During the replacing of an electrical wiring or connection of new lines it is required to choose the optimum section of a cable. The correct selection will ensure trouble-free operation and reliability of a system and also fire safety of all house.
It is required to you
- - calculation of power consumption of devices;
- - knowledge of characteristics of the automatic switch, protective safety locks, etc.
Instruction
1. At small values of current take a cable with a section not less than 1 mm2 (for a copper vein) or 2 mm2 (for an aluminum vein).
2. At big currents choose the section of a wire on the connected power. At first calculate what device of power will be connected. You can look at requirements of the device in documents or the instruction to application.
3. If you need to calculate section for the whole room or the house, count all devices which are inside and which are planned to be bought. Approximately estimate, how much?techniciansyou can include at the same time in the most loaded day (for example, in new year or at a wedding). Increase the received general load of simultaneity coefficient, for example, by 70%.
4. Calculated on the basis of the power according to which loading in 1 kW demands 1.57 mm2 of section calculate values of sections for a certain wire. For example, for an aluminum wire this value will be equal 5 A on mm2, and for copper – 8 A on mm2.
5. Using the received value, calculate wire section for your device. For example, if you need to install the water heater on 5 kW, then the wire should be chosen such that it was designed not less than for 25 A. Thus, you choose a copper wire with a section not less than 3.2 mm2.
6. Pay attention that for aluminum wires the section should be chosen higher as their conductivity is about 62% in comparison with copper. For example, if you expected that the wire with a section of 2.5 mm2 is suitable for the required loading, then the aluminum wire has to be not less than 4 mm2, and to a copper wire of 4 mm2 there corresponds the six-millimetric aluminum wire.
7. If there is an opportunity, always choose a cable of bigger cross section, than left by calculation. It is impossible to foresee in advance, suddenly you decide to connect still something. Do not forget to check whether rated section will be coordinated with the maximum actual load, with current of the automatic switch or the protective safety locks which are, as a rule, near the counter.