How to Install a Hardwired Smoke Detector

Installing a hardwired smoke detector is an essential and required safety feature for protecting your home or building. A hard-wired smoke detector differs from a battery-powered model in that it connects directly to your home’s electrical system. Many hard-wired detectors have a backup battery. The smoke detector will therefore still work if there is a power outage.

If you don’t have smoke detectors (a violation of building codes), or the ones you have are over 10 years old, it’s time to install new alarms. Installing a hardwired system requires some light electrical work, but many people can do it on their own.

Installing Hardwired Smoke Detectors

A licensed electrician can easily install a hardwired smoke detector. But if you’re intent on making this a DIY project, you’ll want to take the following steps:

1. Determine Where to Place the Unit

Are you installing a smoke alarm for your bedroom, or a smoke/carbon monoxide alarm for your kitchen? Ideally, smoke detectors should be placed on the ceiling, in the center or at least four inches from a wall (if installing on the wall, the unit should be within 12 inches of the ceiling). Avoid corners or peaks of vaulted ceilings.

2. Gather Tools and Materials

The tools/items you’ll need include a voltage tester, wire stripper/cutter, wire connectors, and a new smoke alarm. Other things you may need include:

  • Small step ladder
  • Tape measure
  • Pencil
  • Stud finder
  • Cordless drill
  • Drywall saw
  • Wire stripper
  • Voltage tester
  • Electrical box
  • 2-wire/3-wire NM cable

3. Turn Off Power at the Breaker Panel

The circuit serving the room or area where you’re installing the smoke detector must be turned off. Switch off the respective circuit breaker so you won’t encounter live electricity. Hardwired smoke detectors don’t need their own dedicated circuit (any 15- or 20-amp circuit will do), which further simplifies the process.

4. Disconnect the Old Smoke Alarm

If you have one in place, use the voltage tester to verify the power is off, and then mark or sketch where the existing wires go. Then disconnect them and proceed with removing the alarm.

5. Mark Where the Smoke Detector Box Will Go

With the stud finder, locate the ceiling joists or wall studs, and draw an outline of the perimeter of the electrical box.

6. Cutting into the Drywall

Cut an opening in the drywall, where the electrical box for the smoke detector will go. To create a starting point for the saw, drill a pilot hole.

7. Run the Wire/Cable

Run the wire from a source such as a breaker panel, wall outlet, or switch to the location of the detector. You’ll need a 2-wire cable with ground. Leave excess cable extending through the wall after you route it; it will need to be cut to length during installation. If installing multiple smoke detectors, run the 3-wire cable to subsequent units.

8. Insert the Cables

The cables must be inserted into the electrical box with about 8 inches of wire extending into it. Strip away the outer sheathing (1/4 to 1/2 inch of insulation should extend into the box). If connecting solid wire to stranded wire, expose 1/8 inch more of stranded wire than solid wire and then twist the strands together; you can then screw the connector onto both.

9. Mount the Electrical Box

Once the cables are secured, you can secure the electrical box to the drywall opening. Feed the wires through the mounting plate, align the screw holes on the plate, and tighten the screws to secure the retaining tabs to the back of the drywall.

10. Connect the Device

Join black and white circuit wires to leads of the same colors. Bare copper ground wires should be connected together; for a metal box, attach a bare copper or green insulated pigtail wire. Red circuit wires connect to the traveler wire, which is usually yellow.

11. Finish the Installation

Now, you are ready to plug the wire harness into the back of the alarm, install the backup battery, and attach the smoke detector to the mounting plate. To do so, line up the notches on the mounting surfaces, twist the alarm, and make sure it is locked in place and secured on all sides. Then restore the power source and test the alarm.

Need Expert Help? Contact Express Electrical Services

We are the leading Los Angeles smoke detector installation, repair, and replacement company. Our experienced technicians can save you the time and hassle of DIY installation. They ensure your detectors are installed properly and will work when needed. Our expertise is in hardwired smoke detector installation. Call 323-727-7799 to learn more or schedule service.