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Thread: Fire Alarm: Class A Circuit Seperation

  1. #1
    Join Date
    Nov 2009
    West Virginia

    Fire Alarm: Class A Circuit Seperation

    Is there a code of standard that states a minimum distance of separation for outgoing and return conductors for Class A Fire Alarm Circuits?

    I have checked NFPA72,

    Outside of requiring the outgoing and return conductors to be routed separately, NFPA72 does not state minimum distances and pretty much says it is up to the designer/installer and to take the use of the building and hazards into consideration when routing the signaling path.

    Is there another document or code to reference? NFPA70(NEC) only sets requirements for separation from non-fire alarm circuits 760.136

  2. #2
    Join Date
    Feb 2003
    New York, 40.7514,-73.9925
    4,457* All styles of Class A circuits using physical conductors
    (e.g., metallic, optical fiber) shall be installed such that
    the outgoing and return conductors, exiting from and returning
    to the control unit, respectively, are routed separately. The
    outgoing and return (redundant) circuit conductors shall not
    be run in the same cable assembly (i.e., multi-conductor
    cable), enclosure, or raceway.

    Exception: The outgoing and return (redundant) circuit conductors
    shall be permitted to be run in the same cable assembly, enclosure, or
    raceway under any of the following conditions:
    (1) For a distance not to exceed 3 m (10 ft) where the outgoing and
    return conductors enter or exit the initiating device, notification
    appliance, or control unit enclosures
    (2) Single conduit/raceway drops to individual devices or appliances
    (3) Single conduit/raceway drops to multiple devices or appliances
    installed within a single room not exceeding 92.9 m
    2 (1000 ft2)

    in area.

    A goal of is to provide adequate separation
    between the outgoing and return cables. This separation
    is required to help ensure protection of the cables from physical
    damage. The recommended minimum separation to prevent
    physical damage is 305 mm (1 ft) where the cable is installed
    vertically and 1.22 m (4 ft) where the cable is installed

    The appendix is not enforceable, but it helps understand the intent.
    Generally, Class A circuits are required by specification/Contract only, so hopefully there is further description in that project specific document, but nothing enforceable in a code/standard.

  3. #3
    Join Date
    Jan 2009
    I am on my phone right now, but I believe it is specifically listed in 72. One foot vertical four feet horizontal. At least that's what I would do. Anyone else out there feel free to correct me.

  4. #4
    Join Date
    Dec 2007
    North County San Diego
    A6. recommended minimum is one foot vertical four feet horizontal as stated by nhfire77...if this is a Govt project, they will enforce these minimum seperations.

  5. #5
    Join Date
    Nov 2009
    West Virginia
    Thanks for the code reference. I didn't look at the appendix. Thanks

  6. #6
    Join Date
    Mar 2009
    Right now ??, previously VT
    Any State codes you have to follow?
    Vermont Beer Tree, very rare

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