Reuse Conduit for a Class A system

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I have been told that it is authorized to reuse the same conduit for outgoing and return circuits for a Class A fire detection system, but found no reference related to this in NFPA 72 or NEC 760.

Is this permissable? I don't see much benefit for installing class A if outgoing and return circuits are in the same conduit considering a conduit and cable cut situation. I guess the other devices upstream could still provide information back to the panel in case of a trouble on a downstream device.

 

[ron]

Re: Reuse Conduit for a Class A system

NFPA 72 2002
6.4.2.2.2 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 m2 (1000 ft2) in area.