Fire pumps are the most critical equipment in a fire. Lose power, the pump stops, sprinkler pressure drops, the system collapses. NFPA 20 mandates redundant power: primary + alternate feed, ATS (Automatic Transfer Switch), diesel pump or NFPA 110 generator. A practical design guide below.
Power Supply Options
- Single feed: Grid only; unacceptable (NFPA 20 prohibits).
- Primary + alternate grid: Two separate substations; simultaneous loss unlikely.
- Primary + generator: Grid loss → generator starts (via ATS).
- Electric + diesel pump combination: Each pump 100% capacity.
NFPA 20 Feeder Design
Electric pump requires:
- Separate tap: not shared with other loads
- Overcurrent protection: 125-175% of pump FLA
- Short-circuit protection: motor protection OK; thermal overload prohibited (pump must keep running)
- Cable: FR-rated (2-hour), separate raceway, away from fire zone
ATS (Automatic Transfer Switch)
ATS switches between normal and emergency power. NFPA 110 Level 1 mandatory.
- Transfer time: max 10 seconds
- Delay: generator warm-up (30 s) + stabilization (10 s)
- Open transition (break-before-make) or closed transition (make-before-break, 100 ms)
- Bypass switch: service without outage
- Weekly automatic test: generator under real load
NFPA 110 Generator Requirements
- Level 1: fire pump included. Max 10 s transfer.
- Class 48: minimum 48-hour fuel reserve
- Diesel preferred (NFPA 37 rules)
- Environment: climate-controlled, -20 to +40°C
- Monthly 30 min test, annual 4-hour load test
Diesel Pump Option
Diesel pump instead of or alongside electric pump; power-independent:
- NFPA 20 Chapter 11 compliant
- Fuel: day tank (8-hour run) + main tank
- Two battery sets with auto charger
- Auto start: within 10 s of pressure drop
- Pro: power-independent; con: maintenance-heavy, exhaust management
Turkey Application Examples
Large malls, hospitals, data centers use electric + diesel. Mid-size: electric + generator. Small buildings often electric only — not NFPA 20 compliant but allowed by BYKHY in some cases. Result: in fire-related outages, pump doesn't run.
Common Mistakes
- No ATS: Manual transfer; no one does it during fire.
- Generator not tested weekly: Doesn't start in fire.
- Stale diesel fuel: Over 6 months; clogs turbines.
- No FR cable: Cable burns, pump loses power.
- Thermal overload trips pump: Overheat should cut; motor burned instead.
Conclusion
A fire pump isn't just mechanical equipment; it's inseparable from electrical reliability. Without primary + alternate + ATS + generator or diesel backup, the first outage collapses the system. Power supply is NFPA 20's most overlooked chapter — yet the most critical.
Pump power calc in SprinkCalc
Electric pump load calc, ATS transfer simulation, generator sizing.
Learn MoreCore references: NFPA 20, NFPA 110, NFPA 37. Original NFPA post: NFPA Today - Fire Pump Power.