What wire section is needed for 3 kW and others - we are studying the issue from different angles
Being engaged in laying electrical wiring in a new house or replacing an old one during repairs, every home master asks the question: what section of wire is needed? And this question is of great importance, since not only the reliable operation of electrical appliances, but also the safety of all family members depends on the correct choice of the cable section, as well as the material of its manufacture.
Which wire to choose - the material of manufacture comes first
The most common types of wiring in our homes are aluminum and copper. Which one is better is a question that still haunts users of numerous forums. For some, copper is a priority, while others say that there is no need to overpay and aluminum will do for a home network. In order not to be unfounded, let's do a little analysis of these options and then everyone will be able to choose an option for themselves.
Aluminum wiring is lightweight, due to which it has found its wide distribution in the electric power industry. It is used for laying power lines, since in this way it is possible to minimize the load on the supports. In addition, it has gained popularity due to its cheapness. An aluminum cable costs several times less than a copper counterpart. During the Soviet Union, aluminum wiring was very common, it can still be found in houses built some 15-20 years ago.
However, aluminum cable also has its downsides. One of these points, which is definitely worth mentioning, is the short service life. Aluminum wiring after two decades becomes highly susceptible 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 that aluminum is subject to reduces the useful cross-section of the cable with a simultaneous increase in resistance, and this leads to overheating. Another significant disadvantage of aluminum is its brittleness. It breaks quickly if the cable is bent several times.
Important! The PUE prohibits the use of an 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. Copper cable is much easier to work with, because it bends without breaking and withstands repeated twisting. The downside of copper cable wiring is the cost. To replace the power cable in the entire apartment, you will need a significant amount of money. In order to save money, some craftsmen combine the laying of aluminum wires with copper. The entire light part is mounted from aluminum, and the socket part is made of copper, since lighting does not require such a large load as electrical appliances powered by the mains.
Section selection - what you need to know and what to look for
If earlier the equipment in the apartment was limited to a refrigerator and a TV, then nowadays you can’t find anything in an apartment: vacuum cleaners, computers, hair dryers, microwave ovens, etc. All this requires power, and depending on the time of day, the load from devices connected to the network can vary greatly. And in order to choose the right cable for each point to which the device is powered, you need to know:
- current strength;
- voltage;
- power consumption of the device in watts or kilowatts.
For single-phase networks that are present in our apartments, there is a certain formula that allows you to determine the current strength of devices:
I = (P × K and) / (U × cos(φ)), where
I - current strength;
P - power consumption of all electrical appliances (it is necessary to add their nominal value):
| Boiler single-phase | 5–7 kW |
| Fan | up to 900 W |
| Oven | from 5 kW |
| Computer | 600-800W |
| Microwave | 1.2–2 kW |
| Mixer | 300 W |
| Freezer | 150-300W |
| Lighting | 100–1000 W |
| Grill oven | 1 kW |
| Dishwasher | 1.8–2.5 kW |
| Vacuum cleaner | 1200 W |
| Juicer | 250 W |
| Washing machine | 600-2500W |
| TV | 100-200W |
| Warm floor | 0.7–1.5 kW |
| Toaster | 750-1000W |
| Iron | 1000-2000W |
| hair dryer | 500-1000W |
| Fridge | 150-300W |
| Electric hob | from 5 kW |
| Electric coffee maker | 700-1000W |
| Electric meat grinder | 1000 W |
| Electric stove | 9–12 kW |
| Electric fireplace | 9–24 kW |
| electric boiler | 9–18 kW |
| Electric kettle | 2 kW |
K and - the coefficient of simultaneity (often, for simplicity, the value 0.75 is used);
U - phase voltage, it is 220 (V), but can range from 210 to 240 (V);
Cos (φ) - for household appliances, the value is unchanged and equals 1.
For simplicity, you can use the formula: I = P / U.
When the current is determined, the wire section can also be determined from the following table:
Table of power, current and section of cable and wire materials
ALUMINUM |
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Voltage, 220 V | Voltage, 380 V |
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power, kWt | power, kWt |
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Conductor cross section, mm | ||||
Voltage, 220 V | Voltage, 380 V |
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power, kWt | power, kWt |
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If, during the calculations, it turned out that the value does not coincide with any given in the table, then the next larger number should be taken as the basis. For example, if your value is 30 A, then when using aluminum wiring, you should choose a wire section of 6 mm 2, and 4 mm 2 is enough for copper.
Typically, a modern apartment consumes approximately 10 kW.
We determine the cross section of the wire by diameter and by the method of laying the wiring
When buying a wire, it would be useful to check its cross section, since many manufacturers work according to specifications. Because of this, not all products meet the declared characteristics. Therefore, it is necessary to stock up on a caliper and measure the diameter of the core, which will help us determine the real value of the wire cross section. To simplify the work, we present the simplest formula, thanks to which you will not need to perform additional calculations: S=0.785d 2, where S is the required section; d is the core diameter. The final value must be rounded up to 0.5. So, if you get a value of 2.4, then you should choose a cable with a cross section of 2.5 mm 2.
In most of our houses, the cable is laid in the walls. This is called closed wiring. Wires can go through a cable channel, pipes, or simply be walled up in a wall. In some houses, and this applies to wooden buildings and old housing stock, you can find open wiring. It is noteworthy, but for open laying, you can use a cable of a smaller cross section, since such a wire heats up less than the one that is immured in the wall. For this reason, for laying wires in strobes, it is recommended to choose a cable with a larger cross section. So the cable will heat up less, which means that its wear will occur more slowly. In the table below, you can find out how many squares of cable you need to take for devices of different capacities, be it 1 or 6 kW:
Cable section, mm 2 | open wiring | Laying in channels |
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Aluminum | Aluminum |
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