NFPA13, NFPA14, water demand 1

[fayazdin1]

I am designing an apartment building in Libya. The building footprint is 10,000 sq. m with 5000 sq. m courtyard in the middle, has a below ground parking garage and apartments are arranged in square shape around courtyard.

Basement garage is partially sprinkled because it is semi-enclosed. Apartments are arranged in multiple modules. Each module is 4-6 stories high with common stairs in the middle of two apartments on each floor.

Hydraulic calculations for the garage sprinkler system require 1500 L/min at 8-bars.Apartments building is unsprinkled.

How much water demand should be added for the fire-hose cabinets? There are total of 106-apartments. One fire-hose cabinet for every two apartments (53-hose cabinets) plus 14-cabinets in basement garage in addition to sprinklers. A dedicated fire water tank will be located in the courtyard and a combination of fire-pump, diesel-pump and a jokey pump will be used to pump the water.
NFPA 13, 2002 11.2.3.1.8 (7 A-C)
NFPA 14, 2000 5.9.1.1 & 5.9.1.2
Conflicting ? I am confused. Please help

 

[DavidCR]

NFPA is not very easy to understand when hose cabinets are required. The modern NFPA concept does not include hose cabinet protection for occupant use, provided sprinklers are a better protection with less water demand.

Depending on the place, NFPA 1, 101, building code, or local AHJ requires hose cabinets for occupants not NFPA 13.

NFPA 13 addresses that an additional water flow should be included, but the design pressure for the sprinklers may not be enough for the hose cabinets, and NFPA 13 does not tell how to deal with it.

So what I would have to do here(Costa Rica), is to consider them as separate calculations, for the parking sprinklers just add the respective hose allowance to accomplish NFPA 13. But for the hose cabinet system you must calculate the system to provide enough flow and pressure for cabinets.

In our case, our local AHJ asks for 200gpm @65-85psi for class II, 1-1/2 hose connections for occupant use (we do not have a specific requirement for non collapsible hose)and 500gpm @85-100psi for class I connections (on the most hydraulically remote points).

So, in hydraulic calculations we must check if the system can provide such requirement in addition to sprinkler calculations. When we have to provide class I/III hose connections the water demand is bigger or similar than for sprinklers, but the pressure is usually higher, and sometimes too high for the sprinklers. So it could be a problem to have them on the same riser. So if you have to provide enough pressure for the 6th floor hose cabinet, it may lead you to a high pressure for the sprinklers on the basement. This is where pressure reducing valves other considerations are needed.

 

[fayazdin1]

Thank you David,
That is exactly what I ended up with.
I designed basement sprinkler systems with NFPA 13 and class III hose cabinet for apartments with 500 gpm for the most remote cabinet and 250 for each additional, water demand not to exceed 1250-gpm for 30-minutes per NFPA 14.

I am using a pump with a header in the basement. One 4" riser with PRV for basement sprinkler and one 6" riser for cabinets. I added water demand for cabinets and sprinklers to size storage tanks.

Again, thank you for your help.
Fayaz Din P.E

 

[sprinkler1000]

Fayaz :

I do not see why the PRV for the basement sprikler system? Are you exceeding 175 psi?
It would make sense lowering pressure for the hoses.

regards