Multiple risers in firefighting systems 1

[Miangoni]

thread184-195655
SprinklerDesigner2 (Mechanical)
Sir, You've mentioned in above thread that the only time a manifold would be advantageous is when the building requires multiple risers due to its large size. Large size means exceeding 52,000 sq. ft. in a light or ordinary hazard occupancy or 40,000 sq. ft. in extra hazard or storage occupancies.
For 52,000 sq. ft. coverage area in ordinary hazard occupancy,is there any code to support this claim or it is just a standard practice?

 

[SprinklerDesigner2]

From NFPA #13 2013:

8.2 System Protection Area Limitations
8.2.1 The maximum floor area on any one floor to be protected by sprinklers supplied by any one sprinkler system riser or combined system riser shall be as follows:
(1) Light hazard — 52,000 ft2 (4831 m2)
(2) Ordinary hazard — 52,000 ft2 (4831 m2)
(3)* Extra hazard — Hydraulically calculated — 40,000 ft2 (3716 m2)

Why 52,000 sq ft and not 50,000 or 100,000?

Used to be a system was limited to 400 sprinklers and with a 130 sq ft maximum area of coverage for Light and Ordinary Hazard Occupancies 400*130=52,000 sq ft.

Storage and Extra Hazard was 100 sq ft per head so 400*100=40,000.

So for standard systems the maximum number of heads went away but the maximum square footage never did.

 

[Miangoni]

Thanks , I've got my answer