A smaller pump used as a supplemental pump in booster applications. Its purpose is to take over in low consumption periods and thus contribute to lower the energy consumption of the booster as a whole.
A pilot pump takes over the operation from the main pumps in periods when the consumption is so small that the stop functions of the main pumps are activated. The pump is smaller flow-wise than the main pumps, but is often able to supply higher pressure in order to ensure that the pressure in low consumption periods does not go below the system’s set point.
A pilot pump is often used to optimise energy consumption of a booster set. If an application has a consumption profile with continually flow in low consumption periods, it is often more economical to have a small pump running than starting and stopping the larger main pumps.
A compact solution
A pilot pump also has the benefit of reducing the needed size of the diaphragm tank, since the diaphragm tank is sized after the pilot pump thus reducing the footprint of the system as well as the amount of stored water.
When to use pilot pumps
Pilot pumps are, as mentioned, often used in booster application where the consumption profile has large periods with low flow, i.e. in residential buildings where flow rate at night is very low.
The need for a pilot pump has to be assessed for each application. Typically it should be considered when the main pumps’ size exceed 5.5kW, but it also depends on how well the main pumps of the booster system perform in low consumption periods.