- About The Store
- Home Safety FAQs
- View Cart
The First Alert SA521CN-3ST Interconnected Smoke Alarm allows owners to create an interconnected fire alarm system without the cost and hassle of wiring. Use this smoke detector to replace an existing hardwired smoke alarm and then install additional First Alert Wireless alarms for an interconnected safety network (additional alarms sold separately). This hardwired smoke detector can connect and communicate with up to 18 compatible alarms, so when one alarm is triggered, the entire system reacts. An integrated battery backup ensures the smoke alarm continues to work even during power outages.
Photoelectric Sensor Warns of Smoldering Fires
The First Alert Wireless Interconnect Smoke Alarm comes equipped with a photoelectric sensor to provide the earliest possible warning of fire. The sensor is optimized to detect larger smoke particles produced by smoldering fires, such as those caused by unextinguished cigarettes. It also distinguishes between real threats and smoke/vapor produced during showering, cooking, and other everyday activities, helping minimize the number of false alarms. A patented smoke entry system helps ensures reliable detection by providing a direct air pathway to the sensor.
Interconnectivity for Larger Areas
The hardwired smoke alarm can be connected to other compatible BRK and First Alert hardwired alarms for larger buildings such as dormitories, office buildings, and apartments. Connect up to 18 compatible devices: up to 12 smoke alarms and six compatible devices like horns and repeaters. First Alert helps you create a comprehensive warning system for you and your property.
Battery Backup for Continuous Coverage
In the event of a power outage, the smoke alarm is still able to function thanks to its two AA backup batteries. An indicator sound is emitted when the batteries need to be replaced. The inclusion of an optional drawer and mounting bracket lock will discourage tampering.
Test and Silence Button
Mute Button has been included to serve the dual purpose of silencing nuisance alarms and testing the functionality of your alarm.
EZ-Access Battery Door
The addition of an EZ Access Battery Door removes the hassles and burdens associated with changing your alarm's batteries.
This product is intended for non-professional do it yourself installation. If you would like information about a professionally installed and monitored system, please contact First Alert Professional at 1-800-921-6025. First Alert Professional is not affiliated with BRK Brands, Inc.
First Alert Wireless Interconnect Hardwired Smoke Alarm SA521CN-3ST
Average Customer Rating Based on 43 reviews:
Smoke alarm - 09/25/2018
Reviewer: Alan Del Rossa
Tested good. Synced to other smoke alarm.
Works well - 05/31/2018
It was easy to install since we had older BRK / First Alert units. Connected with the other units flawlessly.
Awesome product - 01/05/2018
Reviewer: William Rogers
This product installation is quick and easy. The set up is very labor efficient. This product is loud and will notify you immediately. This is a very good system and needs to be put out to people to let those know about it without alarm systems. Pricing is very reasonable.
Expanded Home System - 05/15/2017
Reviewer: Thomas Piorkowski
I had old smoke alarms that I wanted to replace: 2 upstairs, 1 main floor and 1 in the basement. Three I replaced with combo smoke/CO2, the 2nd upstairs unit I purchased a bridge unit to connect the old hard wired to the 4 new battery units. The hardest part was the wired units because the old connectors didn't match any brand of new unit. The detectors came with easy directions and it wasn't that hard. Once set up, all work perfectly together. I like the voice indication, telling you where the fire or co2 issue is located. I am very pleased with the purchase and feel more comfortable with my expanded zone. No extra cost for wiring so although the units are a little more expensive it doesn't cost as much as an electrician!
Great Product - 05/15/2017
Reviewer: rick christoffersen
Hardwired systems seamlessly integrated with the multiple First Alert wireless smoke alarms we installed. Now all alarms are integrated throughout our home. Awesome!
Reviewer: rick christoffersen
Great product. We integrated with 8 other Wireless Smoke Alarms. All linked perfectly together as advertised and we now have comfort of knowing any alarm activation will set off alarms throughout the house.
Had some programming problems - 12/16/2016
Reviewer: Charles Hinton
For some reason it was hard to link this one. I have used them before and never had a problem till now. It worked in the end
Reviewer: Barbara Clark
The quality of this product is very good and responds to my needs.
Easy whole house protection - 11/22/2016
Reviewer: James Davis
It was very simple to sync all the smoke alarms in our home. Now we are comforted knowing that if a fire starts in the basement, we will know about it instantly 2 floors above in our bedroom.
Reviewer: Dale Welch
I spoke with someone in technical support on a Sunday who was extremely helpful in advising me which products to buy to make my house compliant for a house sale. I ordered 5 products. They all arrived on time and in good shape. They were very easy to install and all worked immediately.
Other reasons include: It could be a different device or appliance such as a security system, monitor, carbon monoxide alarm, or other device which has a similar low battery or alert signal. Some of the same factors that cause unwanted alarms can cause intermittent alarms: dust and insects in the alarm or power interruptions in hardwired alarms. Improper wiring on AC or AC/DC smoke alarms. AC alarms will chirp every 5 seconds if the interconnect wire is grounded. The orange interconnect wire should NEVER be grounded; it should only be used to interconnect other smoke alarms or compatible devices.
We make it as easy as possible to ensure you get the lowest prices available: