Cable products are now presented on the market in a wide range, cross section cores range from 0.35 mm.sq. and above, this article will give an example cable cross-section calculation.

To calculate the conductor resistance, you can use the conductor resistance calculator.

Wrong selection of cable cross-section for household wiring, can lead to the following results:

1. A linear meter of too thick core will cost more, which will cause a significant “blow” to the budget.

2. The conductors will soon begin to heat up and will melt the insulation if the wrong conductor diameter is selected (smaller than necessary) and this can soon lead to a short circuit or spontaneous combustion of the electrical wiring.

In order not to waste money, it is necessary to carry out the correct installation before installing electrical wiring in an apartment or house. cable cross-section calculation depending on current, power and line length.

Calculation of cable cross-section based on the power of electrical appliances.

Each cable has a rated power that it can withstand when operating electrical appliances. When the power of all electrical appliances in the apartment exceeds the calculated rating of the conductor, an accident will soon be inevitable.

You can calculate the power of electrical appliances in an apartment or house yourself; to do this, you need to write down the characteristics of each appliance separately on a sheet of paper (TV, vacuum cleaner, stove, lamps). Then all the obtained values ​​are summed up, and the finished number is used to select the optimal diameter.

The power calculation formula looks like this:

Ptotal = (P1+P2+P3+…+Pn)*0.8, where: P1..Pn is the power of each electrical appliance, kW

It is worth paying attention to the fact that the resulting number must be multiplied by a correction factor - 0.8. This coefficient means that only 80% of all electrical appliances will work at the same time. This calculation will be more logical, because a vacuum cleaner or hair dryer will definitely not be in use long time nonstop.

An example of calculating cable cross-section by power is shown in the tables:

For conductor with aluminum conductors.

For conductor with copper conductors.

As can be seen from the tables, their data has meanings for each specific type of cable, you just need to find the closest power value and look at the corresponding cross-section of the cores.

For example calculation of cable cross-section by power looks like that:

Let's say that in the apartment total power of all devices is 13 kW. It is necessary to multiply the obtained value by a factor of 0.8, as a result this will give 10.4 kW of actual load. Then the appropriate value must be found in the table column. The nearest figure is 10.1 at single-phase network(220V voltage) and with a three-phase network the figure is 10.5. This means we choose the cross-section for a single-phase network on a 6 mm conductor or for a three-phase network on a 1.5 mm conductor.

Calculation of cable cross-section based on current load.

More accurate calculation of cable cross-section for current, so it is best to use it. The essence of the calculation is similar, but in in this case It is only necessary to determine what the current load on the electrical wiring will be. First you need to calculate the current strength for each of the electrical appliances using formulas.

Average power household electrical appliances

An example of displaying the power of an electrical appliance (in this case, an LCD TV)

To calculate, you need to use this formula if the apartment has a single-phase network:

I=P/(U×cosφ)

When the network is three-phase, the formula will look like this:

I=P/(1.73×U×cosφ), where P is the electrical power of the load, W;

• U - actual network voltage, V;
• cosφ - power factor.

It should be noted that the values ​​of the table values ​​will depend on the conditions of laying the conductor. Power and current loads will be significantly greater during installation open wiring than if the wiring is in a pipe.

It is recommended to multiply the resulting total value of currents for the reserve by 1.5 times, because over time, more powerful electrical appliances can be purchased for the apartment.

Calculation of cable cross-section along the length.

You can also calculate the cable cross-section based on length. The essence of such calculations is that each of the conductors has its own resistance, which contributes to current loss as the length of the line increases. It is necessary to choose a conductor with larger cores if the loss value exceeds 5%.

Calculations proceed as follows:

• The total power of all electrical appliances and current are calculated.
• Then the resistance of the electrical wiring is calculated using the formula: conductor resistivity (p) * length (in meters).
• It is necessary to divide the resulting value by the selected cable cross-section:

R=(p*L)/S, where p is the tabular value

You should pay attention to the fact that the length of current passage must be multiplied by 2 times, since initially the current flows through one core and returns back through the other.

