1. When to use a diesel engine fire pump
NBR 13714 and São Paulo IT 22 accept a centrifugal fire pump driven by an electric motor or a combustion engine. IT 22 requires at least one electric or internal combustion pump when the supply relies on a pump, used for that purpose only. Neither rule makes diesel mandatory by occupancy type: the drive follows from the available energy, the pump’s role in the system and what the approved design and the purchaser require.
In Goiás, CBMGO NT 22 sets the minimum number of pumps by function. A booster arrangement is one main pump with a backup power source; a fixed arrangement is two pumps, main and standby, the standby with a backup power source, and a jockey pump may also be needed. In low-hazard buildings, with a fire load up to 300 MJ/m², a fixed arrangement may omit the standby pump, and the main pump then has the backup power source.
Main and standby pumps do not run at the same time: with the standby running because of a power failure, the electric main pump does not start when power returns.
The backup power source may be a generator or another source, such as batteries, and NT 22 allows it to be omitted when the pump has an internal combustion engine. In São Paulo, IT 22 allows the electric pump to be fed by a diesel generator when utility power fails, with a supply independent of the general load; in a medium-voltage facility with a safety generator, the supply may be connected ahead of the building’s main low-voltage switch.
A generator and a diesel pump set handle a power failure in different ways: with a generator, the pump remains electric; with a diesel pump set, the pump’s engine has its own fuel tank, starting batteries and control panel in the pump room.
For a quotation, state the jurisdiction and the contract standards, the pump role (main, standby or booster), the flow and pressure from the design report, the suction condition and the altitude and temperature of the pump room.
FB Bombas builds the FBFS diesel set, with a diesel engine-driven main centrifugal pump, a jockey pump and a dedicated controller, and the FBFS electric + diesel set, with one pump per drive and controls for each; the role of each pump comes from the fire protection design.
2. Fuel tank: NFPA 20, IT 22 (São Paulo) and NT 22 (Goiás)
Since the 2022 edition, as worded by TIA 22-1, NFPA 20 sizes the tank for at least 12 hours of engine run time, based on the fuel consumption in the engine manufacturer’s published data, plus 5% of volume for expansion and 5% for the tank sump. When engine consumption is not known, the minimum capacity is 1 gal/hp (5.07 L/kW), with the same 5% and 5%.
The 8 hours still seen in specifications come from the former rule: the NFPA 20 annex explains that 1 gal/hp is equivalent to 1 pint/hp (0.634 L/kW) per hour for 8 hours. In the revision that introduced 12 hours, the technical committee justified the change by the requirement to refill the tank when it reaches 66% of capacity, which preserves 8 hours of engine run time.
The same annex recommends a reserve fuel supply, with means of transfer to the main tank, where prompt replenishment is unlikely.
In São Paulo, IT 22 requires enough fuel to keep the pump set at full load for at least twice the operating time of the water supplies of each system in the building, with the tank installed to the manufacturer’s specifications; NBR 13714 contains the same rule.
In Goiás, NT 22 ties the volume to the minimum autonomy of the pumps at full load, which depends on the fire load: 2 hours up to 1,200 MJ/m², 4 hours from 1,200 to 2,400 MJ/m² and 6 hours above 2,400 MJ/m². Under all three rules, the tank sits over a containment basin of at least 1.5 times its capacity.
With more than one combustion engine, each has its own tank and its own supply piping to the injection pump (IT 22, C.3.7; NT 22, C.5.7; NBR 13714, B.3.7). In the proposal, the tank calculation should show the consumption from the selected engine’s data sheet, the time required by each applicable rule, the resulting usable volume, the expansion and sump allowances when NFPA 20 applies and the volume of the containment basin.
Warning
When the contract requires NFPA 20 and the site is in São Paulo or Goiás, the tank must meet both rules at once, and the larger volume governs. Calculate with the consumption on the selected engine’s data sheet, never a generic figure, and do not confuse nominal capacity, usable volume and autonomy.
3. Starting: two battery sets, dual charger and alarms
The engine batteries are kept in the pump room and held charged by automatic float charging from a dual battery charger; IT 22 requires them to sit on suitable racks.
The float system serves the two battery sets, main and standby, independently, and recharges a discharged battery within 24 h without damaging its plates, with ammeters and voltmeters showing the state of charge of each set (IT 22, C.3.10 and C.3.11; NT 22, C.5.10 and C.5.11; NBR 13714, B.3.10 and B.3.11). Battery voltage and capacity come from the engine manual, not from a standard value.
The alarm panel of an internal combustion pump has a push button to start the pump manually and visual and audible signals for at least panel energized, pump running, low battery charge and switch in manual position or panel off (IT 22, C.1.16.2; NBR 13714, B.1.14.2); NBR 13714 requires this panel where there is constant supervision.
Inside the pump room, a control panel indicates pump running and automatic system off, with the selector switch in the manual position (IT 22, C.3.9).
Where there is a single fire pump driven by a combustion engine, starting is always automatic (IT 22, C.3.12; NT 22, C.5.12). Once started, the pump is stopped only manually, at its control panel in the pump room; automation includes at least one manual start point in a safe, easily accessible location, and the pumps reach full operation about 30 s after starting (IT 22, C.1.6, C.1.7 and C.1.9).
