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#97806 - 03/28/06 01:46 PM Fire Alarm Wiring
George Little Offline
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Registered: 01/18/04
Posts: 1488
Loc: Michigan USA
Based on the 2002 NFPA72, is it now permissible to have the outgoing and return conductors in the same bridle rings when installing a Class A fire alarm circuit??

[This message has been edited by George Little (edited 03-28-2006).]
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#97807 - 03/28/06 02:31 PM Re: Fire Alarm Wiring
Ron Offline
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Registered: 03/13/02
Posts: 582
Loc: White Plains, NY
Generally yes, same bridle ring, different cable, unless specified by Contract differently.

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.

[This message has been edited by Ron (edited 03-28-2006).]

[This message has been edited by Ron (edited 03-28-2006).]
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#97808 - 03/28/06 07:26 PM Re: Fire Alarm Wiring
George Little Offline
Member
Registered: 01/18/04
Posts: 1488
Loc: Michigan USA
What happened to the required spacing (recommended) called out in the appendix?
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#97809 - 03/30/06 08:02 PM Re: Fire Alarm Wiring
Ron Offline
Member
Registered: 03/13/02
Posts: 582
Loc: White Plains, NY
The annex text is still there, but Annex A is not a part of the requirements of the NFPA document but is included for informational purposes only.

A.6.4.2.2.2
A goal of 6.4.2.2.2 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 horizontally.



[This message has been edited by Ron (edited 03-30-2006).]
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