Wire cross-section for home wiring: how to calculate correctly

The installation of a household electrical network must be carried out in such a way that users can simultaneously turn on several powerful electrical appliances without any problems.Therefore, it is necessary to select the wire cross-section for home wiring based on a competent calculation of the parameters of the apartment and house electrical networks.

There are several calculation methods. We suggest that you familiarize yourself with different approaches and choose the best option. In addition to the technology for calculating the wire cross-section, the article describes the main parameters for choosing electrical wiring and indicates regulatory restrictions on the maximum power of electrical appliances.

Why know the wire parameters

Standard electrical sockets are designed for a continuous current of 16 A, which corresponds to a maximum power of 3.52 kW when the device is turned on. Usually they are connected to a copper cable with a cross-section of 2.5 mm², which can be misleading when choosing the type of wire for the rest of the electrical wiring.

In parallel with the increase in the cross-sectional area of ​​the cable, its price also increases. However, you should not save on electrical wiring - this can lead to much greater financial costs in the future.

When electrons move through a metal, some of the energy is dissipated as heat. With a large current and a small cross-section of the cable, the thermal component can lead to overheating of the metal and melting of its sheath.

In domestic conditions, this can initiate both an intra-wall short circuit and a fire in exposed wires, especially in kinked areas.

As a result, the following situations may arise:

1. Large-scale fireif there is flammable material near the cable.
2. Leakage current in case of incomplete melting of the core shell. This leads to wasted energy consumption and the possibility of electric shock to residents.
3. Unnoticeable wire break in the wall. As a result, part of the apartment or the entire room is de-energized. After this, a search for the break point and subsequent replacement of the wiring with local wall repairs are required.

Choosing a thick electrical wire for an apartment, with a margin, also has one drawback - overspending of funds, which does not make sense. Therefore, it is better to select the wiring cross-section using calculation methods in order to avoid all of the above problems.

Factors for choosing wire cross-section

It is not only the power of the device that determines the nature of the required electrical wiring. There are other factors, the influence of which must be taken into account when calculating the required cable cross-section. They can affect heat generation in the conductor, its fire hazard and performance characteristics.

To such wire selection factors include:

1. Core material: copper, aluminum.
2. Type of insulation: PTFE, PVC, PE and other plastics.
3. The length of the wire from the current source to the device.
4. Wiring method: open installation, hidden in the wall or using cable channels.
5. Temperature conditions in the room.
6. Number of phases and network voltage.
7. Wiring diagram.

Copper has less resistance than aluminum, so calculations for these materials are carried out separately. The cross-section of a copper core can be approximately 1.5 times smaller than that of an aluminum core.

The insulation material also affects the choice of electrical wire.There are special sheaths that can withstand high temperatures without melting or changing resistance, so such cables can be subjected to increased loads and used at elevated temperatures.

The degree of voltage drop depends on the length of the wire and its cross-section, so for the operation of sensitive electronics it is necessary to take these parameters into account.

Electrical wires closed in boxes or plastered in the wall lose heat to a lesser extent under prolonged loads, so they overheat faster and require a larger design cross-section.

The wiring running from the meter to the distribution boxes may generally experience simultaneous load from several devices plugged into different sockets. Therefore, the cross-section of these cable sections must be calculated separately.

Also, the load on the electrical cable depends on the voltage and the number of phases supplied. But since in everyday life predominantly single-phase wiring with a voltage of 220 V is used, the influence of this factor will not be considered.

Method for determining the cross-section of home wiring

When calculating the cross-section of an electric cable core at home wiring installation many factors are taken into account. There are special computer programs that allow you to take into account all the features of the house and the needs of its residents. But you can determine the cross-section required for wiring yourself using the described method.

It is important to understand that the diameter of the wires in the apartment may differ from room to room. At the entrance to the electric meter there is only one; at the distribution box the wire cross-section may already be smaller, at sockets and lamps - even smaller.

At each section of electrical wiring, it is advisable to determine the parameters necessary for it, so as not to overpay for excessively thick wires.

If you do not want to calculate the cross-section of the wiring being laid, you can use the recommendations of experienced electricians who claim:

Calculation of device power

The simplest method for determining the required wire cross-section is to calculate it taking into account the power of the electrical appliances in use and correction factors. This technique involves several stages.

Stage No. 1. Summing the power of electrical appliances. Ideally, you should know the rated energy consumption of each device, which is indicated on its label. If the living space is not yet equipped, then the approximate need for electricity can be calculated using table No. 1 below.

Household appliances of the same functionality and size can have power consumption that differs by 2-3 times, so its value must be looked at on each device (+)

When calculating, you can also use the parameters of devices that are located in similar apartments of relatives or friends. There is another option - go to a household appliance store, look at its characteristics, and at the same time look for a suitable model of equipment for your home.

Stage No. 2. Determination of the simultaneity factor. It can be expressed as a percentage or as a numerical value from 0 to 1. The coefficient shows the ratio of electricity consumption by devices simultaneously connected to the network to the total power of all home devices, calculated at the first stage.

Usually the coefficient is 0.8, but you can calculate it yourself based on the habits of home residents.

Do not overuse portable sockets, tees and extension cords. It is advisable to use only equipment with a built-in safety mechanism that turns off the power when the current is high.

Stage No. 3. Determination of safety factor. This indicator takes into account the possible increase in electricity consumption in a few years. Usually it is taken equal to 1.5-2, but if the house already has a full set of electrical appliances, then the coefficient value can be taken 1.2-1.3. The main thing is not to regret the small cross-section of wires in the future.

Stage No. 4. Calculation of maximum permissible load.

