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Tools & Technical Reference

 
 

Choosing the Correct Pump for Your Recirculating Chiller

Centrifugal Pump GraphChoosing the right type of pump is critical when configuring a Kodiak recirculating chiller to meet your requirements. Using your system's pressure drop as the basic decision rule should help.

  1. Ask yourself , "What is my system's pressure drop?" Overlay your system's pressure versus flow curve onto the chiller's pump curve. The intersection of the two curves indicates the expected flow through your system using this pump. Once you know the expected flow you can follow the Selecting a Recirculating Chiller example to ensure the system has enough capacity to remove your heat load. You may need to check several curves to find one which provides enough flow.
  2. If you don't know your system's pressure drop, a positive displacement (PD) pump is recommended. The flow rate for a PD pump is independent of the system pressure drop. For system safety, this pump has an internal bypass which is factory set at 90 PSI. Therefore, if your system pressure drop is greater than 90 PSI this pump will operate in bypass mode. You will need to reduce your system's pressure drop by using shorter hoses with large diameters.

There are several other issues to consider when selecting a pump.

  1. Filters
    a. Positive Displacement pumps are sensitive to particles in the water system. If you opt for a positive displacement pump, you will want to include a water filter. If you include a water filter on your recirculating chiller, we recommend that you check the water filter weekly. With a new system the filter quickly accumulates foreign matter introduced during system setup which can lead to a decrease in system performance. Inspect the filter cartridge one day after you set up a new system to ensure the filter is clean and the system runs at maximum capacity. After this initial filter inspection, check the filter weekly. We recommend you have a supply of replacement filters on hand. To further prolong the pump life, we recommend you periodically inspect and clean the pump strainer. Check your manual for recommended frequency.
    b. Water filters and deionization cartridges are not recommended with centrifugal pumps. They increase the pressure drop too much, thereby reducing the flow. If you need a water filter or a deionization cartridge, we recommend you move to a turbine pump which is less affected by pressure drop.
  2. Pump Life
    a. Positive Displacement Pumps have graphite fins which as mentioned above are sensitive to particulates. In addition to recommending a water filter, we suggest you swap out the pump every 7,000 hours of use. This will avoid damaging the unit and cost associated with excessive downtime.
    b. Centrifugal and Turbine pumps are more tolerant of particles in the water stream and therefore have a longer lifespan than PD pumps. We recommend these pumps are replaced every 28,000 hours.
  3. Cost - Lytron's standard chiller contains a positive displacement pump. To upgrade to a centrifugal or turbine pump, there is an additional charge, typically between $340 and $1000, depending on the pump size.

If you need additional help selecting a pump, please contact a Lytron application engineer at +1-781-933-7300.