Circulating pumps are centrifugal pumps that generate a forced circulation in a closed system. They are particularly widespread as heating circulators in heating systems for hot water: The warm water is supplied to the radiators to heat to rooms being supplied while the cooled-off water is returned to the heating system at the same time where it is heated again. In swimming pools, circulating pumps are used for operating the filter unit. In industrial installations, circulating pumps are also used in heat transfer systems or in reactor circuits.
Heating systems originally used uncontrolled circulating pumps whose output could not be adjusted. Besides high energy costs, they frequently caused an undesired pressure increase, which resulted in additional energy loss. Up-to-date energy-saving circulating pumps, on the other hand, feature an electronic control, so that their energy consumption can be reduced significantly.
When used in industrial environments, a distinction can be made between circulating pumps with and without shaft seal as well as circulating pumps with special designs. Pumps with a shaft seal are generally designed as a horizontal pump, that is, with horizontal shaft. They are used in systems up to a pressure of approx. 100 bar. Circulating pumps without shaft seal are generally vertical pumps, e.g., condensate pumps or shaft-driven submersible pumps. Depending on the requirement, special designs can feature specific sealing systems, protective linings, impellers or other special features.