Spurious smoke alarm

Thread Starter

BobTPH

Joined Jun 5, 2013
9,132
In the last couple of weeks, we have experienced spurious alerts on our smoke alarms. This seems to happen every couple of days. The alarms sound for about 30 seconds then stop. Three times have been in the middle of the night, two in the afternoon. On one occurrence, it happened twice within minutes, the others alarmed only once and stopped.

These are sophisticated alarms with voice alert, so, no, it is not a battery low condition, it would say so. All have 10 year lithium batteries.

What we have is AC powered interconnected alarms, some smoke only, some smoke and CO, as per code here in Massachusetts.

There are two sets of alarms, 8 in the main house that were installed 8 or 9 years ago, two in an addition built in late 2021, less than 2 years old.

Thinking the 8 older alarms were more likely the culprits, I replaced all of them since they were near end of life anyway. That night it alarmed again!

So I am left with the other two alarms, or some cause not associated with the alarms themselves.

The only electrical work done in the timeframe that the alarms started was I replaced ballasts in two kitchen lights. But these were definitely off when the nighttime alarms occurred.

Any brilliant ideas, other than replacing the last two alarms and hoping? They are connected with the main house alarms as I can see the power wire going from an alarm in the basement to the new addition.
 

Thread Starter

BobTPH

Joined Jun 5, 2013
9,132
Update:

All alarms at Kidde brand. The newer ones are model P4010ACS add CO for the dual ones.

The other two are also Kidde and look identical, so probably the same model.

These are wired via a 3 wire cable: black, white, and red. Red is the interconnect wire, black and white are the normal US line and neutral.

My research says the signaling of an alarm is done by putting 9V on the red wire.
 

djsfantasi

Joined Apr 11, 2010
9,181
Leave the alarms hanging from the ceiling and disconnect the red wire from each. The next time it happens, find the alarm going off and there’s your culprit.
 

Thread Starter

BobTPH

Joined Jun 5, 2013
9,132
Great suggestion, thanks. The alarm that is signaling actually has a red flashing light, so it could be identified that way without disconnecting. The reason we haven’t done that is it only goes for about 30 seconds, not enough time to go around the 3700 sq ft house looking at them.

I had the idea of putting a web cam with recording capability pointed at each one so we see the red light afterwards.

I might end up using your suggestion, at least the sound could give us a general idea. If it was in the addition, I doubt that we would even hear it, though.
 

Thread Starter

BobTPH

Joined Jun 5, 2013
9,132
Maybe the alarm is real and is caused by a wiring problem that might soon burn down your home?
Maybe someone has began smoking or vaping?
Pretty sure the alarm is not real, since it does not continue for even a minute. When my cooking sets one off, even when you press the button to mute, it goes way longer.

I think I accidentally discovered the culprit. I pressed the test button on one of the remaining not replaced ones, and it said “smoke previously detected”. After the test cycle, it did not repeat that message, so we have a way to find out who has cried wolf, I mean fire!
 

MisterBill2

Joined Jan 23, 2018
18,960
Here is another guess, which is an electrical disturbance, either in the mains circuit or picked up by the communications link. For that, either ferrite beads on the signal line or else bypass capacitors between the signal line and the common line.
Also try contacting the Kidde customer service folks because some companies actually will provide useful support.
 
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