How to choose a wire in their section and power

Selection of cable cross-section is an important power supply design stage house or apartment. When there is insufficient cross-section wire overheating that can lead to melting of the insulation and short circuit, the consequences of which are unpredictable.

Sections of the wires are selected by the value of currents flowing in them and can be determined from tables or calculated. Table-section for installation wiring requirements are specified in the "Rules for Electrical Installation" (PUE). In the same normative document contains a table with the maximum permissible currents depending on wire size and operating conditions. Below is a table of cases, most often encountered when laying wiring in houses and apartments.

It should be borne in mind that, according to the SAE-section of copper wires for homes must be at least 2, 5 sq. mm to meters and 1, 5 square. mm after them. Before wiring the study PUE provisions concerning residential buildings. Compliance with these requirements will allow them to increase the reliability of electricity supply and avoid claims Energonadzor bodies.

The nominal current load of wires As can be seen from the table, the rated load current of wires depends on the conductor cooling conditions. Wire, laid in the walls, channels and pipes are not blown by air, so cool down slowly. Thick wire transfer heat worse than thin and kept smaller current density. The current density is determined by dividing the allowable current to the wire size. For aluminum wires it is within 5 - 10 A / sq. mm, for copper - 7 - 15 A / sq. mm. By multiplying the load current on the current density is possible to determine the required wire size.

Use for wiring on the copper wire flat - they are less oxidized and do not break at the joints, so are more reliable.

The use of aluminum in hazardous occupations prohibited without reason. Calculation of the cross section for power consumers of electricity wires Calculation of wire sizes to start with determining the total load on the electric power network. It is especially important to take into account the powerful electrical consumers, having the following characteristics: Iron - 1 - 2 kW; washing machine - up to 2 kW; vacuum cleaner - 1 - 2 kW; water heater - about 2 kW; electric furnace - 1 - 2 kW; Microwave - 0, 6 - 2 kW; electric - up to 2 kW; Air conditioning - up to 3 kW; refrigerator - about 1 kW; electric heating boiler - 2 - 5 kW; lighting - power one light bulb, multiplied by their number. Power electrical appliances can be specified in the instruction manual. Calculate the total consumer power and dividing its value by 220 volts, determine the load current.

Further tables or find current density cross-section of the conductors.

When calculating the power you need to keep in mind that not all consumers are included at the same time - if the heating boiler works, air conditioning, no one uses. This fact can be taken into account by multiplying by a factor of the total power demand. Empirically it found that for apartments with a total capacity of up to 14 kW it is equal to 0, 8, and 20 kW - 0, 65, 50 kW - 0, 5. For example, consider the selection of cable cross-section from the junction box to kitchen outlets. The kitchen has a fridge capacity of 1 kW, dishwasher - 1 kW electric kettle - 2 kW microwave - 0, 8 kW electric oven - 2 kW and air conditioning - 2 kW.

The total capacity is 8, 8 kW. Multiply this value by a factor of demand for 0, 8, and get 7, 04 kW. Translate kilowatts in watts (1 kW = 1000 W) and determine the load current: I = 7040/220 = 32 A. As the table flush select twisted pair copper wire cross-section Q3. mm or aluminum - 5 sq. mm. The same section we obtain by dividing the current average on its density. Sometimes available unknown wire section. Knowing diameter section easily determined by the formula S = 0, 785D2, where D - diameter of the conductor. Results for stranded wires is multiplied by 0, 785.

How to properly prepare the walls to shtroblenie under wiring and what options exist shtrobleniya, tell our article, previously placed in the group.