Interconnected smoke alarms

[R D S]

I have some confusion regarding the correct way to connect some mains powered interconnected smoke alarms.

My original plan was to power each alarm from the nearest ceiling rose and run a single interconnect wire. Apparently this is not 'allowed'. Is this correct?

So if I connect them all to one single mains supply I will be running 3 cores between them all but cannot use the earth wire for interconnect.

So i'm looking at either 2 lots of T&E, or some 3 core & earth cable, black, brown and blue. Which is live?

I wish i'd bought the radio ones!

[Dave Liquorice]

Not the blue, that is neutral. Brown is the accepted single phase live leaving black for the signalling interconnect.

Cables work...

[R D S]

I assumed it was brown-live as per a plug but remembered that the yanks use black as live.

Cheers.

[The Natural Philosopher]

Brown is live Blue is neutral Black is the 'switched live' that links em.

As long as you connect the same colors consistently to each terminal, it doesn't matter.

the last one in the chain doesn't need to carry the switched live to the CU, just use T&E

They are rubbish really.

Bite the bullet and take the pain. The result is worth it.

3 core + earth is standard cable used wherever you need a 'switched live' like between intermediate lighting switches etc. Or some thermostats. Or smoke alarms.

[The Natural Philosopher]

A general rule of thumb is that anything the Yanks do may be safely disregarded.

[Pete Shew]

..and old French.

I had to do some work in an English refurbished French house that had incoming blue neutral and three black phase wires. The house was wired in red/black T&E (contrary to French regs which require the earth to be insulated like the other conductors as well as the incorrect colours). I was installing a cooker using French three core in Brown/Blue/Green and Yellow.

That was the easy bit - the gas and water in 14mm AND 15mm copper didn't help!

Pete

[ARWadsworth]

3 core & earth cable has brown, black and greys inner cores.

The brown would be the live, the grey would be oversleeved with blue and used as the neutral and the black would be the interconnect wire

[Jethro]

Am I correct in vaguely recalling at least one type of smoke/fire alarm, which "listens" to hear if any other alarm is going off, and goes off itself ? No need for cables or wireless.

[Ian Jackson]

Best remembered as "black death" (bubonic plague), and "white is a neutral colour" (not coloured).

[Bob Eager]

Dunno, but we have intelligent door wedges at work that retract when they 'hear' the alarm.

[John Rumm]

Its certainly not good practice. Either run them all from a dedicated circuit, or from one lighting circuit.

True. You need to use 3&E cable...

All of them ;-)

Black, brown, and grey usually for modern 3&E

Typically you would use Brown as live, Sleeve the grey with blue and use at the neutral, and use the black for the interconnect.

[John Rumm]

Black is a line colour here too now. (and even blue (i.e. neutral) is technically still a live wire (although not a line (or as was, phase) wire).

[dennis]

Did anyone say why they aren't battery powered with 10 year batteries and use an interconnect that runs at about 9V over "alarm" cable? They only have a life of about 10 years anyway so battery changing isn't a problem. Testing is the same with mains.

[Nick Leverton]

I asked in our local CEF for some battery interlinked smoke alarms, since there weren't lighting circuits where I wanted them, and the spotty youth on the counter advised me to try Wilko's for battery operated ones ! I got them online from TLC in the end and haven't been back into CEF ...

Nick

[Mr Pounder]

Pay for a professinal job. Errrr, brown is live.

>

[Andrew Gabriel]

The French also allow wiring premises all conforming to BS7671. Any EU country is supposed to allow premises wiring using any other EU country's wiring standards providing those standards have been brought into line with the CENELEC harmonised documents. The only cases I've heard of are the use of BS7671 in France by ex-pats, but I don't know which other EU countries are now also aligned with CENELEC standards and which aren't. They are all supposed to move that way.

Yes, but they still use 1/2" screwed plumbing fittings;-)

[Pete Shew]

Yeah, but daft. It confuses local sparks, could lower the value of the property and means that all locally sourced electrical stuff needs the plug changing. When buying white goods the shop normally comes and installs it and then the man throws up his hands in horror at the UK sockets.

Indeed, one of the few last bastions of imperialism (bring back Whitworth and BSF). I think wheel rim diameters are another.

Pete