The most important element of the mains is the electric cable, and when it fails, all systems will become impossible to work. To prevent such a situation, as well as to avoid fire, you need to know how to calculate the cross-section of the wire for the correct load of the mains.
Personally, this gives me confidence that the operation of all electrical appliances in the house, as well as the entire electrical network as a whole, is safe. And for me, confidence in the safety of my family is more important, otherwise, with an incorrect calculation of the cross-section of the wire and its electric shock, overheating, melting of the insulation and its damage may well occur, but this is already a direct threat of a short circuit in the network, and, as consequence of the fire.
The main indicator in calculating the cable section, and determining its brand, will be the permissible current load during long-term operation. This is the amount of current that a wire can pass through under continuous load without heating up.
It is not difficult to calculate the cross section of the wire, it is enough to perform an arithmetic action on the addition of the power consumption of all electrical appliances included in the network. Let's consider it in more detail.
To calculate the safe value of the cross section of the electric wire according to the current load, which allows you to safely use the available electrical devices, you need to calculate the current strength.
This value for a single-phase electric network is equal to the sum of all the power of electrical appliances included in the network, multiplied by the correction of the simultaneity coefficient, which is 0.75 and divided by the value of the mains voltage.
In a single-phase electrical network the magnitude of its voltage is 220 volts.But there is a three-phase network, the voltage of which is 380 volts. How to calculate the cross section of the wire in this case?
It is necessary to take the total power of all the included electrical appliances, and divide by the voltage of 380 V, multiplied by the root of the three. Thus, we get the exact value for finding the wire of the desired cross section.
In order not to make such calculations on your own, there are finished table with all these meanings. Using it, you can easily determine which cable you need and with what section.
Maybe the value of the current obtained in the calculation will differ from the data in the table. Then I advise you not to save money, but to choose the nearest value for the wire cross section, but upward. Let the margin of safety be better than its deficiency later.
Which wire to choose?
Often when calculating the cross section of the wire, the question arises as to which wire to choose - aluminum or copper.
Copper wires are more flexible. They do not break as quickly on folds as aluminum ones.
In addition, compared with the latter, more durable. Copper is less oxidized, therefore, its contacts during switching in distribution compartments are better.
In terms of conductivity, the copper wire is 1.7 times higher than aluminum. Therefore, with equal load, the copper cable can be taken of a smaller cross section.
The cost of aluminum wires is cheaper, but according to modern standards, their use in domestic facilities is prohibited. In private construction, they are still used quite successfully, especially for external wiring, but it is recommended to conduct copper cables indoors.
Video: How to choose a cable