How to measure wire thickness with a caliper

You can often find electrical products in supermarkets without tags or identification marks. Among it there could easily be a coil of wire or cable. How do you know if the wire size is appropriate for your specific situation? The answer is simple - measure it or consult the seller.

Anyone who sells cables and wires can tell you what load they can withstand. In addition, inscriptions (numbers) are stamped on the wires, characterizing the cross-section and number of cores. But in real practice, not everything is as simple as it seems. The quality of cable products has recently deteriorated noticeably.

Problems with the quality of manufactured wires

Many manufacturers of cable and wire products, trying to make more money, artificially reduce the thickness of the insulation and increase the diameter of the cable. By specifying a larger wire cross-section than in reality, the manufacturer saves a very large amount. For example, to produce thousands of meters of copper wire with a cross-section of 2.5 mm2, 22.3 kg of copper is required, and to produce a wire of 2.1 mm2, only 18.8 kg is required. This results in a saving of 3.5 kg of copper.

Another way to reduce the cost of products is to manufacture a conductor from low-quality raw materials. When adding cheap impurities, the current conductivity decreases, therefore, cable length calculations must be changed.

Undersized wire cross-section - what is the danger?

So, let's consider the dangers that await us when using low-quality wires in everyday life. It is clear that the current characteristics of current-carrying conductors decrease in direct proportion to the decrease in their cross-section. The load capacity of the wire decreases due to the reduced cross-section. According to the standards, the current that the wire can pass through is calculated. It will not collapse if less current passes through it.

The resistance between the cores decreases if the insulation layer is thinner than required. Then, in an emergency situation, when the supply voltage increases, a breakdown may occur in the insulation. If, along with this, the core itself has a reduced cross-section, that is, it cannot pass the current that, according to standards, it should pass, the thin insulation begins to gradually melt. All these factors will inevitably lead to a short circuit and then to a fire. A fire occurs from sparks that appear during a short circuit.

Let me give you an example: a three-core copper wire (for example, with a cross-section of 2.5 sq. mm.), according to regulatory documentation, can pass 27A through itself for a long time, usually 25A is considered.

But the wires that come into my hands, produced in accordance with the specifications, actually have a cross-section of 1.8 square meters. mm. up to 2 sq. mm. (this is with the stated 2.5 sq. mm.). Based on the regulatory documentation, the wire has a cross-section of 2 square meters. mm. can carry a current of 19A for a long time.

Therefore, if such a situation happens that along the wire you have chosen, which supposedly has a cross-section of 2.5 square meters. mm., the current designed for such a cross-section will flow, the wire will overheat. And with prolonged exposure, the insulation will melt, followed by a short circuit. Contact connections (for example, in a socket) will collapse very quickly if such overloads occur regularly. Therefore, the socket itself, as well as the plugs of household appliances, may also be subject to melting.

Read also: Reversing switch designation on the diagram

Now imagine the consequences of all this! It’s especially disappointing when a beautiful renovation has been made, new appliances have been installed, for example, an air conditioner, an electric oven, a hob, a washing machine, an electric kettle, a microwave oven. And so you put the buns in the oven to bake, started the washing machine, turned on the kettle, and even the air conditioner, since it became hot. These switched on devices are enough to cause smoke to come out of junction boxes and sockets.

Then you will hear a pop, which is accompanied by a flash. And after that the electricity will disappear. It will still end well if you have circuit breakers. What if they are of low quality? Then you won't get away with a bang and a flash. A fire will start, accompanied by sparks from the wiring burning in the wall. The wiring will burn in any case, even if it is tightly walled under the tile.

The picture I described makes it clear how responsibly you need to choose wires. After all, you will use them in your home. This is what it means to follow not GOSTs, but TUs.

Why do you need to calculate the cable load?

This question often arises when installing wiring in an apartment or home. First, all planned loads are considered, and then the required wire cross-section is determined. Then the necessary material is purchased from the store and electrical wiring is installed in the house.

As a result of using new wiring, the circuit breaker on the electrical panel first “knocks out”, and then damage to the wire is discovered. Moreover, it often turns out to be completely melted, as a result of which a short circuit occurs. It turns out that the calculations were made incorrectly, and how can you find out the minimum permissible value of the wire cross-section in this case?

To avoid serious overloads, it is necessary to calculate how many electrical appliances in the apartment will be used simultaneously. Among the most powerful household appliances that are usually used at home when preparing food and creating our comfort are:

• electric stove;
• air conditioner;
• microwave;
• electric kettle;
• iron;
• washing machine and dishwasher;
• coffee grinder;
• vacuum cleaner.

The power consumption of these household appliances ranges from 1 to 2 kilowatts (with the exception of electric stoves).

Important! If the cross-section of the wire is indicated incorrectly (underestimated), then when using it, it is natural for large overloads to occur, which lead to a fire in the wiring.

Why is the calculation made?

Wires and cables that carry electrical current are the most important part of electrical wiring.

The wire cross-section must be calculated to ensure that the selected wire meets all the requirements for reliability and safe operation of electrical wiring.

Safe operation is that if you choose a cross-section that does not correspond to its current loads, this will lead to excessive overheating of the wire, melting of the insulation, short circuit and fire.

Therefore, the issue of choosing a wire cross-section must be taken very seriously.

What you need to know

The main indicator by which a wire is calculated is its long-term permissible current load. Simply put, this is the amount of current that it is capable of passing for a long time.

To find the rated current value, you need to calculate the power of all connected electrical appliances in the house. Let's consider an example of calculating the wire cross-section for an ordinary two-room apartment.

Table of power/current consumption of household electrical appliances

Once the power is known, the calculation of the cross-section of a wire or cable comes down to determining the current strength based on this power. You can find the current strength using the formula:

1) Formula for calculating current for a single-phase 220 V network:

current calculation for a single-phase network

where P is the total power of all electrical appliances, W; U—mains voltage, V; CI = 0.75 - simultaneity coefficient; cos for household electrical appliances - for household electrical appliances. 2) Formula for calculating the current in a three-phase 380 V network:

current calculation for a three-phase network

Knowing the magnitude of the current, the wire cross-section is found from the table. If it turns out that the calculated and tabulated current values ​​do not coincide, then in this case the nearest larger value is selected. For example, the calculated current value is 23 A, we select the nearest larger one from the table, 27 A - with a cross-section of 2.5 mm2.

