Electricians in London

Electricians in London


Electricity comes into the house from the mains electricity system via a 2-wire service cable usually laid underground, but in rural areas it often comes via an overhead service cable. The cable terminates in a sealed unit containing the Electricity Board’s service fuse, and mounted on the same board is the electricity meter which registers the electricity consumption in units (KWHs). Fixed close to the meter is the householder’s consumer unit containing a double pole main switch and the circuit fuses, though in some installations miniature circuit breakers (MCBs) are fitted instead of fuses. The consumer unit is linked to the meter by a pair of large size PVC insulated and sheathed cables, one red, the other black in colour. There is also a green, or green yellow PVC insulated earth conductor running from an earth terminal block in the consumer unit to an earth terminal which is usually an earthing clamp secured to the metallic sheath of the Electricity Board’s underground service cable. In some older installations the earthing clamp is on the mains water pipe (which may no longer be used as the sole means of earthing).

Where the Board is unable to provide earthing facilities an earth leakage circuit breaker (ELCB) is fitted in conjunction with an earthing rod driven into the ground outside the house. This circuit breaker is a double pole main switch which automatically trips and cuts off the electricity to all circuits when a line/earth fault (a live conductor coming into contact with earthed metalwork) occurs in the installation. This ELCB is normally wired into the mains between the consumer unit and the meter but some consumer units incorporate this as the main switch. The electricity supply throughout the UK is standardised at 240 volts AC 50 Hz and is a 2-pole service. One pole is termed the live (or line) the other is termed the neutral. As the neutral is solidly connected to earth in the mains distribution system the live pole has a voltage of 240 volts above earth and the neutral is at potential which means zero volts between neutral and earth.

It is because the neutral is earthed that anyone who is standing on a concrete floor or on the earth itself or in contact with earthed metalwork and touches a live wire or contact will receive an electric shock of up to 240 volts which can be fatal. Or if metalwork such as the casing of an electric kettle or heater is not properly earthed and through a fault becomes live with mains electricity, a person touching it will receive a serious electric shock. Normally, should a live conductor come into contact with earthed metalwork a heavy surge of current results and this blows the fuse or trips a circuit breaker, so cutting off the electricity feeding the fault.

Heating and ventilation for a garden office

Heating and ventilating a garden home office can be a problem. But do not neglect them; their importance is usually underestimated when building a garden office. Irritability when you are too warm, and lack of control when your hands are cold, will lead to bad working conditions and can be unproductive. Whatever type of electric heating you use, it will be cheaper in the long run if you insulate old buildings. You can opt for an electric radiator or electric underfloor heating.

electric underfloor heating

A common mistake is to fit a free-standing electric fan, which just moves stale air around the room, instead of a proper extractor set in an outside wall. Ventilation ducts such as airbricks should also be fitted to let in fresh air to replace the extracted stale air.

Power drills tools

Handy power drills do a lot more than just drill. A huge number of fittings can be attached to the basic drill unit, enabling it to do almost anything that can be done by a specialised power tool-perhaps not quite so fast or accurately, but certainly well enough for general use. Basically, a power drill is a compact electric motor fitted with a projecting shaft at one end on which is mounted a chuck-a revolving clamp that grips and drives drill bits or other attachments.

builder using power tool drill

The motor unit is held in the hand by a pistol grip, and the motor is started by pressing a ‘trigger’ at the top of the grip. For safety reasons, the motor stops if pressure is released on the trigger, but most drills have a locking pin that can be engaged to hold the trigger in the ‘on’ position. Electric power is supplied to the drill by a cable that enters the machine through the bottom of the handle or by a battery. On all modern drills, a complex system of insulation is built in to keep the user from getting an electric shock. The motor is cooled by a built-in fan that draws air through slots in the side of the drill. These slots must be kept uncovered and free of sawdust, or the motor may overheat and burn out. Many drills can be adjusted to run at different speeds.

The normal type is a multi speed drill geared to run at up to 1,000 rpm and 2,500-3,000 rpm. The speeds are suitable for most household jobs, and a two speed machine is probably the best type for the householder to buy. Variable-speed drills, where the speed can be infinitely varied by an electrical device, are also made, but these are specialist tools. It is false economy to buy a single-speed drill and a separate electrical speed reducer, because although single-speed machines are cheaper, the cost of the two units together will be higher than that of a good two-speed dri1l. The most suitable speeds for various woodworking and other operations are shown in the table below. Drills come in various sizes, which are graded by the capacity of their chuck-i.e. the largest drill bit that can be fitted into it.

