EN 12845 Pump Controllers and Monitoring

Two independent pressure switches, the manual-only stop rule, the alarm matrix, and the typical errors in BMS integration.

Commissioning a logistics warehouse, the electrician had wired the pump to a single pressure switch and added an automatic stop after 30 seconds through the PLC — on the reasoning that "if the fire goes out it stops, so the pump doesn't run for nothing". From an EN 12845 perspective that is two offences at once: a single switch and an automatic stop. This article covers what the pump controller must do, what it must not do, and how the alarm matrix connects to the BMS.

Two independent pressure switches

The standard is explicit: two pressure switches shall be provided for each pump set. The pipe from the trunk main to the switches must be at least 15 mm in diameter, and the connection arranged so that the pump starts when either switch closes — an OR circuit. If one switch fails, its contact welds, or its connecting pipe blocks, the other still does its job.

The site error: connecting both switches to the same tee. A blockage in the common connection then disables both. The correct arrangement takes two separate small pipes from the trunk main, one to each switch. Each switch must also be individually testable; where an isolating valve is fitted for that purpose, a check valve is mandatory in the parallel line, so that a pressure drop still reaches the switch with the valve closed.

The first pump starts when trunk main pressure falls below 80 % of the closed valve pressure. In a two-pump arrangement, the second pump must have started before pressure reaches 60 %. Those two thresholds do not come from the same switch pair; each pump has its own pair, set in stages.

Manual-only stop — why is automatic stopping prohibited?

The standard states that once the pump has started, it shall continue to run until stopped manually. The pump controller's third basic function is stopping the motor only by manual action. For diesel, the same rule is repeated with an addition: engine monitoring devices may not be arranged to stop the engine.

The logic is two-layered. First: whether the fire is out is decided by the firefighter on site, not by a pressure switch. After a sprinkler opens, pressure may recover momentarily — a closed compartment pressurises, say — while the fire continues. Second: a diesel engine continuing to run with falling oil pressure or rising water temperature is better than one that stops and delivers nothing. So engine monitoring devices raise alarms; they do not make shutdown contacts.

In practice: once the pump has started, the only way to stop it is the red stop button on the controller panel. Neither the PLC, the BMS nor a timer has authority to stop the pump. Any witnessed test that finds an automatic stop circuit produces a red report.

The controller's three basic functions

What is required of an electric pump controller, in one paragraph:

• a) Start the motor automatically on a pressure switch signal;
• b) Start the motor manually from a button on the panel;
• c) Stop the motor only by manual action.

The controller must also carry an ammeter. Unless the pump is submersible, the controller sits in the same compartment as the motor and pump. Contactors must be rated to EN 60947-1 and EN 60947-4 in category AC-3 — capable of motor starting duty, not merely resistive switching.

The supply itself is also governed: the feed to the pump controller must be dedicated to the sprinkler system, taken from the supply side of the main switch where the utility permits, with HRC fuses capable of carrying the starting current for at least 20 seconds. Drawing any other load from that fuse conflicts with the standard.

The four signals that must be monitored

For an electric pump:

• Power available to the motor (all three phases on AC);
• Pump demand (pressure switch closed);
• Pump running;
• Failure to start (signal received but motor not turning).

All four must be indicated visually and separately in the pump room. Pump running and a general fault alarm must additionally be given both audibly and visually at a continuously attended location. The visual fault indication is amber; the audible signal at least 75 dB and capable of being silenced. A lamp test button is mandatory — at monthly maintenance you press it and replace any lamp that fails.

For a diesel pump, four additional signals are required:

• Operation of any switch that takes the pump out of automatic mode;
• Failure to start after six attempts;
• Pump running;
• Diesel controller fault.

In field practice, battery fault (no charger output), low fuel level and an exhaust alarm are commonly added. They are not in the standard's minimum list, but the authority often asks for them.

Alarm types and transmission

The alarm transmission annex divides sprinkler alarms into two classes: Type A (fire alarm) and Type B (technical or fault alarm). Type A demands immediate response; Type B goes to responsible personnel for prompt attention, without automatically calling the fire service. The signals from the pump room distribute as follows:

Signal	Type
Water flow alarm (alarm valve)	A
Trunk main low pressure	B
Electric pump — demand	B
Electric pump — failure to start	B
Electric pump — running	A
Electric pump — no power	B
Diesel pump — automatic mode off	B
Diesel pump — failure to start	B
Diesel pump — running	A
Diesel pump — controller fault	B
Priming tank low level	B

"Pump running" is listed as Type A because if the pump is running, either a sprinkler has opened or a main has burst — both warrant a fire alarm level of response. The annex allows it to be treated as a trouble alarm depending on local conditions, but Type A is the default.

