"rrh" wrote in message
. uk...

"thankyousam" wrote in message
oups.com...
I'm adding a couple of mains fed smoke alarms to my lighting circuit.
The first one is simple enough as there is a run of cable above the
location in the hallway. I'm intending to "loop in" the smoke alarm as
you would with a ceiling rose - allbeit without a switch

I'm not sure how to build the second alarm (upstairs) into the circuit.
Can I simply spur it off the downstairs smoke alarm using three+earth
(for the interconnect)? Or do I need to "loop in" the second alarm as
well? I've tried to illustrate both. I can't see why the first method
would be a problem, just wanted to check.

Spurred: ( = T&E, ||| 3&E Interconnect)

Rose ==== Smoke Alarm 1 ==== Rose
|||
|||
Smoke Alarm 2

Full Loop In: ( = T&E, =~= 3&E Interconnect)

Rose ==== Smoke Alarm 1 =~=~= Smoke Alarm 2 ==== Rose


You can just spur it off the first alarm.

That's a bit dodgy innit? If your lighting is set up as one circuit to cover
the whole house, it may be OK but if the downstairs lights are on one fuse
and the upstairs lights a different fuse, someone could pull the fuse for
the upstairs and expect the smoke alarm to be safe to work on when it's not.

Steve.