Carrier AQUASNAP 30RBM Series Installation, Operation And Maintenance Instructions page 64

Chiller
LEN communication
DC free cooling
For an optimal free cooling operation, the chiller has to be
configurated:
-
using the water inlet temperature control,
- using the delta temperature control for the variable speed
pump option.
12.2.11.2 - Communication to control the drycooler
When the option is selected, a specific electronic board is
integrated in the drycooler control panel. An LEN
communication bus connected between the drycooler (AUX1
board) and the chiller 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 control panel has
analogue inputs for the outside air temperature (item 1), water
loop return (item 3), and drycooler water outlet temperature
(item 2) sensors, 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 water outlet temperature sensor (factory-
fitted),
-
water loop temperature sensor (to be fitted on the
common pipe upstream of the valve),
- Control & 230V power supply for 2 two-way valves or
one three-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.
12.2.11.3 - Configuration of the fan control
To set the configuration corresponding to the drycooler
installed (number of fans, control type – fixed or variable
speed), please refer to the instructions in the Smart View
control manual. Following these parameters, the Smart View
control will activate the adequate number of digital outputs
to control the fans.
Smart View controls the automatic switching of all fans, based
on operating time and number of start-ups, to ensure the fan
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V2V control
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motors provide a long service life.
Compatible fans configuration:
- 1 to 20 fans,
- fixed speed or variable speed
- fans in one l or 2 lines
Refer to the drycooler wiring diagram to see the arrangement
of the fan stages.
12.2.11.4 – Valves on the water loop
The free cooling system requires two 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 two
two-way valves.
Recommended motor valve (per default): 230V 3 points
See the drycooler wiring diagram for cabling the valves to the
customer terminal strip.
12.2.11.5 – Guidelines for system installation
For the physical properties, dimensions and performances: see
the drycooler documentation.
For the electrical connections, see the electrical wiring diagram
supplied with the drycooler.
For software configuration information, refer to the control
documentation of the chiller.
For correct installation of the drycooler, the rules for
calculation and sizing relating to the following areas must be
observed:
- sizing of the water piping.
- pressure drops (check the operating pressure of the unit's
pump is sufficient in relation to the pressure drops in the
pipes and valves - perform this check for all operating
modes).
- maximum height of the drycooler (in relation to the unit's
relief valve).
- suitable positioning of the temperature sensors: outdoor
air temperature and water loop temperature.