Fitting a bell, buzzer or door chime is a simple job, since many are sold in kit form specifically for DIY installation. All work off a low voltage supplied by dry batteries or a small safety transformer which is permanently connected to the mains and reduces your 240 volt household supply to 3, 5, 8 or 12 volts. You will need a transformer system for a bell push with a light; if you just want a bell or chime without illumination, a system operated on dry batteries is easier and cheaper to install. Batteries normally last for about 12 months, depending on the amount of use. Prices vary considerably according to the signal which is produced and the kind of external fitting used.
An electro-magnet causes a hammer to vibrate against a metal gong (or dome) and produces the familiar clear ringing tone.
An electro-magnet causes a diaphragm to vibrate. Pitch and volume can be varied and some produce a tone similar to a fog horn.
These have a double-ended plunger, mounted on a spring drawn through an electromagnet, which strikes the metal chime bars and produces a double note. Some can be wired to a second bell push on another door, which will produce a single note so you will know which door to answer.
Sonic musical signals
Produced in a variety of preprogrammed tunes, this type gives an individual touch to surprise any caller.
How they work
Bells, buzzers, chimes and sonics may be operated by battery or transformer (in some cases either), but check first with the manufacturer’s installation instructions. Some are specially made so they do not cause interference on a television set or radio. The bell push is a spring-loaded switch; as it is pressed two contacts join to complete the circuit.
Usually manufacturers supply installation instructions and wiring diagrams with their kits, but the basic principle is a simple circuit which is completed when the bell push is operated.
Batteries are often fitted inside the case of the bell or chime and connection to the push is by twin core flex usually called bell wire. This is often sold in white or cream; you can paint over it to match your existing wall colour. Since domestic fittings are operated off a low voltage, there is no danger of getting a shock or of causing a fire with this wire. It can be left exposed along the edge of skirting, round door frames or even along the edge of coving. Small insulated fitting clips secure the wire to the surface, but take care not to sever the wire when nailing. Bell wire should be clipped to the surface at about 300mm (or 12in) intervals.
How they are installed
- The hall is the best site for the sounding unit, but this will obviously depend on what sort of accommodation you have. Many people have them in the kitchen, but there is a risk of steam corroding both batteries and sounding unit.
- If the distance between bell and push is more than about 9m (30ft) you may need to increase the voltage of the battery or the thickness of the wire because. The resistance of the wire reduces the effective voltage. The loss of about I volt for every 9m (30ft) of wire may not be noticeable when the batteries are new, but after a while the bell or chime signal will weaken and then stop altogether.
- It is a simple matter to install a bell push at the front and back doors to operate one sounding unit; you can also fit a second sounding unit to work from the same push — this is useful in a large house or where the occupant has hearing difficulties. Two methods can be used to wire a second bell or set of chimes.
This method is for bells or chimes which have the same resistance.
This system is for bells or chimes which do not match. Here increased voltage is necessary, otherwise either only one bell will work or neither will give a loud enough sound. The series system cannot be used for trembler bells.
- If you fit a transformer, you must connect it to the mains using I sq mm twin core and earth cable. It can be connected as a spur from a ring circuit, but most consumer units have a 5amp fuseway designed for this connection. If you take a spur from the ring circuit, use a fused connection unit with a 3amp fuse.
- Transformers usually have three connections on the output side. If you take the bell wire to the outer connections, this gives an 8 volt supply; taken to the middle and one of the outer connections, it gives a 5 volt supply; and taken to the middle and the other outer connection a 3 volt supply. Transformers are also available which give a 12 volt supply for use when two fittings are run in series or for long wiring runs. All this is clearly marked on the transformer case, so you should have no difficulty selecting the right connections.
- To fix the unit you have chosen, drill a hole through your door jamb to run the bell wire from the bell push to the battery and sounding unit. The bell push must be wired to its two terminals before it is screwed into the jamb. You should leave a loop of wire inside the push so it can be removed for inspection. Alternatively fix the bell push to the door and run the wire from the push through a hole in the door to the hinged side and onto the jamb, leaving some slack wire between the door and the jamb to prevent excessive bending when the door is opened and closed; otherwise the bell wire will very quickly break. Ideally, form the slack wire into a small coil by wrapping a few turns round a pencil before attaching the wire to the jamb. Continuous conductor hinges are available which overcome the need for slack wire, but these are expensive.
- Attach the housing of the sounding unit to the wall with plugs and screws, and clip or screw the cover over it. Usually the cover is made of plastic or wood, but some manufacturers make more decorative ones in such materials as ceramic. Make the electrical connections according to one of the circuits illustrated.
How to correct faults
If your bell stops working, it may be due to a flat or damaged battery, a loose connection, faulty bell push or dirt in the sounding mechanism.
Any contact in a bell or buzzer can be cleaned by rubbing a piece of card between the contact and screw, but don’t use abrasive material. You need a soft brush, dipped in lighter fuel, to clean the solenoid spring and plungers on a chime to ensure the plunger can move freely.
Always disconnect the fitting before servicing any unit.