• The voltage loss is calculated: the current is multiplied by the calculated resistance.
• Next, the amount of losses is determined: voltage losses are divided by the network voltage and multiplied by 100%.
• The final number is analyzed. If the obtained value is less than 5%, then the selected core cross-section can be left, but if it is more, then it is necessary to select a thicker conductor.

Resistivity table.

It is imperative to make calculations taking into account losses along the length if the line is stretched over a fairly long distance, otherwise there is a high probability select cable section wrong.

Conductor cross-section for power and current for electrical wiring in an apartment

Electrical installation work is a complex and responsible undertaking. If your qualifications are sufficient to do the electrical wiring in the apartment with your own hands, these will come in handy useful tips. If not, then use the services of electrical installation specialists. So, let's talk about choosing the cross-section of wires for current and power in detail.

Calculation of the length and maximum load of electrical wiring

Correct calculation of wire cross-section for power and current - important condition uninterrupted and trouble-free operation of the electrical system. First, calculate the total wiring length. The first way is to measure the distances between panels, switches and sockets on the wiring diagram, multiplying the number by the scale. The second way is to determine the length according to the location where the electrical wiring is designed. It includes all wires, installation and installation cables along with fastenings, support and protective structures. Each segment must be extended by at least 1 cm, taking into account the wire connections.

Next, the total load of consumed electricity is calculated. This is the sum of the rated powers of all electrical appliances that will operate in the house (*see table at the end of the article). For example, if in the kitchen an electric kettle, electric stove, microwave, lamps are turned on at the same time, Dishwasher, we sum up the powers of all devices and multiply by 0.75 (simultaneity coefficient). The load calculation must always have a margin of reliability and strength. We remember this figure to determine the cross-section of the wire cores.

A simple formula will help you determine the current consumption of any electrical appliance yourself. Divide the power consumption (see the instructions for the device) by the network voltage (220 V). For example, according to the passport, the power of the washing machine is 2000 W; 2000/220 = maximum current during operation will not exceed 9.1A.

Another option is to use the recommendations of the PUE (Electrical Installation Rules), according to which standard apartment wiring with a continuous load of 25A is calculated for the maximum current consumption and is carried out with copper wire with a cross-section of 5mm 2. According to the PUE, the cross-section of the core must be at least 2.5 mm 2, which corresponds to a conductor diameter of 1.8 mm.

This current is set to circuit breaker at the entrance of wires into the apartment to prevent accidents. In residential buildings, single-phase current with a voltage of 220 V is used. We divide the calculated total load by the voltage value (220 V) and obtain the current that will pass through the input cable and the machine. You need to buy a machine with exact or similar parameters, with a margin of current load.

Choosing a cable for electrical wiring in an apartment

* Table of power consumption and current
household electrical appliances with a supply voltage of 220V

Household electrical appliance	Power consumption depending on the model of the electrical appliance, kW (BA)	Current consumption, A	Note
Incandescent lamp
Electric kettle			Continuous operation time up to 5 minutes
Electric stove			For power greater than 2 kV, separate wiring is required
Microwave
Electric meat grinder
Coffee grinder			During operation, the current consumption varies depending on the load.
Coffee maker
Electric oven			During operation, the maximum current is consumed periodically
Dishwasher
Washing machine			Maximum current consumed from the moment of switching on until the water is heated
			During operation, the maximum current is consumed periodically
			During operation, the current consumption varies depending on the load.
Desktop computer			During operation, the maximum current is consumed periodically
Power tools (drill, jigsaw, etc.)			During operation, the current consumption varies depending on the load.

When renovations are planned in a house or apartment, replacing the wiring is one of the most important jobs. Not only the durability of the electrical wiring, but also its functionality depends on the correct choice of wire cross-section. The correct calculation of the cable cross-section by power can be carried out by a qualified electrician who can not only select a suitable cable, but also carry out installation. If the wires are chosen incorrectly, they will heat up, and under high loads they can lead to negative consequences.

