Quieter repetitive noise at same time every morning

[Guest Keith]

We have 3 Ei141 smoke alarms.I have just replaced the old ones - they were out of date - with 3 new Ei141RC alarms, using the same base plates. I did this because last week the first alarm in the circuit made the same noise every morning at 7. The noise was quieter than the alarm beeps, repeated rapidly for 2minutes before it stopped. This alerted me with the old Ei141s being over 10 years old. However, after one morning without that sound the same thing has happened again, two days running. so the problem is unresolved. It has made me wonder what this noise actually indicates - being different from the loud alarm sound - and why it happens at the same every morning. Any ideas about what's going on and how to stop it? I will start all over again with the lighting circuit off, taking out the batteries and reinstalling. I could also replace the old base plates with the ones that came with the new alarms but can think of no logicl expalnation why that would make a difference. 

[Safelincs]

Hi Keith, the plates cannot be the cause, as they have no sounder and have not changed. My hunch is that you have a CO alarm or some other device nearby, maybe even an old hidden alarm clock.

Harry

[green-foam]

I would be inclined to agree with Harry, but for similar reasons.

The base has no sounder, but even a smoke detector does not have a "timer" as such, and as you say it happens at the same time once a day, that implies a timer of some description and what better timer / sounder than an alarm clock or maybe an old mobile phone, in a drawer maybe?

[Guest Keith]

Thanks for your suggestions. No CO alarm, I saw mention of that somewhere already and checked. Are you suggesting that there may be a device with a timer somewhere that triggers this? If so does it have to be on the same lighting circuit or can it be anywhere? Leaving aside what may trigger it can anyone tell me what the noise coming from the alarm actually indicates. It's not the loud sound of the alarm, it is much quieter, but rapid, and last for two minutes. To be honest I don't even hear it until I go down and check it but my wife does.

[green-foam]

I for one do not believe it is your alarm making a noise. I am suggesting it is something entirely different which may or may not be supplied by the mains (I would say its not) The other suggestion would be to ask is there a loft space? and if so have you looked / listened in there.

[Keith2603]

It is definitely coming from one of the alarms, the one downstairs, nearest the fuse box. I waited by it this morning hoping nothing would happen but it did. There is a loft room, the system was installed when that conversion work was done. One of the three alarms is up there. All three alarms interact when tested, all batteries are Ok when tested with lighting circuit switched off. 

 

[Tom Sutton]

Keith you need to be sure it is the smoke alarm causing the beeping, I would suggest you you get up before 0700 and remove the smoke alarm from the base plate, then wait to 0700 to see if you hear the beeps. This will establish if it is the smoke alarm because there is no electronic equipment in the base plate only connection to the mains supply. Replace the smoke alarm and wait until next day, then get back to us with the results.

[Keith2603]

Thanks Tom, I had thought I would try turning off the relevant lighting circuit but your approach sounds more logical i.e. see if the sound is still there when it can't possibly be coming via the alarms. Meanwhile I am continuing my survey of any device in the home that has a timer that may trigger this or, in the light of what the experts are saying, actually be responsible for it. As it only started a week or so ago I should really only be looking for things that may have changed then, including the possibility that a neighbour purchased a Mynah bird. Whatever else proves to be the case at least this flagged up the fact that the alarms were over 12 years old. And introduced me to the ease with which these devices can be updated without replacing the base plates.