4. Engine: speed control, power and continuous operation
The engine has a speed controller that holds rated speed within a 10% band at any load, and manual operating means, preferably on the engine itself, that always return to the normal position (IT 22, C.3.1.4 and C.3.1.5; NBR 13714 writes the band as ± 10%). The rules require the controller without specifying whether it is mechanical or electronic: the type follows from the selected engine and the contract standard.
The set must be able to run at full load, at the installation site, for 6 h without interruption and without damage (IT 22, C.3.2; NT 22, C.5.2; NBR 13714, B.3.2). For that reason, engine power is checked under pump room conditions, including altitude, air temperature and the type of air intake, natural or turbocharged (C.3.1.3), and not only at the pump’s rated point.
The engine nameplate states manufacturer, type, model, serial number, power in CV (metric horsepower) for continuous duty and rated speed (IT 22, C.3.8). The pump nameplate, which IT 22 describes in its section on electric motor-driven pumps (C.2.15), gives manufacturer, serial number, model, rated flow and pressure, operating speed and impeller diameter. At delivery, check that the nameplate data match the data sheet and the approved design report.
The main pump is coupled directly to the engine through a flexible coupling, with no belts or chains, with an isolation valve upstream and a check valve and an isolation valve downstream (IT 22, C.1.5; NT 22, C.1.6). In the proposal, request the pump curve, the engine data sheet with continuous-duty power and fuel consumption, and the base, coupling and panel arrangement.
5. Testing: fortnightly under NBR 13714, weekly under NFPA 25
NBR 13714 requires the fire pumps, with all their accessories and alarm devices, to be operated fortnightly for at least 15 min; audible alarms may be silenced right after they activate. The periodic inspection takes place at intervals of no more than three months, and carrying out the maintenance plan, prepared by the designer, should not take longer than one year.
In São Paulo, the sample commissioning and periodic inspection report in Annex F of IT 22 includes a statement that the owner or the person responsible for the building’s use is aware of their responsibilities for maintenance and periodic inspections under NBR 13714.
NFPA 25 covers the inspection, testing and maintenance of water-based fire protection systems and should not be confused with NFPA 20, the installation standard. For a diesel pump, it requires a weekly no-flow (churn) test with the engine running for at least 30 minutes; the start is automatic, by draining the sensing line to simulate a pressure drop, not by the panel push button; the standard allows an automatic timer that drains the pressure control line through a solenoid valve.
The frequency may be extended through an approved risk analysis, and qualified personnel attend the run unless automated testing is performed as the standard allows.
In the NFPA 25 test, observe the cranking time and the time to reach running speed, follow oil pressure, speed and water and oil temperatures, and check cooling water flow through the heat exchanger. Record suction and discharge pressures and the starting pressure read at the pressure switch or transducer, monitor the discharge water temperature and shut the pump down if needed to prevent overheating.
At acceptance, NBR 13714 tests the automation at the control manifold, including the pressure switch settings of the jockey and main pumps and alarm operation, and starts the pump from the manual start point to stop it at its own panel; the procedure is completed, performed and signed by a legally qualified professional.
Periodic inspection reports are signed by the person responsible for the system and by the operational manager of the protected area, with the period’s corrective maintenance attached (NBR 13714, 5.10.1, 5.10.2.1 and Annex C).
Engineering note
Build the plan from all applicable rules together. In São Paulo, under a contract that adopts NFPA 25, the diesel pump runs the NFPA 25 weekly test of at least 30 minutes; with accessories and alarms included, that test also covers the fortnightly 15 min operation of NBR 13714. Record each test for comparison with the commissioning values.
6. Pump room: temperature, cooling, air and exhaust
The combustion engine is installed in a space whose temperature is never below the manufacturer’s recommended minimum, or it is fitted with permanently energized preheating (IT 22, C.3.1; NT 22, C.5.1; NBR 13714, B.3.1). The pump room provides access all around the pumps, space for any local maintenance on the pumps and the panel, and room to remove any pump completely (IT 22, C.1.2).
The rules accept four cooling systems: direct water injection from the pump into the engine block, to the manufacturer’s specifications, with the cooling water outlet rising at least 15 cm above the block and ending where the discharge can be observed; a heat exchanger, with cold water supplied directly from the pump intended for that purpose and pressure limited by the engine manufacturer; a radiator on the engine; and fans or a blower.
With a radiator or fans, the fan is driven directly by the engine or by multiple belts (IT 22, C.3.3.1 to C.3.3.4; NT 22, C.5.3.1 to C.5.3.4; NBR 13714, B.3.3.1 to B.3.3.4).
Cooling is by air or water, without compressed air, and combustion air intake may be natural or turbocharged, with a suitable filter on the air inlet (IT 22, C.3.1.2, C.3.1.3 and C.3.4). On the pump room drawing, show the combustion and ventilation air inlets and outlets, and confirm with the engine manufacturer the airflow the selected arrangement requires.
The exhaust has a silencer to the manufacturer’s specifications and discharges the gases outside the pump room, with no chance of returning inside (IT 22, C.3.5; NT 22, C.5.5). Fire pumps are not installed in a room with any other type of machine or engine, except those serving fire protection systems (IT 22, C.2.5; NT 22, C.1.18).
IT 22 limits the exception to systems that use water as the extinguishing agent and also allows the building’s domestic water pumps in the same room.