As you know, when a wire overheats, its conductivity decreases, which ultimately leads to even greater overheating. When a wire overheats, its insulation can become damaged and lead to a fire. So that after installation new wiring do not worry about your home, you should initially perform the correct calculation of the cable power and give this issue special importance and attention.

Why carry out cable calculations based on load current?

Wires and cables through which leaks electricity, are the most important part of electrical wiring. The wire cross-section must be calculated to ensure that the selected wire meets all reliability requirements and safe operation electrical wiring.

An incorrectly selected cable cross-section will lead to overheating of the wire and, as a result, after a short time you will have to call a specialist to troubleshoot electrical wiring problems. Calling a specialist today costs a lot, so in order to save money, you need to do everything correctly from the beginning, in which case you can not only save money, but also protect your home.

It is important to remember that the electrical and fire safety of the room and those who are or live in it depends on the correct choice of cable cross-section.

Safe operation lies in the fact 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 affects the calculation of the cross-section of a wire or cable

There are many factors influencing, which are fully described in paragraph 1.3 of the PUE. This paragraph provides for the calculation of cross-section for all types of conductors.

In this article, dear readers of the “Electrician in the House” website, we will consider the calculation of wire cross-section based on power consumption for copper conductors in PVC and rubber insulation. Today, such wires are mainly used in houses and apartments for installing electrical wiring.

The main factor for cable cross-section calculation The load used in the network or the current is considered. Knowing the power of the electrical equipment, we will obtain the rated current as a result of a simple calculation using the formulas below. Based on this, it turns out that the cross-section of the wires is directly related to design power electrical installations.

When calculating the cable cross-section, the choice of conductor material is also important. Perhaps every person knows from physics lessons at school that copper has much higher conductivity than the same wire made of aluminum. If we compare copper and aluminum wires of the same cross-section, the former will have higher performance.

Also important when calculating the cable cross-section is the number of cores in the wire. A large number of the veins heat up much higher than a single-core wire.

The method of laying the wires is also of great importance when choosing a cross-section. As you know, earth is considered a good heat conductor, unlike air. Based on this, it turns out that a cable laid under the surface of the earth can withstand a greater electrical load, unlike those in the air.

When calculating the cross section, do not forget that when wires are in a bundle and placed in special trays, they can heat up against each other. Therefore, it is quite important to take this point into account when making calculations, and, if necessary, make appropriate adjustments. If there are more than four cables in a box or tray, then when calculating the wire cross-section, it is important to enter a correction factor.

As a rule, on right choice The cross-section of the wire also affects the air temperature at which it will be operated. In most cases, the calculation is made from the average ambient temperature + 25 degrees Celsius. If temperature regime does not meet your requirements, then in table 1.3.3 PUE there are correction factors that need to be taken into account.

The calculation of the cable cross-section is also affected by the voltage drop. If in extended cable line If a voltage drop of more than 5% is expected, then these indicators must be taken into account in the calculations.

Calculation of wire cross-section based on power consumption

Each cable has its own power rating, which it can withstand when an electrical appliance is connected.

In the case when the power of the appliances in the house exceeds the load capacity of the wire, then in this case an emergency situation cannot be avoided and sooner or later the wiring problem will make itself felt.

To independently calculate the power consumption of appliances, you need to write down on a piece of paper the power of all available electrical appliances that can be connected simultaneously (electric kettle, TV, vacuum cleaner, hob, computer, etc.).

Once the power of each device is known, all values ​​must be summed up to understand the total consumption.

Where K o is the simultaneity coefficient.

Let's look at an example calculating wire cross-section for regular two-room apartment. The list of necessary devices and their approximate power is indicated in the table.

Based on the obtained value, you can continue calculations with the choice of wire cross-section.

If the house has powerful electrical appliances with a load of 1.5 kW or more, it is advisable to use a separate line to connect them. When making your own calculations, it is important not to forget to take into account the power of the lighting equipment that is connected to the network.

