How to Install a Hardwired Smoke Detector

Hardwired detectors take fire safety to a whole new level. Learn how to add this feature to your home in just three steps.

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Keeping your home and family safe is always a top priority. And when it comes to fire or carbon monoxide detection, there's little room for error. That's why learning how to install a hardwired smoke detector is such a good idea. These sensors are wired in a series, so when one alarm sounds, they all sound.

In some areas, hardwired smoke detectors that include battery backup are required, so check local codes before deciding what type of detector is best for your home. If you choose hardwired detectors, know that running the cable is the hardest part of the job. The time required for the task depends on the layout of your home. In addition, you'll need to tie into a single power source.

Expect to spend about 5 hours running cable and installing three detectors. You'll need to know how to install boxes, run cable into boxes, and strip, splice, and connect wires to terminals.

What You Need

  • Voltage tester
  • Drill
  • 1/2-inch bit
  • Drywall saw
  • Fish tape
  • Screwdriver
  • Strippers
  • Long-nose pliers
  • Lineman's pliers
  • Smoke detectors
  • Boxes
  • 14/2 and 14/3 cable
  • Electrician's tape
  • Wire nuts

Step 1: Install Boxes


For each detector, cut a hole for a standard 4-inch octagon or single-gang box. Run 14/2 cable to the first detector in the series and 14/3 cable to the others. The yellow lead from each detector interconnects the system, so all detectors sound at once. Install the boxes.

Step 2: Align and Attach


Align the slots of the mounting plate and attach the plate to the box. Gently pull the wires through the plate. After connecting the first box in the series, connect wires as shown.

Step 3: Connect to Power


After securing the wire nuts with electrician's tape, gently push the wires into each box. Install the detectors, activate the backup batteries, and connect to the power source.

Bonus: Install a Plug-in Carbon Monoxide Alarm


Carbon monoxide, an odorless, colorless, poisonous gas, results from combustion. Faulty venting for appliances, wood or charcoal burners or the incursion of auto exhaust can put your household at risk. Plug-in units have a battery backup and help protect you and your family from harm.

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