Replacing Old Smoke Detectors

By Dave Rongey - Summary:

How do connect the wires for a new smoke detector? Identifying Smoke Detectors and Wiring to ensure proper compatibility.

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Wiring Smoke Detectors

Electrical Question: How do connect the wires for a new smoke detector?

  • A small water leak in the ceiling damaged a 10-15 year old smoke detector.
  • A plumber fixed the leaking joint, and now I’m replacing the old smoke detector.
  • The old unit has connections for 8 wires: 2 black, 2 brown, 2 blue and 2 red.
  • The new smoke detector has 3 wires: red, black and white.
  • I assume red to red, black to black, but I’m not sure about connecting the brown and blue leads.

This electrical wiring question came from: Jim, a Homeowner from Dallas,Texas.
Dave’s Reply:
Thanks for your electrical wiring question Jim.

How to Wire a New Smoke Detector

Application: Installing or Replacing a Smoke Detector.
Skill Level: Beginner to Intermediate – Best performed by a Licensed Electrician.
Tools Required: Basic Hand Tools and Safe Ladder.
Estimated Time: Depends on personal experience and the number of smoke detectors and access to them.
Precaution: Smoke Detectors are required by code to be installed in specific areas of the home. Never remove or leave a smoke detector disconnected or never leave the smoke detector circuit power off.
Notice: Smoke detector type alarms should be tested frequently to make sure they are functioning correctly.Installing or upgrading electrical wiring should be done according to local and national electrical codes with a permit and be inspected.

Identifying Smoke Detectors and Wiring for Compatibility

  • The original or existing smoke detectors will need to be identified to verify the voltage.
  • The wiring and the type of interconnected alarm method will also need to be identified.
  • The verified information will need to be compared to the replacement smoke detector to be sure of proper compatibility of all smoke detector units and devices.
  • If a smoke detector is over 10 years old then you should consider replacing it with the appropriate replacement.
  • If the replacement smoke detector is compatible with the existing devices then the wiring connections will need to be cross referenced to understand the proper connections.
  • The typical connections will include the white circuit neutral wire, black circuit power, and the red or yellow wire for the alarm signal wire.
  • After the replacement smoke detector is installed then the test button should be pressed at each smoke detector to ensure the system is functioning and sounding the alarm properly as described in the documentation which is included with the replacement smoke detector.

More about Smoke Detectors

Wiring Smoke Detectors

  • How to Install Smoke Detectors

  • Take the mystery out of smoke detector wiring.
  • Smoke alarms provide the earliest warning of both fire and smoke.

Smoke Detectors


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