When properly produced, each room will provide approximately 3 kW, but do not be afraid of these figures, since all devices will not be used at the same time, and, therefore, this value has a certain margin.

When calculating the total power consumed in the apartment, it turned out result 15.39 kW, now this indicator should be multiplied by 0.8, which will result in 12.31 kW actual load. Based on the obtained power indicator, you can use a simple formula to calculate the current strength.

Calculation of cable cross-section for current

The main indicator by which a wire is calculated is its longevity. Simply put, this is the amount of current that it can pass for a long time.

Knowing the current load, you can obtain more accurate calculations of the cable cross-section. Besides, everything cross-section selection tables in GOST and regulatory documents are based on current values.

The meaning of calculation is similar to that of power, but only in this case it is necessary to calculate the current load. To calculate the current cable cross-section, the following steps must be carried out:

• - select the power of all devices;
• - calculate the current that passes through the conductor;
• - Use the table to select the most suitable cable cross-section.

To find the rated current value, you need to calculate the power of all connected electrical appliances in the house. What you and I, friends, have already done in the previous section.

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 strength for single-phase network 220 V:

• - P - total power of all electrical appliances, W;
• - U - network voltage, V;
• - for household electrical appliances cos (φ) = 1.

2) Formula for calculating the current strength in three-phase network 380 V:

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 from the table the nearest larger 27 A - with a cross-section of 2.5 mm2 (for stranded copper wire laid through the air).

I present to your attention tables of permissible current loads of cables with copper and aluminum conductors with insulation made of polyvinyl chloride plastic.

All data is taken not from the head, but from normative document GOST 31996-2012 “POWER CABLES WITH PLASTIC INSULATION”.

For example, you have a three-phase load with a power of P = 15 kV. It is necessary to select a copper cable (over-the-air installation). How to calculate the cross section? First, you need to calculate the current load based on the given power; for this we use the formula for a three-phase network: I = P / √3 380 = 22.8 ≈ 23 A.

According to the table of current loads, we select a cross-section of 2.5 mm2 (for it the permissible current is 27A). But since you have a four-core cable (or five, there is not much difference), according to the instructions of GOST 31996-2012, the selected current value must be multiplied by a factor of 0.93. I = 0.93 * 27 = 25 A. What is permissible for our load (design current).

Although, in view of the fact that many manufacturers produce cables with a reduced cross-section, in this case I would advise taking a cable with a reserve, with a cross-section an order of magnitude higher - 4 mm2.

Which wire is better to use: copper or aluminum?

Today, for the installation of both open and hidden electrical wiring, copper wires are, of course, very popular. Copper, compared to aluminum, is more effective:

1) it is stronger, softer and does not break in places of inflection compared to aluminum;

2) 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;

3) the conductivity of copper is higher than that of aluminum; with the same cross-section, a copper wire can withstand a greater current load than aluminum.

As for the conductor material, only copper wire is subject to consideration in this article, since in most cases it is used as electrical wiring in houses and apartments. Among the advantages of this material are durability, ease of installation and the ability to use a smaller cross-section compared to aluminum, with the same current. If the cross-section of the wire is large enough, then its cost exceeds all the advantages and the best option would be to use an aluminum cable rather than a copper one.

For example, if the load is more than 50 A, then in order to save money, it is advisable to use cables with an aluminum core. Usually these are areas where electricity enters the house, where the distance exceeds several tens of meters.

An example of calculating the cable cross-section for an apartment

Having calculated the load and decided on the material (copper), consider an example calculating wire cross-section for certain consumer groups, using the example of a two-room apartment.

As you know, the entire load is divided into two groups: power and lighting.

In our case, the main power load will be the socket group installed in the kitchen, living rooms and bathroom. Since the most powerful equipment is installed there (electric kettle, microwave, refrigerator, boiler, washing machine and so on.).

1. Water cable

Input cable cross-section(the section from the switchboard on the site to the distribution board of the apartment) is selected based on the total power of the entire apartment, which we received in the table.

