EN 12845 Diesel Pump Weekly Exercise Test

How the weekly routine is actually done: the 20 minute run, pressure, oil and temperature monitoring, the log book, and why the "five minute nudge" is a non-conformity.

Reviewing weekly maintenance records at a logistics warehouse after commissioning, one thing stood out immediately: every line in the log book said the diesel pump was "run, OK" — with no running time. Talking to the operator, the picture emerged. A small screwdriver was pushed into the pressure switch, the pump turned for five minutes, then shut down and the book signed. It had been done that way for years. Had we been slower to act, at the first real alarm the diesel would either not have started at all, or would have seized within ten minutes on a cold, unlubricated block.

The weekly routine in EN 12845 is the living part of a sprinkler installation. However correct the design and however clean the installation, if the diesel engine is not exercised every week the pump room stays a mock-up. This article covers the correct method, what each parameter is measured for, and the errors most often seen on site.

What the standard requires

The weekly user routine is defined as two separate tests: first an automatic start on falling pressure, then a 20 minute run and a manual restart.

Automatic pump start test:

• Fuel and engine oil levels checked on diesel engines.
• The water pressure at the starting device reduced, simulating the automatic start condition.
• When the pump starts, the starting pressure checked and recorded.
• Oil pressure checked on diesel pumps, and cooling water flow observed on open circuit cooling systems.

Diesel engine restart test:

• The engine run for 20 minutes, or the period recommended by the supplier. It is then stopped and immediately restarted with the manual start button.
• Water level checked in the primary circuit of closed circuit cooling systems.

Throughout the test, oil pressure, engine temperature and cooling flow must be monitored continuously, with a visual inspection for oil, fuel, coolant and exhaust leaks. That detail is written into the standard — the operator must stand by the machine during the test, not go for tea.

Why 20 minutes? The oil and block regime

Oil viscosity in a diesel engine is high when cold; rings, bearings and the injection pump run partly dry in the first minutes. Turning a cold engine for five minutes pushes oil only as far as the cylinder head; the engine stops before the crank bearings have built a full oil film. The purpose of a proper exercise run:

• Oil film formation: the hydrodynamic film settles fully in all bearings only after 15–20 minutes.
• Coolant circulation: the thermostat opens at 75–85 °C; before that the coolant does not leave the engine and the block heats unevenly.
• Battery recharge: the alternator runs near its ceiling for the first ten minutes, and returning the amps drawn by cranking takes about twenty.
• Fuel system air purging: small air pockets in the fuel line clear themselves only with the engine at operating speed.
• Exhaust moisture: water vapour from combustion condenses in the exhaust during a cold start; twenty minutes at temperature dries it out. Otherwise the silencer corrodes from the inside.

The standard says 20 minutes or the supplier's recommendation. Engine suppliers commonly recommend 30 minutes, because their own curves show full operating temperature at 25–28 minutes. So the common "minimum 30 minutes" practice does not conflict with the standard; it is a more cautious reading of the supplier's-recommended-time provision.

The test line and flow during the weekly test

A frequently confused point: the weekly test is run without flow. The pump is started by reducing pressure at the test valve; there is no flow outlet and the pump runs at minimum flow — either shut head or the supplier's minimum continuous flow. The full load flow test belongs to the annual routine, through a test line connection coupled to the pump delivery branch downstream of the pump outlet non-return valve.

Even so, the test line must be ready in the pump room during the weekly test. If the supplier does not permit 20 minutes at minimum flow, the flow loop valve may need to be partly opened, with water routed through the sight glass back to the tank refill line. The continuous minimum flow figure is always in the supplier's catalogue; running below it at shut head raises rotor temperature quickly and burns the seal housing.

Parameters measured and recorded

Parameter	Typical range	Note
Automatic start pressure	0.5–1.0 bar below system operating pressure	Recording is mandatory
Pump discharge pressure (closed)	Shut-off head from the curve, typically 1.2–1.4 × duty point	Supplier curve
Oil pressure at operating speed	2.5–5.0 bar depending on engine type	Required check
Coolant temperature	75–90 °C at temperature	The thermostat must open
Fuel tank level	At least 50 %, with capacity for 6 hours of running	Required check
Battery voltage (off load)	≥ 12.4 V (12 V) / ≥ 24.8 V (24 V)	Monthly electrolyte check separately
Cooling water flow (open circuit)	Above the supplier's minimum, visually confirmed	Required check
Oil / fuel / exhaust leaks	None	General inspection for leakage
Running after manual start	Starts first attempt, stable idle	Restart test

Authorised personnel and the log book

The installer must leave the user a documented inspection and checking procedure, covering emergency manual pump starting, what to do on a fault, and the detail of the weekly routine. Typical shortfalls on site:

• Unauthorised personnel: everyone from cleaners to security enters the fire pump room, and whoever is on shift that day runs the test. The procedure should be signed off for a trained person, usually the mechanical technician.
• A squared notebook behind the door instead of a log book: a signed and dated report is required for each inspection. Weekly records deserve the same rigour as the annual report.
• Writing only "OK": without the numerical values, the trend over a period — falling oil pressure, a tiring battery, coolant loss — stays invisible. A meaningful log is a numerical log.

