Smoke alarms

[stedon1]

Another query while I'm on the site this evening. I was thinking of wiring some mains powered smoke alarms. Do they have to be RCD protected? Any other pointers I might need?

 

[Taylortwocities]

If you are providing a new circuit for the smoke alarms and the wiring is concealed less than 50mm from a surface then you will need an RCD to comply with BS7671 2008.

You could just connect them to an existing lighting circuit instead..

 

[Spark123]

If you are using normal 3c and earth, have cables concealed in a wall or partition burried less than 50mm then you need RCD protection. If you don't have concealed cables, or use some other type of cable which has an armouring or earthed metalic sheath then you may not need RCD protection, with the exception of TT systems where RCDs will probably be needed for disconnection times anyhow.

 

[mattylad]

I have often seen advice not to add them to an existing RCD protected ring final circuit so any nuisance trips do not remove your detector protection.
(putting them on their own RCD circuit).

 

[sparkyspike]

That was 16th edition thinking. With an RCBO, as long as they are on a separate circuit, they will only trip if there is something wrong with them - which is obviously a good thing.

One system is to protect the general circuits with two RCDs, and then special circuits such as fridges, computers and alarms can have individual RCBO protection.