Interlinked smoke alarms

Discussion in 'Electricians' Talk' started by "Professional" DIYer, Aug 3, 2004.

  1. Job, to fit a 5 inter-linked smoke alarms.

    In the install guide (see TLC tec section) they quote that 3 core T+E should be used to power and inter-link alarms from a single power source.

    However in a large building, at lease one of the alarms must be wired through conduit outside, the conduit is shared with other ELV cables (data/tel) etc. And alarms will be located in areas not powered from the same CU on sub-mains.

    What I wanted to do was wire the power for each alarm from the local lighting circ (reg used, alarms bat backup) and then use red (if I can get instead of brown!) 1.0mm single and run this between each of the inter-connect terminals.

    Any ideas if this might work?? Thanks.
     
  2. Minesa Pint

    Minesa Pint New Member

    If it did work - do you hink it would be safe, especially considering that you might not be the only person ever to open up one of these smoke alarms?

    Try Aico radio-link bases, expensive but brilliant.
     
  3. it will work as the third core is only used as a "switch". the different phases wont make a difference but if cant run the power for the smokes in with elv circutits. it will induce a voltage on the other cables
     
  4. chtechie

    chtechie Member

    If your building is that big are you sure you don't need a full blown fire alarm system. I'd have a word with the local building control before I quoted.
     
  5. plugwash

    plugwash New Member

    it all depends on if the interlink wire is neutral relative or earth realative

    if its earth relative you should be ok using a single and earth cable

    but frankly i agree if it's big enough to be considering this sort of thing its probablly big enough to reqire a proper alwarm system

    finally if you do wan't to run a full interlinked alarm cuircuit outside you could use a 3 core (or 4 core if you wan't to use a core for earth) swa
     
  6. Electro-tech

    Electro-tech New Member

    I have a feeling that you should have a fire alarm circuit seperate and clear of any other utilities,not in the same conduit.
     
  7. Basically its one building, though the extension is on a sub-main.

    The reason conduit is needed, is because it is not possible to chase a cable into the wall or go under floor etc for the new rooms with a peaked roof, so the cable is routed outside between two lofts.

    A full fire alarm is a bit OTT, even the fire co who check the extinguishers said it probs wasn't necessary.

    So its really a question, if something along these lines can be setup, or if basic alarms are used instead, which are far from providing a decent level of protection.

    The RF bases are a good idea, but well above budget.

    Would the interlinked core carry power 24/7? I'd imagine only during alarm. The ELV is CAT5 so shouldn't induce anything into the single core, however if the core was powered it could induce into the CAT5.

    Also, if 3core T+E was used voltage drop would start to be an issue.
     
  8. salem2000

    salem2000 New Member

    If the devices have a backup power supply, they can be installed on a local lighting circuit.

    Read B1 Sec 1.17 of Building Regs as regards power supplies for Smoke Alarms:

    Click Here

    Also gives document gives details of requirements for different types and uses of buildings.
     
  9. ban-all-sheds

    ban-all-sheds New Member

    Would the interlinked core carry power 24/7? I'd imagine only during alarm.

    Stop imagining things and find out.

    Take 2 out of the boxes, wire them up, connect a voltmeter to the link terminals, and set one off with a smouldering rag.
     
  10. salem2000

    salem2000 New Member

    I was under the impression that the interlink cable was a LOW voltage signal only. (12-24v)
     
  11. plugwash

    plugwash New Member

    quite likely

    are you aware what it is realtive to?

    if it is earth relative then it should be possible to run it between alarms on different cuircuits/phases without problems

    i think there is a need to experiment here

    try connecting two interlinked alarms with no earth to one of them and see if the interlink still works
     
  12. I'll stick on my lab coat and give it a go. Results will be with you shortly.
     
  13. Minesa Pint

    Minesa Pint New Member

    Take 2 out of the boxes, wire them up, connect a
    voltmeter to the link terminals, and set one off with
    a smouldering rag.

    Best just use the test button, in case you burn the place down.
     
  14. ban-all-sheds

    ban-all-sheds New Member

    Now that would be ironic!

    If the test button also tests the interlink function, and sets off the other alarms, then yes, this would probably be better.
     
  15. sparks

    sparks New Member

    Sounds to me as though a good read of BS5839 Pt 1 & Pt 6 would be a good idea and then maybe a chat with local building control.
     
  16. Addie

    Addie New Member

    there is a smoke alarm on the market Aco i think with a radio link base this would suit your requirment
     
  17. Minesa Pint

    Minesa Pint New Member

    there is a smoke alarm on the market Aco i think with
    a radio link base this would suit your requirment

    Read the topic - he said they are too expensive..........
     
  18. chocolateblock

    chocolateblock New Member

    BAS if you ever wired up smoke alarms you would know that when you try one test button that the others should also sound, basic building control regs, so stop being so dogmatic and condescending to people and put your brain into gear before opening your trap.
     
  19. ban-all-sheds

    ban-all-sheds New Member

    Blimey - WTF rattled your cage?

    The question was "Would the interlinked core carry power 24/7? I'd imagine only during alarm", so I suggested wiring a couple up, and finding out. Minesa Pint pointed out that using the test button would be a better method than the one I'd suggested, and I said that if it would exercise the link then it would be better.

    Where on earth do you get your "dogmatic and condescending" from?
     

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