First, we find the rated current in this section relative to a given load:

The current is 56 Amperes. Using the table, we find the cross section corresponding to a given current load. We choose the nearest larger value - 63 A, which corresponds to a cross section of 10 mm2.

2. Room No. 1

Here the main load on the socket group will be such equipment as a TV, computer, iron, vacuum cleaner. The load on the wiring section from the apartment panel to the distribution box in this room is 2990 W (rounded up to 3000 W). We find the rated current using the formula:

Using the table, we find a cross section that corresponds to 1.5 mm2 and the permissible current is 21 Amperes. Of course, you can take this cable, but it is recommended to lay the socket group with a cable with a cross-section of AT LEAST 2.5 mm2. This is also related to the denomination circuit breaker, which will protect this cable. It is unlikely that you will power this area from a 10 A machine? And most likely install the machine at 16 A. Therefore, it is better to take it with a reserve.

Friends, as I already said, we power the socket group with a cable with a cross-section of 2.5 mm2, so for wiring directly from the box to the sockets we choose it.

3. Room No. 2

Here, equipment such as a computer, vacuum cleaner, iron, and possibly a hair dryer will be connected to the sockets.

The load in this case is 4050 W. Using the formula we find the current:

For this current load, a wire with a cross-section of 1.5 mm2 is suitable for us, but here, similarly to the previous case, we take it with a margin and accept 2.5 mm2. We also do the connection of sockets.

4. Kitchen

In the kitchen, the socket group powers the electric kettle, refrigerator, microwave, electric oven, electric stove and other appliances. Perhaps a vacuum cleaner will be connected here.

The total power of kitchen consumers is 6850 W, the current is:

For such a load, according to the table, select the nearest larger cable cross-section - 4 mm2, with a permissible current of 36 A.

Friends, I stipulated above that it is advisable to connect powerful consumers with a separate independent line (your own). The electric stove is just that, for her cable cross-section calculation performed separately. When installing electrical wiring for such consumers, an independent line is laid from the switchboard to the connection point. But our article is about how to correctly calculate the cross-section and in the photo I did not do this on purpose for better assimilation of the material.

5. Bath

The main consumers of electricity in this room are st. car, water heater, hair dryer, vacuum cleaner. The power of these devices is 6350 W.

Using the formula we find the current:

Using the table, we select the nearest higher current value - 36 A, which corresponds to a cable cross-section of 4 mm2. Here again, friends, it is advisable to power powerful consumers with a separate line.

6. Hallway

In this room, portable equipment is usually used, for example, a hair dryer, vacuum cleaner, etc. There are no particularly powerful consumers expected here, but we also accept a wire with a cross-section of 2.5 mm2 for the socket group.

7. Lighting

According to the calculations in the table, we know that the total lighting power in the apartment is 500 W. The rated current for such a load is 2.3 A.

In this case, the entire lighting load can be powered by a wire with a cross-section of 1.5 mm2.

It is necessary to understand that the power in different sections of the electrical wiring will be different, and accordingly the cross-section of the supply wires will also be different. Its greatest value will be in the introductory section of the apartment, since the entire load passes through it. The cross-section of the input supply wire is selected 6 - 10 mm2.

Currently, for installation of electrical wiring, it is preferable to use cables of the following brands: VVGng, VVG, NYM. The “ng” indicator indicates that the insulation is not subject to combustion - “non-flammable”. These types of wires can be used both indoors and outdoors. The operating temperature range of these wires varies from “+/-” 50 degrees Celsius. The warranty period is 30 years, but the service life may be longer.

If you know how to correctly calculate the current cross-section of a conductor, you can install electrical wiring in your house without any problems. If all requirements are met, the safety and security of your home will be guaranteed to be as high as possible. By choosing the right conductor cross-section, you will protect your home from short circuits and fires.

