How to calculate the cross section of cable and wire

The standards describe in detail the dimensions( cross section), the mass, the type of insulation and the core material, but the main thing is missing - the transmitted power. More precisely, test values ​​that differ in the lower direction specified in the manufacturer's prices come across. That break the master's head with the calculation of the cross section of cable and wire. You do not want to overpay, and putting less than necessary, we risk the start of a fire! It is necessary to search in PUE 6, the new edition has deleted the necessary tables.

How a cable section is chosen for installation in an apartmentAssumes the number of lines is not less than the number of rooms. Automata are used at 10 A on the assumption that the actuation happens earlier than the insulation begins to melt.
  • For outlets, the wiring is taken at 2.5 square millimeters on copper. It is supposed to place on every 4 meters of the room perimeter on the point. The kitchen has 4 sockets, and a double is counted for a couple( in residential areas it is not counted).For example, two tandems crash into the kitchen, and for the hall, according to the number of meters of the perimeter( a steam room is considered one).Automatic machines are taken at 16 A.
  • If the house has an electric cooker, the wiring goes to the shield. Such a socket is not doubled, otherwise the rule prescribed in the standards is violated. The copper section is taken six square millimeters, and the capacity of the machine increases to 20 A.
  • The choice of cable for the apartment

    We need to take into account a number of points. First, the recommendations of A. Zemskov are available to anyone who does not want to bother and consider the cross section of the wires in the cable. Proven methodology: the machine will turn off before the start of melting wiring. Many are not satisfied with the quantitative side. Suppose a machine with 20 A can withstand 20 x 220 = 4.5 kW of power. Get an idea of ​​the amount of consumption is not so simple.

    Typically, burners are on 1 kW.In practice, a considerable contribution is made by efficiency. Actually electric stove for 4 burners can consume from 6 kW and above. A. Zemskov calls this figure, speaking of the automaton at 20 A. Readers will notice a discrepancy: with a consumption of 6 kW, much more current is needed. In fact, most automata can work an hour with overload by 45%.So, our RCD at 20 And in time will be cut out.

    The above will happen at full load. Consumption from 6 kW means use to the full extent of all burners. This happens infrequently. The rest of the time, the electric cooker rests and the wiring cools down. Equilibrate and relay contacts inside the machine. RCD is capable and does not shut down at all, despite the formal excess of rated current. Note that according to the dealers, when the wire is closed, the power per 6 square millimeters of the cross-section for copper is 7.4 kW( current 34 A).The author reinsured what to do when arranging the electrical wiring in the apartment.

    Automatic will work earlier. Already at a current of 34 And he will not work even half an hour. Therefore, the insulation will not overheat and not melt. This is a guarantee of durable work. From what has been said, readers should already learn how to determine the cross-section of a wire by power.

    Electricity consumption per branch

    The branch consumption is estimated first. If these are LED bulbs of the upper illumination, the assessment is allowed not to be made simply by selecting the thinnest and cheapest( but certainly copper) core. If you need to power the welding machine, you have to think about brains. The use of equipment in the home is not implied, but you can estimate the power consumption already on the plate on the case. Suppose a current of 220 A at 27 V means that 6 kW is formed on the secondary side of the inverter.

    Standards prescribe connecting high-power equipment directly to a switchboard( not in parallel).You should choose the place of use of the equipment, for example, a balcony. By the way, there is no outlet in the storeroom according to the rules( the fire hazard class is too high).Therefore, in the allowed place lay the distribution point.

    Do not forget to put the machine. Welding has individual conditions. Suppose we talked about 6 kW, but actually the inverter is obliged to operate in this mode no more than 70% of the working cycle. Consequently, it is necessary to worry, rather, not about the long-term mode, but about the start. From this point of view, RCDs are divided into tolerance classes for short-term current overshoot.

