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
Both share one aim: no protective device may stop the pump during a fire. There is no overload (thermal) protection in the pump controller. EN 12845 achieves this through its stopping rule: once started, the pump runs until stopped manually (10.7.5.2). 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) | No fuse requirement in the EN 12845:2015+A2:2026 text; the pump is stopped manually only (10.7.5.2) |
| Fuse carrying starting current | Branch circuit approach | No requirement in the EN 12845:2015+A2:2026 text |
| 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 | Electric: at nominal capacity within 15 s (10.8.1.3); diesel: referred to EN 17451 (10.9.1) |
| Automatic shutdown | Prohibited; where permitted, a 10 min timer | Prohibited; manual stop only (10.7.5.2) |
| Pressure switches | Sensing line per controller | Two switches per pump set; either one starts the pump (10.7.5.1) |
| Diesel battery sets | Two sets, alternating | No requirement in the EN 12845:2015+A2:2026 text; diesel pump sets referred to EN 17451 (10.9.1) |
| Diesel cranking attempts | About 15 s crank / 15 s rest | No requirement in the EN 12845:2015+A2:2026 text; referred to EN 17451 (10.9.1, 10.9.3) |
| Fuel tank | By hazard and duration; dedicated tank | No duration in the EN 12845:2015+A2:2026 text; referred to EN 17451 (10.9.1) |
| Weekly test duration | 30 minutes | Diesel: 20 minutes or the time recommended by the supplier (20.2.2.5) |
| Annual full load test | 3 points (churn, rated, 150 percent) | Nameplate values at full load; 3 points not imposed (20.3.4.2.1) |
| Overload flow point | At least 65 percent of rated pressure at 150 percent flow | No such characteristic in EN 12845:2015+A2:2026; pumps conform to EN 17451 (10.1), and for pre-calculated HHP/HHS the nominal flow and pressure conform to 7.3.2 (10.7.2) |
| Closed valve pressure | Must not exceed 140 percent of rated | 12 bar limit at equipment connections, except during testing (8.2.1) |
| Pump room fire resistance | Separation; AHJ dependent | At least 60 minutes; used for fire protection only (10.3.1) |
| Pump room temperature | Engine manufacturer's limit | Minimum: electric 4 °C, diesel 10 °C (10.3.3) |
| Controller and motor in one room | May be separate; the controller must be within sight of the motor (visible, not more than 15 m; 10.2.1, 3.3.32), with a glazed opening recommended if outside the pump room (A.10.2.1) | No requirement in the EN 12845:2015+A2:2026 text; 10.8.5.2 requires monitored conditions to be indicated in the pump room |
| Cabling | NFPA 70 Article 695 protected route | Flame retardant cable on a protected route, otherwise E 90 fire-resistant cable (10.8.2) |
| Pressure maintenance (jockey) pump | Separate; a fire pump may not be the jockey | Sized so that it cannot supply the flow and pressure of a single open sprinkler (10.6.2.5) |
The three rows most often misread
- Weekly test duration. NFPA 25 states 30 minutes from the outset; for diesel engines EN 12845 says "20 min, or the time recommended by the supplier" (20.2.2.5). 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.
- Fuel volume. EN 12845:2015+A2:2026 does not give a fuel duration in its own text; 10.9.1 refers to EN 17451. NFPA ties the duration to system demand. On a mixed project, always take the larger.
- Controller and motor in the same room. The EN 12845:2015+A2:2026 text has no requirement on this; 10.8.5.2 requires each monitored condition to be indicated individually in the pump room, and pump sets are referred to EN 17451 by 10.1.
The mixed-project rule: where NFPA 20 and EN 12845 are both required, apply whichever is stricter in each row. If the insurer also requires FM DS 3-7, a third layer arrives: FM Approved pumps, drivers, controllers and relief valves only.
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. Overload protection is deliberately absent: EN 12845 (10.7.5.2) requires the pump, once started, to run until stopped manually. 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. For diesel engines EN 12845 asks for 20 minutes or the time recommended by the supplier (20.2.2.5); 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 12845:2015+A2:2026 does not state a fuel tank duration in its own text; for diesel pump sets 10.9.1 refers to EN 17451. NFPA ties the duration to system demand; on a mixed project take the larger.
Can the controller and motor be in separate rooms?
The EN 12845:2015+A2:2026 text has no requirement on this; pump sets are referred to EN 17451 by 10.1. NFPA 20 requires the controller to be as close as practical to the motor and within sight of it (visible and not more than 15 m away) (10.2.1, 12.2.1 for diesel, 3.3.32); if the controller must be outside the pump room, it recommends a glazed opening in the pump room wall to observe the motor and pump during starting (A.10.2.1).
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Download MEP Calc on the App StoreNFPA 20 Standard for the Installation of Stationary Pumps for Fire Protection (2025). EN 12845:2015+A2:2026 pump clauses. EN 17451 (sprinkler pump sets). FM Global DS 3-7. Values are for information only.