Code for Installing Wired Smoke Detectors

Discussion in 'Electrical Forum discussion & Blog' started by seaneys, Jul 26, 2007.

  1. seaneys

    seaneys New Member

    Messages:
    192
    Location:
    Chicago Suburbs
    Hello,

    I'm in the process of a basement remodel and 800 ft sq addition. I'm doing the electrical and plumbing myself. The project is 'official' and will be inspected.

    My village does not require wire smoke detectors, but it seems like it would be a good idea. Are there any good references that discuss connection requirements (I'm assuming dedicated conduit, dedicated circuits, etc), alarm types, and alarm locations?

    I looked in the NEC, but did not find anything.

    Thanks,
    Steve
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    Don't take this as gospel, but here are the salient points as I understand them: put them on a dedicated circuit breaker so an accidental trip by something else doesn't inactivate them; power to the first one only needs two wires (they usually aren't grounded, but if you use metal boxes, you'll want one), but from there to the others, you'll need three wires - the third acts to trigger the others on the daisy chain when any one goes off (this cannot be the ground wire); code calls for one in each bedroom. There may be more...I just don't know.
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,531
    Location:
    North Carolina
    Smoke alarms are not required by the NEC but instead by the Building Code.

    The placement if ruled by the building code not the electrical code. At one time smoke alarms was required to be on a shared circuit so if the overcurrent device opened there would be an indication of it being opened.

    This nonsense of smoke alarms needing a dedicated circuit that is not protected by arc fault is nothing more than ignorance expressing itself.
    Smoke alarms are required to be powered by battery back up so in the event that there was a loss of power they would still function.
    Smoke alarms are required to be interconnecting only in new installation or that part that is new installation. In the event of a room addition there is no requirement to interconnect the new alarms to the existing ones.
    In the event that there are none existing then battery powered alarms can be installed in those areas where none are now.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    I've seen wired detectors both with and without battery backup. A battery backup is always a good idea, but if you don't have one, I still think it's a good idea to have it on its own circuit. If you use a lithium backup, and don't have too many power outages, it could last the life of the detector (10-years as recommended by the fire codes).
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    You have to be careful using the terms "lithium" and "10 year". In general, the 9 volt lithium batteries are specified as having a 10 year SHELF LIFE. But Firex, as one example, sells more than one detector which comes with lithium batteries, but ONLY ONE of them is spec'd as a 10 year unit. In other words, lithium batteries do not per se have a tremendously greater capacity than a duracell or whatever. One of the issues with smoke alarms is you don't know how long the unit has been in inventory somewhere, and alkaline batteries do die off on the shelf. Lithiums have a long shelf life, but unless the smoke alarm is designed with special ultra-low current draw circuitry, it will not necessarily go 10 years on one battery/.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    If used in only as a battery backup in an a/c powered device, it should last that time, since it is essentially sitting on the shelf. I wouldn't expect one to run a battery detector for that long.
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,531
    Location:
    North Carolina
    Here is what the IRC has to say about the power supply to smoke alarms no matter what anyone's idea is.

    SECTION R313
    SMOKE ALARMS
    [F] R313.1 Smoke alarms. Smoke alarms shall be installed in
    the following locations:
    1. In each sleeping room.
    2. Outside each separate sleeping area in the immediate vi-
    cinity of the bedrooms.
    3. On each additional story of the dwelling, including base-
    ments but not including crawl spaces and uninhabitable
    attics. In dwellings or dwelling units with split levels and
    without an intervening door between the adjacent levels,
    a smoke alarm installed on the upper level shall suffice
    for the adjacent lower level provided that the lower level
    is less than one full story below the upper level.
    When more than one smoke alarm is required to be installed
    within an individual dwelling unit the alarm devices shall be in-
    terconnected in such a manner that the actuation of one alarm
    will activate all of the alarms in the individual unit. The alarm
    shall be clearly audible in all bedrooms over background noise
    levels with all intervening doors closed.
    All smoke alarms shall be listed and installed in accordance
    with the provisions of this code and the household firewarning
    equipment provisions of NFPA 72.
    [EB] R313.1.1 Alterations, repairs and additions. When
    interior alterations, repairs or additions requiring a permit
    occur, or when one or more sleeping rooms are added or
    created in existing dwellings, the individual dwelling unit
    shall be provided with smoke alarms located as required for
    new dwellings; the smoke alarms shall be interconnected
    and hard wired.
    Exceptions:
    1. Smoke alarms in existing areas shall not be re-
    quired to be interconnected and hard wired where
    the alterations or repairs do not result in the remov-
    al of interior wall or ceiling finishes exposing the
    structure, unless there is an attic, crawl space, or
    basement availablewhich could provide access for
    hard wiring and interconnection without the re-
    moval of interior finishes.
    2. Repairs to the exterior surfaces of dwellings are ex-
    empt from the requirements of this section.

    R313.2 Power source. In new construction, the required
    smoke alarms shall receive their primary power from the build-
    ing wiring when such wiring is served from a commercial
    source, and when primary power is interrupted, shall receive
    power from a battery.Wiring shall be permanent and without a
    disconnecting switch other than those required for overcurrent
    protection.Smoke alarms shall be permitted to be battery oper-
    ated when installed in buildings without commercial power or
    in buildings that undergo alterations, repairs or additions regu-
    lated by Section R313.1.1.
    Last edited: Jul 26, 2007
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