The choice of cable cross-section for an apartment, house, cottage

The table of permissible currents is not entirely clear, the permissible current depends not only on the cross section, but also on the insulation material and the material of the conductor (although there is only copper), the number of cores and the way of laying. If the material is even less clear (few people will sculpt a cable with paper insulation such as ASB at the cottage or home), then the way of laying and the number of wires are important. So I probably would have climbed onto the manufacturer’s website before buying a cable and, using their catalog, specified how much cable passes under different conditions. Regarding the cross sections, I do not quite agree. Maybe 0.5 and a ride at short distances, but if you reduce the cross-section, then you need to calculate the voltage drop so that there are no badly burning lamps.

Tell me, can I use a 0.5 mm square cable for a 60 W bulb?

Petrovich: what voltage is the network? If 220 volts, then enough.

August 21, 2013 specially went through the electric shops of our city. I measured the diameter of the wires of the VVGng 3x2.5 wire. The required diameter for such a wire is 1.78 mm. Actual 1.5mm. The actual cross-section is 1.76 square.
I also measured a 3x4 wire. The actual diameter of 1.9 mm instead of 2.25 mm laid.
This means a section of 2.83 squares versus 4 on the price tag.
An explanation of the sellers is interesting: in these cables there is especially pure copper with reduced resistance, therefore, "The actual cross-section of the conductors may differ from the nominal one if the electrical resistance meets the requirements of this standard." (GOST 22483-77 p.1.4.a). Those. it is not forbidden to reduce the cross section, subject to the required resistance. GOST does not indicate the minimum and maximum value of the section, but only the nominal.

Dmitriy,
27.08.2013
It is forbidden, and 90% of manufacturers have such a story, it is all over Russia so that few people run around with a micrometer. But there are 10% who have everything as it should, respectively, and the price tag is higher and difficult to find, but possible. Good luck in your endeavors.

September 20, 2013
Returning to my comment from 08.21.13., I consider it necessary to give the arguments of the owner of the e / cable products store under the name Elektrolend:
"... The specific resistance of copper depends on the purity of its processing - the less impurities in the alloy, the lower the resistance, the less conductor cross-section can be made."
"... what does the resistance have to do with it? Ohm’s law is completely forgotten? The lower the resistance - the greater the current, hence the cable for wiring is selected. There is a standard series of sections to which standard resistances are attached.And if this resistance does not correspond to the declared section, then it’s necessary to declare deception, the diameter in this case does not play a role at all. "
"... accordingly, measuring the diameter of the wire, calculating the actual cross-section and then scolding Ukhta shops is wrong."
"... if you insist that you are being deceived - take a cross-section larger than the calculated one, then the supply will be guaranteed, even with a" trick. "In our practice, there were cases when clients for apartment wiring took six for outlets and four for light."

Dmitriy,
What kind of nonsense? 4mm2 and 6mm2 for stock? Where to the sockets? To sockets that hold 16A maximum?

You are now advising people ... The wiring in 4 squares will be intact, but all the sockets will play all the same (together with the apartment).

1.5mm2 (copper) for light and sockets, believe me, enough above the roof. Throw 2.5mm2 (kitchen) on the most swirling ones and only in rare cases will you need 4mm2 on the oven (and it’s very powerful).

In my apartment there are only 1.5mm2 and 2.5mm2 - and no problems, although there are enough powerful EFs. He’s been in electrics for 20 years, so listen to “practitioners” and not “theorists”

October 11, 2013
Vitaly, this is not my nonsense, this is nonsense of the owner of an electrical products store in our city. To my claims on the truncated diameter of the cores, he gave arguments, indicated by quotation marks. Our debate took place at the city forum Ukhta 24.
Everyone remained unconvinced.

Vitaliy, the section was taken with a margin, but the machines, as I understand it, were left at 16A. With this installation, the sockets will remain safe and sound, do not scare people :)

the conductor is selected by the smallest permissible rated current ... All !!! want to argue?

I will not argue, but I always chose the section and I will choose with a margin. It’s cheaper to buy an expensive wire than to build a new house.

