Centrifugal pumps are one of the fundamental parts of a closed-loop system to circulate a medium (water, glycol, etc.) throughout a building for typically heating and cooling purposes. A closed-loop system can contain multiple pumps, but it does not necessarily mean they should be running together. For example, two-pump system designs can have pumps operate in the following:
two pumps are to run individually or together
one pump operates while the other pump is a spare
lead-lag configuration.
A multi-pump system designed to run together have the pumps configured in either a series (in-line) or parallel configuration to achieve different capacities. A series system increases the head capacity while a parallel system increases the flow rate. These setups can be beneficial for better capabilities.
Multiple pumps runnings at the same time could be detrimental to a system if not designed with that intention. Pump systems designed for one pump to operate and the others as spares or standby may not have taken into consideration of other pumps running simultaneously. All pump motors and impellers in that system may not be identical, and might not be able to handle the possible increase in resistance. This improper operation will lead to decreased pump reliability and lifespan.
Understanding the pump system design can improve the overall reliability and performance of the equipment. Improperly running a system can lead to lead to costly repairs and replacements.