consumed by the electric motor, taking into account efficiency and cos φ, is approximately two times greater than that created on the shaft, which must be taken into account when choosing the wire cross-section based on the motor power indicated in the plate.
For example, you need to connect an electric motor that consumes power from a 2.0 kW network. The total current consumption of 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 three-phase 380 V 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 current consumption, 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 (the motor windings are connected in a delta pattern) is 1.2 A, and at a voltage of 380 V (the motor windings are connected in a delta pattern) "star" circuit) is only 0.7 A. Taking the current indicated on the nameplate, using the table for selecting the wire cross-section for apartment wiring, select a wire with a cross-section of 0.35 mm 2 when connecting the electric motor windings according to the "triangle" or 0.15 mm pattern 2 when connected in a star configuration.
About choosing a cable brand for home wiring
Making apartment electrical wiring from aluminum wires at first glance seems cheaper, but operating costs due to low reliability of contacts over time will be many times higher than the costs of electrical wiring made from copper. I recommend making the wiring exclusively from copper wires! Aluminum wires are indispensable when laying overhead electrical wiring, as they are light and cheap and, when properly connected, serve reliably for a long time.
Which wire is better to use when installing electrical wiring, single-core or stranded? From the point of view of the ability to conduct current per unit of cross-section and installation, single-core is better. So for home wiring you only need to use solid wire. Stranded allows multiple bends, and the thinner the conductors in it, the more flexible and durable it is. Therefore, stranded wire is used to connect non-stationary electrical appliances to the electrical network, such as an electric hair dryer, an electric razor, an electric iron and all the others.
After deciding on the cross-section of the wire, the question arises about the brand of cable for electrical wiring. The choice here 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 Glavgosenergonadzor “On the ban on the use of wires such as APVN, PPBN, PEN, PUNP, etc., produced according to TU 16-505. 610-74 instead of APV, APPV, PV and PPV wires according to GOST 6323-79*" is prohibited for use.
Cable VVG and VVGng - copper wires in double polyvinyl chloride insulation, flat shape. Designed for operation at ambient temperatures from −50°С to +50°С, for wiring inside buildings, outdoors, in the ground when laid in tubes. Service life up to 30 years. The letters “ng” in the brand designation indicate the non-flammability of the wire insulation. Two-, three- and four-core wires are available with core cross-sections from 1.5 to 35.0 mm 2 . If in the cable designation there is a letter A (AVVG) before VVG, then the conductors in the wire are aluminum.
The NYM cable (its Russian analogue is the VVG cable), with copper cores, round in shape, with non-flammable insulation, complies with the German standard VDE 0250. Technical characteristics and scope of application are almost the same as the VVG cable. Two-, three- and four-core wires are available with core cross-sections from 1.5 to 4.0 mm 2 .
As you can see, the choice for laying electrical wiring is not large and is determined depending on what shape the cable is more suitable for installation, round or flat. A round-shaped cable is more convenient to lay through walls, especially if the connection 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 wires
There are hopeless situations when you urgently need to lay wiring, but there is no wire of the required cross-section available. In this case, if there is a wire with a smaller cross-section than necessary, then the wiring can be made from two or more wires, connecting them in parallel. The main thing is that the sum of the sections of each of them is not 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 handle up to 50 amps. Yes, you yourself have repeatedly seen the parallel connection of a large number of thin conductors to transmit large currents. For example, welding uses a current of up to 150 A 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 when starting the engine, the starter consumes current from the battery up to 100 A. And when installing and removing the battery, the wires must be taken 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 be used only 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 the same reel.
Online calculators for calculating the cross-section and diameter of a wire
Using the online calculator presented below, you can solve the inverse problem - determine the diameter of the conductor by 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 resulting result by their number.
Let's look at an example. There is a multi-core 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 = 0.19625 mm 2, after rounding we get 0.2 mm 2. Since we have 15 wires in the wire, to determine the cable cross-section 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 will withstand a current of 20 A.
You can estimate the load capacity of a stranded wire without measuring the diameter of an individual conductor by measuring the total diameter of all twisted wires. But since the wires are round, there are air gaps between them. To eliminate the gap area, you need to multiply the result of the wire cross-section obtained from the formula by a factor of 0.91. When measuring the diameter, you need to make sure that the stranded wire does not flatten.
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. Using the table (see below), we determine that this stranded wire will withstand a current of up to 20 A.