The choice of wire for apartment wiring is a very crucial moment. From the correct choice of wire or cable for wiring depends on its reliability and, accordingly, the period of trouble-free operation. The main selection criterion is the cross section of the wire or cable core. The required cross-section is selected by the magnitude of the load that will be on this wiring line. The choice is made according to the reference tables, where, in addition to the load, the place and method of laying the wire (cable), as well as the material from which it is made, are taken into account. In addition, one more criterion for choosing conductors for wiring an apartment can be noted - this is the material from which the conductive core of the wire or cable is made.

I am the owner of the very shop that is here to mention.

I’ll ask you not to run into mine, as well as other stores - we sell what our factories produce, make claims, file them against them, and not against us. As for the cable - it is available in 2 types - according to TU and GOST. Almost everyone sells cable manufactured in accordance with TU - as it is cheaper and suits 99% percent of buyers, including professional installers. The GOST cable is much more expensive, for especially fastidious customers who come with micrometers, we can bring it to order, BUT - and there the diameter of the wire is sometimes less than calculated, although it is clearly written on the label - GOST.

Do not be foolish, gentlemen, electricians - do not look for the ends there.

The cross section of any wire (including cable for electrical wiring) is determined by the value, which is called "permissible current density". If you do not climb deep into physics, then the cable is enough for electrical wiring in the apartment: 1.5 mm2 (two-wire) for lighting and 2.5 mm2 (three-wire) for sockets, power electrical equipment - 4 mm2 (three-wire).A three-core cable with additional grounding should be laid even in old houses in which grounding is not provided, perhaps in the future you will finish it (if we are talking about a private house). More information can be obtained from the tables. As you can see, the cross-section of the hidden wiring is slightly larger (about 25-30%), this is due to the fact that the open wiring is freely cooled, while the wired or hidden in the boxes does not have this possibility.

electrolend,
TovariSCH "elektrolend" - the owner of an electric store. You can’t even trade seeds. You have real shovel thinking that directs arrows (blame) from yourself to the producers, justifying and bleaching yourself. People give (trust) money to you and with you DEMAND. And they should NOT run around the manufacturers NE BANNER TO WHERE.
You (and only you) know those and are in contact with those unscrupulous manufacturers of low-quality products. And you (and only you) can refuse them a piece of dirty bread which they eat without accepting their poor-quality goods. Such a mentality of many such people destroys and undermines the whole country, deceiving each other and, as a consequence, of himself, without understanding who is to blame and the reason for the difference in living standards of developed and underdeveloped countries.
Please do not be offended. I am stating facts that I can quite see and have a great experience in life.

Dear! Especially the director of Mr. ElectroLand! What is the pointless argument? It came to the conclusion that many manufacturers of wire cross-section of 1.5 square meters. label and sell as 2.5 square meters. And where does the quality and purity of copper from which this wire is made? It is written on the cable 2.5 kV, and in fact 1.5 kV, means a direct fraud of buyers. (Unless it is written about this on the price tag). And the buyer has every right to return this cable to the seller and receive money back or buy another cable that suits him.

They need a geometrically correct cable. Read the GOSTs for cable products first, and they are also called electricians.
Hey, Egorovich, you first read the law on consumer protection - I’ll see who takes the cable back to you in the store. You first look for where it is cheaper, and then you whine that you were sold to Mr..
And you, from America, who sit under your chocolate monkey and don’t blather. If a store will sell supposedly the right cable for 50 rubles per meter, and the rest of the shops around will sell the same brand, but the allegedly wrong cable for 30 rubles, do you think it will last a long time for the right store?
All of you are smart in the internet.

1992 year replacement of wires in the apartment with copper (Soviet). Lighting 0.35 squares lamp 100 W-0.5 A. Simple sockets 0.75 squares, for powerful consumers 1.5 squares, everything holds without problems. There are DC lamps in the bathroom in the kitchen and hallway. Here the cross section is different, since it depends on the voltage drop. Everything needs to be calculated.

