30Rw Units Without Evaporator And Condenser Pump, Three-Way Valve Configuration For Low Outside Temperature Application; Drycooler Installation; 30Rwa Unit Operation With Remote Air-Cooled Condenser; Operating Principle - Carrier Aquasnap 30RW Installation, Operation And Maintenance Instructions

11.5 - 30RW units without evaporator and condenser
pump, three-way valve configuration for low outside
temperature application
30RW units can be supplied from the factory without evapo-
rator and condenser pump. If year-round low-temperature
operation is planned, the chiller will be installed with a
three-way valve that is not supplied with the chiller.
In this case Pro-Dialog Plus should be configured for
three-way valve system control from an analogue 0-10 volt
output on the NRCP type master board. An adequate
condensing temperature will be maintained with constant
condenser flow rate. This configuration permits year-round
system operation down to -20°C outside temperature.
Control and changeover of the fan stages are described in
the paragraph "Configuration of the number of fan stages
and automatic changeover of the fan stages" is identical in
this case.

11.6 - Drycooler installation

For the drycooler installation follow professional guidelines.
• Water pipe sizing
• Maximum piping and shut-off valve pressure drops
based on the available pressure of the 30RW pumps
• Maximum drycooler elevation in relation to the chiller
(safety valve at 4 bar on the 30RW water circuit).
• Fan stage control (see "Fan stage control").
• Good positioning of the outside air temperature and
drycooler leaving water temperature sensors.
12 - 30RWA UNIT OPERATION WITH REMOTE AIR-
COOlED CONDENSER

12.1 - Operating principle

30RWA units are specially designed to optimise the opera-
tion of split installations using air-cooled condensers as the
chiller heat rejection system. The installation of an operational
system is limited to the connection of the air-cooled
condenser entering and leaving piping to the 30RWA unit.
The Pro-Dialog Plus control system of the 30RWA units
incorporates the logic to permit control of the different fan
versions (single-circuit, dual-circuit, fixed and variable-
speed fan, separate ventilation or interlaced ventilation at
the circuit level).

12.2 - Master fan

The physical position of the air-cooled single- or dual-circuit
air-cooled condenser with fixed or variable-speed fans
depends on the position of the leaving liquid refrigerant
manifold. In all cases there is always a so-called master fan.
This is the fixed or variable-speed fan that is physically the
closest to the leaving liquid refrigerant manifold.
This ensures optimum subcooling on the leaving condenser
side, especially at part load. This is the first fan to start in
each circuit and the last fan to stop. A fan configuration
with fixed-speed fans permits year-round system operation
down to 0°C outside temperature.
A fan configuration with a variable-speed master fan permits
year-round operation down to -10°C outside temperature.
12.3 - Dual-circuit condenser with separate ventilation
and interlaced ventilation
For dual-circuit air-cooled condensers the most frequent and
recommended configuration is with an air-cooled conden-
ser with completely independant circuits at fan level. This
configuration is called "separate ventilation" by circuit.
It is also possible to control ventilation of a dual-circuit
air-cooled condenser where the fans are not independant
by circuit. This is called "interlaced ventilation".
The Pro-Dialog Plus service configuration of the fans
per-mits setting up these two dual-circuit air-cooled
condenser types.
12.4 - Auxiliary electronic analogue input and output
and discrete output board (AUX1) for control of the
air-cooled remote condenser
This is the same board as the one used in the drycoolers (see
paragraph "Auxiliary electronic analogue input and output
and discrete output board for control of the drycooler").
Refer to the assignment od the discrete output of the board
based on the air-cooled condenser type installed (single-
circuit, dual-circuit with separate ventilation, dual-circuit
with interlaced ventilation).
See paragraph "Possible fan arrangements based on the
air-cooled condenser type used in the installation".
0-10 V dc analogue outputs connectors J4 and J5:
Used for master fan speed variation of circuits A and B of
the air-cooled condensers for operation at low outside
temperature.
• Connector J6: Analogue inputs CH 11 for outside
temperature sensors
• Connector J9: Communication with the master basic
board of the 30RW unit.
12.5 - Configuration of the number of fan stages and
fan type based on the air-cooled condenser model
used in the installation
Please refer to the instructions in the Pro-Dialog Plus IOM
for the 30RW/30RWA units to carry out the parameter
setting of the air-cooled condenser used in the installation:
• Single-circuit or dual-circuit condenser
• Use of speed variation on the master fan(s)
• Dual-circuit condenser with separate or interlaced
ventilation
• Number of fixed-speed fans
Based on the parameter setting used, the arrangement of the
discrete and corresponding analogue outputs controlling
the fans will be activated by the control.
The minimum configuration of the number of fan stages is
2 for correct operation (2 fixed-speed or 1 variable-speed +
1 fixed-speed fan).
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