Smoke detectors under raised floor

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jcbaka

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Does anyone know what is the code requirement for mounting spacing of smoke detectors under raised floor?
 
jcbaka said:
Does anyone know what is the code requirement for mounting spacing of smoke detectors under raised floor?
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I am not sure what you are asking. Why would you put a smoke detector under the floor and not on the ceiling?

Please elaborate. The instruction sheet that comes with the detectors should tell you where to mount them with relationship to walls. For instance every one I have installed has instructions not to mount them too close to the wall if on the ceiling or too close to the ceiling if on the wall.
 
The application is for a server room with 12" raised floor. NEC requires smoke detection under a raised floor and to meet code, is to install smoke detectors.


K8MHZ said:
I am not sure what you are asking. Why would you put a smoke detector under the floor and not on the ceiling?

Please elaborate. The instruction sheet that comes with the detectors should tell you where to mount them with relationship to walls. For instance every one I have installed has instructions not to mount them too close to the wall if on the ceiling or too close to the ceiling if on the wall.
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jcbaka said:
The application is for a server room with 12" raised floor. NEC requires smoke detection under a raised floor and to meet code, is to install smoke detectors.
Click to expand...

If you could point me to the particular section and paragraph of the NEC that requires the detectors I may be able to help you better.

Edit: Also which year NEC are you bound to comply with?
 
I can't cite any code, but I've seen a raised floor two places. One floor was only raised 5 inches and the smokes were screwed to the bottom of the floor tile. The other rasied floor is about 12 inches and they mounted the smokes to the metal uprights about halfway up that support the floor.
 
NFPA 72 "National Fire Alarm Code" is the code you're looking for.

(NFPA 72 2002 ed.) 5.7.3.2.3(A) "Spacing of 9.1 m (30 ft) shall be permitted to be used as a guide"

(NFPA 72 2007 ed.)5.7.3.2.3.1 "In the absence of specific performance-based detection criteria, smoke detectors shall be permitted to be located using 9.1 m (30 ft) spacing"

You should check with the AHJ to ensure what they require as requirements may vary. NFPA 72 also dictates how smoke detectors will be mounted beneath a raised floor:

2002 ed. - 5.7.3.2.2 and A.5.7.3.2.2
2007 ed. - 5.7.3.2.3.1 and A.5.7.3.2.3.1

Also, I'm sure you'll have to have a licensed fire system installation company provide plans to the AHJ for review before installation. Such a company in your local area will be able to provide accurate performance and design specs.
 
See NEC 2008 Article 645.5.D.4.


K8MHZ said:
If you could point me to the particular section and paragraph of the NEC that requires the detectors I may be able to help you better.

Edit: Also which year NEC are you bound to comply with?
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If you need to comply with NEC Article 645, then you need smoke detectors under the floor.
No 645, then generally no smokes under the floor, unless there is suppression under the floor.
Smoke detectors under the floor with low air flow is 30' spacing. When high airflow is present, NFPA 72 has a chart that could take you as close as 125 sq ft per detector.
 
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