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Hardwired Ionization Smoke Alarm w/ Adapter Plugs

Enhance your household's fire safety and enjoy greater peace of mind with the First Alert SA9120BPCN Hardwired Smoke Alarm with Adapter Plugs. Equipped with an ionization sensor, this 120-volt hardwired smoke alarm reliably detects smoke from fast-flaming fires and alerts you with an 85-decibel alarm. Included adapter plugs eliminate the need for re-wiring during installation, while a backup battery helps keep the unit running in case of a power outage. Designed to maximize accessibility and ease of use, this hardwired smoke detector features a single button that allows you to test and silence the alarm. And thanks to the universal mounting bracket, this smoke alarm is easy to install.

Ionization Sensor Reliably Detects Flaming Fires

The First Alert SA9120BPCN Hardwired Smoke Alarm with Adapter Plugs comes equipped with an ultra-reliable ionization sensor to provide the earliest possible warning of a fast-flaming fire. The sensor is optimized to detect flaming fires, such as those caused by paper, kitchen grease, and other fast-combusting materials.

Adapters Included for Easy Installation

To facilitate hassle-free installation, this smoke alarm comes with adapter plugs that eliminate the need for rewiring if you are replacing an existing First Alert or BRK branded detector. The universal mounting bracket further eases installation and covers up drywall cutouts, while tamper-resistant locking pins keep the alarm secure.

Battery Backup for Detection during a Power Outage

This smoke alarm is designed for hardwired installation, but it also features a battery backup that helps ensure continued functionality in the event of a power outage. The smoke detector comes with a 9-volt battery and features a pivoting, easy-to-access battery drawer that allows you to replace the battery without dismounting the alarm.

Works in Tandem with Other First Alert Alarms

In addition to functioning independently, this smoke alarm can also integrate with up to 12 other First Alert or BRK hardwired alarms for coverage of larger spaces. If one smoke alarm in the series is triggered, they will all sound. The alarm features a latching indicator to identify which unit triggered the alarm, alerting you to the area of danger.

The First Alert SA9120BPCN Ionization Smoke Alarm meets UL standards and features a 10 year limited warranty.

How to Install First Alert SA9120BPCN Hardwired 120-Volt Smoke Alarms:

In this guide, we'll be showing you how to install First Alert Hardwired Smoke and Carbon Monoxide Alarms. Here are a few items you'll need before starting the installation process: Needle-nose pliers or utility knife, screwdriver, wire stripper, wire nuts and a ladder.

Hardwired Smoke or Carbon Monoxide Alarm Requirements:

  • 120V household electrical circuit (unswitched 120VAC)
  • Standard wiring junction box to a 4 in. (10 cm) size, on either the ceiling or wall
  • Selecting an appropriate location to install your smoke and carbon monoxide alarms (see below guidelines for additional information):
    first alert smoke alarm install guide
    • When installing an alarm on the wall, the top edge of an alarm should be placed between 4 in. (100 mm) and 12 in. (300 mm) from the wall/ceiling line.
    • When installing an alarm on the ceiling, place the alarm as close to the center as possible.
    • In either case, install the alarm at least 4 in. (100 mm) from where the wall and ceiling meet.
    • First Alert Smoke Alarm FAQs
    • First Alert Carbon Monoxide Alarm FAQs

Connecting First Alert Hardwired Alarms to 120V Wiring

To begin, turn off power at the junction box and connect your alarm to the building's electrical wiring.

  1. Locate the junction box and turn off power
  2. Remove the power connector from the new alarm's packaging
  3. Using wire nuts, attach the hot (black), neutral (white), and interconnect (orange) wires
first alert smoke alarm hardwired install guide
first alert wired in smoke alarm install guide
Black wire
Attach to black wire on power connector
White wire
Attach to white wire on power connector
Orange wire

Standalone (single-station) alarm: This wire is not needed; tuck the orange wire into the junction box.

Interconnected alarms:

  • Strip 1/2 in. from the orange wire on the connector
  • Use a wire nut to attach it to the orange wire in the junction box (see image below).

Mounting First Alert Hardwired Alarms

  1. Secure the mounting bracket to the ceiling or wall using screws (included in the package)
  2. Insert the power connector into the plug on the back of your alarm
  3. Tuck any hanging wires into the junction box
  4. Position the base of the alarm onto the bracket and turn it clockwise until it's secured
  5. Remove the pull-tab to activate the backup battery
first alert carbon monoxide alarm install guide
first alert smoke and co detector install guide

Installing Additional and/or Interconnecting First Alert Hardwired Alarms

If you are installing more smoke or carbon monoxide alarms, you'll want to repeat the process throughout the building. Interconnected smoke and co alarms must meet all requirements:

  • The same fuse or circuit breaker must power all interconnected alarms.

