First Alert Smoke Alarm SA521CN-3ST
- 120 VAC hardwired with battery backup
- Wireless interconnect with up to 18 compatible alarms
- Photoelectric sensor
- 85 dB audible alarm
- Single button silence and test
- 2 x 5 x 5 inches, 10.4 oz
Updated 23 days ago · Based on the Amazon listing and published specifications, not hands-on testing.
A hardwired smoke alarm with a battery backup and a wireless link to other First Alert alarms. The power source field says battery powered, which conflicts with the hardwired description.
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ASIN: B000EVO9D4Model: SA521CN-3ST
Overview
A homeowner replacing an existing hardwired smoke alarm gets a photoelectric unit that links wirelessly to other compatible First Alert alarms. A single button silences false alarms and tests the unit.
The wireless link lets all linked alarms sound together without new wiring, and the battery backup covers outages. Extra alarms are sold separately, and the power fields in the listing disagree.
Who it's for
A homeowner upgrading a unit already in place and wanting linked alarms without new wires will find the setup suited. Anyone starting from battery only alarms, or wanting a full set in one box, should look at other models.
Pros and cons
- Single button silence and test
- Replaces an existing hardwired alarm
- Additional alarms sold separately
- Power fields disagree
- Only compatible First Alert alarms link
Performance notes
A photoelectric sensor detects smoke by light scattering, which the description ties to fewer false alarms from cooking smoke and steam. The wireless link passes the alarm signal to other linked units, so all sound at once, and a backup battery runs the unit if mains power fails.
Specifications
| Brand | First Alert |
|---|---|
| Model | SA521CN-3ST |
| Dimensions & fit | |
| Item Dimensions D X W X H | 2"D x 5"W x 5"H |
| Item Weight | 10.4 ounces |
| Power & efficiency | |
| Power Source | Battery Powered |
| Construction & materials | |
| Color | White |
| Included components | |
| Unit Count | 1 Count |
| Other details | |
| Alarm | Audible |
| BuiltIn Media | Electrical & Heating;Security and Intrusion Monitoring;smoke-detectors |
| Item Type Name | Hardwired one link Wireless Smoke Alarm, 120 Vac, Photoelectric, 85 Db |
| Mfr Part Number | SA520B-SA521CN |
| Product Style | Standard Detection |
Frequently asked questions
Do I need an electrician to install the First Alert SA521CN?
The description presents it as a replacement for an existing hardwired smoke alarm and avoids new wiring for interconnection. It does not give wiring steps.
How many alarms can the SA521CN connect to?
Up to 18 compatible First Alert wireless alarms, which are sold separately.
Is it hardwired or battery powered?
The description says a 120 VAC hardwired alarm with a battery backup, while the power source field says battery powered.
How loud is it?
The item type name lists 85 dB.