How To Install a Hard Wired Smoke Detector

Updated: Dec. 15, 2023

Follow these steps for easy and safe installation.

Next Project

An hour or less




$20 - $70


Replace smoke detectors before they fail. It only takes about 10 minutes to replace a hard-wired type safely

Tools Required

  • Electrical tape
  • Ladder or stepstool
  • Screwdriver
  • wire stripper
  • Wire tester

Materials Required

  • Batteries
  • Smoke alarm
  • Wire nuts

Installing a hard wired smoke detector is an essential safety measure for any home. It provides peace of mind and could be a lifesaver in the event of a fire.

Installation involves connecting the new detector to others throughout your home. This ensures all alarms sound simultaneously when one detects smoke or gas. I admit, it’s not the most fun activity to do over the weekend. But I knocked it out a lot faster than I expected.

Side note: If you have children, other people or pets in the home who dislike the sound of annoyingly loud smoke alarms, maybe do this when they’re not around. I made sure to put my dog in the backyard because I know loud noises scare him.

New detectors are relatively inexpensive; the ones I picked up were less than $30. If you are planning to replace more than one smoke detector, buy multiples of the same brand and model and replace them all at the same time to prevent any complications.

Project step-by-step (7)

Step 1

Remove and disconnect the old smoke detector

Safety first: Before starting any electrical work, turn off the power at the breaker panel. Use an electrical tester to verify the power is off.

Twist your old smoke detector to loosen it from its mounting plate. Disconnect the old wiring harness from the wires in the remodeling box and unscrew the plate.

Step 2

Attach the mounting plate

Fasten the new smoke detector mounting plate to the remodeling box with a screwdriver.

How To Install A Hard Wired Smoke Detector Fhmvs23 Mf 10 31 Installsmokealarm 1 Ss EditTMB STUDIO

Step 3

Connect the wires

Strip 3/4-inch of insulation from the ends of the wires. Use wire nuts to connect the stripped NM cable wires to the corresponding color harness wires. Wrap the wire connectors with electrical tape for extra protection.

Tuck the excess wire length and wire connectors into the remodeling box, leaving the plug-end of the wire harness out.

How To Install A Hard Wired Smoke Detector Fhmvs23 Mf 10 31 Installsmokealarm 2 Ss EditTMB STUDIO

Step 4

Activate the backup battery

Pull out the cover tab to activate the battery in the detector. My alarm came with a sealed battery that didn’t need to be replaced for 10 years, but some require batteries you’ll need to install.

How To Install A Hard Wired Smoke Detector Fhmvs23 Mf 10 31 Installsmokealarm 3 Ss EditTMB STUDIO

Step 5

Attach the smoke detector to the mounting plate

Line up the notches on the back of the device with those on the mounting plate, then twist until the detector locks into place. Ensure it’s secure on all sides.

Once you’ve connected all the wiring and the detector is secure on its mounting plate, turn on the power at the breaker panel. Confirm the detector’s power light is on.

Step 6

Test the smoke alarm

Press the test button on each detector to ensure they’re working correctly. You should hear all the alarms sound during the test.

If the alarms don’t sound, turn off the power at the breaker panel and double-check your wire connections. If everything seems correct but a unit’s power light won’t come on, you may need to replace the unit.

How To Install A Hard Wired Smoke Detector Fhmvs23 Mf 10 31 Installsmokealarm 5 Ss EditTMB STUDIO

Step 7


When should I replace my hard wired smoke detector?
Replace your smoke detectors at least every ten years. If it’s no longer working properly, replace it ASAP.

Do I need an electrician to replace hard wired smoke detectors?
Not necessarily. It can be DIY if you understand the process and take certain precautions to ensure safety. If you have any doubts or concerns, call a pro.

Should hard wired smoke detectors be mounted on the wall or the ceiling?
The ceiling. That’s because smoke rises and tends to accumulate near the ceiling. Ceiling mounts offer the earliest possible warning in the event of fire, when seconds count.