Jump to content

Mains Powered Smoke Alarms all go off when power switched on

Guest Neil T

Recommended Posts

Guest Neil T

I have replaced the 9V batteries in 7 BRK mains with battery backup interlinked smoke alarms in a rental property I own (currently empty). I isolated the alarms from the mains using the breaker on the distribution board before removing each alarm and replacing the batteries. Once all the batteries had been replaced and alarms put back up, I switched the power back on. The alarms then all went off and did so for a perhaps a minute or more without stopping. In order to avoid alarming the neighbours and not knowing if they would stop or not I isolated the power again and the alarms stopped. Is this normal, or are they going off when connected to mains power because there is an issue.


Any advise would be greatly appreciated.

Link to comment
Share on other sites

I would suggest you "start again" and change the battery in one detector then switch the mains on, and repeat for each detector, it sounds like you have a battery / detector incompatibility  problem. This is the easiest non technical way to find out, although somewhat tedious, and also check the age of all smoke detectors, the life span is 10 years.

Link to comment
Share on other sites

  • 3 years later...

Hi, did you ever get to the bottom of the issue? I’m having exactly the same issue, carbon monoxide detector was beeping, tenants thought it was smoke alarm so they took 2 of the hardwired alarms down, now when I put them back up soon as I connect them alarm goes off. The alarms are good as I tried them in my own house no issues, can’t see any loose wiring, no idea what’s going on. 

Link to comment
Share on other sites

Hello RyanS, the post you replied to (Neil T) was posted in 2020 (3 years ago) and he has never been back since, so will never reply to you.

I have a few questions for you. (I have to ask, as I am not there, you are)

1) Make of each smoke alarm

2) Model of each smoke alarm

3) Age of each smoke alarm

4) When you connected them on site, how many "went off"

5) You said "They took 2 of the hardwired alarms down" to say that implies there are more smoke alarms, how many smoke alarms are there in total?

6) When you tried them at home, did you connect them to the mains and interlink them?

7) Did you press the test button when you were at home. (What happened)

8 ) When on site, when did they "go off" (e.g. soon as you connected one, as soon as you connected a 2nd one, after a few seconds, after a minute......)


Link to comment
Share on other sites

Join the conversation

You are posting as a guest. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...