The issue of choosing a cable cross-section for installing electrical wiring in a house or apartment is very serious. If this indicator does not correspond to the load in the circuit, then the wire insulation will simply begin to overheat, then melt and burn. The final result is short circuit. The thing is that the load creates a certain current density. And if the cable cross-section is small, then the current density in it will be high. Therefore, before purchasing, it is necessary to calculate the cable cross-section according to the load.

Of course, you shouldn’t just randomly choose a wire with a larger cross-section. This will primarily hit your budget. With a smaller cross-section, the cable may not withstand the load and will quickly fail. Therefore, it is best to start with the question, how to calculate the cable load? And only then, based on this indicator, select the electrical wire itself.

Power calculation

The easiest way is to calculate the total power that the house or apartment will consume. This calculation will be used to select the cross-section of the wire from the power line pole to the input circuit breaker in the cottage or from the entrance switchboard to the apartment to the first distribution box. Wires in loops or rooms are calculated in the same way. It is clear that the input cable will have the largest cross-section. And the farther you are from the first distribution box, the less this figure will decrease.

But let's get back to the calculations. So, first of all, it is necessary to determine the total power of consumers. Each of them (household appliances and lighting lamps) has this indicator marked on the body. If you can’t find it, look in your passport or instructions.

After which all powers must be added up. This is the total power of the house or apartment. Exactly the same calculation must be made for the contours. But there is one controversial point. Some experts recommend multiplying the total indicator by a reduction factor of 0.8, adhering to the rule that not all devices will be connected to the circuit at the same time. Others, on the contrary, suggest multiplying by an increasing factor of 1.2, thereby creating a certain reserve for the future, due to the fact that there is a high probability of additional household appliances appearing in the house or apartment. In our opinion, the second option is the optimal one.

Cable selection

Now, knowing the total power indicator, you can select the wiring cross-section. The PUE contains tables that make it easy to make this choice. Let's give some examples for an electric line running at 220 volts.

• If the total power is 4 kW, then the wire cross-section will be 1.5 mm².
• Power 6 kW, cross-section 2.5 mm².
• Power 10 kW – cross-section 6 mm².

There is exactly the same table for electrical network voltage 380 volts.

Current load calculation

This is the most accurate value of the calculation carried out on the current load. The formula used for this is:

I=P/U cos φ, where

• I is the current strength;
• P – total power;
• U – network voltage (in this case 220 V);
• cos φ – power factor.

There is a formula for a three-phase electrical network:

I=P/(U cos φ)*√3.

It is by the current indicator that the cable cross-section is determined according to the same tables in the PUE. Again, let's give a few examples.

• Current 19 A – cable cross-section 1.5 mm².
• 27 A – 2.5 mm².
• 46 A – 6 mm².

As in the case of determining the power cross-section, here it is also best to multiply the current indicator by a multiplying factor of 1.5.

Odds

There are certain conditions under which the current inside the wiring can increase or decrease. For example, in open electrical wiring, when the wires are laid along walls or ceilings, the current strength will be higher than in closed scheme. This is directly related to temperature environment. The larger it is, the more current this cable can carry.

Attention! All of the above listed PUE tables are calculated under the condition that the wires are operated at a temperature of +25C with the temperature of the cables themselves not exceeding +65C.

That is, it turns out that if several wires are laid at once in one tray, corrugation or pipe, then the temperature inside the wiring will be increased due to the heating of the cables themselves. This leads to permissible load current is reduced by 10-30 percent. The same applies to open wiring inside heated rooms. Therefore, we can conclude: when calculating the cable cross-section depending on the current load at elevated temperatures operation, you can choose wires with a smaller area. This is, of course, a good saving. By the way, there are also tables of reducing coefficients in the PUE.

There is one more point that concerns the length of the used electric cable. The longer the wiring, the greater the voltage loss in the sections. Any calculations use a loss of 5%. That is, this is the maximum. If the losses are greater than this value, then the cross-section of the cable will have to be increased. By the way, it’s not difficult to independently calculate current losses if you know the wiring resistance and current load. Although best option– use the table of PUE, which establishes the relationship between the load moment and losses. In this case, the load torque is the product of the power consumption in kilowatts and the length of the cable itself in meters.

