Electricians in London

Electricians in London

Camden Electricians

Electricians in Camden

We use only fully qualified electricians, NICEIC registered and with a vast amount of experience in all types of electrical work.

Fault finding, Full rewiring, Inspections & reports, Wiring installations, Garden electrical lights & sockets, Electric underfloor heating, Sockets, Lights & switches, Bathroom electrical showers

Running electrical cables

The hardest part of the average electrical job is running the cables: it takes up a lot of time and a lot of effort. But there are certain techniques used by professional electricians which can make it much easier.

running electrical cables

Before you get involved in the details of how to install the wiring, there are few questions you must answer. Does it matter if the cable runs show? Is it safe ? Does it comply with the Electrical Regulations? This is because there are only two approaches to the job of running cable. Either you fix the cable to the surface of the wall, or you conceal it. The first option is far quicker and easier but doesn’t look particularly attractive; it’s good enough for use. in, say, an understairs cupboard. For a neater finish, using this method, you can smarten up the cable runs by boxing them in with some trunking. Many people, however, prefer to conceal the wiring completely by taking it under the floor, over the ceiling, or in walls.

Planning the route

With concealed wiring, the position is more complicated. When running cable under a floor or above a ceiling, you must allow for the direction in which the joists run – normally at right angles to the floorboards – and use an indirect route, taking it parallel to the joists and/or at right angles to them. When running cable within a wall, the cable should always run vertically or horizontally from whatever it supplies, never diagonally.

Concealing cables in walls

There are two ways to conceal cable in a wall. With a solid wall, chop a channel (called a ‘chase’) out of the plaster using a club hammer and bolster chisel, carefully continuing this behind any skirting boards, picture rails, and coverings.However, to give the cable some protection, it is better to fit a length of PVC conduit into the chase and run the cable through this before replastering.

To continue the run either above the ceiling or through the floor before you position the conduit, use a long drill bit so you can drill through the floor behind the skirting board. If a joist blocks the hole, angle the drill sufficiently to avoid it. With a hollow internal partition wall, the job is rather easier, because you can run the cable within the cavity. First drill a hole in the wall where the cable is to emerge, making sure you go right through into the cavity. Your next step is to gain access to the timber ‘plate’ at the very top of the wail, either by going up into the loft, or by lifting floorboards in the room above.

Drill a 19mm (3/4in) hole through the plate, at a point vertically above the first hole, or as near vertically above it as possible. All that remains is to tie the cable you wish to run to a length of stout ‘draw’ wire – singlecore earth cable is often used – and then to tie the free end of this wire to a length of string. To the free end of the string, tie a small weight, and drop the weight through the hole at the top of the wall. Then all you do is make a hook in a piece of stout wire, insert it in the cavity, catch hold of the string and pull it (and in turn the draw wire and cable) through the hole in the room below.

What are the snags?

There are two. You may find that, at some point between the two holes, the cavity is blocked by a horizontal timber called a noggin. If this happens, try to reach the noggin from above with a long auger bit (you should be able to hire one) and drill through it. Failing that, chisel through the wall surface, cut a notch in the side of the noggin, pass the cable through the notch, and then make good.

The second snag is that you may not be able to reach the top plate to drill it. In which case, either give up the ideas of having concealed wiring, or try a variation on the second method used to run cable into the cavity from below the floor. Here, it is sometimes possible to lift a couple of floorboards and drill up through the plate forming the bottom of the wall. Failing that you have to take a very long drill bit, drill through the wall into the cavity, then continue drilling through into the timber plate. You can now use the weighted string trick to feed the cable in through the hole in the wall, and out under the floor.

Running cable beneath a floor

The technique for running cable beneath a suspended timber floor depends on whether the floor is on an upper storey and so has a ceiling underneath, or is on a ground floor with empty space below. If it’s a ground floor, it may be possible to crawl underneath and secure the cable to the sides of the joists with cable clips, or to pass it through 19mm (3/4in) diameter holes drilled in the joists at least 50mm (2in) below their top edge. This prevents anyone nailing into the floor and hitting the cable.

