The Role of Split Case Pumps in HVAC Systems

Posted by angroup on December 19, 2023

Heating, ventilation, and air conditioning (HVAC) systems are essential for maintaining comfortable indoor environments in residential, commercial, and industrial buildings. A key component that allows these systems to function properly are pumps, which circulate fluids like water or glycol through the closed loops of piping. One type of pump commonly used in HVAC applications is the split case pump. In this article, we will examine the design, benefits, and appropriate applications of split case pumps within HVAC systems.

What Are Split Case Pumps?

Split case pumps, as their name implies, feature a casing that splits axially to allow access to the inner workings and impeller. The casing is divided into two separate chambers - the motor chamber and the impeller chamber. These chambers are connected via a shaft seal around the pump shaft. Split case pumps use an electric motor to turn an impeller within the casing. As the impeller spins, it generates centrifugal force to pull fluid in through the eye of the impeller and push it out under pressure to the discharge nozzle.

centrifugal split casing pump

Key Components and Operation

The motor provides the rotational force that powers the pump. Motors may use open, enclosed, or sealed fan cooling systems depending on the pump application and liquid properties. The impeller is responsible for moving the fluid by accelerating it radially outward from the eye to the tip of the vanes. Impellers may be single or multi-stage and can be designed in various ways to optimize efficiency based on required pump capacity and head. The volute collects the liquid discharged from the periphery of the impeller and directs it to the pump nozzle outlet. Split case pumps also utilize wear rings to prevent internal recirculation and maintain tight clearances for efficiency. The bearings support the shaft and enable smooth rotation within the pump. Finally, the seal prevents liquid from leaking out along the shaft from the impeller chamber.

Benefits of Using Split Case Pumps in HVAC

There are several important reasons why HVAC designers often select split case pumps for system applications:

  1. Adaptability - They can be easily customized to deliver various head and flow rate combinations by changing internal components like impellers without replacing the entire casing. This versatility enables the pump to meet specific system resistance requirements.
  2. Reliability - Their rugged construction and number of wearing components make split case pumps well-suited for continuous or frequent cycling operation as is often required in HVAC systems. The separable design also allows for convenient maintenance, inspection and repairs when necessary.
  3. Efficiency - They typically offer better hydraulic and mechanical efficiency compared to other types of pumps like end suction, circulator or turbine pumps in the flow and head ranges used in HVAC. High efficiency results in lower utility costs over years of operation.
  4. Low NPSH - The split case design provides strong fluid velocity entering the eye of the impeller. This allows efficient pumping even with positive suction heads as low as 3-5 feet, eliminating nuisance air binding issues.
  5. Quietness - Split case pumps generate less turbulent flow and run quieter compared to horizontally mounted single stage end suction pumps. Reduced noise is often an advantage for indoor mechanical rooms.
double suction centrifugal pump

Typical HVAC Applications

The diversity of flow rate and pressure combinations available with split case pumps makes them well suited for a variety of HVAC pumping applications:

  • Chilled Water Distribution - Split case pumps circulate chilled water from central chillers at up to 8,000 gpm capacity to air handler coils or other cooling equipment. Head requirements are typically below 150 feet. Their high efficiency can significantly reduce chiller system energy usage over thousands of annual operating hours.
  • Condenser Water - In water-cooled HVAC systems, split case pumps move warm condenser water to outdoor cooling towers at capacities up to 20,000 gpm. Their ruggedness handles water treatment chemicals and intermittent tower operation without increased wear.
  • Boiler Circulation - Where larger heating capacities are required, split case pumps distribute hot boiler water to heating coils in air handlers or unit ventilators. Their low NPSH prevents cavitation erosion damage.
  • Glycol Solutions - For low temperature HVAC applications, split case pumps circulate inhibited propylene or ethylene glycol solutions for anti-freeze protection. Their seal designs and materials are compatible with these additives.
  • Domestic Hot Water - In large hotels, hospitals, universities or military bases, split case pumps provide domestic hot water circulation at temperatures up to 200°F. Their high efficiency saves thousands in annual fuel costs.
  • OEM Installations - Split case pumps are commonly installed by HVAC equipment OEMs within large built-up central station air handlers or packaged rooftop units to quietly circulate fluids through cooling and heating coils.

In summary, split case pumps offer significant benefits that make them a common choice for circulating liquids in HVAC applications. Their flexible hydraulic design, high efficiency, reliability and quiet operation translate to lower operating costs over the lifespan of commercial building environmental systems. Engineers would do well to consider split case models when selecting pumps for their next HVAC pumping system design.

Need help selecting the right split case pumps for your HVAC application?
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