View Full Version : Smoke Alarms, do they ALL work WITHOUT AC Power?[/

01-20-2009, 01:32 PM
Smoke Alarms, do they ALL work WITHOUT AC Power?

My house was built in 1991: 2 floors and basement.
Each floor has a smoke detector (120V/9V back-up type) that is wired together (interconnecting).
When one smoke detector goes off, ALL 3 go off (I tested it).
But this is when there is AC power.

My question is: When there is no AC Power: when one smoke detector goes off, do ALL 3 smoke detectors go off? The mfg's tell me I need AC Power for all 3 to go off.
But reading different websites (Kidde, First Alarm etc.) ----> conflicting statements.

My thinking is: The Black and White wires go to the smoke alarm. The Red wire is the interconnecting wire ----> so even without AC Power, the 9V battery should be able to alarm all 3 detectors??? Any thoughts....

01-20-2009, 01:44 PM
Turn off the circuit breaker that feeds them and try it. They are suppose to work together on battery backup but older ones may not.

You should replace smoke detectors older then 10 years of age anyway.

01-20-2009, 05:56 PM

I just disconnected the circuit breaker for AC Power Supply for the smoke detectors.
It worked, i.e., when one some detector is activated, the rest are ALSO activated.

Now I know that even with AC power off, all smoke detectors still "talk" to each other.

Thanks again for the tips.