If you cannot crawl underneath, then the cable can be left loose in the void. But how do you run it without lifting the entire floor? The answer is you use another trick, called ‘fishing’. For this, you need a piece of stiff but reasonably flexible galvanised wire, say 14 standard wire gauge (swg), rather longer than the intended cable run, and a piece of thicker, more rigid wire, about 1m in length. Each piece should have one end bent to form a hook; Lift a floorboard at each end of the room and use a push and pull action to get the electrical cable in place.

Hollow internal partition wall

Drill a hole in the top or bottom plate, then drill another in the wall where the cable is to emerge. Drop a weighted piece of string through one of the holes and hook it out through the other. Use this to pull through a stout draw wire which is attached to the cable.
• if the weighted piece of string gets obstructed by a noggin or its way to the hole in the wall, use a long auger bit to drill through the noggin.
• don’t pull the cable through with the weighted string – the string tends to snap
• never run cable down the cavity of an external wall – treat these as solid walls.

Under floors

Use a technique known as fishing:
• lift the floorboards at either end of the run
• thread stiff wire beneath the floor through one hole and hook it out of the other with another piece of wire • use the longer piece of wire to pull the cable through.

• if there’s a gap beneath a ground floor you can ‘fish’ the cable diagonally across the room under the joist
• if the gap under the joists is large enough you can crawl in the space clipping the cable to the joists
• where the cable crosses the joists at right angles, run it through holes drilled 50mm (2in) below their top edges.

Over ceilings
If you can get above the ceiling into a loft, you can clip the cables to the joists. Otherwise you’ll have to ‘fish’ the cable across.

Socket Mountings

Metal boxes are recessed into the wall and provide a fixing for the socket itself. Knockouts are provided in the back, sides and ends to allow the cable to enter the box. Rubber grommets are fitted round the hole so the cable doesn’t chafe against the metal edges.

Elongated screw slots allow box to be levelled when fixed to wall. Adjustable lugs enable final adjustments to level of faceplate on wall. Boxes are usually 35mm deep, but with single-brick walls boxes 25mm deep should be used, along with accessories having deeper-than-usual faceplates.

wall socket mounting electrical

Adding a spur socket to a ring electrical circuit

Adding a spur socket to a ring electrical circuit

CHECKING OUT A RING CIRCUIT These instructions assume that your installation conforms to the Wiring Regulations. If it seems to have been modified in an unauthorised way, get a qualified electrician to check it.
Start by undoing a socket near where you want to install the new socket.

Adding a spur to a ring

Once you’ve established you’re dealing with a ring circuit and what sockets are on it, you’ll need to find out if any spurs have already been added. You can’t have more spurs than there are socket outlets on the ring itself. But unless the circuit has been heavily modified, it’s unlikely that this situation will arise. You’ll also need to know where any spurs are located – you don’t want to overload an existing branch by mistake. You can distinguish the sockets on the ring from those on a spur by a combination of inspecting the back of the sockets and tracing some cable runs. But remember to turn off the power first. When you’ve got this information, you can work out whether it’s feasible to add to the ring circuit. And you’ll have a good idea where the cable runs.

Installing the socket

It’s best to install the socket and lay in the cable before making the final join into the ring, since by doing this you reduce the amount of time that the power to the circuit is off. You can either set the socket flush with the wall or mount it on the surface. The latter is the less messy method, but the fitting stands proud of the wall and so is more conspicuous.

Flush-fixing a socket on a plasterboard wall is a little more involved. If you choose to surface-mount the socket, all you have to do is to fix a PVC or metal box directly to the wall after you’ve removed the knockout (and, if metal, useagrommet) where you want the cable to enter. The socket can then be screwed directly to this.