Which wire is better to use

Today, for installation of both open and hidden electrical wiring, copper wires are, of course, very popular.

• Copper, compared to aluminum, is more effective:
• it is stronger, softer and does not break in places of inflection compared to aluminum;
• less susceptible to corrosion and oxidation. When connecting aluminum in a junction box, the twist points oxidize over time, which leads to loss of contact;
• The conductivity of copper is higher than that of aluminum; with the same cross-section, a copper wire can withstand a higher current load than aluminum.

The disadvantage of copper wires is their high cost. Their cost is 3-4 times higher than aluminum ones. Although copper wires are more expensive, they are still more common and popular in use than aluminum wires.

How to calculate?

Experienced electricians can “by eye” determine the wire cross-section with great accuracy. This is much more difficult for an ordinary person to do. Therefore, it is best to calculate the cable cross-section by diameter right in the store. At least it will be much cheaper than eliminating the consequences of a short circuit due to an overload in the electrical network.

Experts strongly recommend learning to find out the wire cross-section yourself.

Let's try to do this with specific examples using arithmetic formulas in school mathematics.

Everyone roughly understands what a wire cross-section is. If you bite it across with wire cutters, you can see the round cross-section of a copper or aluminum core. It is measured using a standard mathematical formula: as the area of ​​a circle. Where r is the radius of the circle, squared and multiplied by the constant “pi” (π=3.14).

The larger the diameter of the cable/wire, the more current can pass in a certain amount of time. And, accordingly, the more energy consumed by electrical appliances, the larger the cross-section of the wire should be.

From the simplified formula Scr = 0.785d2 it is clear that to calculate the cross-sectional area you need to know the exact diameter of the wire. To do this, it is necessary to remove the insulation from the core.

How to choose the cable cross-section when installing electrical wiring?

The choice of wire cross-section in this case depends on the permissible current density delta, which is measured in A/mm². This current density shows the load on the wire, and depends on the operating conditions, which can vary from 2 A/mm² - for closed wiring and up to 5 A/mm² if the wires are in fireproof insulation. The required wire diameter can be determined by the selected current and its density value using the following formula:

In the case of electrical wiring, the current density delta ( Δ

) equal to 2 A/mm², and then the above formula is converted into:

The wire cross-section can be found using the following formula:

This current density value of 2 A/mm² is chosen with a large margin because the electrical wiring is embedded in the wall, and it is very difficult to get burnt electrical wiring out from under the plaster and finishing of the walls.

The cross-section of the cable and wire for closed wiring is taken to be 30% larger than for open wiring, since in the hidden version the cable is practically not cooled.

Calculation for stranded wire

Stranded wire (stranded) consists of single-core wires twisted together. Anyone who is even a little familiar with mathematics understands perfectly well that it is necessary to count the number of these wires in a stranded wire. After this, the cross-section of one thin wire is measured and multiplied by their total number. Let's consider the following options.

Calculation using a caliper

The measurement is carried out with a caliper with a conventional scale (or micrometer). Experienced craftsmen always have this tool at hand, but not everyone is a professional electrician.

To do this, using the VVGng cable as an example, cut the thick sheath with a knife and spread the wires in different directions.

Then select one core and strip it with a knife or scissors. Next, measure this core. The size should be 1.8 mm. Please refer to the calculations to prove the measurement is correct.

The figure 2.54 mm2 obtained as a result of the calculation is the actual cross-section of the core.

Measuring with a pen or pencil

If you don’t have a caliper at hand, you can use improvised methods using a pencil and ruler. First, take the wire to be measured, strip it and wind it around a pencil or pen so that the turns lie close to each other. The more turns, the better. Now let's count the number of wound turns and measure their total length.

For example, we got 10 turns with a total winding length of 18 mm. It is easy to calculate the diameter of one turn; to do this, divide the total length by the number of turns.

As a result of all the calculations made using the formula, you will obtain the required diameter of the core. In this case it is 1.8 mm. Since the diameter of one core is known, it is not difficult to calculate the cross-section of the entire VVGng wire using the already known formula.

You can see that the results were equal.

Using tables

How can you find out and measure the cable cross-section if you don’t have a caliper, a ruler, or a micrometer at hand? Instead of racking your brains over complex mathematical formulas, just remember that there are ready-made tables of values ​​for measuring cable cross-section. There are, of course, very complex tables with many parameters, but, in principle, to begin with it is enough to use the simplest of the two columns. The diameter of the conductor is entered in the first column, and the ready-made values ​​​​of the wire cross-section are given in the second column.

Wiring cross-section table for closed wiring

There is another “approximate” method that does not require measuring the thickness of individual wires. You can simply measure the cross-section (diameter) of the entire thick scroll. This method is usually used by experienced electricians. They can find out the cable cross-section both “by eye” and with the help of tools.

Source: 220.guru

Determining wire cross-section - review of effective techniques

There are different ways to determine the cross-section of a wire. First of all, the core diameter is calculated, after which the obtained value can be analyzed.

No. 1. Using a caliper

There are a number of engineering instruments that make it easy to determine the cross-section of a wire by diameter. This is a mechanical and electronic micrometer, mechanical and electronic caliper. This method is accurate, but purchasing devices is worth it if you use this method regularly, and not once or twice.

The wire cross-section is measured using the following formula:

No. 2. Using a pencil and ruler

There is a simple “old-fashioned” way to find out the cross-section of a wire using a wire, a simple pencil and a ruler.

You need to strip the core of insulation, then wrap it tightly around a pencil. Use a ruler to measure the total length of the winding.

Then you need to divide the resulting figure by the number of cores. The value you get is the cable diameter cross-section.

To accurately determine the cable cross-section, it is necessary to take into account the following features of this method:

• The accuracy of the result depends on how many cores are wound on the pencil. The minimum number of turns is 15;
• The turns should be pressed against each other as much as possible. There should be no free space, which will increase the error in the calculations;
• A similar procedure must be done several times, the accuracy indicator depends on this.

In addition to the positive aspects (ease of use and time saving), it is worth noting the disadvantages:

1. Only thin wires are suitable for calculations, since it is problematic to wind a thick cable.
2. Before purchasing, you need to purchase a small piece of cable for measurement.

