A twin pump is a circulating pump consisting of two separate centrifugal pumps in a common pump casing and a spring-loaded change-over flap located in the discharge nozzle. A twin pump can be used for parallel operation (additional pump start-up in case of peak load) as well as for single-pump operation (one pump on stand-by). For this reason it is particularly suitable for hot water heating systems (e. g. circulator pump) in which a stand-by pump which can be started up at any time is required to comply with safety regulations or to provide a higher level of comfort.
In this case one centrifugal pump serves as the duty pump and the other as the stand-by pump.
Electrical switchgear ensures that the stand-by pump is started up immediately in the event of a duty pump failure. The necessary shut-off elements (see Valve) for the change-over are integrated in the pump set.