Electricity: Doorbells and Chimes

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Above: A typical single-button doorbell circuit.

A doorbell or chime system consists of the sounding device, a front-door button, an optional rear-door button and a transformer that reduces 120-volt current to the lower voltage most systems require. Bell wire connects the components. The transformer must be connected to an unswitched branch circuit in a junction box, often in the basement or near the service panel.

When estimating cable, measure the distances between components and add another 15 ft. (4.5 m) for connections and route turns. Follow the manufacturer’s instructions. Although bell wire can be exposed, fish it behind finished surfaces where possible.

If you’re replacing a doorbell, check the old transformer to make sure it has the same voltage rating. Replace the transformer, if necessary. Before repairing a doorbell, check the service panel for a tripped breaker or blown fuse.

Above: A chime unit wired to both front and back door buttons.

Caution: Before installing the transformer, turn off the power to the circuit you’re tapping into and use a volt age tester to make sure the power is off.

Installing a Doorbell or Chimes

1. With power off, remove a knockout from the junction box; insert transformer wires. Fasten transformer to box with locknut. Use wire connectors to join one transformer wire to a black wire, the other to a white wire.

2. Drill holes for door button wires and mounting screws at doorknob height adjacent to the door’s edge. After running the bell wiring, connect one wire from the transformer and one from the bell or chime unit to the button’s terminal screws.

3. Determine chime location on the wall. Drill wire-access and mounting- screw holes for chime. Mount chime unit and connect wires from the transformer and door button(s) to the correct terminals on the chime unit (they’re usually marked by the manufacturer).


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Troubleshooting and Repairing

1. If the doorbell won’t ring, remove the button cover and clean contacts with sandpaper; pry them up with screwdriver. If this fails, loosen mounting screws and pull out the button. Disconnect wires and touch ends together. If the bell rings, the button is faulty; replace it.

2. Turn off power when working at the transformer. Tighten loose wires at the bell or trans former. Wrap frayed wires with electrician’s tape. To repair breaks, strip ends; join with wire connectors.

3. Test transformer by restoring power to its circuit.

(Remember, incoming wires will be hot!) Set a multimeter to its AC volts scale and turn the dial to the 50-volt range. Touch multimeter probes to the transformer’s low-voltage terminals. If the tester registers no voltage, the transformer is defective; replace it.

Smart Shopping: A Simpler Way

Wireless chimes offer an alternative to wired units. They can be used in new construction or to replace older units where wires inside the wall may be damaged or broken and hard to access. The battery-powered push-button transmitter sends a radio signal to the battery-powered chime unit. Transmitter buttons can't be mounted on metal surfaces that will interfere with signal performance.

Last modified: Saturday, 2007-11-03 1:22 PST