Serious question

If you plan to replace electrical wiring, then first of all you need to decide what cross-section of wire is needed. When you calculate the planned current load on the wire, it will immediately become clear what cross-section is needed for normal operation. For this purpose, use the table below.

Current selection

Let's say, having calculated everything, you have determined the current strength to be 27 A. It turns out that you need a two-core wire with a cross-section of 2.5 mm2. You went to the store, bought a good wire, with a cross-section of 2.5 mm2 declared by the manufacturer, and installed the electrical wires. After the time has passed when the system was up and running, the machine on your dashboard turns off. This may indicate a damaged line.

After you inspect the wiring, you may find that there was a short circuit. The reason is simple - the insulation on the wire melted due to strong heating. But how can this be? You did everything right, calculated it, purchased the necessary wire. And the whole point is not in the calculations and your error with the connection. The whole reason lies in deception. Yes, precisely in deception, since very often manufacturers producing wires supply goods that do not correspond to the declared cross-section. For example, you bought a cable with a wire area of ​​2.5 mm2, but when you checked it yourself, it turned out that the cable cross-section is only 2.1 mm2, which is less than what you need in terms of power. So it turns out that the wire heats up, and the risk of a short circuit increases.

Wire with damaged insulation

But why would cable companies do this? It's all about greed, since by lowering the cross-section of the wire, the manufacturing company saves quite a significant amount of money. Judge for yourself: to make 1000 m of wires with a cross-section of 2.5 mm2, you will need approximately 22.3 kg of copper. But if you make them with a smaller cross-section, 2.1 mm2, then their production will require 18.8 kg. It turns out that the savings in favor of the manufacturer are 3.5 kg of copper. And when large volumes of products are produced, this figure increases significantly.

So it turns out that determining the wire cross-section is an important and serious step that must be performed when installing wiring. This way you can avoid insulation melting, short circuits and, as a result, fire.

How to use a miter box

To obtain a right or 45º angle without marking, it is convenient to use a device called a miter box. Using a miter box, it is convenient to cut trim for doors, moldings, baseboards and much more to size at an angle. The cut is obtained with the required angle automatically.

It is enough to measure the length, place a strip of material between the vertical walls of the miter box and, holding it with your hand, make a cut. To obtain a high-quality end of the board, use a saw with fine teeth. A hacksaw works well for metal. It is possible to saw even varnished boards without chipping the varnish.

An angle of 45 0 when sawing using a miter box is obtained as easily as a straight one. Thanks to the high guide walls of the miter box, you can saw boards of different thicknesses.

You can buy a miter box ready-made, but it is not difficult to make it yourself from available material. It is enough to take three boards of wood or plywood of a suitable size, and screw the other two to the side ends of one of them with self-tapping screws. Make guide cuts at the required angles and the miter box device is ready.

In order to successfully buy a wire, before purchasing you need to measure the diameter of the wire , otherwise you can become a victim of deception. You will also have to measure the cross-section of the wire if you add a new electrical point on the old wiring, since there may not be a letter marking on it. The information below will help you choose the right method for measuring wire diameter and use it effectively in practice.

At the same time, the question will immediately arise: “What is the point of a company spoiling its reputation?” There may be several explanations for this: But the whole point is that even after making the correct calculations of the wire cross-section, you may still encounter a problem, despite the fact that you buy a wire with the appropriate diameter . An accident may occur due to the fact that the marking of the wires will indicate a cross-section of conductors that does not correspond to the actual one. This may happen as a result of the fact that the manufacturing plant saved on the material, or the company producing this product did not comply with all the characteristics of the product. You can also find wires on the shelves that have no markings at all, which initially casts doubt on their quality.

1. In order to save money. For example, the factory made the wire diameter smaller by only 2 mm. sq. with a 2.5 mm core, which made it possible to win several kilograms of metal per linear meter, not to mention the profit in mass production.

2. As a result of great competition, the company reduces the price of electrical wiring, trying to lure most of the consumers. Naturally, this occurs due to a decrease in the diameter of the wire , which cannot be determined with the naked eye.

Both the first and second options take place in the sales market, so you better play it safe and make your own accurate calculations, which will be discussed further.

How can you determine the cable cross-section

So, you bought a wire, let's find out how you can measure its cross-section. For this purpose you will need:

• calipers;
• calculator;
• the cable itself;
• utility knife or stripper for removing insulation.

Measuring with a caliper

The cross section is determined by the diameter of the wire. Let's look at how to do this step by step.

1. Take the wire and remove the insulation from it using a stripper or a utility knife.
2. Using a caliper, measure the diameter of the wire.
3. Now, you will have to remember your geometry lessons at school. In order to determine the area of ​​a circle, there is a certain formula:

Skr= π r2,

where the number π = 3.14, and r is the radius of the wire.

But here we have a problem: using a caliper it is impossible to measure the radius - only the diameter. Therefore, the formula needs to be slightly modified to suit the diameter. As we know, the radius is half the diameter. In order for our data to fit, the formula needs to be redone like this:

Skr= ( π d2)/4,

where d is the core diameter.

In this case, the formula can be shortened by dividing the number π by four. As a result, we arrive at the standard formula for calculating the cross-section of the core by diameter:

Skr=0.785d2

All that remains is to substitute the numbers into the formula and get the area of ​​the circle, which will be its cross section. For example, the diameter of your copper wire is 1.68 mm. This number squared is 2.8224. Multiply 2.8224 by 0.785. If we round, then in the end the desired cross-section is 2.2 mm2.

That's all, as you can see, this procedure will not take much time and effort, but it is a very important part of the electrical installation work. After all, even a deviation of a few tenths of a millimeter can play a cruel joke. But what if you are not an electrician and you don’t have a caliper at hand? Don’t rush to run to the store; there is a simple method for calculating the diameter using available tools.

How to find out the cable cross-section by the diameter of the core

Greetings, friends!

You are making repairs and decide to change the electrical wiring yourself. And now you need to select a cable. What do you need to do? You need to go and buy cables for your repair, unless, of course, you are the owner of a cable factory.

But what do we have in store? And there is very little choice. Both TU and GOST. But even a cable made according to GOST does not guarantee you the technical data declared by the manufacturer. Manufacturers, wanting to reduce the cost of producing their products, use various tricks. And one of them is underestimating the cross-section of the cable cores. I'm not even talking about TU cables, everything is bad there. Once I measured the cross-section of the cable TU VVG Zx2.5, so in general it was one and a half squares.

