How to Install Old Wired Smoke Detectors

How to Install Old Wired Smoke Detectors


Smoke detectors are an essential safety device in any home. They can alert you to a fire in the early stages, giving you precious time to escape. Many homes still have older wired smoke detectors that were installed years ago. These older models may not have some of the newer features like interconnectivity, but they can still provide an important early warning. Updating to new smoke detectors is recommended, but in the meantime the old wired units can still be made functional. Installing them correctly is important for proper operation.

What You'll Need

Finding Power for the Smoke Detector

Older wired smoke detectors require a nearby power source to operate. This usually means tapping into a nearby electrical junction box. Options for providing power include:

Always turn off the circuit breaker to the junction box before wiring a smoke detector to it. Test for power with a voltmeter before touching any wires.

Mounting the Smoke Detector

Smoke detectors should be mounted high on walls or ceilings, at least 4 inches from corners. Avoid installing near vents, windows, or anywhere that airflow could impact performance.

When mounting on a ceiling:

When mounting on a wall:

Use the provided mounting bracket and screws to secure the smoke detector. For drywall, use the provided anchors.

Wiring the Smoke Detector

Here are the steps for wiring an old smoke detector:

  1. Cut power to the junction box you are using. Verify with a voltmeter.

  2. Run 14/2 or 12/2 NM wire from the junction box to the smoke detector mounting bracket. Leave 6-8 extra inches at the detector for connections.

  3. Strip 1/2 inch of insulation from the wire ends at the smoke detector. Connect the black (hot) wire to the connector marked "BLK". Connect the white (neutral) wire to the connector marked "WHT".

  4. Connect the ground wire to the grounding connector on the mounting bracket.

  5. Secure the wired connections with wire nuts and electrical tape.

  6. Mount the smoke detector onto the bracket and screw it into place.

  7. Restore power and test that the smoke detector powers on.

Testing and Maintaining Smoke Detectors


While newer smoke detectors have great benefits, older wired models can still provide protection if installed and maintained properly. By tapping into a nearby junction box for power and following safe mounting guidelines, they can continue alerting you in the event of smoke or fire. Just be sure to test them regularly and replace units that are over 10 years old.