This pump setup allows the ability to add or subtract flow capacity.
Grundfos
01/29/2019
Many of today’s pumps are installed to operate under variable flow conditions, so understanding the concept of parallel pump control is a must. First, it is critical to know how parallel pumps will operate upon installation. The idea behind parallel connected pumps is the ability to add or subtract flow capacity and/or provide redundancy. Image 1 shows three parallel connected pumps. For the purpose of this discussion, assume they are each of equal capacity. The pump head-capacity curves are shown in Image 2.
![Three parallel connected pumps and pump head-capacity curves](/sites/default/files/0119/Grundfos0119-diagram-1_2.jpg)
![System curve starts at zero flow/zero head and head required in system is constant](/sites/default/files/0119/Grundfos0119-diagram-3_4.jpg)
![Realistic control curve and control curve does not intersect head capacity curve for Pump 1N](/sites/default/files/0119/Grundfos0119-diagram-5_6.jpg)
![Operating range when variable speed drives are used for pump control](/sites/default/files/0119/Grundfos0119-diagram-7.jpg)