New installation Q, pt2 (Smoke alarms)

[GaryinAshby]

As per my post the other day, single storey side extension, 4 rooms (dining, living, bathroom, utility). BCO has requested that I replace the two battery smoke alarms in the house with two mains units (but none in the extension which surprised me).

I have asked the two electricians that quoted to supply & fit two alarms in the house (as per BCO instruction) and also one in the extension.

Shouldn't these also incorporate some kind of fused switch as neither of them think its necessary, stating that the protection for the lighting circuit is adequate?

Don't think I'm in a habbit of "questioning professionals" but I know from reading posts on here that the level of competance of professionals does vary.

 

[EdwardCurrent]

Hello Gary,

It is ok to 'wire' your smoke/roh alarms both off of a local, regularly used lighting circuit, or their 'own' circuit.

I personally prefer to use a lighting circuit. This way they are not turned off and forgotten about.

Ed

SORRY , just read your other post. Seeing as all your circuits are now RCD protected (new C/U fitted) then it is advisable to wire them into the lighting circuit rather than on their own circuit.

 

[Chri5]

Linked units with battery backup.

The battery will take over if the MCB for the light circuit trips, important since we all suffer from light circuit trips due to filiment shorts. You will need to run a 3C+E for the link between the units.

 

[GaryinAshby]

Thanks folks.

Rather than running 3C+E linking the three new alarms, couldn't I just use three "indepenadant" alarms, each taking a feed from the closest lighting circuit? Trying to run 3C+E between them would be a nightmare due to there location, plus the house is still being lived in by me, clumsy wife, 4 y/o daughter & inquisitive labrador! Those and taken up floors just don't mix!!!

 

[AndrewSchofield]

I've just had some fitted as part of a loft conversion - mains powered, interlinked with battery back up as above - and was told they should be wired into 'a regularly used lighting circuit' otherwise you could have a power outage on your alarm circuit, the battery back-up would kick in and you'd be none the wiser, whereas if they are powered from the same circuit as the lights on your stairs and you have a loss of power you'll notice your stairs lights don't work and get it sorted!!!

 

[rebuke]

It depends though - I've added some in on a new circuit (notified to LABC before anybody asks) as part of a load of work I've been doing. They've got battery backup - if the batteries start getting low they beep every 45 seconds, so even if I don't notice the tiny green LED you can see through the cover has gone out, I'll hear them beep when the batteries start getting low.

I could have run them off a lighting circuit, but the instructions in the alarms recommended running them off their own one.

GaryinAshby - I suspect your BCO will want them to be interlinked, at which point you have to run cable between them, and for the vast majority of alarms, they have to be off the same circuit (i.e. while you can power them off the lighting circuit, they have to all be powered off the SAME lighting circuit) - so the normal way to do this is to feed e.g. the downstairs one from the downstairs lighting circuit, and then run 3C+earth from that to the rest...

 

[comms]

Use RF linked detectors & power them off the lighting circuit, no need to run any cables between detectors then.
http://www.tlc-direct.co.uk/Main_Index/Fire_and_Smoke/Smoke_Alarms_Radiolink/index.html

 

[GaryinAshby]

I like the sound of the RF interlinked ones, but considering what Rebuke posted, would both the upstairs & downstairs one have to be powered from the same lighting circuit or could I power the upstairs one from the upstairs lighting & the downstairs one from the downstairs lighting?

 

[rebuke]

I hadn't seen RF interlinked ones before - I'd see no reason why they have to be powered off the same circuit, the only reasons the wired interlinks do is so that the interlink works properly (i.e. if power is on, they all send/receive mains (and don't trip RCDs by being on different neutrals etc), if it's off they all send/receive battery in some way), but an RF one won't care if it's on mains or battery, it'll be the same signal (I assume anyway - check the user manual to be sure).

 

[GaryinAshby]

Thanks for all the replies. I've emailed my BCO to confirm that he's happy with the RF ones, if he is, I'll use those as it makes installation easier.