Laying in the cable

Because cable is expensive, it’s best to plan the spur so that it uses as little cable as possible. When you channel cable into a wall you’ll need to chase out a shallow run, fix the cable in position in oval PVC conduiting. It won’t give any more protection against an electric drill, but it’ll prevent any possible reaction between the plaster making good and the cable sheathing.
Always channel horizontally or vertically, and never diagonally, so it’s easier to trace the wiring run when you’ve completed decorating. You can then avoid the cable when fixing something to the wall. Normally the cable will drop down to below floor level to connect into the circuit. Rather than remove the skirting to get the cable down to chip out a groove.

You’ll then have to drill down through the end of the floorboard with a wood bit. Alternatively, you can use a long masonry bit with an electric drill to complete the task. But if the floor is solid, the ring is usually in the ceiling void above, in which case the branch will drop down from the ceiling. And this will involve a considerable amount of channelling out if you want to install the new socket near floor level. Stud partition walls also present a few problems. If the socket is near the floor, you should be able to get a long drill bit through the hole you cut for the socket to drill through the baseplate and floorboard. You can then thread the cable through. But if the socket is to be placed higher up the wall, noggings and sound insulation material may prevent the cable being drawn through the cavity. In this case you will probably have to surface-mount the cable. In fact, surface-mounting is the easiest method of running the cable.

All you do is fix special plastic conduit to the wall and lay the cable inside before clipping on the lid. But many people regard this as an ugly solution. When laying cable under ground floor floorboards you should clip it to the sides of the joists about 50mm (2in) below the surface so that it doesn’t droop on the ground.

When you have to cross joists, you’ll need to drill 16mm (5/sin) holes about 50mm (2in) below the level of the floorboards. The cable is threaded through them and so is well clear of any floorboard fixing nails. Connecting into the circuit If you use a junction box, you’ll need one with three terminals inside. You have to connect the live conductors (those with red insulation) of the circuit cable and the spur to one terminal, the neutral conductors (black insulation) to another, and the earth wires to the third.

You might decide that it’s easier to connect into the back of an existing socket rather than use a junction box, although this will probably mean some extra channelling on the wall. Space is limited at the back of a socket so it may be difficult to fit the conductors to the relevant terminals. However, this method is ideal if the new socket that you’re fitting on one wall is back-to-back with an existing fitting. By carefully drilling through the wall a length of cable can be linked from the old socket into the new.

Adding a powerpoint or socket

Electrical equipment is now used more and more in the home. You should never overload an existing socket, but fit an extra one instead.

electrical testing

There’s nothing really difficult about installing a new power point. It’s easier than putting in a new light as you don’t have to worry about a switch cable. Ever since the early 1950s, the power supply to the sockets has almost always been wired as a ring circuit, where the cable starts and ends at the consumer unit. Houses rewired since then will almost certainly have had this system installed. This means that once you’ve decided where you want the new outlet point – by a shelf in the living room for a hi-fi system, dvd, computer, or over a worktop in the kitchen, for example – all you then have to do is to run a ‘branch’ or ‘spur’ to it from a convenient point on a nearby ring circuit. The connection could be made at any socket on the ring (unless it already has a spur coming from it), or by using a threeterminal junction box inserted into the cable run.

Each spur can have either two singles or one double socket fitted to it, or else a fused connection unit. But new regulations will come into force from the beginning of 1983 and then you’ll only be able to install one single or one double socket on the spur.

Checking your circuits

Although it’s very likely that your house has ring circuits for the power supply, it’s important to make sure. A ring circuit serves a number of 13A power outlets, and the sockets themselves take the familiar three-pin plugs with flat pins. But having this type of socket doesn’t necessarily mean you’ve got a ring circuit – a new radial circuit may have been installed with these fittings, or an old radial circuit may simply have been modernised with new socket outlets. If in doubt, get an electrician to check the circuit.

