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12 - OPTIONS
12.2 - Free cooling dry cooler (option 313)
12.2.1 - Valves on the water loop
The free cooling system requires 2 two-way valves (one normally
open, one normally closed) or a three-way valve, not supplied with
the unit or the drycooler.
A two-way valve kit is available in the list of accessories for the
drycooler.
The drycooler control panel has a 230 V power supply for 2
two-way valves.
Recommended motorised valve (default component): 230 V
3-point.
Refer to the wiring diagram for the drycooler for wiring the valves
on the customer terminal strip.
12.2.2 - Operating principle
The units have been designed to optimise the operation of
systems, using drycoolers as a free cooling system (method using
low outdoor air temperatures to chill the water in the air conditioning
system).
This system enables substantial energy and cost savings, which
is at its most effective when the outdoor air temperature is low.
The unit's SmartVu™ control system includes algorithms to permit
constant automatic optimisation of:
■ The operation of the drycooler fans,
■ The flow rate variation in the water loop,
■ The cooling capacity (the drycooler and chiller can operate
independently or simultaneously),
■ The positions of the valves depending on the operating mode
The control defines the optimal configuration, taking the water
setpoint value, outdoor air temperature, and water loop
temperature into account (the control will give priority to the
drycooler).
Parallel control of the fans and of the variable flow rate of the water
loop enable the system to operate at outdoor temperatures of
down to -20°C without any additional control.
WARNING: The drycooler and chiller both need to be equipped
with the Free cooling management option.
Chiller plant
LEN communication
bus
Drycooler free cooling
For optimal free cooling operation, the chiller has to be configured:
■ Using the water inlet temperature control,
■ Using the delta temperature control for the variable-speed pump
option.
12.2.3 - Communication to control the drycooler
When the option is selected, a specific electronic board is
integrated in the drycooler control panel. A LEN communication
bus connected between the drycooler (AUX1 board) and the cooler
is needed for overall control of the system.
This cable must be a 3-point Wago type cable (5 mm spacing or
equivalent) and must be shielded.
The board integrated in the drycooler electrics box has analogue
inputs for the outdoor air temperature sensor (1), water loop return
sensor (3) and drycooler leaving water temperature sensor (2),
as well as digital outputs for controlling the fans.
The option works as a system split in two parts:
The chiller (with free cooling option):
Dedicated control algorithms supplied with the LEN connector to
control the drycooler.
The drycooler (with free cooling option):
■ AUX board with the I/O,
■ Room air temperature sensor to be placed outdoors,
■ Drycooler leaving water temperature sensor (factory-fitted),
■ Water loop temperature sensor (to be fitted on the common
pipe upstream of the valve),
■ 230 V power supply and control for two 2-way valve or one
3-way valve.
The difference between the drycooler outdoor air temperature and
the water loop sensor temperature determines whether or not it
is possible to activate free cooling mode.
3
NO
NC
2
2-way valve control
1
OAT
75
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