Electricity is dangerous and can be hazardous. In doubt? Call a qualified electrician.
For a very long extension it is undoubtedly better to purchase an extension lead on a drum. These are very cheap and are easily wound up to keep them safe and tidy when not in use. However you may wish to fit a detachable flex connector instead.
There are two ways of extending flex the first uses a detachable flex connector and the second a trailing socket.
First detach the two parts of the flex connector. One part should have three pins sticking out and the other part should have three sockets. The side with the pins must be attached to the appliance, on no account should this be the other way round, as this results in the exposed pins being live when the extension is plugged in, which could be a fatal mistake.
Open the side of the connector with the three pins and attach this to the appliance:
First strip and prepare the wires (see Preparing the flex for connection). Next put the outer cover of the connector over the flex and screw the earth conductor (yellow/green) into the centre screw termina. Now screw the brown conductor (live) into the top and the blue (neutral) into the lower terminal.
Before replacing the cover of the connector, assemble the other half. Once again prepare the end of the extension flex first. Then fit into the socket half of the connector, so that when the two halves of the connector are joined, the brown goes to brown (Live), blue goes to blue (Neutral), and green/yellow goes to green/yellow(Earth). Once connected up the cable grips can be fitted to both sides of the connector and the covers replaced.
Finally attach the plug to the other end of the extension flex, see the Wiring a plug page for more details.
The advantage of a trailing socket is that it can be used for a number of appliances. The appliance’s flex you wish to extend does not require any alteration if it already has a plug fitted. If it doesn’t then see the Wiring a plug and fit a plug to it. Next decide on a length of flex required for the extension. On one end of this extension the trailing socket will be fitted and on the other end a 13amp plug will be fitted. The trailing socket can be either a single or double socket, but a double might prove more useful, depending on your requirements.
With a trailing socket it is very important that the socket end is assembled first and on no account should the plug be plugged in until everything is complete.
It is also very important that the trailing socket is attached to the end of the extension flex and not on the appliance. On no account should there ever be a plug to plug cable that results in live pins being accessible. The pins of a plug must always be concealed in a socket when live.
On the first end of the extension flex, strip and prepare the wires (see Preparing the flex for connection) before taking the cover off the trailing socket. The socket should have three screw terminals. One marked L or Live, one marked N or Neutral, and the other one marked E or Earth or 
. The brown conductor from your extension flex should be fixed into the L (live) terminal. the blue conductor should be fitted into the N (neutral) terminal and finally the green/yellow conductor should be fitted into the E(earth) terminal.
Tighten the cable grip to make sure the flex can not be pulled out and replace the cover. Next fit a 13amp plug to the other end of the extension flex (see Wiring a plug for further details). This shouldsuccessfully and safely complete the extension lead.
Our forum is the perfect place to ask questions and get help. Join us, post your question/comment now!