First you’ve got to check whether you’ve got a modern consumer unit or separate fuse boxes for each of the circuits. Having a consumer unit is a fair indication that you’ve got ring circuit wiring, and if two cables are connected to each individual 30Afuseway in the unit this will confirm it. Normally each floor of the house will have a separate ring circuit, protected by a 30A fuse or MCB.

If you have separate fuse boxes, look for the ones with 30A fuses. If they have one supply cable going into them and two circuit cables coming out, this indicates a ring circuit. It’s easy to identify the sockets on any particular circuit simply by plugging in electrical appliances, such as table lamps, turning off the power and then removing a 30A fuse from the fuse box or consumer unit, or switching off a 30A MCB. When you restore the supply, the equipment that remains off will indicate which sockets are on the circuit.

Dealing with radial circuits

Where a house hasn’t got ring circuits, then the power sockets will be supplied by some form of radial circuit. Because there are different types of radial circuit, each governed by separate regulations controlling the number and location of sockets on the circuit, the size of cable to be used and the size of fuse protecting it, it’s not possible to connect a spur to a nearby radial circuit. In all probability you’ll have to install a new circuit starting at a new, separate fuse box or else at a spare fuseway in a consumer unit.

If you’ve still got unfused 15A, 5A and 2A round-pin plugs, then this is a sure sign of very old radial circuits, which were installed more than 30 years ago. Rather than extending the system you should seriously consider taking these circuits out and replacing them with ring circuits,-as the wiring will almost certainly be nearing the end of its life-. You’ll then be able to position the new sockets exactly where you want them. If you’re in any doubt about the circuitry in your house you should contact your local electricity authority or a qualified electrician before carrying out any work.

Ceiling lights and switches

Most ceiling lights are positioned centrally in a room to give general lighting. But by adding another light, or changing the position of an existing fitting, you can highlight particular areas and enhance the decoration.

Putting in a new pendant ceiling light and switch, or changing the position of an existing one, usually presents few problems – even if you have little or no experience of electrical work. A pendant is the most common ceiling light and consists of a lampholder wired to a length of flexible cord which hangs from a ceiling rose. Another type can be plugged into the ceiling rose – in this case the flexible cord has to have a special fitting which slots into a batten holder. Know your system Installing a new ceiling light requires making a simple connection into a nearby lighting circuit either by inserting a junction box or at an existing loop-in rose and then running a cable to a switch. In order to connect into the circuit you’ll first need to know how the lights in your house are wired and which lights belong to which circuit.

Then you’ll be able to work out whether you can actually add another light to the circuit that is nearest to the new light’s position. There are two principal methods of wiring a lighting circuit. In the loop-in method the cable runs from ceiling rose to ceiling rose, stopping at the last one on the circuit, and the switches are wired into the roses. With the junction box system the cable runs to a number of junction boxes each serving a switch and a light. You may well find that both methods have been used in the same circuit to simplify and reduce the cable runs. It’s possible to connect into a nearby rose provided it’s a loop-in type. You can check this simply by turning off the power and unscrewing the rose cover.

A loop-in rose will have more than one red insulated wire going into the central terminal bank of the three in-line terminal banks. However, it can be quite fiddly to fit another cable, given that the terminal banks are very small, so you might find it easier to insert a junction box in the main circuit. And if there isn’t a loop-in rose you’ll have to use this method anyway.

Earthing for lighting circuits

Modern lighting circuits are protected by an earth. But if you’ve got a fairly old system (it’s likely to be based on junction boxes), you might find that it doesn’t have one. So when you’re extending such a circuit, you’re now required to protect the new wiring, light fitting and switch by installing an earth. Consequently, you have to use two-core and earth cable for the extension, which will most probably connect into the existing circuit at a junction box. You then have to run a 1.5mm2 earth cable from this point to the main earthing point.