Do not mislead people with tables. Each manufacturer has its own table, but they can match. And they sell you the correct wires GOST-ovskie + -. The section is indicated nominally (estimated) and here the seller is right. He sells you a wire corresponding to a cable, for example, 3x2.5 VVGng brand, the plant itself conducts tests and makes products adding or removing impurities gets a core of 1.98 mm2 corresponding to the cable. Learn the part of the nominal voltage in the network 220V, and the actual one is different and can be 190V and 250V, and there is no need to say that, what else, and electricity is not in accordance with GOST.

To correctly determine the cross section of the wire, it is necessary to calculate the maximum load that all your electrical appliances consume - this is especially important when choosing an input conductor.It is not difficult to do this on your own, all information on household appliances that interests you will be indicated in the data sheet or on the equipment case. Further, according to the resulting total number, using the tables of sections of the conductors, we find the section of interest to you. In principle, if you live in a medium-sized apartment with a centralized heating system and natural gas, a conductor with a cross section of 2.5 - 4 square meters will be enough at the input. mm For wiring in rooms - 1.5 - 2.5 square meters. mm depending on the equipment installed there.

You, Egor, apparently know the materiel very well. Please tell me what kind of impurities will allow to reduce the cross-section of a copper wire to 1.98 mm2 with an allowable resistance of 7.41 Ohms per 1 km? Bullshit, you, Egor write. Impurities will only lead to an increase in the cross section, since they only worsen the conductivity of the core. The maximum diameter, by the way, is apparently in the case of completely non-pure copper, from which the wires are not supposed to be made, is specified in GOST.

If we calculate for a nominal section 2.5 mm2 according to GOST tolerances (not more than 7.41 Ohms per 1 km) and take the resistivity of the purest copper, we get the smallest section 2.3 mm2. Not at all 1.98 ...

The section of the conductive conductor of wires and cables is selected according to the condition of heating with a long rated current in normal and post-accident conditions and checked for voltage loss, compliance with the current of the selected protection device and environmental conditions according to the PUE (chapter 13), GOST R 53769-2010 or according to the tables given manufacturers of appropriate cable products.

The owners of the grammar store are very bad!