The thickness of the cable core insulation is also reduced. But we will talk about the section.

Of course, a cable produced in accordance with GOST has an advantage over TUSH cable. But its price is also much higher. Therefore, in order to reduce the cost of repairs, many use TU cable. Among the products produced according to the Technical Specifications, there are more or less high-quality products. But it is not possible to determine the cross-section of the cable core by eye (only approximately), so I will tell you how to do this quite accurately.

What can we measure on a cable? Diameter only.

A simple method for determining diameter

Section determination method

Everyone has everything they need at their fingertips. For this method you only need a pencil or pen and a ruler.

1. First of all, take the wire whose cross-section you need to find out and remove 300–400 mm of insulation along its length.
2. Take a pencil, pen, felt-tip pen, or whatever you have on hand, and wrap a wire around it. In order to achieve the most accurate result, the turns must be fitted closely one to one. The more turns you make, the more accurate the result will be. The recommended quantity is 10 or more turns.
3. Then count the number of turns you wound around the pencil and write that number down or remember it.
4. Using a ruler, measure the total length of the counted turns. For example, you got 19 turns that are 32 mm long.
5. To determine the diameter of the wire, all that remains is to divide the length by the number of turns. It turns out like this: 32/19 = 1.68 mm.

That's all, now all that remains is to substitute the diameter of the wire into the formula and you will get a wire cross-section of 2.2 mm2. This result can be considered accurate under two conditions: the turns were wound closely, and their number exceeds 10 pieces - the more, the better. As a result, you won't have to spend extra money.

The only disadvantage of this method: if the core has a large cross-section, you won’t be able to wrap it around a pencil.

How to measure a large diameter pipe

The caliper jaws, with a measuring range from 0 to 125 mm, are 40 mm long and therefore allow you to measure pipes with an outer diameter of up to 80 mm. If you need to measure a pipe of a larger diameter or if you don’t have a caliper at hand, you can use the traditional method. Wrap the pipe around the circumference with one turn of non-stretch thread or wire, measure the length of this turn using a simple ruler, and then divide the result by the number Π = 3.14.

Despite its simplicity, this method of measuring pipe diameter allows for an accuracy of 0.5 mm, which is quite enough for a home craftsman. For a more accurate measurement, you need to wind more turns.

How to measure the cross-section if the wire is stranded

Stranded Stranded Cable

Well, you say, if there is only one wire, it’s easy to calculate the cross-section. But what if it is multi-core? There are a lot of such individual wires, how can you recognize it in this case? Determining the cross-section of a stranded wire is not as difficult as it seems. All you need to do is determine the cross-section of one of the cores.

1. First, take the wire and strip the insulation from it.
2. Now all the wiring needs to be disconnected and their number recalculated.
3. Take one of the wires and measure its diameter.
4. Using the formula presented above, determine the area of ​​one core.
5. Having the cross-section of one core, you can find out the total cross-section. To do this, multiply the area of ​​one wire by their total number. For example, you have a wire consisting of 15 cores. You learned that the cross-section of one wire is 0.2 mm2. In order to find out their total cross-section, 0.2 must be multiplied by 15. We get: 0.2 × 15 = 3 mm2.

Difference between stranded and stranded cable

But it should be taken into account that all the wires in the wire cannot be connected closely. Because they are round, there is an air gap between them. It needs to be taken into account. To do this, multiply the resulting result by 0.91. Let’s say if the wire cross-section is 3 mm2, then multiplying it by a factor of 0.91, we get a cross-section of 2.7 mm2. That's all. There is nothing complicated, you just need to follow the instructions.

As you can see, anyone who knows how to use formulas can determine the wire cross-section. But, despite the simplicity of this work, it is one of the most important steps that must be done before wiring throughout the house.

How to measure with a micrometer in practice

You can obtain the size of products with an accuracy of 0.01 mm by taking measurements with a micrometer. There are many modifications, but the most common is a smooth micrometer of the MK-25 type, which provides a measurement range from 0 to 25 mm with an accuracy of 0.01 mm. It is convenient to use a micrometer to measure the diameter of the drill, the thickness of the sheet material, and the diameter of the wire.

The micrometer is a bracket, on one side of which there is a support heel, and on the other there is a stem and a high-precision thread into which a microscrew is screwed. The stem has a metric scale on which millimeters are counted. The microscrew has a second scale with 50 divisions, on which hundredths of mm are measured. The sum of these two quantities is the measured size.

In order to take a measurement with a micrometer, the part is placed between the heel and the end of the micrometer screw and rotated clockwise by the ratchet handle (located at the end of the micrometer screw drum) until the ratchet makes three clicks.

There are two scales on the stem with a step of 1 mm - the main one, digitized every 5 mm, and an additional one, shifted relative to the main one by 0.5 mm. The presence of two scales allows you to increase the accuracy of measurements.

The readings are taken as follows. First, they read how many whole millimeters, not covered by the drum, were obtained according to the digitized, lower scale on the stem. Next, check on the upper scale for the presence of risks located to the right of the lower scale. If the risks are not visible, then proceed to taking readings from the scale on the drum. If the mark is visible, then another 0.5 mm is added to the whole number of millimeters obtained. The readings on the drum are measured relative to a straight line drawn along the stem between the scales.

For example, the size of the measured part is: 13 mm on the lower scale, there is an open mark on the upper scale, there is no mark to the right of the open mark on the lower scale, which means there is no need to add 0.5 mm, plus 0.23 mm on the drum scale, as a result of addition we get: 13 mm+0 mm+0.23 mm=13.23 mm.

A micrometer with a digital readout of measurement results is more convenient to use and allows measurements with an accuracy of up to 0.001 mm.

If, for example, the battery runs out, then with a digital micrometer you can take measurements in exactly the same way as with a smooth MK-25, since there is also a division reading system with an accuracy of 0.01 mm. The price of micrometers with digital readout of measurement results is high and unaffordable for a home craftsman.

