"Andrew Gabriel" wrote in message
...
In article
,
Richard Russell writes:
In our (new build) house the three linked, mains (and battery)
powered, smoke detectors were supposed to be fed from a separate
breaker in the consumer unit. Except that they weren't - at some
point during the build the connection was broken and the only
practical way to restore operation was to wire them into the lighting
circuit instead. The electricians assure me it's perfectly OK to do
that, but what are the pros and cons of having a separate breaker for
the smoke detectors?

IMO, it's much better to have the smoke detectors on a lighting
circuit. You will notice quickly if they aren't working, and
there's no temptation to trip them off to hush them, and then
forget.



My suggestion to the council that smoke detectors should run (in their
houses) "from the TV socket, as a power failure there would be noticed
faster than any other power failure" fell on deaf ears.

As for the OPs question. A mains powered interlinked smoke alarm set up with
a battery back up should last over a year without mains power and still
function correctly. When the batteries start to lose power then warning
bleeps are given out by the alarms to let you know. These warning bleeps
will happen with or without mains power as it is the battery they test.
Personally I prefer the smokes to be on the lighting circuit.

Adam