A medium-sized machine-say, should be adequate for all ordinary jobs, though the smallest may be too light for some. An indispensable accessory that every drill user will need is an extension cable. This enables the tradesman to use the tool in places remote from a power outlet. Cables are available in standard lengths from 8m to 100m, or you can make up your own. The longer the cable, the thicker it needs to be to prevent power loss. Heavier machines also need thicker cables. You must also have an isolating RCD if using a power tool out of doors; the shop that supplies the drill can advise you.

Drill bits and fittings

Many types of bit are sold for cutting different sizes and shapes of hole in different materials. The ‘everyday’ sort are twist bits, used for drilling all sizes of hole in metal, and holes in wood . Larger holes in wood are drilled with Jennings bits, which have a wide spiral to remove the surplus wood, and a centre spur or spike to keep the cut accurate when it is being started. They cut neat, flat-bottomed holes, but they have to be cleaned out more often than auger bits. Dowel bits are like twist bits with a wood-drill-shaped point for extra accuracy. Very large holes are drilled with flat bits. The flat bit has a flat, spadeshaped cutter with a central spur to hold it in place. The hole saw has a revolving toothed ring attached to a central twist bit the ring removes wood like a revolving pastry-cutter.

Different sizes of ring are available. Very long holes, such as those up the shaft of standard lamps, are drilled with shell or parrot-nosed augers. They are generally used on a lathe, and not in a hand-held drill. Other types of bit include countersink bits, for countersinking screw holes, and drill countersinkers, which are specially shaped to drill and countersink (or counterbore) a hole for a particular size of screw.

For drilling hard masonry, a hammer attachment to a drill is useful. This makes the bit vibrate up and down as it revolves.

Glass and tiles are drilled with a spear point drill, which also has a hardened tip.

Ventilation for bathrooms

Building regulations in Britain require you to make sure that new bathrooms have proper ventilation,that is, having enough changes of air per hour. You can not do this simply by opening windows regularly or by mechanical means such as a small extractor fan. You should incorporate an electric relay switch, linking it to the light switch which will start the fan when the light is switched on and continue to run for about fifteen minutes after it is switched off. (This sort of device makes internal bathrooms, which would normally be cut off from adequate light and ventilation, a practical project.)

Electrician installing extractor fan in bathroom

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Replacing and Repositioning Light Switches

A light switch is always fixed in a flush or surface mounting box. The box is usually made of metal or plastic when embedded in the wall or ceiling, and has lugs which take the screws used to fix on the switchplate , and knockout holes – removable discs – in the back and side for cables.
light switch

The red conductor/wire carries current from the mains via a ceiling rose or joint/junction box to the switch, and the black/brown takes the current on to the light bulb when the switch is in the ON position.The multicoloured (yellow & green) wire is the earth wire, for safety.The wiring connections are made on the back of the switchplate, and thus completely contained within the box.

switches and digital control panel

The basic arrangement holds any type of switch. Rocker switches with a seesaw movement are the commonest, having mostly replaced the old tumbler switches. Most modern switches are digital or sensor based. Switch plates with up to 12 rocker switches are available. Ceiling switches used for safety in bathrooms, have a cord for control.
bathroom with cord switch

A refinement of the ON/OFF switch is the dimmer, with a rotating disc for adjusting the lighting level.
dimmer switch chrome

All these designs are reliable, and unlikely to develop electrical faults. But sometimes a switchplate needs to be replaced. You may also wish to substitute one sort of switch, such as a dimmer, for another. If you are installing a dimmer, the maximum wattage must not be lower than the wattage of the light bulbs it controls.

Switch boxes can be mounted on the wall or sunk into the plaster or plasterboard.Flush switches are neater than surface ones, and safer because they are less likely to be knocked and damaged.

Be safe – always use Professional & Qualified Electricians for rewiring.

Plastic electric light bulbs

Effect of multi-walled carbon nanotubes on electron injection and charge generation in AC field-induced polymer electroluminescence

We are lucky that Science is still doing OK. Researchers from United States are claiming that they managed to develop what is in essence – plastic light bulbs. The new light bulbs could replace the fluorescent bulbs because they provide light not heat.

The new source is made from layers of plastic and is said to be more efficient while producing a better quality of flicker-free light.

The scientists behind it say they believe the first units will be produced in 2013.

The new light source is said to be twice as efficient as fluorescent bulbs

Lighting accounts for around 19% of global electricity use
A worldwide switch to low-energy bulbs could save the output of around 600 power plants