It is impossible to determine the cross section of the input cable by the power of electrical appliances available in the apartment. Tomorrow you will buy, for example, an oil heater with a capacity of 2.2 kilowatts or a washing machine with a power of 2 kilowatts or an air conditioner with a power of 1 kilowatt. So what? Change the wiring in the apartment? (an additional outlet may even appear). Well, the apartment wiring is simple. According to SNiP, for every two square meters of living space there should be one outlet, and a double or triple outlet is also considered one outlet. So, you must first choose the number of outlets and their location, and if the room has powerful power consumers, then you need at least two groups of lines to the outlets, for general use and for a powerful consumer. There may be an electric stove in the kitchen, a wire of at least 6 millimeters square in copper is needed on it, and an automatic machine for a rated current of 25 amperes, 32 amperes already. And on other sockets - a wire of 2.5 millimeters square on copper and an automatic machine on each line for a rated current of 16 amperes. For lighting, by the nature of the work in the apartment panel, we select a machine for a nominal current of 10 amperes and a wire with a cross section of 1.5 mm square on copper. At the same time, you need to think about the fact that if too much load is included in any outlet, then, according to the current characteristics of the machine, a 16 ampere circuit breaker can "hold" a current of 24-25 amperes for 40-50 minutes, although several lines to sockets is unlikely. Well, have decided on the number of lines and machines, their values. Now we determine the maximum possible current load per apartment, given that any machine can be loaded at 100% current and it will not turn off. We summarize the rated currents of all machines and multiply by a utilization factor of 0.7. For example, we got 120 amperes. 120 * 0.7 = 84 amperes.Yes, of course, such a load is possible in rare cases, for a short time, and if we used LED lamps for lighting, then a machine with a nominal current of 10 amperes will never be loaded with a current of 10 amperes, but the input cable should work reliably in any case. For such a load, only a 60 amp counter is suitable; at a higher rated current, oblenergo allows counters to be installed only in exceptional cases. Well, since we use LED lamps for lighting, then such a counter is suitable. He will withstand a very short overload. Now, the input circuit breaker should be at such a rated current that it would allow short-term overload without shutting down. Considering that a maximum cable or wire with a cross-section of 10 millimeters square in copper can be connected to a meter with a rated current of 60 amperes, we select an input circuit breaker of 40 amperes. It will reliably protect the meter. According to the time-current characteristics of the group C machine, it can be seen that it can withstand a current of 60 amperes for 40-50 minutes. Now you need to measure the resistance of the phasanol loop at the place of installation of the apartment shield to make sure that the current cutoff of the machine is working. It should be no more than 0.5 Ohms, otherwise you will have to reduce the rated current of the machine and redo the entire apartment shield. Make sure everything is in order. Now check the cross section of the input cable or wire. The rated current of a two-core copper cable or wire is -55 amperes according to the PUE. By load and overload, it passes. We check it by the heating temperature at an ambient temperature of 40 degrees Celsius. In summer, the lead-in line, even without current, can warm up to such a temperature, especially in a closed apartment panel, where both machines and relays give off heat, and the rated ambient temperature according to the PUE is -25 degrees Celsius. Therefore, we apply a reduction factor for the current load of 0.81. So in the summer in hot weather the input cable can withstand no more than 40 * 0.81 = 44.55 amperes, about 45 amperes. This is not enough for the current reserve in the event of an overload of 60-70 amperes. The cable can go out of order. In addition, one input cable to the apartment does not meet SNiP for reliability of power supply. Therefore, we finally accept - lay the input with two independent lines according to the "two for one "cable or wire with a cross section of 10 millimeters square on copper. We check. In the worst case, each cable or wire can withstand up to 45 amperes of current, two -85-90 amperes. Even with an overload of 50%, the cables will withstand the load in any heat. We put a terminal strip in the floor shield, lay a section from the meter with a single-core copper wire with a cross section of 10 millimeters square in copper, withstanding a rated current of 80 amperes according to the PUE, from the terminal block two cables or wires are laid in parallel along the route to the apartment shield, connecting them in parallel on the terminal block and in on the introductory machine. In the event of failure of one cable, we simply bite it and change it, and the apartment receives power through the remaining cable, which meets the requirements of SNiP for reliability of power supply. Well, there was a riser in the entrance. If it is made of aluminum wire of 6 millimeters square, you can temporarily reduce the value of the input automatic machine in the apartment panel to 25 amperes or 32 amperes or use apartment wiring in view of this circumstance, otherwise protection against overload in the panel house will work. But the bottom line is that your area of ​​responsibility and separation of powers begins at the ends of a wire or cable connected to the meter. And everything else is not your competence. So let them change the wiring on their sites in accordance with modern loads and requirements for it.

The wire makrovanny 2.5 sq mm has an actual cross section of only 1.13 sq mm, see silver diluted)))

Anatoly Mikhailov, 40 * 0.81 = 44.55 with mathematics is apparently not good.

Guys! Are you going to jerk here or solve serious issues? Well, yes, a person made a mistake when multiplying, so what? Correct and move on. Ask the right questions. This means that the solution must be working, and not pin up each other. Do not like it - go somewhere to the philosophical forum and discuss there. Here I rummaged through the whole Yandex in search of a solution to replace the wiring in an old two-story single-entrance house. Plus, you need to figure out all the protective equipment, floor shields, lighting in the staircase on the floors. In short, make a list of everything for a complete replacement of the internal wiring, including shields (which were not and are not). But here it’s not clear what. And they discuss not urgent problems, but determine the degree of fault of the seller. If you are so smart, then, having measured the diameter of the wire, buy the one you need by calculation, and not by money. Cheaper in the end will be. I wish you success!

The calculation selects the cable section. Do not want to deal with formulas, there are calculators on the Internet. For the calculation, initial data are needed: power, conductor material, line length are set. The calculation is performed according to the main parameters of the line: heating, short-circuit current, voltage loss.