The most common field errors

1. Running five minutes and shutting down. A non-conformity, and the first item an insurance surveyor notes.
2. The wrong discharge route during the test. A pump forced to run at shut head burns its seal and shaft bearing. Have the supplier's minimum flow figure to hand.
3. Skipping the manual restart. The standard requires stopping and immediately restarting manually. On site the operator stops the pump and walks away, so the manual start button goes untried for years. If the automatic circuit has failed, the pump then never starts at a real alarm.
4. Testing one battery instead of two. Two separate battery sets are required on a diesel engine. Only ever exercising set A lets set B sulphate quietly. Alternate them.
5. A fuel valve left closed. If the fuel valve is left half shut after maintenance, the pump runs five minutes and stops as fuel starves. "Fuel valve fully open" belongs on the end-of-test checklist.
6. Coolant consumption not reported. On open circuit cooling, a 30 minute weekly test consumes roughly 100–300 L of water, which must return either to the drain or to the refill loop. Otherwise the tank level drops silently.
7. The test bypass valve left closed. Forgetting to reset the test valve or pressure switch line after the test leaves the system apparently pressurised while the pressure circuit is broken, so the pump will not start at a real alarm. The system must be returned to proper operational condition.

Comparison with NFPA 25

The equivalent on the NFPA side is NFPA 25, Inspection, Testing and Maintenance of Water-Based Fire Protection Systems. Some differences:

• NFPA 25 requires a 30 minute weekly diesel run; EN 12845 sets a 20 minute minimum. The EN lower bound is looser; NFPA states 30 from the outset.
• NFPA 25 requires the annual full load flow test at three points (churn, rated, 150 % of rated); EN 12845 says full load condition without explicitly imposing three points, though good engineering practice is the same.
• Alternating battery testing exists in NFPA too; in EN 12845 it is combined with the monthly electrolyte check.

Both standards share the same philosophy on weekly exercise: a diesel engine left standing will not run when it is needed.

Turkish context

BYKHY treats EN 12845 and NFPA 13 as equally valid references for sprinkler installations, and for maintenance refers to the periodic tests required by the relevant standard. In practice, fire brigade inspections ask for two documents:

• The fire pump room log book, with the last twelve months of weekly records.
• The annual full load flow test report from an accredited body.

Insurers require full compliance with the inspection and maintenance clauses before granting a sprinkler discount. That discount — typically 20–50 % — disappears along with the claim if the weekly tests are incomplete. Explaining that is the fastest way to make a building owner understand why the diesel must run for 30 minutes.

Practical weekly checklist

1. Open the pump room, put the log book on the desk, pen ready.
2. Record every gauge reading: system pressure, jockey discharge, main pump head.
3. Record tank levels: main, jockey, diesel fuel.
4. Visually confirm all main stop valves are in the open position.
5. Sound the water motor alarm for at least 30 seconds.
6. Test the electric pump first if there is one, then the diesel.
7. Open the diesel test bypass valve to drop the pressure at the switch; the pump starts automatically and the starting pressure is written down.
8. For 20 minutes — 30 if possible — monitor oil pressure, water temperature, cooling flow and battery voltage, and walk around the engine looking for leaks.
9. Stop the engine. Press the manual start button immediately; it should start first time and settle to a stable idle.
10. Let the pump cool for 5–10 minutes, close the test bypass valve, return the system to normal operating condition.
11. Enter in the log: date, time, name, signature, all numerical values and any abnormality observed. If there is none, write "none", not "OK".

Frequently asked questions

How long must the diesel pump run?

20 minutes, or the supplier's recommended period. On site at least 30 minutes is usual, because the block and oil only reach operating temperature after that.

Is there flow through the test line during the weekly test?

No. The weekly test starts the pump by pressure drop at the test valve, with no load applied. The full load flow test through the test line is part of the annual routine.

Is five minutes enough?

No. Five minutes on a cold diesel proves only that it turns; it does not bed the rings, bring the oil to temperature or recharge the battery. The standard requires 20 minutes, and a shorter test is a non-conformity however often it is logged.

What should the log book contain?

Date, tester's signature, the pressure at which the switch operated, pump discharge pressure, engine temperature, oil pressure, battery voltage, fuel level, running time and any abnormality. A documented inspection and checking procedure must be handed to the user.

If it started automatically, does it also need a manual stop and restart?

Yes. The automatic start on falling pressure is verified first; then after the 20 minute run the engine is stopped and immediately restarted with the manual button, proving both circuits are healthy.

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