Fitting Electrical Switches

The modern rocker-operated 5A lighting switch is a square plateswitch containing 1, 2, or 3 switches on the one plate and has two screw holes for fixing to the lugs of a one-gang plastic shallow surface box or a metal plaster-depth flush box.

Each box contains an earth terminal to which is connected the sleeved earth conductor of the circuit cable. On the top edge and sometimes also on the bottom edge of a metal box is a PVC grommeted cable entry.

The traditional height for a lighting switch is 1.5m above floor level, but any other convenient height is satisfactory.

Installing a plateswitch

For surface mounting, hold the box in place against the wall and mark the positions of the fixing holes. Drill and plug the holes. Knock out a section of thin plastic on the top edge, thread in 100mm of cable and fix the box using gauge 8 wood screws. For flush mounting, cut a chase in the plaster so that when the box is inserted the front edge will be flush with the wall surface.

Prepare the end of the cable by stripping off the sheath, leaving about 12mm within the box. Slip green/yellow PVC sleeving over the bare earth wire and connect the wire to the box earth terminal.

Slip red PVC sleeving over the black

switch wire. Connect the wires to the terminals and fix the switch using the two M3.5 metric screws supplied.

Cord-operated ceiling switch

A ceiling-mounted switch either has an integral backplate similar to that of a ceiling rose or it is mounted on a plastic pattress.

The ceiling switch or its pattress is fixed to a joist or to a piece of timber inserted between the joists. The ends of the cable are prepared as for a wall switch and the wires are connected to the respective terminals on the switch.

The connections for a two-way ceiling switch are the same as those for a plate-switch.

Installing a dimmer switch

A dimmer switch has the same number of terminals as the equivalent one-way or two-way rocker switch. It is a plateswitch and will usually fit the shallow switch mounting box. A few versions require a 25mm depth box. Fitting a dimmer switch therefore requires the same procedure as a rocker switch.

A dimmer switch can replace an existing rocker switch without modification to the wiring being necessary or a new box. A dimmer switch is unsuitable for controlling fluorescent lighting unless the fluorescent control gear is modified, a special dimmer is used and an extra wire run from the switch to the light.

Burglar deterrent switch

An electronic timing device in the form of a switch can be fitted in place of a rocker switch. The switch is solar operated and has an over-ride switch for use out of programmed hours.

Wiring a two-way switch

These materials are required: a quantity of 1.0mm2 three-core and earth PVC sheathed cable; earth wire sleeving; two two-way rocker switches plus a mounting box; or a one-way rocker switch plus a cord operated two-way switch; cable clips, wood screws and wall plugs.

Run the cable from the existing switch to the new switch position following the easiest route.

Turn off the main switch and remove the existing switch. Run the new cable into the existing box. Strip off the outer sheathing and about 9mm of insulation from the end of each of the three insulated wires. Slip PVC sleeving over the bare end of the earth conductor and connect it to the earth terminal in the box. Connect the yellow wire to the Common terminal of the two-way switch. Connect the red wire and the existing red wire to the Ll terminal; enclose the existing black wire in red PVC sleeving and connect this wire and the new blue wire to the L2 terminal. Fix the switch to the box using the original screws.

If the second switch is a wall switch fix the box to the wall, or if a flush box, fix it into a chase cut in the plaster. Insert the cable and prepare the end as at the first switch. Connect the red wire to the Ll terminal of the switch, connect the yellow wire to the Common terminal and connect the blue wire to the L2 terminal. Connect

the earth wire to the box earth terminal.

If the second switch is of the cord operated type fix it to a joist or a piece of timber fixed between the joists. Connect the wires to the switch terminals as for a wall switch.

Fitting a door bell

Door chimes operate at a voltage of from 6 to 12 volts and bells require a voltage of 3 to 6 volts.

Many models of bells and chimes will accommodate batteries in the casing so making separate batteries unnecessary.

With the self-contained type it is necessary only to run a length of twin bell wire to the push fixed to the door post outside the front door or in any other position. The bell wire is fixed by enamelled tacks which are pushed through the wire between the conductors.

Bells and chime kits are available, the only necessary additions being the batteries or other power source. The alternative power source is a bell transformer which is connected to the mains and has an output of 3-5-8 volts from a three-terminal block. Some models of chimes require 12 volts for which a special transformer is available.

Another refinement is an illuminated bell push, some models of which contain a nameplate.

An illuminated push can be fitted only where the bell or chime is powered from a mains transformer for, if used with batteries, the batteries would last only a day or so.

An alternative to a bell is the buzzer which is especially useful for operation in conjunction with a bell from a second push as one can be distinguished from the other.

Mains transformer

The transformer must be one designed for the purpose, and it will then meet the requirements of the regulations. The transformer can be supplied from a 1.0mm2 twin and earth PVC sheathed cable connected to the lighting circuit fuseway in the consumer unit and fixed next to the unit.

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