Kodiak Recirculating Chiller Technical Manual
Manual # 820-0109, Rev. Y, 07/08/10
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Check Lytron’s website
www.Lytron.com
for the most current technical information.
GENERAL INFORMATION
Chiller System Description
Your chiller consists of a refrigeration system, a coolant loop, associated controls and plumbing. The
pump draws coolant from the internal reservoir and pumps it out to cool the process equipment, and
then the coolant flows back to the chiller. The fluid then flows through the evaporator, where the heat is
removed, and then back to the reservoir.
Coolant Loop
Kodiak chillers are designed to operate with continuous coolant flow through a closed loop. This loop
contains the system pump, temperature sensor, reservoir, internal and external plumbing lines and
fittings, and the external heat load. The external plumbing and the heat loads are provided by the end
user and are generally unique to the user’s process or location.
Refrigeration System and Hot Gas Bypass
The chiller uses a standard refrigeration system to keep the coolant at the process temperature set
point. The compressor compresses the refrigerant vapor. The vapor then passes through the
condenser where it is cooled and turns to a liquid. The refrigerant then passes through the evaporator.
The coolant also flows into the evaporator, through passages separated by thin layers of metal from the
refrigerant. The refrigerant evaporates, drawing heat from the coolant. The refrigerant vapor returns to
the compressor and continues the cycle.
Many refrigeration systems, such as those used in household refrigerators, control the temperature by
turning the compressor on and off. This is a simple, inexpensive method of controlling the cooling, but
its temperature control is not precise and the frequent on-off cycles causes wear on the compressor
motor.
Lytron’s recirculating chillers use a better method for controlling the cooling rate: a hot-gas bypass
system. This employs a liquid line solenoid valve and a hot-gas bypass valve to meter the refrigerant
flow through the evaporator when cooling is needed. When the coolant reaches its set point
temperature, the liquid line solenoid valve closes, causing the hot-gas bypass valve to open. The hot-
gas valve lets hot gas from the compressor discharge into the evaporator, adjusting the temperature in
the evaporator to maintain the correct coolant temperature. When refrigeration is needed the liquid line
solenoid valve opens, the hot-gas valve closes and the cycle starts again.
This hot gas bypass control method provides precise temperature control. It also minimizes wear on
the compressor motor, since the compressor runs continuously and does not experience the stress of
repeated cycling.
