Anyone know why my wired smoke alarm cables still have voltage after fuse switched off?

[Billyjoe8]

Hi all,

As above, the plan was to disconnect all wired ones (3), and push cables into ceiling (in box). And replace with 3 battery nest units.

I assumed turning the fuse off would leave them with no power at all and be totally safe!?

 

[JohnW2]

As above, the plan was to disconnect all wired ones (3), and push cables into ceiling (in box). And replace with 3 battery nest units. I assumed turning the fuse off would leave them with no power at all and be totally safe!?

There probably is no 'real power' there, just 'stray pickup' by a very sensitive meter. If you connected something (like a light bulb) across the meter, the apparent 'voltage' would probably more-or-less disappear.

Kind Regards, John

 

[mikeyd]

14 volts is OK. Well done for asking though, not everyone knows about electrics. Presumably you are testing DC volts there. AC also hurts.
I'll get shot down for suggesting this but if you see anything over 50 volts AC or DC don't touch it, run away etc.
If when you are measuring it and the volts goes down, from 14 don't stick your tongue on it.

 

[RandomGrinch]

Presumably you are testing DC volts there

The multimeter shows AC if you zoom in!

As an aside, if the other interlinked smoke detectors are still mounted in their bases, I believe (and I may be wrong) 9V DC would be detected in the black (grey sleeved) interlink cable, supplied by the detectors battery backup.