Basic Electrical Installation Work

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Strana 136 z 399

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1 A twin and earth PVC insulated and sheathed cable. Extensions alterations existing single-phase installations not require marking the interface between the old and new fixed wiring colours.2). Around this sheath placed armour protection steel wires twisted along the length the cable, and final PVC sheath covering the steel wires protects them from corrosion. ● The PVC insulation becomes brittle at low temperatures and may be damaged during installation. Both new and old cables must be marked.1 shows sketch of twin and earth cable. ● IEE Regulation 522. The conductors are covered with colour-coded PVC insulation and then contained either singly with others PVC sheath (see Fig.2. PVC/SWA cable PVC insulated steel wire armour cables are used for wiring underground between buildings, for main supplies dwellings, rising sub-mains and industrial installations. PVC insulated and sheathed cables Domestic and commercial installations use this cable, which may be clipped direct surface, sunk plaster installed conduit trunk- ing. Alterations three-phase installations must marked the interface L1, L2, for the lines and for the neutral. Great care should taken before undertaking extensions, alter- ations repair that all conductors are correctly identified. The conductors are covered with colour-coded PVC insulation and then contained singly with others PVC outer sheath. Figure 6. However, warning notice must fixed the consumer unit or distribution fuse board which states: Caution this installation has wiring colours two versions BS 7671. Appendix 7671: 2008 deals with harmonized cable core colours. Cable core colours from 31st March 2004 onwards. 6.1. Safety First PVC cables ● PVC cables should not be installed when the surrounding temperature below 0°C. the simplest and least expensive cable. The armour sheath also provides the circuit protective . They are used where some mechanical protection of the cable conductors required. Sheath Cable insulation Stranded copper conductor FIGURE 6.Basic electrical circuits and cables 125 ● Three-phase supplies brown, black and grey line conductors, blue neu- tral conductors and green combined with yellow for earth conductors. These markings are preferred coloured tape and caution notice again required the distribution board