Circuit additions

Usually there’s a lighting circuit for each floor of a house and in a single storey dwelling there are likely to be two or more. But it’s easy to identify the individual circuits simply by switching on all the lights, turning off the power and taking out a 5A fuse from the consumer unit or switching off an MCB. When you restore the power you’ll know that the lights that remain off all belong to the same circuit. Generally speaking, a lighting circuit serves six to eight fixed lighting points. In fact it can serve up to 12 lampholders provided the total wattage of the bulbs on the circuit doesn’t exceed 1,200 watts. This means that unless other lights have previously been added – wall lights for example – there shouldn’t be a problem of connecting in another light.

Remember, when adding up the bulb wattages, a bulb of less than 100 watts counts as 100 watts and not its face value. The place for lights Apart from bathrooms, where special regulations apply, you can position lights and switches in any place you like inside the house. But bear in mind they are there to fulfil a function, so switches, for example, should be conveniently located – by a door is often the most satisfactory position. Usually they are set on the wall 1.4 metres (4ft 6in) above floor level.

But they can be higher or lower to suit your needs. You mustn’t install pendant lights, especially plain pendants with exposed flexible cords, in a bathroom. This is for your safety. Flexes can become frayed, and if, say, you tried to change a bulb while standing in the bath and touched an exposed conductor you could electrocute yourself. Consequently, all light fittings here must be of the close-mounted type and preferably totally enclosed to keep off condensation. If instead you use an open batten lampholder it must be fitted with a protective shield or skirt which makes it impossible for anyone changing the bulb to touch the metal clamp.

A wall-mounted switch must also be out of reach of a person using the bath or shower. In modern small bathrooms, however, this is often impossible. The alternative is to place the switch just outside the room by the door, or to fit a special ceiling switch operated by an insulating cord which doesn’t have to be out of reach of the bath or the shower.

Putting in switches

There is a great variety of switches available, but all perform the same function of breaking or completing an electrical circuit so you can turn the light off or on. Modern switches are of the rocker type; a one-gang switch has a single switch on the face plate; a two-gang switch has two switches on the same faceplate, and so on. Dimmer switches are slightly different in that you can vary the power flowing to the bulb (so reducing or increasing its brightness) by rotating a control knob. With a new light, you can either connect it into an existing switch position (fitting a two gang switch in place of a one-gang one, for example) or a new switch.

Depending on how you connect into the existing circuit, you’ll have to run the switch cable above the ceiling from a rose or a junction box down the wall to where you are going to locate it. If you want to conceal the cable on the down drop you’ll have to cut a shallow channel – which will damage the existing decoration.

Making the connection

Once you’ve decided where you want to put the light fitting and switch, you then have to decide where it’s best to make the connection into the existing circuit. Wiring runs may require some detective work to find out what each cable is doing – you don’t want to connect into a switch cable by mistake. This may mean climbing into the roof space or raising a few floorboards. You’ll need to do this anyway to run in the new cables to the required positions. As cable is expensive, it’s best to plan your runs to use as little as possible. But when you measure along the proposed route, don’t forget to allow about 200mm extra at the switch, rose and junction box for stripping back the conductors and joining in.

Changing the position of a ceiling light is even easier than adding a new one. If after you’ve turned off the power you undo the existing rose you’ll see immediately the type of lighting circuit you are dealing with. If there is only a black, a red and an earth wire going into it on the fixed wiring side then you have a junction box system. All you have to do is to disconnect the wires from the rose and reconnect them to the respective terminals of a new three-terminal junction box that you’ll have to put in directly above the old fitting. You can then lead off another cable from this junction box to the repositioned ceiling rose. The switch remains unaffected. If the rose is a loop-in type, you have to carry out a similar modification, but this time the switch wires have to be incorporated in the new junction box, which must be a fourterminal type.

Safety with electricity

• never work on a circuit with current on.