How and with what to measure the diameter of a wire (wire)

To measure the diameter of the wire, a caliper or micrometer of any type (mechanical or electronic) is suitable. It’s easier to work with electronic ones, but not everyone has them. You need to measure the core itself without insulation, so first move it aside or remove a small piece. This can be done if the seller allows it. If not, buy a small piece to test and take measurements on it. On a conductor stripped of insulation, measure the diameter, after which you can determine the actual cross-section of the wire from the found dimensions.

Measuring wire diameter with a micrometer is more accurate than with a mechanical caliper

Which measuring device is better in this case? If we talk about mechanical models, then a micrometer. Its measurement accuracy is higher. If we talk about electronic options, then for our purposes they both give quite reliable results.

If you don't have a caliper or micrometer, take a screwdriver and a ruler with you. You'll have to strip a fairly decent piece of conductor, so you'll hardly be able to do without buying a test sample this time. So, remove the insulation from a 5-10 cm piece of wire. Wind the wire around the cylindrical part of the screwdriver. Lay the coils close to each other, without a gap. All turns must be complete, that is, the “tails” of the wire must stick out in one direction - up or down, for example.

Determining wire diameter using a ruler

The number of turns is not important - about 10. You can have more or less, it’s just easier to divide by 10. Count the turns, then apply the resulting winding to the ruler, aligning the beginning of the first turn with the zero mark (as in the photo). Measure the length of the section occupied by the wire, then divide it by the number of turns. You get the diameter of the wire. It's that simple.

For example, let's calculate the size of the wire shown in the photo above. The number of turns in this case is 11, they occupy 7.5 mm. Divide 7.5 by 11, we get 0.68 mm. This will be the diameter of this wire. Next, you can look for the cross section of this conductor.

What is the difference between cross section and diameter?

The cross section in the shape of a circle must have a diameter. The section itself is a cut of a cable or any other object at right angles to the longitudinal axis. The diameter is a chord, that is, a segment that connects two points on a circle and passes exactly through its center. Not only a circle or circle has a diameter, but also a sphere or ball. These quantities have little in common, since one determines the distance, and the other the area.

It is difficult to calculate the area of ​​such a cable on your own.

Note! The section is always used in practice for volumetric bodies, and a cable or wire is a volumetric object that is most often made in the form of a long cylinder (if divided into parts) that has a cross section. Its diameter can also be determined, but it so happens that it is the area that is indicated.

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We are looking for the wire cross-section by diameter: formula

The wires in the cable have a circular cross-section. Therefore, when calculating, we use the formula for the area of ​​a circle. It can be found using radius (half the measured diameter) or diameter (see formula).

Determine the cross-section of the wire by diameter: formula

For example, let's calculate the cross-sectional area of ​​the conductor (wire) based on the size calculated earlier: 0.68 mm. Let's use the radius formula first. First we find the radius: divide the diameter by two. 0.68 mm / 2 = 0.34 mm. Next, we substitute this figure into the formula

S = π * R2 = 3.14 * 0.342 = 0.36 mm2

You need to calculate it like this: first we square 0.34, then multiply the resulting value by 3.14. We obtained a cross-section of this wire of 0.36 square millimeters. This is a very thin wire that is not used in power networks.

Let's calculate the cable cross-section by diameter using the second part of the formula. It should be exactly the same value. The difference may be in thousandths due to different rounding.

S = π/4 * D2 = 3.14/4 * 0.682 = 0.785 * 0.4624 = 0.36 mm2

In this case, we divide the number 3.14 by four, then we square the diameter and multiply the two resulting numbers. We get a similar value, as it should be. Now you know how to find out the cable cross-section by diameter. Whichever of these formulas is more convenient for you, use that one. No difference.

Tips from an electrician

If you are selecting a VVGNG wire or cable to power the electrical network, pay attention to the following points:

• Look at the color of the copper and aluminum wire, as the manufacturer could save money and use an alloy, which significantly increases the electrical resistance and does not allow the use of permissible cross-sectional loads.
• No matter how thin the insulation of a flexible cable is, to calculate the cross-section you still need to measure only the core. Since the extra millimeters will allow you to use a wire with a smaller cross-section to power an excessive load, and this is fraught with damage.
• If at some stage you doubt the sufficiency of the cross-section or realize that using devices of lower power will not work, it is better to mount the wiring with a thicker wire.

Table of correspondence of wire diameters and their cross-sectional area

You don’t always want or have the opportunity to make payments in a store or on the market. In order not to waste time on calculations or to avoid making mistakes, you can use the table for the correspondence of diameters and cross-sections of wires, which contains the most common (normative) sizes. You can rewrite it, print it and take it with you.

How to work with this table? As a rule, the cables have a marking or tag indicating its parameters. The cable marking, number of cores and their cross-section are indicated there. For example, VVNG 2x4. We are interested in the core parameters and these are the numbers that appear after the “x” sign. In this case, it is stated that there are two conductors having a cross section of 4 mm2. So we will check whether this information corresponds to reality.

To check, measure the diameter using any of the described methods, then check the table. It states that with such a cross-section of four square millimeters, the wire size should be 2.26 mm. If your measurements are the same or very close (there is a measurement error, since the devices are not ideal), everything is fine, you can buy this cable.

Stated sizes do not always correspond to real ones

But much more often, the actual diameter of the conductors is much smaller than the declared one. Then you have two options: look for a wire from another manufacturer or take a larger cross-section. Of course, you will have to overpay for it, but the first option will require a fairly long period of time, and it is not a fact that you will be able to find a cable that complies with GOST.

The second option will require more money, since the price significantly depends on the declared cross-section. Although, it’s not a fact - a good cable made according to all standards may cost even more. This is understandable - the cost of copper, and often also for insulation, subject to technology and standards, is much higher. That’s why manufacturers cheat by reducing the diameter of the wires in order to reduce the price. But such savings can turn into disaster. So be sure to take measurements before purchasing. Even trusted suppliers.

And one more thing: inspect and feel the insulation. It should be thick, continuous, and have the same thickness. If, in addition to changing the diameter, there are also problems with insulation, look for a cable from another manufacturer. In general, it is advisable to find products that meet the requirements of GOST, and not made according to specifications. In this case, there is hope that the cable or wire will serve for a long time and without problems. It's not easy to do these days, but whether you're wiring your home or running electricity from a utility pole, quality is very important. Because it’s probably worth looking for.

How to determine whether the parameters match?

