Issue:
Why should the chiller control the chilled water pump?
Resolution:
The RTAC chiller is equipped with a Falling Film evaporator. Similar to a flooded evaporator, this type of evaporator contains water inside the copper tubes and refrigerant within the shell surrounding these tubes. There is a possibility of a significantly higher mass of liquid refrigerant remaining in the system compared to water when the chiller is turned off and the flow of chilled water through the evaporator stops. Shortly after the compressor stops operating (particularly if the outdoor temperature is lower than the water temperature), the remaining liquid refrigerant in the evaporator will transfer to the condenser as it rapidly cools. The saturation temperature of the refrigerant will quickly decrease and approach the ambient temperature at the condenser. Meanwhile, the stationary water in the tubes will release its heat, causing the refrigerant liquid to vaporize and transfer its heat energy to the condenser. Due to the larger mass of liquid compared to water and a substantial condensing surface exposed to the cold ambient temperature, the refrigerant can easily dissipate enough heat to freeze.
During operation, the chiller's microprocessor monitors various parameters such as the amount of liquid refrigerant in the evaporator, the temperature of saturated refrigerant, and the inlet and outlet water temperatures. If there is a risk of freezing, the pump output will signal the pump to start, allowing water to circulate through the tubes and prevent freezing.
Notes:
Refer to RLC-PRB012-EN for additional information about pump control for RTAC chillers.
Other Question/Problem/Cause Statements:
- Why does the chiller need to control the chilled water pump?
- Pump control question
- Chilled water pump control.
Facts:
- Air-Cooled Chiller (Pueblo) (RTAC)
Original HUB Document: DOC-83102
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.