Let's look at an example in which an installed cable 30 mm long in an alternating current network with a voltage of 220 volts can withstand a load of 3 kW. In this case, the load moment will be equal to 3*30=90. We look at the PUE table, which shows that losses of 3% correspond to this moment. That is, it is less than the nominal value of 5%. What is acceptable. As mentioned above, if the calculated losses exceeded the five percent barrier, then it would be necessary to purchase and install a cable with a larger cross-section.

Attention! These losses greatly affect lighting with low-voltage lamps. Because at 220 volts 1-2 V is not reflected much, but at 12 V it is immediately visible.

Currently, aluminum wires are rarely used in wiring. But you need to know that their resistance is 1.7 times greater than that of copper ones. And that means their losses are just as many times greater.

As for three-phase networks, the load torque here is six times greater. This depends on the fact that the load itself is distributed over three phases, and this is a corresponding exponential increase in torque. Plus a double increase due to the symmetrical distribution of power consumption across phases. In this case, the current in the zero circuit must be zero. If the phase distribution is asymmetrical, and this leads to an increase in losses, then you will have to calculate the cable cross-section for the loads in each wire separately and select it according to the maximum calculated size.

Conclusion on the topic

As you can see, to calculate the cable cross-section for loads, you have to take into account various coefficients (reducing and increasing). It’s not easy to do this on your own, if you understand electrical engineering at the level of an amateur or a novice master. Therefore, my advice is to invite a highly qualified specialist, let him do all the calculations himself and draw up a competent wiring diagram. But you can do the installation yourself.

So, the known power of each electrical appliance in the house, a known quantity lighting fixtures and lighting points allow you to calculate the total power consumed. This is not an exact sum, since most values ​​for the powers of various devices are averages. Therefore, you should immediately add 5% of its value to this figure.

Average power readings for common electrical appliances

Consumer	Power, W
TV	300
Printer	500
Computer	500
Hair dryer	1200
Iron	1700
Electric kettle	1200
Toaster	800
Heater	1500
Microwave	1400
Oven	2000
Fridge	600
Washing machine	2500
Electric stove	2000
Lighting	2000
Instantaneous water heater	5000
Boiler	1500
Drill	800
Hammer	1200
Welding machine	2300
Lawnmower	1500
Water pump	1000

And many believe that this is enough to select almost standard copper cable options:

• cross section 0.5 mm2 for wires for lighting spotlights;
• cross section 1.5 mm2 for lighting wires for chandeliers;
• cross-section 2.5 mm2 for all sockets.

At the level household use electricity, such a scheme looks quite acceptable. Until the refrigerator and electric kettle decided to turn on in the kitchen at the same time, while you were watching TV there. The same unpleasant surprise overtakes you when you plug in a coffee maker, washing machine and a microwave.

Thermal calculation using correction factors

For several lines in one cable channel, the tabulated values ​​of the maximum current should be multiplied by the appropriate coefficient:

• 0.68 — for the number of conductors from 2 to 5 pcs.
• 0.63 — for conductors from 7 to 9 pcs.
• 0.6 — for conductors from 10 to 12 pcs.

The coefficient refers specifically to the wires (cores), and not to the number of passing lines. When calculating the number of laid wires, the neutral working wire or grounding wire is not taken into account. According to PUE and GOST 16442-80, they do not affect the heating of wires during the passage of normal currents.

Summarizing the above, it turns out that in order to correctly and accurately select the wire cross-section, you need to know:

1. The sum of all maximum power electrical appliances.
2. Network characteristics: number of phases and voltage.
3. Characteristics of cable material.
4. Tabular data and coefficients.

At the same time, power is not the main indicator for an individual cable line or the entire internal system electricity supply When selecting a cross-section, be sure to calculate the maximum load current, and then check it with the rated current of the home circuit breaker.