As a rule, extreme care on your part allows you to avoid such incidents during the purchase:

• A normal wire must have its marking, which provides the buyer with all the information about the model, operating features, and parameters. If you encounter questionable products, you may find that the product data is not presented in full or is completely missing.
• If the conductor is really good, he must be provided with quality certificates. The technical documentation indicates that it was not only manufactured in accordance with the ND, but also passed the appropriate tests.
• A good wire cannot cost a penny - since the price of materials is quite high, the cheapness should make you wonder if there is some kind of catch in this. If you wish, you can come to the store with a micrometer or caliper and perform a test to clear your doubts.

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Determining the size of the cable cross-section

Cables can be either single-core or multi-core. In the second case, it is best to determine the diameter of each individual core. Also, the core can be single-wire or consist of many wires. Regardless of the type of cable, you can determine its cross-section by diameter.

All wires presented on the market must indicate general information about the type of cable. It is usually indicated on the outer winding of the cable to make it easier for the buyer to make a choice.

However, do not forget that “it’s also written on the fence” and it is best to carry out all the necessary measurements yourself when choosing a wire. Fortunately, carrying them out is not that difficult. Determining the actual wire diameter is possible using available tools. Such tools include a micrometer and a caliper.

Micrometer measurement

The most accurate method for measuring diameter is using a micrometer. For such a measurement, you need to take a conductor and move the measuring screw to it until the characteristic ratcheting sound appears. The exact diameter value consists of two values: on the micrometer rod and on the drum.

Measuring with a caliper

You can also measure the cable diameter using a common tool such as a caliper. To do this, you need to clamp the wire to be measured between the jaws of the meter and read the exact value from a special scale.

Measuring with a ruler

The least accurate type of measurement is using a simple ruler. However, in this case, accuracy can be achieved by measuring a large number of turns. The procedure for measuring with a ruler:

1. A conductor is wound around a certain rod over a certain distance.
2. The length of the wrapped section of the rod is measured with a ruler.
3. The resulting value is divided by the number of turns.

This method still has a certain accuracy due to the reduction in error.

Next, you can determine the cable cross-section by diameter. This can be done using the formula:

S = π*D2/4

where D is the measured diameter of the wire.

The skill of independently calculating the conductor cross-section will help you avoid all sorts of problems in the future, as well as deception on the part of the product supplier.

Only by understanding how to determine the cable cross-section yourself can you protect yourself and your projects from dangerous surprises.

Tables and norms

Another very common method for determining the wire cross-section by diameter is the use of standardized tables that list all the most common and widely used cable cross-sections.

Using a table can eliminate the need for special calculations and measurements, which waste valuable time.

The procedure for selecting the wire cross-section according to the table:

1. First you need to decide on the type of cable.
2. Next, we find the diameter we need in the table.
3. We determine the appropriate section.
4. If necessary, we independently check the indicators using the methods described above and make a decision on purchase.

Table of wire cross-sections by diameter.

The table relating wire cross-section and diameter shows that the formula described above is very fair. The cross-section values ​​given in the proposed table are calculated precisely from it with certain permissible roundings.

So, we already know how to independently find out the wire cross-section. All that remains is to put the acquired knowledge to good use.

When purchasing a cable, you can ask the seller to strip a small section of the wire in order to carry out all the necessary manipulations to measure the product. However, practice shows that not many sellers take such a step. Then the only solution is to first purchase a small section of cable needed for measurements. But after all doubts have disappeared, you can purchase as much wire as you need. Still, the not most joyful fact is that truly attentive buyers often choose a cable with a larger cross-section. After all, in reality they turn out to be somewhat smaller than the formal sizes.

Options by definition

There are several ways to determine the cable cross-section. The need for this usually arises during electrical installation work, when it is necessary to check the existing conductor for compliance with the application standards for a particular area. For example, a person may be doing wiring that requires a cable with a cross-section of at least 1.5 mm. He will need to check his wire for compliance with these conditions, since otherwise, overheating of cables and connections, failure of household appliances and even a fire are possible.

Before measuring, remove the insulating layer

Important! If the conductor has one core, then measurements are made directly on it. It is necessary to untangle one wire from the wire coil, clean it of insulation, and only then take measurements.

Circle area formula

To calculate the cross-sectional area of ​​a round wire through the radius, you need to multiply its square by the number Pi. In practice, it is much easier to determine the diameter and divide it by 2. Based on the measurement methods, the following methods for calculating the cross-section can be distinguished.

By diameter using a caliper or micrometer

The most popular measurement method is to determine the diameter using a caliper or micrometer. Such devices allow you to measure the diameter as accurately as possible, and then multiply half of it by the number Pi.

To operate, you only need a wire and the device itself. The process looks like this:

1. Move the micrometer lock to the “Open” position.
2. Unscrew the handle of the device to a distance that will be sufficient to insert the conductor between the probes.
3. Insert the wire into the probes and twist it with a special hand-held device until a cracking sound is characteristic of the device.
4. Record the diameter readings on the appropriate scale.
5. Unscrew the handle and remove the wire.

A significant advantage of this measurement method is that it allows you to determine the diameter and, as a consequence, the cross-section of any round conductor. Moreover, it can be connected to the network and actively work in one or another electrical device.

Using the caliper is very convenient

Note! The disadvantage of this method is that the devices are quite expensive, and there is no point in buying them for one or two uses.

By diameter using a pencil or pen

This method is based on the use of any ton object on which a wire core can be wound. Typically, a pen, pencil or felt-tip pen is used as such an object. The wire is wound around it in the form of a spiral with the rings compressed as tightly as possible. To eliminate inaccuracies, the insulation is removed along the entire length of the conductor under test.

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All windings have the same width and thickness, so it is necessary to compress them as much as possible and determine the total length using a ruler or centimeter. Next, this value is simply divided by the number of winding rings. The more turns there are, the more accurate the result will be in the end.

The advantage of this approach is that its application does not require any special measuring tools at all, except for a regular ruler. If we talk about the disadvantages, they consist in the low accuracy of measurements and the longer process of preparation for them.

Wrapping around a pencil

Important! If in the previous case everything could be done in a couple of seconds, then here you will have to ensure maximum adherence of all turns to each other. This also only works for thin copper wires. This is not suitable for aluminum.

