Fire Pump Controllers: ATS, Jockey Sequencing, and NFPA 20 Rules

The fire pump matters — but the controller matters just as much. A badly configured control sequence leads to unnecessary pump runs, pressure fluctuation or, in the worst case, no start at all during a fire. NFPA 20 Chapter 10 defines controller requirements in detail. This article outlines the typical architecture of electric, diesel, and jockey controllers.

Three Controller Types

• Electric fire pump controller: starts the electric main pump and manages the generator connection through the ATS.
• Diesel fire pump controller: cranks the diesel engine and supervises two separate battery banks (FM DS 3-7 2.4.24.1 also requires two separate starting batteries per engine).
• Jockey pump controller: starts and stops the jockey pump automatically.

Pressure Sensing

Controllers read system pressure via a pressure sensor or pressure switch. FM DS 3-7 2.4.11.1 requires each pump (including the jockey) to have its own sensing line. NFPA 20 expects:

• Adjustable start/stop setpoints
• Dual redundant sensors on new installations
• Pressure recording for at least 7 days (NFPA 20-2025 10.5.2.1.8.4)

Start Sequence

A typical staged start works like this:

1. Pressure normal, system idle; pumps on standby.
2. At a 10 psi (0.7 bar) drop the jockey starts and makes up small leaks.
3. After a further 15 psi (1.0 bar) drop (25 psi / 1.7 bar in total) the main pump starts. FM DS 3-7 2.4.11.6 recommends a tighter band: the fire pump starts 5–10 psi below the jockey start point.
4. Electric pump first; if it cannot restore pressure, the diesel pump starts at its own setpoint 10 psi lower (10 psi decrements for each additional pump, FM DS 3-7 2.4.11.6). The ATS does not switch between pumps — it switches the electric pump's power sources.
5. Stop: primarily manual. NFPA 20-2025 permits automatic shutdown only during automatic testing or where approved by the AHJ (10.5.4.2); FM DS 3-7 2.4.10.1 calls for manual stopping.

ATS (Automatic Transfer Switch)

On electric pumps, the ATS transfers automatically between two power sources:

• Primary: utility power
• Secondary: generator or a second utility feed

Transfer must take no more than 10 s. The fire pump ATS must be a separate unit from the building's general ATS, with bypass authority kept in the controller itself.

Monitoring Signals

The controller must send the following signals to the fire alarm panel:

• Pump running (run)
• Pump fail (alarm)
• Power loss (supervisory)
• Controller switch in manual (supervisory)
• Phase reversal (electric only)

Diesel-Specific Rules

• Two separate battery banks; if one is out of service, the controller must raise a supervisory alarm.
• Fuel level below 67% triggers a supervisory alarm.
• Weekly automatic 10-minute run test; FM DS 3-7 2.4.9.1 requires personnel to attend it.
• Engine coolant temperature is monitored continuously.

Common Issues (Turkey)

1. Jockey runs constantly: a small system leak goes unnoticed by maintenance and the jockey eventually burns out.
2. Main pump set to auto-stop: NFPA 20-2025 permits automatic shutdown only during automatic testing or where approved by the AHJ (10.5.4.2); FM DS 3-7 2.4.10.1 calls for manual stopping.
3. ATS never tested: skip the weekly test and the first serious outage reveals that the pump does not start.
4. Phase reversal alarm disabled: with phases swapped the pump runs backwards; some sites disable this alarm "to stop the noise", which is a very dangerous habit.

Conclusion

The controller is as critical as the pump. Even with flawless mechanical work, one mistake on the electrical side means the system does not run in a fire. NFPA 20 Chapter 10 rules on start-stop, ATS, and monitoring are minimums; don't skip them in design.

Pump controller schedule in MEP Calc

Weekly test calendar, ATS check, alarm setpoints, and log book.

View on App Store

SprinkCalc — Fire Sprinkler Design Across Three Standards

SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report. One of the few tools that unifies all three major fire protection standards.

Download SprinkCalc on the App Store