My hard-wired system of Kidde smoke/CO alarms shows no indication of a switch to battery power when I flip all of the breakers, and even when I flip the main breaker that shuts off everything in my house (except the smoke alarms) as far as I can tell. If I disconnect the wires, the smoke alarm indicates it is on battery power. What is the next step to determine how my smoke alarms are wired and how to turn the power to them off in order to do some maintenance/replacements/upgrades? Thanks for any help.

 

Welcome to the forums.

Most AC/battery smoke alarms don't give an indication when they are running on battery.
What do you have on the units for wiring.... a red, black and white wire on a plug ?

Do you have a security system in your house ?
They could be connected thru that but I don't think Kidde makes that type of sensor.

 

Are you certain your detectors stay powered even with the main breaker turned off? They should be dead along with everything else in the house when the main breaker is off. To find the circuit for smoke detectors I use a chirping no touch AC current detector on it's power line and go down the line turning off circuits until the detector goes silent.

 

What model detectors are you using?
Geo

 

The detectors are Kidde KN-COSM-IB. The instructions state that the light should be steady green when wired power is supplied, and should flash green every 5 seconds on battery power. The 1 I have disconnected from the system and the 2 that are still connected appear to operate the green light as described. The 1 that is disconnected was removed when we bought the house and I'm finally replacing it because it is over 8 years old and the wires are just hanging out the hole in the ceiling. I'm actually replacing all of them. When I test the one that is disconnected, it makes the noises exactly like the instructions say it should. The other 2 do not do anything when I test them and I don't know if it is because one is removed from the series. They are wired black=hot, white=neutral, red=link, all in a plug that goes to the back of the unit. There is also a bare ground wire in the ceiling at the location of the 1 smoke detector that is disconnected. I assume it is the same at the other 2 locations. When I turn the main breaker panel off, the lights on the 2 that are still hard wired remain on solid green. I also tried every individual breaker. Yesterday I checked the circuit at the removed detector using a light-bulb indicator with the little clip and probe. I put the clip on the bare ground, and when I touched the probe to black, the light came on for an instant one time, and about 10 repeated checks have not reproduced the light which would indicate a live circuit. But the lights on the other 2 detectors are still on solid green.

As far as the security system - there are parts to an old one that has never worked since we bought the place. I don't believe it is still connected because the panel downstairs and keypad near the garage are the only pieces left. There are no other components anywhere that I'm aware of and the system has never been powered on since I've lived here. I recently removed the keypad, put wire nuts and electrical tape over the wires and tucked them into the wall so i could install my wireless security system in the same place. I know the hard-wired detectors have worked since we bought the house - we have accidentally set them off previously.

 

Ok, timeout. Still open to ideas, but I have more information. I just removed another detector from the plug, leaving the plug wired in to the house. The green light did not go out nor begin to blink. Checked the battery, very nearly dead, replaced it. Still doesn't blink - just on steady. Tested it and it stopped halfway through the test. Plugged it back in and test doesn't work at all. Unplugged again and test doesn't work at all. Other detector that has been removed still works as expected on battery power - flashing green light and test function operates. Also, circuit tester light may just be burned out. It did flash once previously, but now I don't see any filament between wires in the lamp.

I appreciate any help, but before I shoot in the dark anymore I'm going to replace the circuit tester light and get my multimeter from my office. If I still have any trouble verifying which breaker the circuit is on, I'll update this post. I'm also going to just get and install the new detectors because I'm not really interested in spending time fixing an expired and possibly broken alarm system.

 

I don't recall seeing the green light on a smoke detector ever staying on when unplugged from AC power. At this point I would just replace all the units. With their age you don't want to mix and match.

 

You can call their tech support # in the instruction page and discuss this with them,but being 8 years older or older,replace them as PJ suggests,The replacement date is supposed to marked on the detector,but I doubt it is.
Geo

 

Smoke alarms should be replaced at 10 years.

 

It depends on the detector. I just replaced all my Kidde smoke/CO detectors (installed in 2007) this year as they manual indicated that at 7 years after 1st power on they will begin to chirp every 30 seconds. Knowing that Murphy's Law would place that 7 year mark at 2 AM, I replaced them ahead of schedule!

 

Only if the mfg. Recommends it, in this case it is 7years
Geo

 

CO detectors have a shorter lifespan than smoke alarms.

 

Any decorator be it smoke, fire or CO2 should not be in service if older than the listed warranty of the unit. EVEN if the units still work they are not considered good past the warranty period be 3 yr, 5 yr or 10 yr or whatever is listed. I make it a big point in our store that when a person buys a detector they undersea this and they must still replace the battery back-up twice a year.

That being said I'm guilty of having a few defectors past warranty limits.

 

Why twice a year, is that a manufacturer's recommendation? My experience is that alkaline batteries used as backup in smoke detectors can easily last 2 years unless there have been frequent long power outages.

 

Twice a year is a convenient method to remind ourselves to do it. It coincides with the time change from standard to daylight. Plus, no battery can be gaurranteed to last a whole year but 6 months is reasonable.

Tip: Do not save or store 9 volt batteries (any battery but 9 v especially) without a piece of tape over the terminals. High risk of fire hazard. As an experiment try taking some steel wool and a used 9 volt. Touch the battery to the steel wool. Be prepared for a flash flame or sparks. Great camping survival trick.

Something We All Have In Our Homes Started This House Fire - The Mother List

 

After AC power is disconnected, a smoke detector indicator light may stay on for a few minutes more.

So you might not have waited long enough to prove anything when you turned off the main breaker and the smoke detectors appeared to remain energized.