Hi Trumpy,
I'm amazed that NZ are only now requiring mains smoke alarms.
Here in Scotland (& possibly the rest of UK) they have been required in new build & refurbished dwellings since 1993.
If you do an alteration to your house requiring building warrant, mains powered smoke alarms with standby supply (battery) must be installed.
I actually install smokes in all rewires I do, regardless of whether building alterations are carried out.
The minimum number of alarms to be installed is one on each storey. Alarms must be installed within 3M of a bedroom door, & within 7M of a kitchen or livingroom door.
Wiring is carried out in standard twin & earth to the 1st alarm, with additional alarms connected with 3 core & earth (L,N,interconnect & E) cable.
A dedicated circuit may be installed or alarms may be wired to a local lighting circuit.
It is recommended that the alarms are wired on to a regularly used local lighting circuit to reduce the possibility of disconnection for "nuisance alarms".