It is produced according to the formula:

P = (P(1)+P(2)+..P(N))*J*K,

Where:

• P – maximum permissible load in W;
• P(1)+P(2)+..P(N) – the sum of the rated powers of all electrical appliances;
• K – simultaneity coefficient;
• J – safety factor.

For example, if the total power of the devices is 7500 W, the simultaneity factor is 0.8, the safety factor is 1.5, then the maximum permissible load will be:

P=7500*0.8*1.5=9000 W.

This indicator will be used in subsequent calculations.

Stage No. 5. Determining the maximum permissible current.

The indicator is determined by a simple formula:

I=P/U,

Where:

• I – permissible current strength;
• P – maximum permissible load in W;
• U – mains voltage – 220 V.

Using the data from the fourth stage, you can determine the maximum permissible current:

I=9000W/220V41A.

The method for calculating the cable cross-section for power and current is described in detail in this article.

Stage No. 6. Calculation of cable cross-section according to the table. Since the optimal choice of wire for home wiring is influenced not only by the parameters of the devices, but also by external factors (core material, its sheath, installation diagram, etc.), each case has its own tables, which are discussed below.

Determination of electrical cable cross-section using tables

There are special tables to determine the optimal wire cross-section for home wiring. All of them are focused on the amount of permissible current, which is calculated separately according to the above method. Next we will consider tabular options determining the wiring cross-section.

Calculation of the cross-section of ordinary household wires is presented in the tables:

Due to the fragility of aluminum, wires from this material are made only with a cross-section of 2 mm. There are also no stranded aluminum wires made of thin wires (+)

Below is a calculation of the cross-section of wires for carriers and extension cords.

Extension cords in stores are rarely available with a wire cross-section exceeding 1.5 mm2, so you should not load them with powerful electrical appliances (+)

The current load on the electrical cable with open and closed installation differs. But they are considered the same if the wire is laid in the ground in a wide tray. This allows the cable to transfer heat to the surrounding air and heat up less.

The calculation of the cross-section for copper and aluminum conductors, depending on the method of laying the cable, is given in the table.

The maximum current also depends on the number of cores in the cable, because each of them generates heat, summed up under a single shell (+)

Similar tables are used when calculating electrical wiring and in industry. Household cables are usually much simpler, so the number of design materials for them is quite limited. The parameters indicated in the tables are not invented, but are indicated in industry standards, for example in GOST 31996-2012.

Voltage drop calculation

Not only the degree of heating of the core, but also the electrical voltage at the far end of the wire depends on the cross-section of the electrical cable. Household appliances are designed for certain parameters of the electrical network, and their constant discrepancy can lead to a reduction in the service life of the equipment.

If the voltage drops on the boiler, it is advisable to install a stabilizer so that the equipment does not experience additional loads due to inconsistencies in the operational characteristics of the electrical network

As the cable lengthens, a voltage drop occurs. This effect can be reduced by increasing the wire cross-section. It is considered critical to reduce the voltage at the end of the wire by 5% compared to its value at the current source.

This indicator can be calculated using the well-known formula:

Upad = I*2*(ρ*L)/S,

Where:

• ρ – metal resistivity, Ohm*mm2/m;
• L – cable length, m;
• S – conductor cross-section in mm2;
• Upfall – drop voltage, Volt;
• I – current flowing through the conductor.

If the calculated voltage drop is more than 5% of the rated voltage, then it is necessary to use a cable with a larger cross-section. This will ensure stable operation of the equipment.

Heating boilers, washing machines and other devices with many relays and sensors are especially sensitive to voltage values. This feature must also be taken into account when using carriers.

Regulatory restrictions

Utility companies that provide electricity to the population have the right to impose restrictions on the maximum total power of appliances in an apartment. This can be achieved by installing electricity meters with a certain capacity.

The device is equipped with automatic disposable or reusable fuses, which operate when the threshold current value is exceeded.

Soviet-style electricity meters are being massively replaced with electronic ones. They are even more sensitive to overloads, due to which they quickly fail

If you remove the plugs from the meter and connect it directly to the apartment wiring, then it is guaranteed to burn out if the operating mode is disrupted for a long time. Most Soviet meters installed in apartments can withstand a peak load of 25 A for up to 1 minute.

After this, they are burned, which can lead to payment for the installation of a new device and a fine for violating operating rules.

The wiring in the entrance is also unable to withstand high loads; if it burns out, it can cut off power to several apartments at once.Therefore, when connecting an apartment to the intra-house network with a 2.5 mm cable, you should not expect that a thicker intra-apartment wire will be able to withstand high loads.

It is especially important to take into account the factor of regulatory restrictions at the stage of planning the installation of electric heating, heated floors, infrared saunas and other energy-intensive equipment.

You must first consult with the relevant utility services about the possibilities of electrical equipment installed in front of the apartment.

If you decide to calculate the electrical wiring parameters yourself, then it will be useful for you to understand such concepts as: current, power and voltage. More details in the article - How to calculate power, current and voltage: principles and examples of calculations for domestic conditions

Conclusions and useful video on the topic

The videos contain practical advice from electricians on choosing and purchasing home wiring. They will help you purchase equipment that matches the cable, which will definitely protect your home from possible problems with network overloads.

Selecting cable cross-section in the store:

Correspondence between the cable cross-section and the parameters of the fuse box:

Selection of cable section and machine:

Mistakes when choosing an electrical cable:

The main factors when choosing a cable for home wiring are the power of household appliances and the limitations of the electrical networks that supply electrical energy to the apartment.

By choosing the right wire cross-section, you can connect all the necessary electrical appliances to the network. This eliminates the inconvenience when operating equipment and helps prevent fires in the wiring.

Do you have anything to add or have questions about calculating the wiring cross-section? Please leave comments on the publication and participate in discussions of the material.The contact form is located in the lower block.