Plenum rated cables

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newbie2004

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Please forgive my ignorance (new to NEC world). I'm in a discussion with several other workers who say that it's ok to use non-plenum cables if the HVAC system can be immediately shutdown (they quote NEC 645). My response has been that according to NEC 800.53, it must be plenum rated cable. The area in which it is to be installed is a typical raised floor, however, the environmental air gets circulated throughout the rest of the floor, to include other rooms. I'm I missing something?
 
Re: Plenum rated cables

What I've learned about the NEC is, the more I know the less I know.
The rules in 645 are an exception to the rest of chapters 1-4, but can only be applied if the room wiring all complies with the long list given.
If it is a 645 scope room, then the area under the raised floor is not a plenum space.
And keep in mind most applications where we use plenum cable are air handling spaces used for 'enviromental air' and are not plemum spaces.
Please see the NEC definition of plemum.
 
Re: Plenum rated cables

You will have to have fire/smoke dampers at points of penetration to other areas. The dampers have to operate on activation of the smoke detectors, and by the disconnect. 645.2(2).

Steve
 
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