Q&A: July

Q1: I have seen a kit that allows a double mains socket to be changed for a triple one. Are these easy to fit and do I need any wiring experience to do this job?

A1: They are easy to fix. However, all the ones I’ve seen have been designed to fit onto a flush mounted socket - that is the type where the socket is flush to the wall. To fit the three way socket you will need to know how to switch the mains off and to remove and re-terminate the wires.

Plug a lamp into the mains socket you want to change and make sure it is lit. Remove the fuse or switch off the MCB and check that the lamp has gone off. If you have an assistant, ask them to remove the fuse or switch off the MCB at least twice so that you know the circuit is off. Unscrew the socket and pull it away from the wall. The red wires (there may be 1, 2 or 3 of them) will be terminated in the L (live terminal). The black wires (there may be 1, 2 or 3 of them) will be terminated in the N (neutral terminal) and the earth wires, which are bare conductors sleeved with yellow/green sheathing, will be connected to the earth terminal on the socket and to the back-box if it is metal. Remove all these wires.

Screw the new plastic box (pattress) onto the existing back-box and re-terminate the wires – red to live; black to neutral and earth to earth. Make sure the terminal screws are tight and then screw the new triple socket into place. Replace the fuse or switch on the MCB and all should be well.

Q2: How easy is it to fit a dimmer switch in place of a switch that is already there?

A2: In essence, it is simply a matter of turning the mains off, removing the wires from the terminals of the old switch and re-terminating them on the new dimmer-switch. However, there are some things to consider. If you are replacing an ordinary switch for a dimmer, the dimmer may not fit into the existing back-box - the dimmer electronics take up a lot more space than an ordinary switch. Most dimmer-switches will be two-way (that is, the lights can be switched off from two different switches, e.g. a landing light). However, if you are replacing a single light switch (the only switch that operates the light) then you will need to use only two of the terminals on the new switch, Com and L1. If the switch is two-way you will use all three terminals; Com, L1 and L2.

Turn the power off to the lights, remove the switch and make a note of where each wire goes. Do this carefully - there are many possible ways that the colours may be terminated onto the terminals - all you need to do is replace the wires under the same terminals as before. Make sure the terminal screws are tight then screw the new switch into place. Switch on at the mains and the light will work. If in doubt, you may find a good DIY manual will help or ask an electrician to do the job.

Q3: I get very confused when I hear about MCBs, RCDs and CUs. Could you please tell me what they all are?

A3: Yes, it does take a bit of getting used to! MCBs (Miniature Circuit Breakers) do the same job as a fuse – they protect a circuit against excess current. However, instead of blowing the way a fuse does, they trip out and all you need to do is switch them back on or push in a button to reset them. If the fault is still there, the MCB will trip out again.

An RCD (Residual Current Device) is often called a trip. If there is a fault in the wiring the RCD will trip out and, in many cases, cut off all the power to the house. RCDs are also available that plug into a socket and protect an extension lead for a mower or drill or any other electrical device (these are a must when working outside).

A CU (Consumer Unit) is another name for a fuse box. The CU will have a mains switch that will turn off the supply to the house. It may also contain an RCD to protect the house wiring against faulty appliances or wiring. Additionally, it will contain all the fuses or MCBs for the house wiring.

Q4: How easy is it to change a one-way switched light to two-way switching? I need to be able to switch the kitchen light on and off at both the back door and the door to the hallway.

A4: I’m sorry to say that this involves quite a lot of rewiring. You will need to run a three core and earth cable from the existing switch to the additional switch location. Fit a new back-box on the wall and then wire up the two switches. To my mind, this is not an easy job. However, you could ask an electrician to suggest what to do and ask her/him to wire it up once you have done the main work.

Q5: I have a terrible centre light fitting in the living room that I would like to change for a more up-to-date one. How difficult is this?

A5: As long as you do not intend to change the ceiling rose that fixes the old light, the wiring is not too difficult. However, if you intend to remove the ceiling rose then it will be necessary to fix a junction box in the space above the ceiling to terminate the new light flex and then find strong fixings in the ceiling to hold the light up.

If you are not removing the ceiling rose, the procedure is as follows. Switch the light off at the main consumer unit (CU) – it is not safe to switch it off at the switch! Unscrew the cover from the ceiling rose. This may be a little difficult. If so, clear any paint away from the base of the rose to allow it to unscrew. Let the cover slide down the flex of the old light and make a note of where the wires from the flex to the light terminate on the rose. Take special note of how the wires are wrapped around two clips in the rose to support the weight of the light. Now get someone to support the light. Use a small screwdriver to undo the terminals that hold the wires from the flex and pull them out – this will free the light.

To fit the new light, thread the cover of the ceiling rose onto the new flex so that it can be screwed onto the rose when the terminations are completed. You may need to remove a little more sheathing (the outside cover) from the flex to allow it to wrap around the support clips in the ceiling rose. Terminate the flex wires on the same terminals as before (in a flexible cable this would be, blue to neutral and brown to live from the switch). If the flex to the new light has an earth wire (yellow/green) in it, terminate this with the other yellow/green sleeved wires on the earth terminal. Now screw the rose cover back into place and switch on at the consumer unit. If you are not sure how to do this ask an electrician to do the job.