Our days can rightfully be called the era of repairs: new homes are being built, and the vast majority of existing buildings are being actively repaired. This is especially true for buildings of the private sector, built in the interval from the 50s to 80s. The materials used at that time had already partially lost their properties due to natural aging, possible soil shifts led to the appearance of a network of cracks on the walls, etc.
In addition, the design approaches have changed and, importantly, the requirements for building functionality have become higher. For example, if earlier the choice of
cable cross-section by load when performing home wiring was done based on a total consumption of no more than 1-1.5 kilowatts, now these values have increased significantly. Now the minimum allowable are 3 kilowatts (current of 16 amperes). Thus, in both private homes and apartments, it is necessary, in accordance with the new requirements, to select the cable cross-section and change the entire wiring.
We did not in vain at the beginning touched on the topic of repair: the fact is that most replacement methods are destructive for interior decoration. To lay a new cable, most often you have to make strobes in the walls. Of course, you can use a
skirting board with a cable channel and plastic boxes, but such a solution will not fit into every interior.
How is the choice of cable section made? Let's say right away: there is nothing complicated about it. Even a schoolboy will cope with the task. You need to sit down at a table with a pen and a sheet of paper, make a list of the most powerful consumers of electricity and analyze which ones will turn on at the same time. Let's look at a simple example of how to correctly select the cable section.
The task is to connect a washing machine to the mains . The choice of cable cross-section begins with a study of the passport data of the device - you should find the value of power consumption. Since manufacturers are a little tricky with respect to cars, you need to carefully approach the issue. We read: "power - 200 watts." However, below you can find an indication of the characteristics of the heating element. For him, already declared 2 kW. Thus, in total, the machine consumes 2.2 kW. It is important to consider such “trifles”, otherwise the wrong cable will simply burn out. It remains to make the choice of cable cross-section by power.
There is a direct correlation between current and power value. The formula is as follows:
P = U * I,
where P is power; U is the voltage; I is the current.
In the home electrical network, the first multiplier is unchanged at 220 volts.
Having learned the value of the machine’s power (2.2 kW), it is necessary to calculate the current using the above formula:
I = 2200 W / 220 V = 10 Amps
Further, reference tables should be used, in which the correspondence of the material of the cable core, its cross section, the laying method (openly, in the pipe, in the wall) and the current value is given. The tables are given in the book "Electrical Installation Rules". They can also be found on the global web - this information is publicly available. In our case, if we take copper veins, their cross-section should be at least 0.75 sq. mm (current of 15 Amps for open wiring). Of course, a 30% margin is excessive, but since the wire is usually not placed openly, the allowable current will be less. In addition, the nearest smaller section (0.5) is designed for 11 amperes, which is not enough.
When choosing home wiring, the same principle is used. The difference is that it is necessary to take into account the sum of the power of the devices, which may turn out to be simultaneously turned on on any branch.