On Sun, 14 Jun 2015 05:20:35 -0700, spuorgelgoog wrote:

On Sunday, 14 June 2015 13:03:03 UTC+1, John Mulrooney wrote:
I'm starting to install some interlinked smoke and heat alarms. Can
they use L & N from different circuits, or sgould they have a seperate
dedicated one.

All alarms must be on the same circuit.

It doesn't have to be a dedicated alarm-only circuit and there are good
reasons for it not being so; but the alarms should then have battery or
capacitor back-up.

On a mixed use circuit you are likely to notice a supply failure more
quickly than if only the alarms are affected.

Or do what I do and put a prominent non-maintained emergency light on the
same circuit. Useful in its own right.