HVAC Chillers

Heating, ventilation and air conditioning (HVAC) chillers are refrigeration systems that provide cooling for industrial and commercial applications. They use water, oils or other fluids as refrigerants. HVAC chillers include a compressor, condenser, thermal expansion valve, evaporator, reservoir, and stabilization assembly. Compressing the refrigerant creates a high pressure, superheated gas that the condenser air-cools to a warm liquid. The thermal expansion valve (TXV) releases refrigerant into the evaporator, converting the warm liquid to a cool, dry gas. Often, a hot gas bypass is used to stabilize the cooling output by allowing the hot gas to warm up the evaporator. This causes a reduction in cooling efficiency, but stabilizes the chilled water temperatures. When water is pumped from the reservoir to the compressor, the chilling cycle begins again.

HVAC chillers vary in terms of condenser cooling method, cooling specifications and process pump specifications. There are several condenser cooling methods. Air-cooled devices use a fan to force air over the condenser coils. By contrast, water-cooled devices fill the condenser coils with circulating water. Remote air or slit systems locate the main part of the chiller in the application area and position the condenser remotely, usually outdoors. Cooling specifications for HVAC chillers include cooling capacity, fluid discharge temperature, and compressor motor horsepower. Typically, cooling capacity is measured in kilowatts or tons of refrigeration. Compressor motor horsepower is a nominal value. Process pump specifications include process flow, process pressure, and pump rating. 

HVAC chillers include a local or remote control panel with temperature and pressure indicators. Some devices include microprocessor controls, emergency alarms, and an integral pump. Others are designed for outdoor installation and can be mounted on rooftops or building exteriors. Modular systems can be configured in different ways based on application requirements. For example, in air conditioning systems, HVAC chillers are used to pump water to coils in different parts of a building. Other applications for HVAC chillers include the cooling of plastics, printing equipment, laser cutting machines, and large-scale medical devices such as magnetic resonance imaging (MRI) equipment.

• Applying Inverters to Centrifugal Compressors in HVAC Chillers (.pdf)
  When applying an inverter to centrifugal compressors on HVAC chillers, there are a number of factors to consider. For some compressors, lubricating oil circulation may be driven by the rotation of the...
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• 4-20 mA Vibration Monitoring of Chillers and Cooling Units
  4-20 mA vibration monitoring of chillers and cooling units Cooling towers, process coolers and HVAC cooling units can be monitored for vibration using the 4-20 mA analog input channels of existing PLC...
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