5
7425MUM661
Model: CWB FC
- Use and Maintenance Manual
Rev02
2.3 F
REE
C
OOLING SYSTEM
:
W
ORKING MODE
The Free cooling equipment allows to supply completely or partially the cooling capacity
produced by the chiller. The unit is equipped with two additional water coils and when the
external ambient temperature is at least 5°C less the water returning from the plant, the free
cooling coils can pre-cool or fully cool the water flow.
Free cooling operation provides an energy saving and this energy conservation increases as
the difference between the water to cool and the external ambient temperature increases.
There are three working mode:
•
SUMMER MODE – FREE COOLING OFF
: during the summer months and when the
ambient temperature is higher than the temperature of the water returning from the
plant, the CWB FC unit works like a traditional chiller;
•
INTERMEDIATE MODE – FREE COOLING ON + CHILLER
: when the temperature of
the ambient air is lower than the temperature returning from the plant, the CWB FC
works in the partial free cooling. Free cooling coils pre-cool the water flow and after
the chiller side cools the water flow to the desired outlet water temperature;
•
WINTER MODE – 100% FREE COOLING
: during the winter months and when the
ambient temperature is lower than the temperature of the water returning from the
plant, the CWB FC works 100% Free cooling mode. The water is completely cooled in
the water coils.
The three way valve grants the correct operation of the machine.
2.4 F
ANS
The fans force air through the condenser’s fins to remove the heat from the condensation of
the refrigerant gas, thus limiting the pressure inside the condenser.
CWB FC
chillers use external-rotor axial fans with thermal protection inside the motor
winding.
2.5 C
ONDENSATION CONTROL
When the temperature of the surrounding air drops, the cooling capacity of the air flow is
significantly increased, causing the pressure inside the condenser to drop; in order to keep
this drop of the condensation pressure from falling below the tolerable limit for the good
functioning of the Refrigerant circuit, the fans slow their rotation, reducing the flow of air.
The speed is controlled by an electronic regulator based on the condensation pressure; this
allows the machine to operate properly even when the temperature of the outside air is low
(see Chapter
8 Operating Limits
) and also maintains a low level of noise compered to its
nominal operating conditions.
2.6 C
ONTROL OF THE WATER TEMPERATURE
The purpose of the chiller is to maintain the temperature of the water produced within a
desired interval as the load on the system varies; this is handled by an electronic controller
and a temperature probe that turn the compressors on and off appropriately (see Chapter
6
Temperature Regulation
)
2.7 P
ROTECTING THE INTEGRITY OF THE MACHINE
In addition to controlling the temperature, the electronic controller uses pressure switches,
thermostats and timers to prevent and handle situations that could compromise the integrity
of the machine (also see Chapter
7 Safety Devices
).
