Select cable cross-section by load. Choice of the cable section of the electrical network

Hello!

I've heard about some difficulties arising in the choice of equipment and its connection (which outlet is needed for the oven, the hob  or a washing machine). In order that you can quickly and easily solve it, as a good advice I suggest you read the tables below.

⃰ Safety shutdown device

Electrical connection at 220V / 380V

When choosing a wire, first of all you should pay attention to the rated voltage, which should not be less than in the network. In the second turn, attention should be paid to the material of the veins. The copper wire has more flexibility than the aluminum wire, and it can be soldered. Aluminum wires can not be laid on combustible materials.

Also note the cross-section of the conductors, which should correspond to the load in amperes. Determine the amperage in amperes by dividing the power (in watts) of all connected devices by the mains voltage. For example, the power of all devices 4.5 kW, voltage 220 V, is 24.5 amps. We will find the required cross-section of the cable from the table. This will be a copper wire with a cross-section of 2 mm 2 or an aluminum wire with a cross-section of 3 mm 2. When choosing the wire of the desired cross section, consider whether it will be easily connected to the electro-devices. The insulation of the wire must comply with the conditions of the gasket.

Marking of wires.

The 1st letter characterizes the material of the current-carrying vein:
   aluminum - A, copper - the letter is lowered.

The 2nd letter means:
   P is the wire.

The third letter designates the insulation material:
   B - shell of polyvinyl chloride plasticate,
   P is a polyethylene shell,
   P - rubber sheath,
   H is the shell of the nitric.
   The marks of wires and cords can also contain letters characterizing other elements of the design:
   O is a braid,
   T - for laying in pipes,
   P is flat,
   F is a metal folded shell,
   D - increased flexibility,
   And - increased protective properties,
   P is a braid of cotton yarn impregnated with an antistatic composition, and so on.
   For example: PV - copper wire with polyvinyl chloride insulation.

Installation wires PV-1, PV-3, PV-4 are intended for supplying power to electrical appliances and equipment, as well as for stationary laying of lighting electrical networks. PV-1 is manufactured with a single-conductor current-carrying copper core, PV-3, PV-4 - with twisted strands of copper wire. The cross-section of wires is 0.5-10 mm 2. The wires are painted PVC insulation. They are used in alternating circuits with a rated voltage not exceeding 450 V at a frequency of 400 Hz and in circuits direct current  with a voltage of up to 1000 V. The operating temperature is limited to -50 ... + 70 ° С.

The installation wire ПВС is intended for connection of electrical devices and equipment. The number of cores can be equal to 2, 3, 4 or 5. A conductor of soft copper wire has a cross-section of 0.75-2.5 mm 2. It is produced with twisted strands in PVC insulation and the same shell.

It is used in electric networks with a nominal voltage not exceeding 380 V. The wire is designed for a maximum voltage of 4000 V, with a frequency of 50 Hz, applied for 1 minute. The operating temperature is -40 ... + 70 ° С.

Installation wire PPPP is designed for laying stationary lighting networks. The number of cores can be 2.3 or 4. The veins have a cross section of 1.0-6.0 mm 2. A conductor made of soft copper wire has a plastic insulation in a PVC sheath. It is used in electric networks with a rated voltage not exceeding 250 V at a frequency of 50 Hz. The wire is designed for a maximum voltage of 1500 V with a frequency of 50 Hz for 1 minute.

Power cables brand ВВГ and ВВГнг are intended for transmission electric power  in fixed installations alternating current. The cores are made of soft copper wire. The number of cores can be 1-4. The cross-section of current-carrying conductors: 1.5-35.0 mm 2. Cables are manufactured with an insulating jacket made of PVC (PVC) plastic. Cables VVGng have low combustibility. They are used with a nominal voltage of not more than 660 V and a frequency of 50 Hz.

The NYM power cable is designed for industrial and household fixed installation indoors and outdoors. Cable wires have a single-wire copper core section 1.5-4.0 mm 2, isolated PVC-plastic. The outer shell, which does not support combustion, is also made of light-gray PVC compound.

Here, seems to be the main thing that it is desirable to understand when choosing equipment and wires to them))

On personal experience I was convinced that the thinner the wires, the worse their use for both devices and for wiring itself.

