AL Fire Sprinkler cheat sheet

Light hazard: design density 0.10 gpm/ft² over 1,500 ft²; ordinary hazard Group 1: 0.15 gpm/ft² over 1,500 ft²; ordinary hazard Group 2: 0.20 gpm/ft² over 1,500 ft².

Sprinkler spacing: max 15 ft between sprinklers on branch lines and max 15 ft between branch lines for light hazard; ordinary hazard allows 15 ft spacing but max 130 ft² per sprinkler.

Minimum sprinkler operating pressure is 7 psi (0.5 bar) unless the listing specifies higher; standard spray upright/pendent sprinklers are typically listed for 7 psi minimum.

Sprinkler temperature ratings: ordinary 135–170°F, intermediate 175–225°F, high 250–300°F; choose a rating at least 25°F above the maximum expected ceiling temperature.

Quick-response sprinklers have a response time index (RTI) ≤ 50 (m·s)^0.5; standard-response sprinklers have RTI ≥ 80 (m·s)^0.5.

The remote area is the operating area at the most hydraulically demanding location; it must be increased by 30% for dry-pipe or preaction systems (unless a listed calculation method is used).

Sprinkler obstruction rules: a sprinkler must be located within 12 in. of a wall or obstruction; obstructions ≤ 4 ft wide may be spaced per NFPA 13 rules, and obstructions > 4 ft wide require additional sprinklers.

Hazard classification drives density and hose allowance: light hazard hose allowance 100 gpm, ordinary hazard 250 gpm, extra hazard 500 gpm (for durations per NFPA 13).

Inspection, testing, and maintenance: main drain flow test annually, waterflow alarm test quarterly (or semiannually for some devices), and gauge/valve inspection weekly or monthly per NFPA 25.

Fire pump rated flow: churn (0% flow) pressure must not exceed 140% of rated pressure; at 150% of rated flow, pressure must be at least 65% of rated pressure.

A fire pump must be sized so that the pump curve does not fall below the system demand point; the pump's rated point should be at or above the required flow and pressure.

Net pump pressure = discharge pressure – suction pressure; brake horsepower (BHP) = (flow in gpm × head in psi) / (1,714 × pump efficiency).

Suction pressure must remain positive; the pump must maintain at least 20 psi residual pressure at the suction flange under all flow conditions (NFPA 20).

Fire pump controllers: automatic transfer switch must transfer to emergency power within 10 seconds; the controller must be listed for fire pump service and sized per NFPA 20.

Weekly fire pump testing: run the pump at no-flow (churn) condition for at least 10 minutes; annual flow test compares performance to the original curve.

Water supply curve: available pressure = static pressure – (flow × friction loss factor); the system demand point must fall below the supply curve for adequate design.

Fire pump bypass and test header: test header flow must be measured with approved flow meters or pitot tubes; the test header must be capable of flowing at least 150% of rated pump capacity.

Acceptance testing per NFPA 20 includes a field acceptance test at 100%, 150%, and churn conditions, with results plotted against the manufacturer's curve.