Ceiling switches can either be surface or flush mounted. If you’re going to surface mount one, you’ll have to pierce a hole in the ceiling so the cables can be drawn through into a plastic mounting box. Before fixing this in position with No 8 wood screws, you should knock a thin section of plastic from the base to align with the hole in the ceiling.
ldeally the box should be fitted against a joist, but if there isn’t one suitably placed, you’ll have to fix a support batten between the joists made from 75 x 25mm (3 x 1 in) timber with a hole drilled in it big enough to let two lengths of 6mm cable pass through. When you’re feeding the cables into the mounting box, it’s a good idea to write ‘mains’ on the end of the circuit cable and shower’ on the end of the shower feed cable. This could be surface mounted on the ceiling and wall, but it’s neater to conceal it in the ceiling void and chase it into the wall, running it in plastic conduit. You can now strip back the insulation and make the connections The mains cable should go to the ‘supply’ side of the switch, with the red core going to the terminal marked L and the black to the one marked N, and the shower cable to the equivalent terminals on the ‘load side. Remember to sleeve the earth cores in green/yellow PVC and connect them to the earth terminal in the switch.
Place the six cores neatly in the box and screw the switch to it, if you’re going to flush-mount the switch you’ll have to mark the size of the mounting box on the ceiling and, using a pad saw, carefully cut out an equivalent size hole. Then cut a piece of timber to f ii between the joists, lay it across the hole and mark the square on it. Knock out a blank from the base of the metal box and drill a hole in the corresponding spot in the timber. Then screw the box to the timber and fix the timber to the joists at a height above the ceiling that allows the box edge to sit flush with the ceiling surface. This can be checked by holding a straight edge across the hole in the ceiling. You should then thread in the two marked cables and make the connections. If you want to fix the switch at a point where there is a joist you can always cut away a section of it. This is best done by using a drill fitted with a 25mm (un) wood bit to remove most of the wood and then chiseling the remainder away. That way you wont need access to the ceiling void as long as you can fish’ the cable across the ceiling using a length of stiff wire. Connecting into the shower The cable to the shower can be run down the wall on the surface, using plastic cable clips or mini-trunking, or buried in a chase chopped in the plaster. The cover of the control unit must be removed to allow you access to the terminal block, but do read fully the manufacturer’s instructions before going any further. Thread in the cable and strip off some of the sheathing and insulation before connecting the red core to the L terminal and the black to the N terminal Before connecting the earth core to the earth terminal make sure you’ve sleeved it in green/yellow PVC. If the unit has a cable clamp, fix the cable in it, double checking that it’s the whole, sheathed cable that is held by it and not just individual cores. This is very important as it serves to protect the connections. Finally, refit the unit cover, finish off the radial circuit connections at the consumer unit, switch on at the mains and test the shower. Fitting a flex outlet plate You’ll have to use a flex outlet plate only if there is already a flex connected to the shower unit. This can be fitted on either a one-gang moulded plastic box for surface mounting, or else in a 35mm (1 metal box for flush mounting, in which case you’ll have to chop a hole. After fixing one or other of the boxes to the wall, run the cable into it through a knockout hole, which, in the case of the metal box, should be fitted with a grommet. The unit has three banks of terminals with two terminal screws per bank and you should connect the green/yellow sleeved earth core to a terminal of the non shielded bank marked E’. Then connect the red insulated core to a terminal of one of the shielded banks and the black to a terminal of the other bank. Prepare the end of the flex by stripping off approximately 12mm (1Mn) of insulation from the end of each core. Remember to thread the flex through the hole in the unit’s cover before you connect the flex to the unit as you won’t be able to fit it after you’ve made the connections. Then connect the earth core, which should be already sleeved in green and yellow PVC, to the other terminal in the ‘E’ bank, the brown core to the bank containing the red core and the blue core to the bank containing the black circud core. Tighten the cord clamp, again making sure that it’s the flex sheath that it grips and not the unsheathed cores as this protects the connections. Lay the six cores neatly in the box and fix the unit to the box with the two screws supplied You can then switch on the power and test the shower.