NFPA 20 and EN 12845 Fire Pump Requirements Compared

Both standards say the same thing: the fire pump must not stop during a fire. But the numbers differ, from starting time to fuel volume, battery count and test regime. This table is the list that belongs on the desk of any engineer moving between the two.

The shared philosophy: continuity, not protection

The unchanging rule in both is this: there is no overload (thermal) protection in the pump controller. Only short circuit protection exists, and the fuse must carry the starting current for at least 20 seconds. The motor must keep turning even beyond its thermal limit. An overload relay fitted on site to "protect the pump" opens the circuit in a real fire and collapses the system.

Side by side

Topic	NFPA 20	EN 12845
Overload protection	None (HRC short circuit fuse)	None (HRC short circuit fuse)
Fuse carrying starting current	Branch circuit approach	At least 20 seconds
Starting method	Reduced voltage listed, but DOL in practice	15 s rated-capacity rule, so DOL in effect
Reaching rated capacity	Controller fully functional within 10 s	At rated capacity within 15 s
Automatic shutdown	Prohibited; where permitted, a 10 min timer	Prohibited; manual stop only
Pressure switches	Sensing line per controller	Two independent switches per pump set
Diesel battery sets	Two sets, alternating	Two sets, alternating
Diesel cranking attempts	About 15 s crank / 15 s rest	6 attempts of 5–10 s, 10–15 s between
Fuel tank	By hazard and duration; dedicated tank	LH 3 h, OH 4 h, HHP/HHS 6 h
Weekly test duration	30 minutes	20 minutes (suppliers usually say 30)
Annual full load test	3 points (churn, rated, 150 percent)	Full load condition; 3 points not imposed
Pressure at 140 percent flow	65 percent of rated pressure rule	70 percent of rated pressure (pre-calculated HH)
Closed valve pressure	Must not exceed 140 percent of rated	12 bar limit at the equipment
Pump room fire resistance	Separation; AHJ dependent	At least 60 minutes (REI 60)
Pump room temperature	Engine manufacturer's limit	Electric 4 °C, diesel 10 °C
Controller and motor in one room	May be separate, with protected cable	Same compartment mandatory (submersible excepted)
Cabling	NFPA 70 Article 695 protected route	Flame retardant on a protected route, or E 90/PH 90
Jockey pump	Separate; a fire pump may not be the jockey	Must not be able to supply one open sprinkler

The three rows most often misread

1. Weekly test duration. NFPA 25 states 30 minutes from the outset; EN 12845 sets 20 minutes as a floor but leaves the door open to the supplier's recommendation. Because engine blocks reach operating temperature at 25 to 28 minutes, 30 minutes is the right field practice; 20 minutes complies but is not conservative.
2. Fuel volume. EN 12845 gives net hours by hazard class (3/4/6). NFPA ties the duration to system demand. On a mixed project, always take the larger.
3. Controller and motor in the same room. EN 12845 requires it except for submersible pumps. Moving the panel into an external corridor for appearance is a clear breach.

Test records

Both standards make records mandatory, and they are the first thing asked for at inspection: the last 12 months of weekly logbook entries and the annual full load flow test report. Writing "OK" in the logbook is not enough; the starting pressure, pump discharge pressure, oil pressure, engine temperature, battery voltage, fuel level and running time must be recorded numerically. A non-numerical log shows no trend, and only the numbers reveal that the oil pressure has been falling through the year.

Frequently Asked Questions

Why is there no overload relay in a fire pump controller?

Because the pump must not stop during a fire. Both standards permit short circuit protection only; overload protection is deliberately absent. An overload relay is exactly the device most likely to trip under fire conditions.

How long must the weekly test run?

NFPA 25 says 30 minutes. EN 12845 sets 20 minutes as a floor but allows the supplier's recommendation; because engine blocks reach operating temperature at 25 to 28 minutes, 30 minutes is the right field practice.

How many hours of fuel must the tank hold?

EN 12845 states it by hazard class: 3 hours for LH, 4 for OH and 6 for HHP and HHS. NFPA ties the duration to system demand; on a mixed project take the larger.

Can the controller and motor be in separate rooms?

Not under EN 12845; the same compartment is mandatory except for submersible pumps. NFPA is more flexible but keeps the cable protection strict.

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