Turn off at mains and isolate circuit by removing relevant fuse. Keep this with you until you restore supply

• never touch plugs and sockets with wet hands
• remove plugs from socket when working on appliance
• always use the correct fuse wire when mending a fuse

The importance of earthing

Earthing is an essential safety feature of all wiring systems. To complete a circuit, electricity either flows down the neutral conductor of the supply cable or it flows to earth. That is why you get a shock if you touch a live wire.
The idea of earthing is to connect all metal fittings and appliances in the house with a good conductor – the ‘earth wire’ in cables and flexes. If a fault occurs that makes this metal live,the presence of the earth wire prevents the voltage from rising much above earth voltage.
At the same time, the fault greatly ; increases the current being drawn to the metal via the supply conductor, and this current surge is detected by the circuit fuse, which ‘blows’ and cuts off the current flow. The earth conductor links socket outlets and appliances (via their plugs) and is connected to a main earthing terminal at the house fuse box or consumer unit. This is usually connected to the outer metal sheath of the underground supply cable. All metal pipework in the house is also earthed by being connected to the earth terminal – this is called ‘cross bonding’.

Old wiring

Some old installations may still be using lead-sheathed or tough rubber-sheathed (TRS) wiring, with the conducting wires insulated in vulcanized rubber, or vulcanized rubber insulated, taped and braided

The right connection

The plug is the vital link between any electrical appliance and the mains and must be connected up correctly if it is to do its job properly. With flex in the new colour codes, connect the BRown core to the Bottom Right terminal, the BLue core to the Bottom Left one and the green-and-yellow core (if present) to the top terminal. With cores in old colour codes, Red goes to the bottom Right terminal, BLack to Bottom Left and green to top.
Old colour codes – Before the introduction of new international colour codes, flex used red insulation to denote the live conductor, black for the neutral and green for the earth.

Warning: Electricity is dangerous.

In some European countries, regulations stipulate that all home electrical work must be carried out by a qualified electrician. These insulating materials deteriorate with age (about 25-30 years) so the wiring can become dangerous. Therefore it really does need to be replaced with modern PVC-sheathed and insulated cable.

Electrical Cable & Flex

Two types of wiring are used in the domestic electrical circuits. Fixed cables are normally concealed, and carry electrical current to switches, ceiling lights, and socket outlets. Flexible cords (flexes) connect portable appliances and light fittings to the fixed wiring.

Fixed wiring

This consists mostly of PVC-sheathed cable containing three copper conductors (cores). The core insulated in red PVC is the live and the one in black the ‘neutral’ though in lighting circuits in the cable to the switch both the black and red are live. (The black core is required to have a piece of red sleeving on it to indicate this, although this is often omitted by incompetent electricians. Cables having two red conductors are made for contract work, but rarely stocked and sold retail).

The third core is the earth and this is uninsulated, but when exposed after the sheathing is removed ready for wiring up it must be sleeved in green/yellow striped PVC before being connected to the earth terminal. In some wiring circuits PVC-sheathed cables having one core only are used, for example, where a live core is looped out of a switch or a neutral core is looped out of a light, to supply an additional light or lights. Three-core and earth cable is used for two-way switching. The conductors are insulated in red, blue and yellow; the colour coding is for purposes of identification only.

Cables for fixed wiring
Most domestic wiring is now supplied in metric sizes which refer to the cross-sectional area of one of the conductors, whether it is composed of one or several strands of wire. Most common sizes of cable are 1.0mm2 and 1.5mm2 used for lighting, and 2.5mm2 used for power circuits. Cable with grey sheathing is intended to be concealed in walls or under floors; white sheathing is meant for surface mounting.

Flexible cords

Flexible cords are made in various sizes and current ratings and the types you’ll most often come across are: parallel twin unsheathed, circular PVC-sheathed, circular braided, unkinkable and heat-resisting. Each conductor is made up of a number of strands of copper and it is this which gives the cord its flexibility. The insulation used round the conductors now conforms to an international colour coding standard – brown denotes the live wire, blue the neutral, and green/yellow the earth, when it is part of the flex. Transparent or white insulation is used for a flex that carries a low current and where it doesn’t matter which wire is connected to the live and neutral terminals of an appliance.