NFPA 13 Sprinkler spacing "small room" provisions.

[DavidCR]

I´m designing a wet automatic sprinkler system for a emergency diesel generator plant room on a hydro power plant.

The respective code (NFPA 851) calls for a density of 0.25 on the generator room.
This room is 5.3mx4.5m = 24.2m2 (17.4´x 14.8´=256sqft).

Following NFPA 13 I´m interpreting that it should be designed as a Extra Hazard Group 1 (the generator diesel tank is under it).

My problem came from checking the sprinkler spacing requirements in NFPA 13 (2002-8.6.3.2.4) (1996-4.6.3.2 where small room provisions are mentioned.

I read the definition of "small room" but it only mentions Light Hazard ocupancies, so I want to know if the small room provisions can be used for Extra Hazard G1 "small room".

If I follow the "small room provisions", two sprinklers woud do fine, but if not, four would be needed (if I´m not too lost in the code).

Thanks a lot in advance, and a merry Xtmas and happy new year to all those who have made this NFPA forum a great tool in my job.

 

[stookeyfpe]

The small room provision only applies to Light Hazard occupancies. In your case you need to follow the conventional spacing requirements in NFPA 13 and provide the four sprinklers.

 

[TravisMack]

As usual Stookey, right on the money. The small room rule allows for different spacing and averaging of sprinklers heads in the room, but is ONLY for LIGHT Hazard.

 

[davidbeach]

I know it isn't an answer to your original question, but I hope you are doing a glycol or, better yet, dry system if you are in a climate where the ambient air can be below freezing. Particularly if you have an engine mounted radiator, you will be pulling very large quantities of outside air through the room, and if that air is below freezing so will your sprinklers be in short order.