Plenum Rated Cabling when Plenum is Dedicated to Single Space

Status
Not open for further replies.
T

ThomasMartin

Member
Location
Milwaukee, WI, USA
Is there any exceptions where plenum rated cabling is not required above a plenum ceiling if the plenum is dedicated for a single space. My understanding of the intent of the code is that toxic smoke will not spread between multiple rooms per single plenum but if single plenum space per room what difference would it make where the smoke originated? The NEC does not seem to address this? Preference is to use cable bus wiring with free air ampacity rating in a plenum space for a large data center installation where no options for plenum rated cabling exists. The owner has many sites where this has already been installed and the AHJ had not raised as an issue during permitting or installation.
 
Is this data center being wired per Art 645?
Plenum is the trade term, the NEC term is space used for environmental air. Is this an environmental air space?
 
Interesting, you apparently have a one room building for the most part. I see it as if everything were the same except no suspended ceiling - plenum rated cables wouldn't be required. Put that ceiling in and we have magically created smoke producing and distributiuon issues.:blink:
 
Because with the ceiling, the blower would pull the fumes and smoke in and spread it all over. No ceiling, no blower and the smoke would be localized.

-Hal
 
hbiss said:
Because with the ceiling, the blower would pull the fumes and smoke in and spread it all over. No ceiling, no blower and the smoke would be localized.

-Hal
Click to expand...
Single roof top unit, yes. Multiple units, it probably still localized to the area it originates from.
 
kwired said:
Interesting, you apparently have a one room building for the most part. I see it as if everything were the same except no suspended ceiling - plenum rated cables wouldn't be required. Put that ceiling in and we have magically created smoke producing and distributiuon issues.:blink:
Click to expand...

Floors can be plenums too. Underfloor spaces seem to be particularly popular in data centers, as I recall. :roll: You could have a Liebert unit, taking air from under the floor, which would certainly make that space a plenum, and discharging into the room. Or you could be doing hot aisle/cold aisle, to make things a little more complicated. Still dealing with a plenum.
 
gadfly56 said:
Floors can be plenums too. Underfloor spaces seem to be particularly popular in data centers, as I recall. :roll: You could have a Liebert unit, taking air from under the floor, which would certainly make that space a plenum, and discharging into the room. Or you could be doing hot aisle/cold aisle, to make things a little more complicated. Still dealing with a plenum.
Click to expand...
I suppose so. I don't know a lot about data centers. Natural convection seems to make return air space somewhat a waste to put it under the floor in such a space, heat will trapped at the ceiling. These places need cooling much more then they need heating from what I do understand, so makes sense to me you should draw return air from near the ceiling. But what do I know?:blink:
 
kwired said:
I suppose so. I don't know a lot about data centers. Natural convection seems to make return air space somewhat a waste to put it under the floor in such a space, heat will trapped at the ceiling. These places need cooling much more then they need heating from what I do understand, so makes sense to me you should draw return air from near the ceiling. But what do I know?:blink:
Click to expand...

The buildings are many megawatt heaters.
 
Status
Not open for further replies.
Top