By diameter using a ruler

This method is suitable for thick wires. The thinner the core, the less accurate the result will be in the end. The diameter can be determined using thread or paper. The second method is more accurate.

Step-by-step measurement process:

1. Tear off a small piece of plain paper and fold it over on one side. It's best to take a thin one.
2. Take a piece of paper and attach it to the conductor.
3. Wrap the sheet around it until the two ends of the paper touch each other.
4. Bend the other end at the junction.
5. Attach the leaf to the ruler and measure the distance from one curved edge to the other.
6. Calculate the diameter using the resulting circumference divided by two Pi numbers.
7. Apply standard formula.

You can find the diameter using a ruler.
The method is suitable for aluminum conductors of sufficient thickness that are difficult to bend. The disadvantage is the very low measurement accuracy.

By diameter using the table

Some are interested in how to determine the cable cross-section by diameter using a table. This approach is used for cables and wires of standard cross-section. For example, a person learned the diameter using any of the methods described above. It is not at all necessary to use formulas. It is enough to look at the table presented and determine the cross section without calculations.

Relation of diameter and sections

By power or current

If a person knows the conductive properties of the wire, then with their help it is also possible to determine the cross-section. To do this, you need to find out either the current or power. Next, it remains to find the value in the table and match the section to it.

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Table for determining cross section based on current and power

Important! It is worth remembering that the result will be different for copper and aluminum conductors.

By formulas

As already mentioned, there are a number of simple formulas that allow you to determine the cross-section of the conductor. More precisely, this is one formula, but in one case the radius of a round wire is used, and in the second - the diameter. To determine it is necessary:

1. Measure the diameter of the wire (its thickness) using any of the methods described above. It is recommended to use a caliper.
2. Record the resulting diameter value.
3. Calculate the cross-sectional area using the formula: S = π × R², where R is the radius (half the diameter), π is the number Pi, which is approximately equal to 3.1415.

A similar table for copper conductors
. Important! You can also use another formula, where instead of the radius, half the diameter (D/2) appears, which is squared. The result will be similar, so it is better to divide the diameter by 2 in advance.

Calculation of stranded conductors

The calculation of the wire cross-section by diameter for a stranded conductor is carried out similarly to a single-core one, however, it is necessary to take into account the correction for the number of cores. The resulting value is multiplied by this amount, and a wire is selected based on this new value. The most difficult problem in such calculations is measuring the diameter of a thin core. Indeed, often in such conductors they have very small cross sections and their measurement is difficult. If, however, it was possible to measure, then the next main criterion for selecting a cable is the conductivity of the wire. As a starting point, the current conductivity of one core is chosen, and only then, using the corresponding dependencies, they arrive at the final value. Based on the general conductivity, the cross section is already selected using the appropriate tables and standards.

Thus, you can select the cable cross-section based on its planned dimensions and current conductivity. And despite the fact that this article does not pay much attention to the second point, it is necessary to understand that it is fundamental in selecting a cable. The so-called rupture current is the line beyond which the electrical system can not only fail, but also provoke extensive, all-destructive fires.

Source: glav-dacha.ru

How to measure the cross-section of a wire with a caliper

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 mm2. 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 mm².

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.

When laying apartment electrical wiring, as a rule, the question arises about choosing a circuit breaker, or, as it is often called, a machine. This issue and the choice of a meter, RCD, and differential circuit breaker are covered in detail in the website article “About the electric meter, RCD and circuit breakers.”

Wire material

As you know, copper and aluminum wires have different resistance, as well as different service life, from which we can conclude that calculations on the power or current of their cross-section must be made separately.

Copper wire, as already mentioned, requires less thickness than aluminum, with the same load on the cable, and here's why. The resistivity of aluminum is higher than that of copper, and therefore the current losses are greater. And it is precisely due to this that the cable heats up, since household electrical appliances do not understand through what material the voltage is applied to them. They take exactly as much as they need.

But copper, which has a resistance equal to 0.017 Ohm*kV mm/m. consumes less electricity for heating than aluminum with its resistivity of 0.028 Ohm*sq. Mmm. As a result, the copper heats up less, the wire needed is thinner, and the efficiency of the copper cable is higher.

This is why, despite the high cost compared to aluminum, copper wires are more in demand in the electrical engineering market.

How to calculate the cross-section when purchasing

When purchasing a cable, you must make sure that its cross-section corresponds to the declared marking. To do this, you can purchase a trial sample. Usually the minimum length on sale is 0.5 meters - this length will be sufficient.

To take measurements, find and take with you a caliper (mechanical or electronic, which is preferable) or a micrometer. Electronic devices, of course, are more accurate, but not everyone has them, but almost everyone has a mechanical one.

But even if it’s not there, a simple screwdriver and a ruler can help out. Now let's try to figure out how to calculate the parameters of the section based on the calculated radius.

Measurements with a micrometer or caliper

In order to calculate the cross-sectional area of ​​the conductor, we first need to strip one of the wire strands whose diameter we require. The sufficient length for measuring in this way is 1 cm. Next, using a caliper or micrometer, the thickness of the core is measured - this, as you might guess, will be the diameter of the cable. But to calculate the ratio of the cross-section to the diameter using the formula, we need a value such as the radius, and therefore we divide the resulting value by 2. After such a conversion, the diameter is no longer used, everything is calculated using the radius data.

After the measurements are taken, a formula is used to calculate the cross-section of the cable, that is, the cross-sectional area of ​​the cable is S = π*r2, where π is a constant value equal to 3.14.

Thus, if the core diameter was 3.6 mm, then the calculations would be as follows:

3.6:2 = 1.8; after 3.14 x (1.8x1.8) = 3.14 x 3.24 = 10.17. It follows that the cross-sectional area of ​​the cable being determined, the core diameter of which was 3.6 mm. equal to 10.17 sq. mm.

In a similar way, you can calculate the thickness of a multi-wire flexible conductive product, but with such calculations you need to measure the diameter of one wire from the core, then multiply the resulting figure by the number of wires that make up the core, and then calculate the thickness of the cable using the above formula.

As it becomes clear, calculating the thickness of a conductor by diameter is not so difficult, and even at the project stage you can convert the cross-section to diameter, then you will not need to calculate the data while standing at the counter, which is the advantage of this action.

