The loads using special tables call “Permissible current loads on cable.” If you have no desire to understand these tables, then it is enough for employment data to know that it is advisable to take a copper cable with a cross-section of 1.5-2.5 mm² for sockets, and 1.0-1.5 mm² for lighting.
6.0 mm² is quite enough to supply one phase to a typical 2-3 room apartment. All the same, your 40-80 m² will not fit more equipment, even taking into account the electric stove.
Many electricians in order to estimate
The requir cross-section, believe that 1 mm² of roberto meireles manager wire can pass 10 A of electric current through itself: accordingly, 2.5 mm² of copper can pass 25 A, and 4.0 mm² – 40 A, etc. If you analyze the table for selecting the cable cross-section a little, you will see that philippines numbers method is only suitable for estimation and only for cables with a cross-section no higher than 6.0 mm².
Below is a shorten table for selecting cable cross-sections up to 35 mm² depending on current loads. For your convenience, the total power of electrical equipment for 1-phase (220V) and 3-phase (380V) consumption is also given there.
When laying a cable in a pipe
The possible current loads on the cable must be less than when laying it openly. This is due to the fact that the cable heats up during operation, and the heat transfer in a wall or in the ground is significantly lower than in an open space.
When the load is nam in kW, we are talking about the total load. That is, for a single-phase consumer, the load will be indicat for one phase, and for a three-phase consumer, for all three. When the load value is nam in amperes (A), we are always talking about the load on one wire (or phase).
Table of loads by cable cross-section:
To independently calculate the requir cable cross-section, for example, for input into a house, you can use a cable calculator or select the requir cross-section from the table.
This table concerns cables and wires in rubber and plastic insulation. These are such common brands as: PVS, VVP, VPP, PPV, APPV, VVG. AVVG and a number of others. There is a separate table for paper-insulat cables, and a separate table for non-insulat wires and buses.
When calculating the cable cross-section, the specialist must also take into account the methods of cable laying: in trays, in bundles, etc.
In addition, the values from the tables on permissible current loads must be adjust by the following ruction factors:
- correction factor corresponding to the cable cross-section and its location in the block;
- correction factor for ambient temperature;
- correction factor for cables laid in the ground;
- correction factor for different numbers of working cables laid nearby.
Calculation of wire cross-section
Let’s start not with the table, but with the calculation. That is, each person, without having the Internet at hand, where the PUE with tables is freely available, can independently determine the cable cross-section by current. To do this, you will ne a caliper and a formula.
If we consider the cable cross-section, it is a circle with a certain diameter.
There is a formula for the area of a circle: S= 3.14*D²/4, where 3.14 is the Archimes number, “D” is the diameter of the measur core. The formula can be simplifi: S=0.785*D².
If the wire consists of several cores, then the diameter of each is measur, the area is calculat, and then all the indicators are summ up. But how can you calculate the cross-section of a cable if each of its cores consists of several thin wires?
The process is a little more complicat but not much.
To do this, you will have to count the number of wires in one core, measure the diameter of one wire, calculate its area using the describ formula and multiply this figure by the number of wires. This will be the cross-section of one core. Now you ne to multiply this value by the number of cores.
If you don’t want to count the wires and measure their sizes, you just ne to measure the diameter of one core, consisting of several wires. You ne to take measurements carefully so as not to crush the core. Please note that this diameter is not exact, because there is space between the wires.
Current to cross-section ratio
To understand how an electric cable works, it is necessary to remember a regular water pipe. The larger its diameter, the more water will pass through it. The same is true for wires.
The larger their area, the greater the current that will pass through them, the greater the load such a wire can withstand. At the same time, the cable will not overheat, which is the most important requirement of fire safety regulations.
Therefore, the cross-section-current
connection is the main criterion us in the selection of electrical wires in the wiring. Therefore, you must first figure out how many household appliances and what total power will be connect to each loop.
For example, a refrigerator, microwave, coffee grinder and coffee maker, electric kettle and sometimes a dishwasher are always install in the kitchen. That is, all these devices can be turn on at the same time. Therefore, the total power of the room is us in the calculations.