    Conclusion of wires

    Estimation of consumption by the maximum

    Secondly, the assessment of consumption currents is carried out. In any case should not reach the limit. To calculate the cable cross-section for power, physics of instrument operation is needed. For example, asynchronous motors at the start consume a higher rated current. If you take the refrigerator, standing in the compressor, it is not so important( power is low).

    Too sensitive automatic( class A) can not be put here. Electric cookers differ in smaller scatter of parameters. For them, they recognize the cable section by the diameter as described above. Do not forget to take into account culinary preferences. Long-cooking dishes impose restrictions. The algorithm comes from the end: we ask the hostess how long the plate is loaded in full mode, find the power from the directories, determine the current, take a margin of 5%, calculate the thickness of the core, make a margin of another 10%, then select the circuit breaker that turns off the networkdetermined by the mistressSo the cable will not work for too long at the limit.

    Combining two or more branches of the

    . When combining branches, the cable section is determined by simple addition in power. It is impossible to operate with squares. To calculate the wire cross section, use the table presented in the figure. Note that the bookmark is supposed to be closed.


    sectional calculation table for sections 0.5 and 0.75 is not recommended to be used unless wiring for lighting from energy-saving( halogen or LED) lamps. Then the problem of determining the wire cross section is not set. Moreover, it is permissible to put an automatic machine on an apartment, it is just not always convenient.

    For each core, a smaller current can flow than the wiring with a cross section of 0.5 square millimeters can withstand copper. Only in the main vein is significant heating. It will remain to merge the branches in the distribution panel. It is recommended to use ABB terminals from brass or to primitively wrap everything in a cap. Use for summing the branches of the conductors of a single cable is not worth it.

    Operating voltage

    To determine the cable conductor cross-section by diameter, the operating voltage is taken into account. By default, this is 220 V, and the wire is three-core. Happens, in new buildings they start 380 V with the use of designs from 4 cores. To calculate the current cross-section, use the second column of the table.

    As you can see, the core already has a lower power density. When calculating for 220 V each( except for grounding) current( say, 34 A), corresponding to a value of 220 x 34 = 7.4 kW, flowed. In the case of a larger number of phases, the power does not grow in direct proportion, but weaker. The more lived goes in a twist or within the same insulation, the more stringent the requirements, because the thermal effects are added. Those who want complex configurations will have to perform an in-depth search.

    How the conductor section varies depending on the method of installation of the

    Requirements for laying the cable with the open method

    If the cable is laid open, the conditions for its cooling are better, the requirements are reduced. The second figure presents a table demonstrating this pattern. With outdoor cabling, power limits increase. In this case, we present sections in aluminum, in addition to copper. Plus the fact that the cable is cheaper and with a larger volume. Aluminum is a light metal, and copper is heavier than steel. From this point of view, the laying of cables may be possible for someone. Therefore, it is necessary to proceed from the price and opportunities. But copper is more durable, has better conductivity and is not subject to electrochemical corrosion.

    Aluminum is not used for connecting high-power devices. Losses in copper cables are one and a half times lower, which is significant at high currents, unlike the scale of home ownership. You need to be guided by technical calculations based on the assessment of the length of the line, its purpose, method of installation. For example, it is known that a kilometer of ordinary wire has low resistance, which cannot be said about a cable.

    Many people are interested in distinguishing cable from wire. There is no separation in GOST, but a cable is usually understood as a product with a large cross section, and with reinforced insulation, for example, steel armor. When laying underground, in the basement and reinforced insulation using cable. Sometimes used oil to protect against corrosion. These parameters are separated wire and cable.

    The main difference is in isolation. Take, for example, a vole for communication. This is a wire with a small thickness of wires, and the type of insulation - cable. Also the power supply wires of the power tool are more likely to be cables for 2-3 cores. They are well protected from mechanical damage and have thick insulation.

    Focus on the reference information, GOST gives for copper greatly underestimated values, in practice significantly overlapping. Most of them are based on OLCs, where the required data for networks in one and three phases are given in Table 1.3.4 and others. It must be remembered that not all chapters of the document are adopted by law, although any right to be used for reference.

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