Installing a Fluorescent Tube Fitting and Switch

Fluorescent tube fittings, like many other types of light fitting, only have a connection terminal for the Live, Neutral, and Earth. Unlike ceiling rose and pendant lights, there is no facility for running the switch cable from the fitting itself. Provision of the switch cable can therefore made at the junction box connected into the lighting circuit.

Fluorescent tube fittings are commonly used for utility lighting in places such as garages, workshops and lofts. In this example, a fluorescent tube fitting is being installed in an upstairs room and the junction box used is fully accessible. A standard screw terminal junction box can therefore be used where the connections are made to the existing lighting circuit and for the switch cable for this light. If a junction box will not be accessible, a maintenance free one should be used instead. More information can be found in our Junction Box article.

1. 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.

Fluorescent Tube Fitting

2. Decide on the location for the new tube fitting. Remove the cover and determine which of the fixing holes in the base of the unit will be most suitable. You should use a minimum of two fixings – one towards either end of the fitting.

Marking the cable entry point and fixings

3. Hold the fitting in position and mark the fixing points with a pencil. Also mark the cable entry point.

Drilling hole through ceiling for cable

4. Put the fitting to one side and drill a small hole in the ceiling at the cable entry point. Make sure there are no services such as cables above the hole to be drilled.

Example of fixing batten for support

5. If the fixing holes do not align with joists in the ceiling, you may have to add battens or timber noggins to provide the required support.

Feeding cable through ceiling

6. Feed a suitable length of twin and earth cable through the ceiling from above. Make sure you allow sufficient cable to reach the terminal connections inside the fitting.

Fixing fitting to ceiling joists

7. Feed the cable into the fitting and mount the fitting on the ceiling with screws. Make sure these screws are securely fixed into timbers above.

Conductors stripped and prepared

8. Strip and prepare the conductors ready for connection, with the insulation of each stripped back by about ½”. Insulate the bare earth conductor with green and yellow sleeving.

Connecting the live conductor

9. Connect the brown (old cable colour = red) to the Live terminal connection of the fitting.

Connecting the neutral conductor

10. Connect the blue (old cable colour = black) to the Neutral terminal connection of the fitting.

Connecting the earth conductor

11. Connect the green and yellow sleeved earth conductor to the Earth terminal of the light fitting.

Securing the fitting cover

12. Replace the cover of the fluorescent tube fitting having checked that all connections are correct and secure. Make sure that the wiring doesn’t get snagged as the cover is replaced.

Fitting the fluorescent tube

13. Fit the tube itself into the fitting. Take care to align the pins at the end of the tube with the sockets on the fitting ends.

New cable fed back to lighting circuit

14. We now need a 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. Run the other end of the cable from the fitting back to the nearest part of the lighting supply circuit and label this cable ‘Light’

Switch cable

15. Take a second length of cable and label it ‘Switch’. Run this cable from here to the position where you want the light switch to be.

Light Switch

Wall cut out for switch back box

16. Cut out the wall to mount the switch box in the same way as for mounting socket boxes. More information on this can be found in our Surface Mounted Box, Flush Mounted Metal Box, and Flush Mounted Plasterboard Box guides

Removing the cable entry blanking piece

17. 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.

Feeding the cable into the switch box

18. Feed the cable through, and then secure the back box to the wall.

Stripping the outer sheath of the cable

19. Strip back the outer sheath and prepare the conductors ready for connection. 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.

Earth sleeved with green and yellow sleeving

20. 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.

Tagging the blue with brown sleeving

21. Tag the blue conductor with a piece of brown sleeving. This is used to clearly identify that this is actually a Live conductor.

Connecting the blue conductor to the switch

22. Connect this to the bottom terminal on the switch, (most one way single gang switches have the top labelled).

Connecting the brown conductor to the switch

23. Connect the brown conductor to the top terminal.

Connecting the earth conductor to the box terminal

24. We’re using a plastic switch and a plastic mounting box so the sleeved Earth conductor is connected to the Earth terminal connection at the back of the box. Arrangements for the earth conductors vary according to the type of switch and mounting box. Full information on this is set out at the bottom of the article.

Easing the switch back to the wall

25. Double check your connections and ease the switch back to the wall folding the cable carefully into the box.

Securing the switch against the wall

26. Secure the switch with its retaining screws tightening them alternately to draw it back evenly.

Connecting the Junction Box

Cutting into the lighting circuit

27. We now need to connect up the junction box to provide a switched supply to the new light. Double check that the lighting supply cable has been isolated at the consumer unit as mentioned at the beginning of this article. At the point in the attic where the light cable and switch cable have been run back to the lighting supply circuit, cut the cable.

Cables stripped and prepared

28. Strip and prepare the ends of the cable that has just been cut, as well as the light cable and the switch cable. Remember to sleeve the bare earth conductors leaving about ½” exposed to match the other conductors.

Sleeving the blue conductor of the switch cable

29. Sleeve the blue conductor of the switch cable with brown sleeving to identify that this will in fact be live.

Mounting a four terminal junction box on the joist

30. Mount a four terminal junction box of suitable rating. This can simply be screwed to a joist or, if needs be, fit a wooden batten to support it on. As mentioned earlier, a maintenance free junction box must be used if the location will not be accessible later. In this example the area is fully accessible.

Connecting the brown of the circuit cables and the switch cable

31. Connect the brown live (old cable colour = red) conductors of the two circuit cables and the switch cable into one of the terminals.

Connecting the earth conductors

32. Connect all the green and yellow sleeved earth conductors into the next terminal.

Connecting the neutral conductors

33. Connect the blue neutral (old cable colour = black) conductors of the two circuit cables and the light cable into the third terminal.

Connecting the switch return and live for the light

34. Connect the brown live conductor of the light cable and the blue tagged with brown sleeving, of the switch cable into the next terminal.

Replacing the junction box cover

35. Make sure that all connections are fully secured with no exposed conductor showing. Ensure that there is no unsheathed cable outside of the junction box. Replace the junction box cover and secure. The cover of most screw terminal junction boxes can be rotated to provide the required number of cable entry points.

Additional Information:

Earth Connection at the Switch

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.

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