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Although all new electrical appliances are now sold with a plug fitted, you may still have to replace plugs that get damaged. And you'll have to connect up a plug if you need to replace a worn or damaged appliance flex. Here's how to do it.
First remove the cover from the old plug by undoing the central screw. Then free the flex from the cord grip and disconnect its cores from the plug terminals. You may have to remove the fuse from the live pin first to reach the live terminal screw. If the plug is a sealed factory-wired one, cut through the flex close to the plug. Deform the pins with a couple of sharp hammer blows so it can't ever be plugged into a socket outlet, and discard it.
Reconnect the flex cores to the terminals of the new plug. With the open plug interior facing you, link the BRown live core to the Bottom Right terminal, the BLue neutral core to the Bottom Left terminal, and the green-and-yellow earth core (if the flex has one) to the top terminal.
With screw-on stud terminals, remove the nut and wind the core clockwise round the threaded stud. Then tighten the nut to trap the core securely. With pillar terminals, loosen the terminal screw and push the core into the hole. Tighten the screw down to secure it.
Replace the plug fuse, after checking that it is the right rating for the appliance. Use a 3-amp fuse (colour-coded red) for appliances rated at up to 700 watts, and a 13- amp one (colour-coded brown) for all more powerful appliances.
Then secure the flex sheath in the cord grip - either by trapping it under a screw-down bar or by pressing it into two nylon jaws - and replace the plug cover.
If you need to replace an appliance flex, or if you have removed a damaged sealed plug, you have to prepare the flex so it can be connected. In the case of a new appliance flex, you also need to check that you have the right screwdrivers to open the appliance casing. Many are now secured with hex or Torx screws, which need special drivers.
You must buy flex of the right rating for the appliance. You need 0.5mm2 flex for lamps, 0.75mm2 flex for appliances rated at up to 1.3kW, 1mm2 flex for appliances rated at up to 2.3kW and 1.5mm2 flex for more powerful appliances. You'll generally need three-core flex, except for table lamps and double-insulated appliances such as hair driers and power tools, which use two core flex.
Start by holding the flex with the last 50mm bent back on itself. Nick the sheath on top of the bend with a sharp knife, and it will split open. Reverse the bend and repeat the operation. This technique avoids any risk of cutting into the insulation on the flex cores. Pull off the section of sheath.
Lay the flex end over the plug, lead each core to its correct terminal and cut it to length with side cutters. Then use wire strippers to remove about 10mm of insulation from each core, taking care not to cut through the fine wires inside. Twist the bare wires neatly together ready for connection to the plug terminals (see above).
Next open the appliance casing so you can gain access to the terminal block. Note how the old flex is routed, then disconnect the cores and withdraw it. Feed the new flex in, via any rubber sleeves or washers, and connect its cores to their terminals. Replace the casing, plug the appliance in and check that it's working.
If you have an appliance that needs a longer flex, you have two choices. You can either remove the existing flex and fit a longer length of new flex, connecting it as described above. Alternatively, you can use a flex connector. Choose a one-part connector for a permanent extension, and a two-part one if you want to disconnect and store the flex extension separately.
Prepare the flex ends, then open the connector and link the cores to the terminals. In a one-part connector, each pair of like cores is connected to a small brass barrel connector. In two-part connectors each core goes to its own terminal. With this type, be sure to fit the part with the pins to the flex leading to the appliance, and the part with the sockets to the flex leading to the plug.
This is how the interior of a correctly wired plug should look, with the flex secure in the cord grip.
Prepare flex for connection to plugs or appliances by removing some of the sheath and core insulation.
This is how the interior of a correctly-wired one-piece flex extender should look
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