The Handyman's Pocket Book: Electrical Repairs.

A shock received from a faulty electrical appliance can be serious and it is therefore essential when effecting repairs to make it impossible for anyone to touch a live connection.  It is particularly important that no appliance such as a fire or kettle should be used in a bathroom.  If the metal portion became alive due to some fault the full mains voltage would pass through the person holding the appliance and through the damp floor to earth, probably with fatal results.  For the same reason, electrical appliances should never be touched with wet hands.

If these rules are observed electrical appliances can be handled with safety.  In any case, repairs should be made with the appliance disconnected from the mains.  Where this is not practicable, the main switch for the house should be turned off.

TRACING FAULTS.  If a light fails it is probably due to a faulty bulb, but first check up on the lights in adjacent rooms.  If these are also not working, a fuse has blown; the method of repairing this will be described later.  If the trouble is confined to the one light, examine the bulb to see is its filament is broken and if so, fit a fresh bulb.

If an electrical appliance fails, first ascertain whether the appliance itself is faulty, or whether the fault is in the mains.  In the case of an electric iron, for instance, disconnect it and plug in, say, a table lamp to see if the circuit is alive.  If not, the fuse has probably blown.  If the lamp lights, then the fault must be in the iron, and may lie anywhere from inside the plug on the end of the flex to the connector of the iron (see Fig. 4).  Repairs to the iron itself should not be attempted.

FUSES.  These are usually mounted on a fuse board, either in the cellar of the house, under the stairs, or in a similar spot.

A fuse acts as a safety valve.  The size of the fuse wire is much smaller than the wire throughout the rest of the circuit, so that, if the latter becomes overloaded, the fuse wire melts and cuts off the current.  It is therefore important not to repair a fuse with wire thicker than that specified.  If a hairpin is put in, for instance, it will restore the current, but if trouble develops later on the hairpin will not melt as fuse wire would, and the wiring inside the walls might overheat, causing a fire.  Before repairing the fuse find out first what caused it to melt and disconnect or remove the cause of the trouble.

To locate a blown fuse, turn off the main switch and examine each fuse in turn to see if the wire is broken.  (The break may be inside the porcelain if the fuse is of the type shown in Fig, 1, A).  When the broken wire is found, remove the remains of it and connect fresh wire between the screws (Fig. 1, B).

The fuse of a lighting circuit usually requires 5 amp. wire, and that of a power circuit 13 to 15 amp.   This is often stated on the porcelain body of the fuse.  Fuse wire is usually sold in various gauges wound on a card, the amperage of each wire being indicated.

3-PIN PLUGS.  A fuse is often incorporated in a 3-pin plug (Fig. 2) and in the event of trouble always fit a new fuse in the plug first to see if this is the remedy.  This type of fuse is a unit in itself and a few spares should always be kept handy.  Note how the wires are connected on a 3-pin plug, the green wire going to the earth pin.  Always use 3-pin plugs whenever practicable since they are much safer than the 2-pin type.  They should be fitted with a "three-core" flex so that the metal frame of the appliance can be connected to "earth".  This prevents the frame from becoming alive should a fault develop, and obviates the danger of shock.

REPAIRING PLUG CONNECTIONS.  If the fault is in the appliance itself (electric iron, etc.), first check up on the flex, which often breaks inside the plug or just where it enters it.  The break may, of course, be towards the middle of the flex or at the other end, but this will be dealt with later.

It is difficult to locate a break, since the wire covering is usually intact, but it can often be detected by the feel of the flex, which bends rather easily at the break.

If the flex is in bad condition throughout, or has a frayed area near the middle, fit a fresh length.  If its condition is good but there is a break at the plug end, unscrew the cover of the plug and cut the wire at point A so as to remove the faulty part (Fig. 3).  Bare the fresh ends of the wires and connect them inside the plug as before.  In fitting plugs, lampholders and any other attachments to flex it is absolutely essential that the two wires should not touch each other at any point.  It is also imperative that the wires on 3-pin plugs are connected exactly as shown in the diagram.  If these wires are changed over the frame of the appliance may become alive.  If in the slightest doubt consult a qualified electrician.  Bare only a short length of the covering from the end of each wire so that, when screwed down, the wires retain their covering to a point just short of the screw.  When finished, make sure there are on odd strands of wire from one screw to the other.

LAMPHOLDER PLUGS.  Instead of a 3- or 2-pin plug, flexes sometimes have a fitting which can be plugged into a lampholder.  When fitting an adapter, connect the flex inside it in the same way as in the lamp holder itself (see Fig. 6).

ELECTRIC IRON CONNECTOR.  Fig. 4 shows the inside of a connector which fits on an electric iron.  A wire often breaks inside, in which case the screws (X) should be removed to open the connector.  Slide the rubber (Y) further back, and cut off the end of the flex to make both wires equal in length.  Bare the wire ends for a short distance and screw them to the sockets as before.  The sockets can be taken out while this is done.  Here again it is essential to prevent the wires touching each other.  In the best way an iron also has an earth wire (green) which should be connected as before.

CEILING FLEXES.  Fig. 5 shows another frequent source of trouble.  Where a light hangs from a bathroom or kitchen ceiling the flex tends to perish owing to the damp atmosphere, and a break often occurs where the flex enters the ceiling rose.  First turn off the main switch for the house and unscrew the cap of the rose.  If the flex is badly perished, use a new piece; if not, cut it just below the break and remove the old wire from inside the rose noting how it is threaded through the body of the rose to prevent any direct pull reaching the connections.  Bare the wire ends, threading them through the body of the rose as before, and connect the wires to the screws (Y).  Note that before connecting up, a single knot is put in the flex at the point shown, thus helping to take the weight of the lamp and shade.

LAMPHOLDERS.  If trouble develops at the lampholder end, or if a new flex has to be fitted, unscrew the holder (Fig. 6) and remove the old wire.  When fitting the new flex note that the wires are passed round the shoulders of the centre piece before being screwed to their terminals.  Remember also that piece A has to go over the flex before the wires are connected inside the holder.

LAMPS.  The flex on table lamps or standard lamps is often defective where it enters the base of the column and it is best to fit a new flex.  Unscrew the holder from the top of the column and take it apart. Its construction is similar to a ceiling lamp holder (Fig. 6) except that the wires pass through two holes before being screwed to their terminals.  Remove the old flex and thread a new length through the lamp column, connecting it inside the holder as before.  If there is difficulty in threading the flex through a standard lamp, push a length of stiff wire through first, attach the flex to the end of it and pull it through.