The most commonly used type of air conditioner pumps in HVAC is the centrifugal pump. One of the most common ways to classify them is the type of impellers in the pump, as this determines how efficient the pump is. Some common impeller types include:
Centrifugal pumps with open impellers have vanes that are attached only to the hub only but are not enclosed by any shroud or sidewall. These vanes are mounted directly onto the shaft. They are relatively inexpensive to produce, but are weak and require more pressure at the suction port of the pump. Their relative structural weakness makes them better suited for use in smaller, inexpensive pumps that handle suspended solids.
Partially open impeller
Open impellers have a shroud that structurally reinforces the vanes and makes them less vulnerable to wear and tear. They are often used for medium-sized pumps that handle liquids that contain suspended solids.
Pumps with closed impellers have both a back and front wall that maximises the structural integrity of the vane. They are used for large pumps and require a low amount of suction port pressure. Due to their durability, they are the most widely used impeller type for centrifugal pumps that handle clear liquids.
Centrifugal pumps also have different numbers of impellers and are also classified according to their number. These include:
Single stage centrifugal pumps have only one impeller and are used for applications that require low-to-moderate rotation speeds.
Multi-stage centrifugal pumps use two or more impellers and are used in applications that require moderate-to-high rotation speeds. In essence, each impeller of the pump is a separate pump by itself, although all the stages are contained within the same pump housing.
When selecting a centrifugal pump, it is important to take note of the type of liquid that the pump is expected to handle and choose the appropriate pump based on the type of impeller it uses. Proper selection of the pump is key to ensure that your HVAC system runs as smoothly and efficiently as possible.