BMS integration: volt-free contacts versus Modbus

Almost every controller panel today can connect to a BMS over Modbus RTU or BACnet. It is an attractive solution, but not sufficient on its own for EN 12845 compliance. The standard requires transmission to a permanently attended location, independent of the sprinkler system's own reliability. An alarm sent to a BMS over Modbus must still be visible when the BMS server is down.

Field practice:

• Primary path: the controller's volt-free contacts wired directly into the fire alarm panel's monitored inputs. The fire panel drives its own monitoring line, so even a broken or shorted cable raises an alarm.
• Secondary path: the same signals sent to the BMS over Modbus or BACnet for information. The BMS gives a good graphic interface, trend tracking and email notification — but EN 12845 compliance rests on the fire panel.

When sending to the BMS, label each signal with its type (A or B); otherwise an operator may read "pump running" as a fault and ignore it. Our recommended configuration: a pop-up requiring no acknowledgement for Type A alarms, and a background list for Type B.

Common errors

• A single pressure switch: the most frequent breach. Even fitting two switches, feeding them from the same tee also breaks the rule.
• An automatic stop circuit: a PLC or timer reasoning "the pump has run for 30 minutes, stop it". Outside the standard.
• Engine monitor wired to engine stop: connecting a low oil pressure signal on a diesel to a shutdown contact. Explicitly prohibited.
• An audible alarm that cannot be silenced: 75 dB is achieved but there is no silence button, so the operator disconnects the cable and the system goes quiet.
• A single supply: the controller fed from the load side of the main switch, so a building power failure takes the pump with it. The supply must come from the supply side.
• Treating the BMS as the sole transmission path: bypassing the fire panel means nobody knows the pump is running when the server fails.
• No lamp test: a lamp that fails during service leaves that signal permanently blind.

Comparison with NFPA 20

NFPA 20 stands in the same place philosophically: automatic start, manual stop. NFPA 20 relaxes the manual stop rule through a minimum run timer — an automatic stop option after at least 10 minutes of running, marked on the controller panel where accepted. EN 12845 offers no such flexibility; manual means manual.

On switch count, NFPA 20 accepts a single pressure switch group with two recording gauges, while EN 12845 requires two independent switches — one of the few points where the European standard is the stricter.

Turkish context

BYKHY references TS EN 12845 for sprinkler systems and adds no provision on pump controllers. At witnessed testing, the technical consultant generally checks in this order: (1) each pressure switch starting the pump independently, (2) manual start and manual stop from the panel, (3) lamp test, (4) the audible alarm above 75 dB and its silencing, and (5) transmission of all four signals to the fire panel over monitored inputs. Where a BMS exists, the same signals are confirmed there too — but the BMS does not replace the fire panel.

Insurance surveys mark the alarm matrix against the annex table item by item; a label plate in the pump room proves local indication, and a mimic diagram in the control room proves remote transmission. Missing either costs points.

Frequently Asked Questions

Why are two pressure switches required?

So that a failed switch, a welded contact or a blocked sensing pipe cannot prevent the pump starting. They are wired as an OR circuit, each from its own take-off on the trunk main.

Why is automatic stopping prohibited?

Because whether the fire is out is a decision for the firefighter, not a pressure switch. A diesel running with a monitoring alarm is better than one that stops and delivers nothing.

Which four signals must be monitored on an electric pump?

Power available, pump demand, pump running and failure to start — all indicated separately in the pump room, with running and general fault also transmitted to a continuously attended location.

Can a BMS be the sole alarm path?

No. Volt-free contacts into the fire alarm panel's monitored inputs are the compliant path; the BMS is a useful secondary layer for graphics and trending.

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.

Download SprinkCalc on the App Store

MEP Calc — 86+ Engineering Calculators

MEP Calc bundles 86+ engineering modules in one iOS app: 21 fire calculations plus heating, cooling, HVAC, plumbing, steam and natural gas.

Download MEP Calc on the App Store