NFPA 20 requires that a fire pump be driven by either an electric motor, diesel engine or steam drive. The electric motor is the most common driver used for fire pumps. It can be supplied with either three-phase or single phase power, depending on the needs of the building.
The diesel engine is most often used in situations where there is no electric motor backup and the building must have a redundant system due to seismic zones, height or other requirements. The diesel engine can be provided with a variety of power sources, including emergency generators.
Diesel engines are more expensive to install and operate than electric motors, however they can be more reliable since they are not susceptible to power outages. The diesel engine also can be more resilient to heat generated by the exhaust, and can be operated at higher temperatures than most electric motors.
A diesel fuel tank is required for the fire pump to be able to operate. Typically, the fuel tank is sized to provide at least eight hours of operation at full load capacity.
The fuel tank must be located inside the fire pump room to maintain a constant temperature and to protect the fuel from contamination. The fuel tank must be protected from freezing and must have a dedicated fill, vent and visual fuel gauge. NFPA 20 also requires that the normal source of power for the diesel fuel tank must be capable of supplying locked rotor current. This may be up to six times the full load amperage of the engine.Diesel Fire Pump