Smoke alarm going off when connected to the mains

[andyj941]

Hi we have a smoke alarm on the landing ceiling that is mains powered with a battery backup. When I went into the loft to the other day and sat on the floorboard above the smoke alarm it started going off until I moved away.

Then today we replaced the existing floorboards with new ones and removed the excess loft insulation the old ones were resting on - it looked like 270mm squashed down ridiculously tightly and nailed with the longest nails I have ever seen.

When I touched the board above the smoke alarm again it started alarming and the only way I could get it to stop was switch it off at the RCD. The insulated grey cable in the loft from the alarm is undamaged and clipped to the side of a joist. I've pulled the smoke alarm off and checked everything was screwed in and undamaged - everything was fine. Still if I switch it on at the mains it alarms and sets off the downstairs one too (they're linked).

I think it's too unlikely to be a coincidence that removing wads of massively compressed insulation on top of the smoke alarm set it off, but I can't see anything that can be fixed. Does anyone have any ideas what could be wrong here? Thanks in advance.

 

[flameport]

Probably full of dust - use a vacuum cleaner to clean it.
If switching off the power stopped it working, the backup battery is useless and needs to be replaced.

As most/all of them are supposed to beep intermittently when the battery requires replacement, it is likely the whole thing is useless and should be replaced.

 

[andyj941]

The battery is working as if I test it now it works fine. I didn't see any dust when I opened it up but I'll give it a vacuum tomorrow to check if that makes any difference. It's only 6 months old!

 

[conny]

Only takes a few particles of loft insulation to fall through the cable hole and into the back of the unit to cause a problem. If it still trips after a light vacuuming try a bicycle pump or a can of compressed air to GENTLY blow away any bits you can't get at with the vacuum.