First, I will touch upon the main problems that arise when the wiring is incorrectly selected:

• Some devices do not have enough current, this is clearly visible on the welding machine, the thinner the wire, the worse it is to cook. But also you can see the difference in the light of the light bulb, if you connect, let's say a 150 Watt light bulb into the wiring with a cross section of 0.5 mm and 2.5 mm, then by 0.5 mm the light bulb will fade by 2.5 mm.
• The thinner the wires and the greater the power of the final instrument used, the more they heat up, to the point that they can ignite. It depends on that ( plain language) that the wires are more difficult to transmit a certain amount of current necessary for the consumption of the device. This is a loaded narrow road.
• This paragraph comes out of 2 points, but I will touch it separately. The places of connection of wires with a smaller section are faster oxidized and burned, as passing through them larger power flows than those calculated on the cross-section, heat these places faster, which subsequently leads to poor contact. Well, there, where the contact is bad, there is a possibility of strong heating, down to ignition of insulation and burning wires.

Always use the cross-section of the wires only that which fits the power of the device!

Now we approach your question.

Just want to warn that wires of the same cross section of the same material can differ in technical specifications, at least by the fact that the copper wires (about which you ask in the question) can be at least two options - single-core and stranded.

The wiring of the apartment uses single-core copper wire VVG, which is what I wanted to tell.

So what are your examples:

Copper wire cross-section 1 square

Virtually not used in the apartment, but can be connected to lED backlight  low power, as well as various light indicators.

Copper conductor cross-section 1.5 squared

These wires are used for lighting in the total value of consumers no more than 4 kW, i.e. consider all the light bulbs in power and the result should not exceed this value. Also they are used (I do not recommend putting them on those outlets where many electrical appliances are turned on) to connect the sockets of one device. For example, separately lights, TV, computer, vacuum cleaner, charging device  etc., in which the power is not more than 4 kW. Of course, you can use several devices in the same outlet, but such combinations as computer + vacuum cleaner + hair dryer are quite dangerous.

Copper wire cross-section 2 squares

This section is practically not used, I did not even see it on sale, so it makes no sense to focus on it.

Copper wire cross-section 2.5 squares

But 2.5 squares is the recommended wiring in the apartment (except as I mentioned above - electric stoves). This cross section is suitable for connecting several devices to one outlet at once, but in total not to exceed 5.8 kW. Either individual devices, such as:

• Fridge
• Water heater
• Washer
• Oven
• Machines working on the engine are not higher than 4,5 - 5,0 kW

For the right choice  section of the wire must take into account the value of the maximum current consumed by the load. The currents can be easily determined by knowing the rated power of the consumers using the formula: I = P / 220 where I is the current strength (A), P is the consumer power (W), V is the circuit voltage (V).
  For example, for an electric heater with a power of 2000W the current will be 9A, for a 60W bulb - 0.3A.
  Knowing the total current of all consumers, and considering the ratio of the current allowed for the current cable (open wiring) to the wire cross section:
- copper wire  10 Amps per millimeter square,
- of aluminum wire  8 Amps per millimeter square.
  When choosing the type of wire, you must also take into account the permissible insulation breakdown voltage.
When performing concealed wiring (in a tube or in a wall), the values ​​given are reduced by multiplying by a correction factor of 0.8.
It should be noted that open wiring is usually done with a wire with a section of at least 4 square meters. mm from the calculation of sufficient mechanical strength.
The above relationships are easy to remember and provide sufficient accuracy.
If it is required to know with greater accuracy the long-term permissible current load for copper wires  and cables, then you can use the table.

Table 1.

Permissible current for aluminum and copper wires.

• When the fuse is overloaded (in case of a circuit overload) to replace it, it is convenient to use a simplified formula that will allow the fuse to be correctly manufactured to any current with sufficient accuracy. For a solid copper wire, the fuse protection current is determined by the simplified formula: Ipr. = 80√ d3, where d is the diameter of the wire in millimeters.

The table shows the results of calculations for some commonly used wires.

To manufacture the fuse, the wire of the desired diameter can be taken from stranded mounting wires, carefully removing the insulation.

• What cable should I choose for wiring inside a dwelling?

  If to be puzzled by a lining electrical cable  inside the residential building, it seems that it is more convenient to work with the so-called "soft" wire. The most interesting, it is easier to bend and generally adapt to the specific features of the room. But the soft conductor has a number of features that must also be taken into account when choosing it.

