Adding a New Light and Switch - One Way
This article explains how a new light is added to an existing lighting circuit. The light will be operated by a single switch which is commonly referred to as a one way switch. For information about operating the same light from two different switches see our Adding a New Light and Switch – Two Way article.
The switch cable for the new light fitting can be provided in one of two ways. In this article a ceiling rose and pendant light are being installed so the switch cable can be connected up at the ceiling rose. The switch cable for light fittings without a ceiling rose can be connected via the junction box used to connect to the supply. This method is detailed in our Installing a Fluorescent Tube Fitting and Switch guide.
Switch off the power at the consumer unit for the circuit from which you are going to take the supply for the new light. If you have removable fuses at your consumer unit, switch off the power at the consumer unit and remove the fuse for this circuit.
Locating the light and switch
1. Decide upon the location for the new light and make a hole in the ceiling large enough to accommodate the cable(s). If possible, choose a position which enables the new ceiling rose to be screwed directly to a joist.
2. Otherwise, mount a wooden batten between the two nearest joists to provide the fixing.
3. Decide where you want the switch for this light.
4. Check that there are no cables, pipes etc buried below the surface.
5. Cut out the wall to mount the switch box in the same way as for mounting socket boxes. You may use a Surface Mounted Box, a Flush Mounted Metal Box, or a Flush Mounted Plasterboard Box.
Solid walls
6. For cables in solid wall, you will need to chase out the wall and house the cable in a protective conduit. Mark a vertical line up from the switch position to the ceiling above, and chase out the plaster for the switch cable. Remember to wear safety goggles when cutting out
7. Above this chase, make a hole through the ceiling so that the cable can be fed through from here.
8. When running the cable, feed it through the conduit as you go, then set the conduit into the chase in the wall. This can be made good with plaster later.
Hollow walls
9. For hollow stud walls, the cable can be fed down the wall to the new switch position without the need for chasing. You will also need to make a hole in the ceiling above the stud wall allowing you to feed the cable in.
10. If there are horizontal timbers or noggins in the stud wall where you wish to run the cable, you will have to make a small cut-out in the plasterboard at this point to enable you notch the timber for running the cable.
Installing the lighting switch cable
11. Feed a suitable cable (see lighting circuits for details) through the hole in the ceiling from above down to the switch. Remember to allow sufficient cable for making the connections at both ends.
12. Remove a cable entry blanking piece from one of the switch box sides. If you are mounting the switch in a solid wall, you will have used a metal box and will need to line the cable entry point with a rubber grommet.
13. Feed the cable through, then secure the back box to the wall.
14. Strip and prepare the conductors ready for connection. Cut through the end of the outer sheath of the cable carefully using a pair of side cutters. Be sure not to cut into the insulation of the conductors.
15. Peel back the sheath to reveal the conductors and grip the end of the bare earth conductor with a pair of pliers. Draw the wire back through the sheath like a cheese wire.
16. Fold the excess back and trim with the side cutters.
17. Separate the conductors and trim the insulation of each back by about 1/2" with wire strippers. For detailed information on this see our Cable Stripping Guide.
18. Insulate the earth conductor with green and yellow sleeving. This should be cut to length and fed over the conductor so that about 1/2" is left exposed at the end to match the other conductors.
19. Tag the blue conductor with a piece of brown sleeving (old cable colour = black; old tag colour = red). This is used to clearly identify that this is actually a Live conductor.
20. Connect this to the bottom terminal on the switch, (most one way single gang switches have the top labelled).
21. If your switch is a two way type that you are using for one way operation, it will have two terminals at the bottom marked ‘L1’ and ‘L2’. Use the terminal marked ‘L2’
22. Connect the brown (old cable colour = red) conductor to the top terminal.
23. If your switch is a two way type that you are using for one way operation, the top terminal will be marked ‘C’ for Common.
Earth Connection
24. What happens with the sleeved earth conductor depends upon the fittings being used.
- Plastic switch and plastic mounting box - the earth conductor is connected to the earth terminal on the back of the mounting box if there is one. Otherwise it is secured in a plastic terminal connector block and tucked safely out of the way. In this situation some people trim the earth right back but this should not be done. If someone wants to fit a metal switch at a later date the earth will be too short.
