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How to Wire Smoke Detectors in a Hardwired System

Residential building codes require smoke detectors to be in every home. Because fires can begin quietly and go undetected until it is too late, these alarms are essential for keeping your family and property safe.

Smoke detectors only work when they have a continuous electrical charge, whether this is from a battery or from being hardwired into the home’s electrical system.

Oftentimes, though, smoke detectors fail due to dead batteries in them. While it’s best practice to change the batteries in the smoke detector every six months, having one hardwired into the home electrical system ensures you’ll never be without a working smoke detector.

What Is a Hardwired Smoke Detector?

When a device or appliance is “hardwired,” it means that it’s directly connected to the home’s electrical circuits and is not “plugged in” to an electrical outlet or running off batteries.

While a hardwired smoke detector may look the same as a battery-powered smoke detector when it’s up on your wall or ceiling, its constant electrical current limits the possibility of failure. It’s important to note that in the event of a power failure (blackout), hardwired smoke detectors have a back-up battery on board to make sure it continues to work.

Mr. Electric® Knows How to Wire Smoke Detectors

Keep reading to learn how the licensed electricians at Mr. Electric install hardwired smoke detectors.

Step 1: Turn Off the Power

The electrician will determine which existing circuit the smoke detectors will be wired into and turn off the power supply to that circuit. Safety first!

Step 2: Cut the Holes

The electrician will use a stud finder to locate the ceiling joist or wall stud as the location for the smoke detector. The electrical box makes a great template to trace around, so the hole is cut precisely in-between the wall studs. Using a level ensures that the outline of the box is level.

The electrician will then drill a pilot hole in the middle of the outline for the electrical box, and then cut around the template outline. The electrical box should be a snug fit, but not too tight. If more than one smoke detector is being wired, your electrician will repeat this process for each unit.

Step 3: Run the Wire

From the power source, the electrician will run wire (with ground) to the location of the smoke detector. The power source can include an existing wall outlet, wall switch, or circuit breaker panel. A good amount of excess cable will be left extending through the hole in the drywall. This ultimately makes installation easier, and your electrician will trim the wire to the proper length when installing a hardwired smoke detector.

If multiple smoke detectors are being installed, your electrician will run a 3-wire cable (with ground) from the first smoke detector to each subsequent smoke detector. The extra wire allows the smoke detectors to communicate with one another so that if one smoke detector detects smoke, all detectors will go off.

Step 4: Attach the Wires to the Electrical Boxes

At each box location, about 8 inches of wire will extend from the hole. Then, the electrician will remove the insulating wrap from the wire using a cable stripper. The wires will then be run and clamped to the electrical boxes.

Step 5: Secure the Electrical Boxes

Once the cables have been secured to each box, it’s time to secure the electrical box in the opening of the drywall.

At each smoke detector location, the electrician will feed the circuit wires through the detector’s mounting plate and align the screw holes on the mounting plate to the hole in the electrical box. Using the screws that came with the smoke detector, the electrician will secure the smoke detector in place.

Step 6: Wire the Smoke Detector

The smoke detector has two parts: the alarm itself and the harness (with wires coming out of it that plug into the alarm after the wires have been connected). Your electrician will connect the wiring harness with the black, white, and red wires coming through the nearest electrical box.

Step 7: Put It All Together

Once the smoke detectors have been wired, the electrician will attach the mounting plate to the electrical box with screws. Then, the wire harness is attached to the back of the smoke alarm. The notches on the back of the alarm align with those on the base, and with a quick twist, the unit is ready to go.

Step 8: Connect to the Circuit

Finally, the electrician will pigtail the wires into the circuit and join the smoke detector cable to the circuit. With the wires joined, it’s time to restore power to the circuit and go through the set-up steps for your new hardwired smoke alarms.

Count on Mr. Electric for Smoke and Carbon Monoxide Alarm Installation

As you can tell, installing hardwired smoke detectors is a complicated process. Your friends at Mr. Electric are happy to help! We’re available to install your hardwired smoke alarm and carbon monoxide alarm system for you. We would also love to discuss the option of using smart smoke detectors, to keep you connected and your home protected at all times. Give us a call at (844) 866-1367 or request an appointment online today.

You can count on Rainbow International, a fellow member of the Neighborly® family of home service brands, for outstanding smoke damage remediation services. Here, they explain how smoke behaves during a house fire