Smoke Alarms

[Jim Frye]

Learned something new yesterday about smoke alarms. Our home was built in 2015 and is equipped with hardwired smoke detectors and CO detectors with backup batteries. Supposedly, these have a ten year life span and sure enough, one of the combination smoke/CO units started complaining that it was defective. Not a bad backup battery, just couldn't pass the self test. Since every device is almost ten years old, I decided to replace all of the detectors in the house. So off to HD for new units. Two combination smoke/CO units and four smoke units. The originals were by Kidde, so I looked for replacements. Of course there were no replacements of the original detectors and a little research found upgraded models. I also learned that Kidde had changed the hardwired plugs. I was expecting to have to put new plugs on the wiring, but Kidde has little adapters that plug into the old plugs and into the new devices. The new devices attached to the old base plates, so the replacement process was pretty simple.

The big surprise was that all of these new devices "talk" to each other if they share a common hardwired circuit. This means that when one detector alarms, all of them sound off and they verbally alarm too. Five of the six units are on one floor in the bedrooms, living room, and the hallway. The cacophony is enough to wake the dead. Sort of like the submarine dive alarms in the old movies.

[Slik Geek]

I worked with a guy that could sleep through the smoke alarm. He literally had done that in a dormitory. The alarm annunciator was right above him and help continued sleeping through the alarm. He had to be shaken to get him to wake up and evacuate the building.
A few years ago, he was asleep in the passenger seat of a work van running at 70 mph on an expressway. A deer ran in front of the van and they nailed it. The van was totaled, grinding to halt because the engine stopped. The air bags deployed, and the driver reported the impact noise was stunningly loud. He panicked when he noticed his passenger was unconscious. No, he wasn't hurt, he hadn't been knocked unconscious.. He simply slept through the impact and the air bag deployment.

[Jim Frye]

The sixth detector is a smoke/CO unit in the basement where the gas furnace and water heater are. So if it triggers, the ones upstairs will sound off.

[Condoman44]

I think by code all detectors have to be on a common circuit so they can communicate.

[LCHIEN]

Interconnection by some means became a requirement between 1989 and the early 90s. Some use a hardwire (usually when line powered) and some use wireless techniques - usually when battery powered or retrofitted.

[Jim Frye]

Likely a local code requirement. Our house was built in 2015 and the code didn't specify interconnected alarms, only locations. The original alarm units were not interconnect capable. Some builders here don't even use hardwired alarms. Our breaker box doesn't have a separate alarm circuit and the wiring for the hardwired units extends from the master bedroom outlet circuit which is sort of centralized to all of the others. Kidde still sells hardwired alarms that don't interconnect and they were $5 less expensive than the interconnected ones I bought.

[LCHIEN]

here is a bit about interconnected smoke alarms - how, by what codes and when

https://chatgpt.com/share/68a0be78-1...c-a2ceac12e67d