5 Key Factors to Consider When Selecting a Condenser Water Pump

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Condenser water pumps circulate return condenser water in open or closed loop systems. These pumps can be electric or engine-driven.

In closed-loop systems, static head losses must be considered, including pressure loss in the piping system, piping elbows and tees, valves, and miscellaneous piping accessories. The resulting system pressure must be maintained at or above the minimum system head required to prevent cavitation.

Flow Rate

Condenser water pumps NYC are required to circulate return condenser water in open or closed loop systems from the chiller to a cooling tower. The pump must be sized properly to meet the required condensing or evaporation rate of the HVAC appliance and application.

The pump must also be sized to handle the amount of drain water discharged by the HVAC per hour. This information is often found in the HVAC equipment specifications and can vary greatly by cooling capacity, location, and climate.

The required flow rate and the system’s pressure are then used to complete the pump schedule shown in Figure 18. This is an important step because some manufacturers will only honor warranties or performance guarantees if minimum flow rates are met or maintained.

Head

The pump must be properly sized to provide the correct amount of flow at the correct pressure. A sufficient head means that the chilled water may not circulate, and cooling towers will be overburdened, while too much head will result in excessive electricity use.

To determine the suction and discharge heads, a system designer must consider the total dynamic head available – the total sum of all pressure losses in the pump system, including the straight-length piping, fittings, and valves. Suction pressure drop is calculated using different equations than those used for pressure loss in piping and valves.

The calculation results in a condenser water pump schedule that contains the total dynamic head, flow rate, and other important information like motor type and speed. This is a great tool for system designers and engineers when selecting the right condenser water pump.

Efficiency

The condenser water pump must be sized properly to circulate the correct amount of water at the appropriate pressure. Too little flow and the building will not get cool enough during peak cooling demand. Too much pump capacity and the system will use too much electricity unnecessarily.

The efficiency of a condenser water pump is also important to consider. The higher the pump efficiency, the more energy it will save.

The efficiency of a condenser air/water pump is determined by its maximum lift rating, friction loss values, and vapor pressure. You can find these parameters in our calculator by entering your suction lift, vapor pressure, and pump speed data. A good rule of thumb is to select a pump with an efficiency above 60%.

Motor

The motor of a condenser water pump is the component that converts electrical power to mechanical energy that turns the shaft and drives the pump. The pump motor can be electric or engine-driven, typically a continuous-duty, centrifugal design.

It’s important to note that undersized pumps can cause a condition known as deadheading – air trapped inside the pump that churns the fluid until it heats up and becomes a vapor and can damage the impeller, bearings, bushings, seals, and elastomers. Over-sized pumps can also cavitate due to a lack of head in the system and can be costly to maintain.

A sample schedule is provided in the condensate pump calculator and shows the flow rate, total dynamic head, suction elevation head, vapor pressure, and net positive suction head available.

Design

The design of the pump is critical to the overall condenser water system. For example, the system design must consider the tower height and whether it is a closed or open circuit. The design should also address the location and sizing of the pump suction and discharge piping.

The sizing of the pump discharge piping is important to avoid a significant pressure drop between the tower and the pump suction. This is critical because cooling tower water is full of air, and any sudden pressure drop can cause an air pocket to “pop” out of the water, enter the pump, and destroy it in short order.

A properly implemented variable chiller condenser water pumping system is an excellent way to save energy on a building retrofit or new construction project. R.L. Deppmann can assist with this solution using the latest tools and technologies for sizing, selection, and implementation.