The simple on/off switch – usually operating with a rocker action – is wired into a lighting circuit to control one or more room lights. Plate switches have one, two, or more individual switches, known as gangs. The basic switch with just two wiring terminals provides “one-way” switching – making it the only control point for the light it serves. A switch with three terminals can be wired for two-way switching -linked to another switch to allow lights to be controlled from either switch. Socket outlets are available as singles, doubles, and triples and, switched or unswitched. The faceplates may have neon indicators to show if the power is on. Fused connection units are used to provide a permanent flex connection for large, fixed appliances. From left to right 1 Cable and pipe detector 2 Insulation tape 3 Wire cutterslstrippers for differing conductor sizes 4 Electrical screwdriver 5 Connector blocks 6 Cable clips 7 Circuit tester for tracing faults 8 Plug fuses 9 Fuse wire • • G e e Wire types and appropriate uses Flex – for connecting appli- ances to the wiring – has either two or three conductors, all e insulated: brown for live, blue for neutral, and green-yellow for earth. Two-core flex is for wiring appliances without an earth terminal, such as non- metallic light fittings. Always use three-core flex where an earth connection is required. From top 1 Bell wire 2 Flat 2- core flex 3 Round 2-core flex 4 Fabric/rubber-covered 3-core flex 53-core flex
How wiring works nowing how electricity works makes understanding your wiring system easier. In a sense, electricity flows between two points, like water through a pipe. The force of flowing water can provide the power to make things work- to turn a waterwheel, for example. So does electricity, creating light and heat when it passes through a lamp, or rotation in an electric motor. In each case, what causes the flow is a difference in pressure between the two points. Electricity can provide power only if it has a circuit to flow around. In the home, the circuit starts at the incoming supply cable, which contains two conducting cores. Think of the electricity as entering your home via the “live” core and leaving via the “neutral”, or phase, core. Each wiring circuit is tapped off the incoming supply, and reconnected to the returning neutral core when its work is done. Electricity can escape from its circuit, so if you touch a live conductor electricity passes through your body to earth. This is why the wiring system is connected to earth, so that current can flow away safely if anything goes wrong. :
Basic Circuits: lighting Lighting circuits are wired radially, the 1 rnrn? cable starting at the 5-amp fuse or miniature circuit breaker fMCB), running to each lighting point and terminating at the most remote one. There are two wiring systems: Loop-in circuits The cable loops from one lighting point to the next, with each switch cable wired into its ceiling rose or fitting. Roses have three sets of terminals. The live cores on the circuit and switch cables all connect to the centre bank. The circuit cables’ neutral cores go to one of the outside terminals, as does the neutral core of the flex to the light fitting. The neutral core of the switch cable ftagged with red tape for identification) is connected to the other outside terminal, as is the live flex core, so that operating the switch breaks the flow of current to the light but does not interrupt the supply to the next rose in the circuit. There is a separate fourth terminal for the earth cores of both cables. Junction-box circuits The cable runs from box to box, at each one connecting to the light, with another cable running to the switch. Each box contains four terminals, wired as in a loop-in rose: the circuit and switch cable live cores to the first terminal, the switch neutral and light cable live cores to the second, the remaining neutrals to the third and the earths to the fourth. Spurs Both loop-in and junction-box circuits may have spurs, often to feed remote lighting points.