Benefits of Variable Primary Flow (I-P Version)

[@Sechelanji]

How can you determine and select the delta P across the evaporator in the VPF?

[@mohammedabdullahkhan4264]

Where, we can use variable primary pumps

[@ashpaksheikh1616]

i have a question, as shown in the system bypass water moves back to pump then how pump can deliver lesser flow with VSD. like in primary and secondary system secondary is VSD and remaining water moves back to primary. pls explain

[@johnsoncontrols]

In a VPF system, fluid will only travel through the bypass valve in one direction, forward, as needed. In a primary/secondary system, fluid is free to move in either direction through the bypass pipe. However, as a rule of thumb to maintain system stability, primary flow should always be equal to or greater than secondary flow. In addition, secondary VSD pumps are controlled to speed up or slow down as needed to maintain system stability.

[@ashpaksheikh1616]

Hi , I know the fact what u have explained, My questions was related to primary variable flow system and not primary secondary system. As you explained in VPF system that primary pump works on VSD but when there are 50% load in system 50% water is bypassed from bypass line and pump gets 100%flow again, then how pump works on variable speed as the water flow is 100%available at pump inlet.

[@masterchef6694]

The bypass line is only to ensure that the evaporator does not get starved for return water. If the plant is 50% loaded, the pump will only circulate 50% of design flow. Bypass will come into the picture when flow reduces to less than 30% of design flow.