A pump is a rotodynamic machine that moves fluids by mechanical or electrical action, consuming energy to perform the work. There are so many categories and classifications of pumps, but for HVAC & Plumbing applications, the centrifugal and positive displacement type of pumps are the two most commonly used having essentially the same operating principle. These two types of pumps behave differently regarding the flow rate and pressure head:
• The Centrifugal Pump has varying flow depending on the system pressure or head.
• The Positive Displacement Pump has more or less a constant flow regardless of the system pressure or head.