  • Up to 18 compatible detectors can interconnect, with a limit of 12 smoke alarms.

  • The total length of wire interconnecting the alarms should be less than 1,000 ft. (300 meters). This type of wire is commonly available at hardware and electrical supply stores.

  • All wiring must conform to all local electrical codes and NFPA 70 (NEC). Refer to NFPA 72, NFPA 101, and your local building code for more information.

  • Interconnect wiring diagram:

first alert alarm install guide

If you have any doubts or reservations about these interconnect requirements, please contact an experienced electrician to install your wiring and hardwired alarms.

Restoring Power and Testing Hardwired Alarms

Once you've installed your hardwired alarms, you'll want to restore power to the junction box. Under regular operation, the power indicator light on the alarm will shine/blink to indicate that it is receiving AC power.

Here's how you can test standalone or interconnected alarms:

  • Standalone Alarms: Press and hold the Test/Silence button until the unit triggers an alarm.

  • Interconnected Alarms: Press and hold the Test/Silence button until the first unit triggers an alarm. All interconnected detectors should sound off. Repeat this process to test each alarm in the interconnected series.

What is the proper placement of smoke alarms?
It is important that you have the proper placement for your smoke alarms. Install your alarms at least 20 feet from appliances like furnaces and ovens, which produce combustion particles. Alarms should be at least 10 feet from high humidity areas like showers and laundry rooms, and at least 3 feet from heat/AC vents. Be sure to install a smoke alarm in each bedroom, one at the top of each stairwell, and one on every level.
Product Details
  1. Smoke particles of varying number and size are produced in all fires. For maximum protection, use both ionization and photoelectric sensing technologies. Ionization alarms are generally more sensitive to fast flaming fires and photoelectric alarms are generally more sensitive to smoldering fires.
Product Specs
Smoke Alarms and Smoke Detectors
Product Manuals

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SA9120BPCN customer reviews

Overall Rating

24 Reviews
24 customers recommend this product
First Alert Hardwired Smoke Alarm with Adapter Plugs - SA9120BPCN Reviews
Jayne S
September 5, 2022
Verified Purchase
Thank You First Alert -Replacing my smoke alarms was a snap!

I ordered four First Alert smoke alarms to replace my Firex alarms which were installed when the house was built. The adapter plugs made the install of the First Alert alarms a snap. The hardest part of this project was moving the ladder from room to room. I ordered from the First Alert store. Items were packed securely and arrived within 4 business days. Five stars for my overall experience with First Alert.

Leon G
April 12, 2021
Verified Purchase
Fire Alarm

works good

Bruce Frye
December 14, 2020
Verified Purchase
Fits like a glove

My First Alert Smoke Alarm plugged right into my existing mount without having to use any adapter. The original alarm from First Alert was installed when my house was built in 2006 and worked great until it finally died last month. Hope the model stays active in your inventory for a long time to come.

Tim Littlefield
March 31, 2020
Verified Purchase

I replaced my old Kiddie smoke alarms with First alert detectors last month. I Salesperson I spoke with was very knowledgeable regarding these detectors. Ordering was easy and the shipment came quickly. Thanks First Alert!

Janet Bowman
November 19, 2019
Verified Purchase
Hardwired Smoke Alarms

We decided to update and replace all of our smoke detectors. The First Alert Hardwired 120-Volt AC Smoke Alarm with Adapter Plugs - SA9120BPCN 1039809 were our most effective and economical choice! Very pleased.

November 7, 2019
Verified Purchase

Works great

John Coviello
November 6, 2019
Verified Purchase
easy to install

good price , easy to install, side pocket battery a great idea

Catherine Pollok
July 7, 2019
Verified Purchase

Product received was exactly what I needed.

Winifred Begley
January 14, 2019
Verified Purchase
Ordered 4 alarms

Good deal on 4 alarms bought one set of 3 at a discounted price plus the extra one I needed. Price was cheaper than Amazon. Came as scheduled. Easy installation. Good service, very happy.

Richard Euhus
September 18, 2018
Verified Purchase
Smoke Detector

Purchased one these detectors a year ago to replace an old 20+ years faulty detector. Works well and it immediately sensed a smoking pan on the stove. Bought this one to replace an equally old detector upstairs.

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