Cable measurements with a ruler

In the absence of high-precision devices for measuring wire thickness, you can use a regular ruler and screwdriver. To measure, you will need to strip at least 10 cm of the core (the more stripped, the more accurately you can calculate the diameter).

After removing the insulation, the bare wire is wound around a screwdriver so that there are no gaps between the turns, and the resulting spiral on the tip of the screwdriver is measured using a ruler. For convenience, it is advisable to take an integer number in millimeters. For example, from the starting edge of the wire to the edge of the 10th turn it is 23 mm. Then you need to divide 23 mm by the number of turns, which will be equal to 23:10 = 2.3 mm. This will be the necessary value in order to calculate the thickness of the cable core. Well, then again using the same formula - 2.3:2 = 1.15x1.15 = 1.3225x3.14 = 4.15. So we converted the diameter to the cross section of the conductor.

Calculations are made similarly for flexible stranded wires.

Method 1

If it is not possible to use a special device. You can use improvised means. To do this, you need an object that has a round oblong shape; it can be any writing utensil - a pen or pencil, a ruler. We strip the wire to a length of at least 30 cm. Then we wrap it tightly around the handle with a spiral. There should be no gaps between the turns.

We count the number of turns and the length of wire used for them. Then divide the length by the quantity.

For example, the wire has 21 turns and a length of 40 millimeters. To calculate the diameter, divide the length by the quantity. That is, we divide 40 by 21, we get 1.904 millimeters.

Formula: S = πr 2, where π – 3.14, S – area of ​​the circle, r – radius of the circle.

Since the number calculated is the diameter, not the radius. Then we change the formula for this measurement: S = (πd 2)/4, where d is the diameter.

The resulting number is substituted into the formula. The result will be the diameter.

For example, d = 3.635. 3.14 × 3.635 ÷ 4 = 2.84

Method 2

This method requires a mechanical or electronic caliper and a micrometer.

Measure with a micrometer. The device has two main parts - handles and semicircular recesses for measuring. The wire is inserted into the micrometer connector, the handle is screwed in until it stops. When the screws come together on the sides, turn the ratchet on the handle of the device until it begins to scroll. The measurement has been completed and is shown by the scale on the micrometer drum.

An electronic micrometer shows accurate numbers, which eliminates human calculation errors.

Calculation of the cross section using a caliper. For proper use, you need to know the structure of the device. It consists of a scale with 1 mm markings, the length of a standard ruler is 15 cm, a measuring sponge, a ruler for depth, and a screw for clamping an object.

Cut the cable and separate the wires. Clear one of them. Spread the jaws, insert the core so that the jaws fit tightly. Secure with screw. Now you can see the length of the object. Next we calculate according to the already known formula.

How to calculate the current cross section?

Table values ​​cannot take into account the individual characteristics of the device and network operation. The specificity of the tables is average. They do not list the parameters of the maximum permissible currents for a particular cable, but they differ for products of different brands. The type of gasket is touched upon very superficially in the tables. For meticulous craftsmen who reject the easy way of searching through tables, it is better to use the method of calculating the size of the wire cross-section by current. More precisely, by its density.

Allowable and operating current density

Let's start with mastering the basics: remember in practice the derived interval 6 - 10. These are the values ​​​​obtained by electricians over many years of “experimental methods”. The strength of the current flowing through 1 mm² of copper core varies within the specified limits. Those. a cable with a copper core with a cross-section of 1 mm² without overheating and melting of the insulation allows a current of 6 to 10 A to easily reach the waiting consumer unit. Let's figure out where it came from and what the designated interval fork means.

According to the code of electrical laws PUE, 40% is allocated to the cable for overheating that is not dangerous for its sheath, which means:

• 6 A distributed per 1 mm² of current-carrying core is the normal operating current density. Under these conditions, the conductor can work indefinitely without any time restrictions;
• 10 A distributed per 1 mm² of copper core can flow through the conductor for a short time. For example, when you turn on the device.

An energy flow of 12 A in a copper millimeter channel will initially be “crowded”. Due to the crowding and crowding of electrons, the current density will increase. The temperature of the copper component will then increase, which will invariably affect the condition of the insulating shell.

Please note that for a cable with aluminum current-carrying conductor, the current density displays an interval of 4 - 6 Amperes per 1 mm² of conductor. We found out that the maximum current density for a conductor made of electrical copper is 10 A per cross-sectional area of ​​1 mm², and normal is 6 A. Therefore:

Hence:

We found out that the maximum current density for a conductor made of electrical copper is 10 A per cross-sectional area of ​​1 mm², and normal is 6 A. Therefore:

• a cable with a conductor cross-section of 2.5 mm² will be able to transport a current of 25 A in just a few tenths of a second when the equipment is turned on;
• it will be able to transmit a current of 15A indefinitely.

The above current densities are valid for open wiring. If the cable is laid in a wall, in a metal sleeve or in a plastic cable channel, the specified current density value must be multiplied by a correction factor of 0.8. Remember one more subtlety in organizing open wiring. For reasons of mechanical strength, cables with a cross-section of less than 4 mm² are not used in open circuits.

Studying the calculation scheme

There will be no super complex calculations again; calculating the wire for the upcoming load is extremely simple.

• First, let's find the maximum permissible load. To do this, we summarize the power of the devices that we plan to simultaneously connect to the line. Let's add up, for example, the power of a washing machine 2000 W, a hair dryer 1000 W and an arbitrary heater 1500 W. We received 4500 W or 4.5 kW.
• Then we divide our result by the standard voltage of a household network of 220 V. We got 20.45 ... A, round up to a whole number, as expected.
• Next, we introduce a correction factor, if necessary. The value with the coefficient will be equal to 16.8, rounded 17 A, without the coefficient 21 A.
• We remember that we calculated the operating power parameters, but we also need to take into account the maximum permissible value. To do this, we multiply the current strength we calculated by 1.4, because the correction for thermal effects is 40%. We got: 23.8 A and 29.4 A, respectively.
• This means that in our example, for safe operation of open wiring, a cable with a cross-section of more than 3 mm² will be required, and for a hidden version, 2.5 mm².

Let's not forget that, due to various circumstances, we sometimes turn on more units at the same time than we expected. That there are also light bulbs and other devices that consume little energy

Let's stock up on some reserve section in case of increasing the fleet of household appliances and, with calculations, go for an important purchase