Wiring for Doorbells

How a Doorbell Works

• A doorbell is made up of three major components: a transformer, a doorbell or buzzer, and a doorbell switch. The doorbell transformer connects to household electrical power and converts this electrical signal into a low-voltage AC signal that the doorbell can readily use. The doorbell switch actuates the doorbell circuit and allows electric current to flow from the transformer to the doorbell or buzzer. When the doorbell or buzzer receives power, there is an audible signal.

Wiring a Doorbell Switch Into the Circuit

• A doorbell switch connects to the doorbell circuit by means of two wires. The first wire going to the doorbell switch connects to the doorbell or buzzer, while the second wire connects to the doorbell transformer. The back of the doorbell switch contains two terminal screws. The wire that connects the doorbell or buzzer to the doorbell switch must be attached to one of the terminal screws, while the wire that connects the doorbell to the transformer must be attached to the other terminal screw.

Wiring a Transformer Into the Circuit

• Doorbell transformers are available in two forms: the plug-in transformer and the hard-wired transformer. A plug-in transformer plugs into a wall electrical socket, whereas a hard-wired transformer must be connected directly to the electrical system through an electrical junction box. When installing a hard-wired transformer, one of the transformer primary (high-voltage) wires must be twisted together with the black wire inside a junction box -- while the remaining transformer primary wire must be twisted together with the white wire inside the junction box. Some hard-wired transformers may also contain a center-tap that serves as a grounding point for the transformer; this center tap must be connected to the green or bare wire in a junction box. Whether the transformer is of the plug-in type or the hard-wired type, the transformer primary must be connected to household electrical voltage.

  The transformer secondary (low-voltage area) contains two wires. One of the transformer secondary wires connects to the doorbell, whereas the remaining secondary wire connects to the doorbell or buzzer.

Wiring the Doorbell or Buzzer Into the Circuit

• The doorbell switch opens and closes the circuit, the transformer provides power for the circuit, and the doorbell or buzzer uses the power from the circuit to create an audible signal. Doorbells and buzzers have two terminal inputs; one of the terminals connects to the doorbell switch, while the remaining terminal input connects to the transformer. When the doorbell switch is pressed, the circuit is closed and electric current flows through the circuit.