mains smoke alarms

[timetotalk]

I am considering installing a pair of mains powered smoke alarms which will be interlinked using 3core and earth. Am i right in saying that the supply cable to the 1st alarm must go from the consumer unit and not an existing circuit. Is it ok to use 1mm twin and earth cable to the 1st alarm? Does this work fall into part p so do i need to notify building regs

 

[nozspark]

If you create a new circuit for the alarms, or install them in a kitchen or bathroom (don't put them in the bathroom!) then it will be part P notifyable.

However if you extend form an existing circuit (lighting for instance) in 1.5mm or 1.0mm T&E and then 1.5mm or 1.0mm 3&E between the alarms and you don't put any in the kitchen or bathroom (see previous DON'T) then it isn't notifyable.

Please remember...
RCD protection for cables burried <50mm in walls if not mechanically protected
Check your main earth is up to regs
Check your protective bonding is up to regs

The Aico RF alarms and bases make installing alarms very easy, just take a power supply from a local light fitting (but cost £30ish more per alarm for the materials)

 

[timetotalk]

Thanks for your reply

existing consumer unit uses plug in fuses with fuse wire. I was thinking on having a sparky put in a new unit. Therefore would i be best in running a new smoke alarm circuit and not connecting to a consumer unit and leaving this until a new unit is installed? would this still be part p notifiable or when the new unit goes in will this cover this work.
None of the circuits are buried 50mm in the walls as its an od victorian house ad when rewired they ran cables against the walls and plastered over

 

[holmslaw]

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[plugwash]

The trouble with putting them on a local lighting circuit is you are supposed to connect them to a local lighting circuit and there is no lighting circuit that is local to the whole property.

 

[Adam_151]

I think the guidence says 'regulaly used lighting circuit' not 'local lighting circuit' so that you'd notice failure of the circuit quickish

The local circuit thing sounds like an EM lighting thing...

 

[LiamPope]

Its a good idea to connect them to the lighting circuit, you will notice a lighting circuit failure, but you would not know that your individual fire alarm circuit has failed.

Though would anyone in their right mind go to the trouble of installing a mains interlinked alarm system and not choose battery backup alarms? And presumably these types would somehow tell you the power has failed and they are running on battery?

 

[timetotalk]

the alarms I am looking to buy are with a battery back up. I think there is a green led to show mains power which turns red upon mains failure.

so with the replys I get the impression that linking them to an existing lighting circuit is the correct way?

 

[ebee]

Yes a well used (indispensable) lighting circuit would be ideal.
With battery back up - prefereably rechargeable and sealed in.
Ticks all the boxes and makes sense

 

[LiamPope]

Looking into it a little more, it would seem current recommendation is to put them on a separate circuit. Manufacturers (eg Kidde) are starting to recommend this too, rather than putting them on a lighting circuit. Also in the 17th, there's reg 560.7.1 which says circuits for safety devices must be independant of other circuits and not protected by an RCD which protects multiple circuits.

Not that it makes a great deal of difference for battery backup units. Mine (heat, smoke and CO) are all going on their own RCBO.

Liam

 

[holmslaw]

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