Compressor Short Cycling 20-60T Chillers

Issue:

Short cycling of the compressors on 20-60 ton chillers

Resolution:

 For CGAF 20-60 ton chillers:

• When the CGAF 20-60 chiller is configured for comfort cooling, the compressor must run for a minimum of 3 minutes.
• For process cooling, the minimum run time is 1 minute.
• However, when the chiller is connected to a short water loop, the compressor's minimum run time may result in cooling the water below the desired chilled water setpoint.
• It is advised to maintain a chilled water loop time of 3 to 5 minutes.
• As a general guideline, the volume of the loop in gallons should be at least 3 times the design gallons per minute (GPM) for a 3-minute loop time.

For other 20-60 ton chillers:

• A recommended loop time of 2 minutes has been suggested for CGWD, CGWE, CGWF, CCAD, CCAE, and CCAF models.
• It is advantageous to maximize the loop time, so a 3-minute loop time, as required for CGAF series chillers, would not have any negative effects.
• Another option is to decrease the flow rate of the evaporator solution. This will increase the loop time, although not as effectively as adding a tank. However, caution must be exercised to ensure that the flow rates for the evaporator do not fall below the minimum published values.
• The installation of a water storage tank can be beneficial. The chilled water loop time should be 3 minutes or longer. In some cases, reducing the chilled water flow rate can increase the chilled water loop time, but it is important to avoid falling below the recommended flow rates for the chiller.

Other Question/Problem/Cause Statements:

• Short cycling of the compressors on 20-60 ton chillers
• Overshooting chilled water setpoint
• What can I do to keep the chiller from overshooting its setpoint?

Facts:

• Short water loop
• Water-Cooled Chiller (PBL) (CGWD, CGWE, CGAD, CGAE, CCAD, CCAE)
• Water-Cooled Chiller (Pueblo) (CGWF, CCAF)
• INTELLIPAK CHILLER 20-60
• Air-Cooled Chiller - Intellipak (CGAC, CGAF)