How to choose a cable?
As you know, a soft wire consists of a set of thin conductors. And therefore, when connecting, the thin wires that make up the wire must be properly compressed. That is, to terminate or press a special tip, turning the end of the thin wires into a monolith. For this purpose, thin conductors can even be soldered together. And this is a certain disadvantage when using a "soft" wire. Because there is an additional operation. If, of course, do everything according to the rules. On the other hand, you can find products that are designed to correctly fix and securely clamp exactly the soft wires in accordance with the requirements of wiring.
The cable in which each conductor consists of a single core is called "hard." It can not be used in areas where frequent bends or vibrations are possible. For household purposes with the same success can be used as "soft" conductors, and "hard." The main thing is the reliability of installation and the compliance of the wiring with the load that it must withstand. If your house was built long ago, and it does not have a grounding conductor in the floorboards, purchase a three-wire house with an additional ground wire. You will need it in the future.
  The last thing you need to decide is the cable brand. The types of cables most commonly used for wiring are listed below.

  NYM (NUM) round cable, formed by copper single-wire veins, having PVC insulation, and two shells, making it more fireproof.
  It is very convenient in mounting due to its softness.


  PVS - is a flexible cable, having a round shape, which consists of stranded stranded annealed copper conductors with PVC insulation. Good flexibility makes this wire an excellent choice for use as a network cable for household appliances. However, for the installation of electrical wiring PVS is quite suitable.

  VVG - the cable consists of copper, single-wire cores and covered with PVC insulation, its shape is round or flat, compared to NYM, this cable is more compact, it is easy to lay in strobes or canals. There is a non-flammable appearance, bearing the BBGng label, it has fireproof additives in its shell and insulation, making its use safer. The cable can be used in wet and dry rooms, it is well suited for installation of electrical wiring of apartments and has a low cost.

Often used in the installation of electrical wiring apartments and wire PUNP, similar double insulation from PVC, but having single-wire veins made of copper. The finer isolation of the PPPP is offset by its lower cost compared to the BBG. The color of the PNPP insulation can be different.
When choosing a cable manufacturer, stop focusing on Moscow companies, since their insulation is slightly thicker than that of other companies.

While doing electrical wiring in the new house or replacing the old one during the repair, every home wizard asks himself: what kind of wire cross section is needed? And this question is of great importance, since it is precisely from the correct choice of the cable cross-section, as well as the material of its manufacture, that not only reliable operation of electrical appliances, but also the safety of all members of the family largely depends.

What wire to choose - the material of manufacture is in the first place

The most common types of wiring in our homes are aluminum and copper. Which is better - a question that still haunts users of numerous forums. For some, copper is the priority, while others say that there is no need to overpay and aluminum will be used for the home network. In order not to be unfounded, let's conduct a small analysis of these options and then everyone will be able to choose the option for themselves.

Aluminum wiring has a low weight, due to which it found its wide distribution in the electric power industry. It is used for laying power lines, because in this way it is possible to minimize the load on the supports. In addition, it has gained popularity due to its cheapness. Aluminum cable is several times less copper analog. During the Soviet Union, aluminum wiring was very common, it can still be found in houses built some 15-20 years ago.

However, the aluminum cable also has its negative sides. One of these moments, which is worth mentioning, is a short service life. Aluminum wiring after two decades becomes highly prone to oxidation and overheating, which often leads to fires. Therefore, if you still have such cables at home, think about replacing them. In addition, the oxidation to which aluminum is exposed reduces the useful cross-section of the cable with a simultaneous increase in resistance, and this leads to overheating. Another significant drawback of aluminum is its fragility. It breaks quickly if the cable is bent several times.

Important! PUE prohibits the use of aluminum cable  for laying in electrical networks, if its cross-section is less than 16 mm.

Copper cable bends well and does not break

As for the copper wire, its advantages include a long service life - more than half a century, excellent conductivity and mechanical strength. With a copper cable is much easier to work, because it bends, not breaking, and withstands multiple twists. The minus of the same posting from copper cable  is the cost. To replace power cable  the whole apartment will need a significant amount of money. In order to save some masters combine the gasket aluminum wires  with copper ones. The entire light portion is mounted in aluminum, and the outlet is made of copper, since the lighting does not require as much load as electrical appliances fed into the network.

Selecting a section - what you need to know and pay attention to

If before the equipment in the apartment was limited to a refrigerator and a TV set, nowadays you will not find anything in the apartment: vacuum cleaners, computers, hairdryers, microwave ovens, etc. All this requires food, and depending on the time of day, the load from the devices included in the network can vary greatly. And to correctly choose the cable for each point, which is fed to the device, you need to know.