- Plastic switch and metal back box – the earth conductor is connected to the earth terminal on the back of the metal mounting box.
- Metal switch and plastic back box – the earth conductor is connected to the terminal on the switch marked with the earth symbol.
- Metal switch with metal back box - the earth conductor is connected to the terminal on the switch marked with the earth symbol. An earth tail is also connected between here and the earth terminal on the back of the metal mounting box.
25. Double check your connections and ease the switch back to the wall folding the cable carefully into the box.
26. Secure the switch with its retaining screws tightening them alternately to draw it back evenly.
27. As you tighten these, ensure that the face is level. One or both of the screw mountings will have allowance for a small amount of vertical adjustment which assists with this.
28. Now take the other end of this cable and feed it through the hole in the ceiling at the position for the new light fitting. Label it 'switch'.
29. Feed another suitable cable through the ceiling to the new light position. Label this ‘supply’.
Connecting the supply cable at the ceiling rose
30. Feed both cables through the backplate of the new ceiling rose and screw the backplate of the rose to the ceiling joist or noggin.
31. Strip and prepare the conductors of the supply cable.
32. Connect the brown (old cable colour = red) to the terminal block marked ‘LOOP’.
33. Connect the blue (old cable colour = black) to the terminal block marked ‘N’.
34. Connect the green and yellow sleeved conductor to the terminal marked with the earth symbol but only secure loosely for the moment as another earth will also need to be connected here.
Connecting the switch cable at the ceiling rose
35. Strip and prepare the switch cable.
36. Connect the brown (old cable colour = red) to the terminal block marked ‘LOOP’.
37. Tag the blue with a piece of brown sleeving (old cable colour = black; old tag colour = red) indicating that it is actually the live coming back from the switch and connect it to the Live terminal alongside the flex connection point.
38. Connect the green and yellow sleeved conductor to the earth terminal.
Lampholder connection
39. Prepare and connect a lampholder to a suitable length of flex. For more information on this, see our Lampholder Fitting and Connecting article.
40. Feed the other end of the flex through the ceiling rose cover, prepare the conductors, and connect to the flex terminals.
41. Connect the brown (L) to the outer terminal next to the switch return conductor.
42. Connect the blue (N) to the other outer terminal next to the supply cable neutral.
43. If your light fitting is metal the flex should also contain a Green / yellow (earth). This should be connected alongside the other earth conductors at the ceiling rose.
44. Ensure that the flex conductors are securly held in the retaining lugs provided.
45. Double check all your connections are correct, secure and have no exposed conductor showing. Fit the ceiling rose cover.
Connecting to the lighting circuit supply
46. The other end of the supply cable can now be connected to the lighting circuit.
47. You will need to decide the best method of providing the supply for this new light. The easiest way is by inserting a new junction box in the supply cable of the lighting circuit.
48. Unless the area where the junction box is going will be accessible, you will need to use a maintenance free type. In this example we are using a Wagobox maintenance free junction box.
49. Double check that the circuit has been isolated at the consumer unit as mentioned at the beginning of this article. Cut the cable of the lighting circuit next to where the junction box is to be fitted.
50. Strip and prepare the new ends remembering to sleeve the bare earth conductors in the usual way.
51. Strip and prepare the ends of the new supply cable as well.
52. Connect the brown Live (old cable colour = red) conductors together in a suitable terminal connector.
53. Connect the blue Neutral (old cable colour = black) conductors together in a suitable terminal connector.
54. Connect the green and yellow sleeved conductors together in a suitable terminal connector. In this example a cage clamp type terminal connector is being used. A push type connector would be equally suitable.
55. Secure the terminal connectors in the maintenance free junction box following the manufacturer’s instructions.
56. Secure the sheathed section of the cables in the cable clamps provided.
57. Fix the lid of the junction box and mount the box on a suitable timber using the bracket provided.
58. Double check all your wiring and connections.
59. Once you are sure that all work has been completed correctly, switch the power back on at the consumer unit. In the case of removable fuses, replace the fuse for the circuit, and switch the power back on.
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