The presence of numerous electrical and electronic partings makes life easier for the modern man at work and at home. A necessary condition for their use - the presence of power supply wiring, which ensures the proper functioning of this technique.
The basis of the power mains make cables and wires, the basis of which form one or more conductive insulated conductors. In addition, the construct is introduced optional elements which improve properties of consumer products. For example, the cable is provided with a common protective sheath.
For wire and cable as an infrastructure element of a modern property to meet a series of requirements.
The main ones are:
- Minimal cost and availability;
- possibility of transmission power required to the load;
- ease of laying and then connect to an outlet;
- high operational reliability (cable and wire fixed wiring should not be replaced throughout the inter-repair life of the building).
Unfortunately, there is no single structure that is able to satisfy even the short list of requirements, ie, selection of wire turns into a solution of a multicriterial problem.
Fortunately, it is possible to solve sequentially at each step of limiting the set of available positions, which are commercially available electrotechnical industry.
1. Determination of the required section lived
The required cross section is completely determined by the load capacity. For copper household wiring is quite possible to use a simple rule: 1 mm2 section allows you to send 10 A current, with a 10 percent margin corresponds to 2 kW load.
For the case of cheaper aluminum conductor wires with a current carrying capacity decreases by one third due to the high specific resistance of aluminum.
2. material conductor
Power wiring can build on the cables with copper or aluminum conductors. Forte aluminum cables - their lower weight and cost.
At the same time, these wires more brittle. In forming the splice with copper conductors must be sure to use an adapter that breaks the line mechanical connection of these metals and blocks, thus, intense corrosive phenomena in the region of their contact.
Thus, the ease of installation of products with aluminum conductors actually results in considerable technical difficulties and the risk of premature failure wiring.
So it is advisable to stick to the rules on the use of preference only copper wires.
3. Flexible or rigid cable
Core may be a rigid single-wire conductor or a structure formed of several finer veins, as the twisted cable 1 + 6, 1 + 6 + 12, etc. Figure 2.
For equal current carrying capacity flexible cable is somewhat thicker. At the same time it is easy to strip, but more difficult to install (if you connect the lighting fixtures should be used tips), it has a higher cost.
With these features when choosing execution cores is generally guided by the rule that the wiring to sockets due to the stationary nature of suitable budgetary solid cable, one of the designs is shown in Figure 1.
Connecting the lighting devices, for which there is a certain probability of replacement once every three to five years, it is better to stay at a flexible structure.
4. Fire safety cable products
Plastic insulation and cable protective sheets when exposed to high temperature and open flames may allocate dense smoke and poison gas that becomes a potential hazard to life.
Products which are purposefully designed so that such discharges do not occur are indicated in indices labeling "ng" (from the non-combustible) and «FR» (flame-retardant). In residential areas it is strongly encouraged to apply only to them, in spite of several worst mass and size parameters and increased costs, Figure 3.
