AEC NEC Central Station Air and Water Cooled Chiller - Manual (Page 28)

NEC Series Water- and Air-Cooled Central Chillers Page 27
4 Sequence Of Operation
4-1 Chilled Water Circuit
Figures 11 through 14
• Process cooling water supply and return connections are made at the evaporator(s) control
nipples.
• Warm coolant (water and ethylene glycol mixture) returns from the process and is pumped
through the evaporator where it is cooled.
• The coolant flows to the process and returns to repeat the cycle.
4-2 Refrigeration Circuit
Figures 11 through 14
NEC chiller air- and water-cooled unit refrigeration cycles differ only in the way the compressed
gas is condensed to a liquid.
• Liquid refrigerant from the condenser passes through a shutoff valve into a filter/dryer.
• The refrigerant then passes through the sight glass and solenoid valves into the thermal
expansion valve which regulates flow and allows the refrigerant to expand and cool the
inside of the heat exchanger.
• The refrigerant flows through the suction line back into the compressor.
• The refrigerant gives up its heat as it re-condenses to a liquid in the condenser.
• An optional hot gas bypass valve may be installed to control cooling capacity during
intermittent or partial load conditions. This helps provide close temperature control and
lengthens the life of a chiller by reducing compressor cycling.