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Sprinkler protection of cable trays?

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Bagge

Mechanical
Mar 11, 2008
32
I am a Danish Sprinkler Engineer. In Europe, we do not use the NFPA 13 rules as primary – but are allowed to if wanted. The NFPA 13 is much more flexible and stays up to date with the development of the new sprinkler types which the European rules does not. Therefore I am beginning to learn the specific in the NFPA 13 – very interesting.

In below I have pointed out a table in the CEA rules. I am interesting how the NFPA 13 relate to that? Of course, I am also reading in the NFPA 13, and it seems it is all different in the NFPA 13. It depends whether or not the material in the concealed space is combustible, right?
Regarding electrical cables – I can not find anything in the NFPA 13. Will I have to protect cable trays if I use the NFPA 13 rules?


“5.4 Protection of concealed spaces
If the height of the concealed space at roof and floor exceeds 0,8m, measured between the underside of the roof and the top of the suspended ceiling or between the floor and the underside of the raised floor, these spaces shall be sprinkler protected.
If the height of the concealed space at roof and floor is no greater than 0.8 m, the spaces shall be sprinkler protected only if they contain combustible materials or are constructed with combustible materials. Electrical cables with voltage less than 250V, single phase, with a maximum of 15 cables per tray, are allowed.
The protection in the concealed space shall be to LH when the main hazard class is LH and OH1 in all other
cases.”
 
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are you talking about cable trays exposed like in a room

or cable trays below a computer type floor??????
 
Cable trays exposed in the concealed space between the suspended ceiling and the roof. Lets say, that there are no combustible materials in the concealed space. So the question is whether or not the cables pose a risk so that they require sprinkler protection?
 
In the NFPA 13 Handbook 17th Ed (Puchovski)they comment that the NFPA 13 has not a clear definiton on when cables on concealed spaces require sprinklers and is a matter of the designer criteria and the risk involved. If there are lots of cables and they are important they require, if there are few cables and the space will not be more critical in the future thay dont. If you have a gas system they don´t. Maybe on NFPA 75 computer rooms and telecomuniction facilities you could find more info.
 
I am not aware of any specific requirements in NFPA 13 to sprinkler cable tray's; however the insurance underwriter, like FM Global, and NFPA 13 will usually require it if the obstruction is 4 feet or wider. It's no different that HVAC duct work or HVAC unit has to have a sprinkler under it due to the obstruction.

Hope it helps,

 
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