Fire Sprinkler System Design
What this domain tests
Design questions ask you to turn an occupancy, an architectural plan, and a water supply into a compliant system: hazard classification, density and remote area, sprinkler spacing and location, hydraulic calculation, and supply analysis.
Core rules
- Classify the hazard first. Light hazard covers offices and schools; ordinary hazard Group 1 includes parking garages, ordinary hazard Group 2 includes mercantile and manufacturing; extra hazard covers high-fuel-load or flammable work. The class sets density, spacing, and hose allowance.
- Density/area design: select density and matching remote area from the NFPA 13 curves, then multiply. That product is the sprinkler demand only.
- Add hose allowance at the base of the riser after the hydraulic calculation. Light hazard is typically 100 gpm; ordinary hazard 250 gpm.
- Spacing limits: light hazard 225 sq ft per sprinkler and 15 ft between sprinklers; ordinary hazard 130 sq ft and 15 ft; extra hazard 100 sq ft and 12 ft. Keep sprinklers no more than half the spacing from a wall.
- Increase the remote area 30% for dry-pipe systems and for combustible sloped ceilings. Do not apply that increase to the hose allowance.
Worked example
An ordinary hazard Group 2 warehouse uses 0.20 gpm/sq ft over a 1,500 sq ft remote area. Sprinkler demand is 0.20 x 1,500 = 300 gpm. Hose allowance is 250 gpm. Total demand at the riser is 550 gpm, and the calculation must show 300 gpm from sprinklers plus 250 gpm of hose at the required pressure.
Traps
Multiplying density by the entire building area; adding hose allowance before the hydraulic calculation; using light-hazard spacing in a mercantile occupancy; forgetting the dry-pipe remote-area increase.