CO Fire Sprinkler cheat sheet

CO Fire Sprinkler Systems

• NFPA 13 is the design/installation standard for commercial sprinkler systems; NFPA 13R covers residential occupancies up to and including four stories, NFPA 13D covers one- and two-family dwellings and manufactured homes.

• Design approach selection: pipe schedule design is limited to systems of 160 or fewer sprinklers per NFPA 13; systems exceeding that or with unusual configurations require hydraulic calculation.

• Light hazard density starts at 0.10 gpm/ft² over 1,500 ft²; ordinary hazard Group 1 is 0.15 gpm/ft² over 1,500 ft²; ordinary hazard Group 2 is 0.20 gpm/ft² over 1,500 ft² - densities increase as hazard increases, remote areas decrease at higher densities per the density/area curves.

• Minimum residual pressure at the most remote sprinkler is 7 psi (0.5 bar) for any design; end sprinkler pressure must be sufficient to produce the required density from the chosen sprinkler K-factor.

• Sprinkler flow: Q = K√P, where Q is gpm, K is the discharge coefficient, and P is pressure in psi. Example: K=5.6 at 15 psi gives Q ≈ 21.7 gpm.

• Wet-pipe systems are the default; dry-pipe systems require the dry-pipe valve trip time and are limited to areas subject to freezing. Dry systems require a larger design area (typically increased 30%) to account for the air-to-water transition.

• Sprinkler spacing: maximum 15 ft between sprinklers on branch lines and 15 ft between branch lines for light hazard; maximum coverage area per sprinkler is 225 ft² for light hazard, 130 ft² for ordinary hazard.

• Acceptance testing: hydrostatic test at 200 psi for 2 hours (or 50 psi above working pressure if higher), flow test of the inspector's test connection, and main drain flow test to verify supply adequacy.