30Wg/61Wg Unit Operation With A Drycooler (Option 154); Operating Principle; Communication To Control The Drycooler; Configuration Of The Number Of Fan Stages And The Automatic Changeover Of The Fan Stages - Carrier AquaSnap 61WG Series Installation, Operation And Maintenance Instructions

14 - 30WG/61WG UNIT OPERATION WITH A DRYCOOLER (OPTION 154)

14.1 - Operating principle

The units have been designed to optimise the operation of
systems, using drycoolers as heat rejection system.
With a variable-speed condenser water pump integrated into the
unit the complexity of traditional systems, using a three-way valve
has been reduced.
The installation of an operational system is limited on the
condensing water loop side to connect the drycooler entering and
leaving water piping to the unit.
The TouchPilot Junior control of the unit includes algorithms to
permit constant automatic optimisation of:
- drycooler fan stage operation
- water flow rate variation in the loop between the condenser
and the drycooler.
Parallel control of the fan stages (up to 8 stages maximum) and
of the variable water flow rate of the loop permit year-round system
operation down to -10 °C outside temperature without any
additional control.

14.2 - Communication to control the drycooler

The electronic board specifically integrated in the control box of
the drycooler, by an option selection on the manufacturer drycooler,
and a communication LEN bus connected to the microprocessor
board of the unit is used for the overall system control.
Pay attention that Dry cooler and Chiller have to be both equipped
with the option Drycooler Management (Opt154)
The option is supplied in the manufacturer's drycooler control box.
Connect the unit to board AUX1 in the drycooler, using a
communication cable. the communication cable should be connect
to the plug with 3 points Wago type (5 mm spacing or equivalent).
the communication cable should be a shielded type.
TouchPilot Junior optimises system operation to obtain the best
efficiency with variation of the water flow rate and the number of
fans required for any thermal load and outside temperature
conditions.
The electronic board (AUX1) integrated in the control box of the
drycooler has analogue inputs for outside air temperature and
drycooler leaving water temperature sensors, as well as eight digital
outputs permitting control of up to eight fan stages.
14.3 - Configuration of the number of fan
stages and the automatic changeover of the fan
stages
Please refer to the instructions in the TouchPilot Junior IOM for the
configuration of the number of fan stages to be controlled. It is
enough to enter the number of fan stages of the drycooler in the
TouchPilot Junior service menu. The number of digital outputs
controlling the fans are activated by the control.
TouchPilot Junior controls the automatic switching of all fan stages,
based on operating time and number of start-ups of the different
stages. This function prevents fan motors from only running a little
or not at all and the shafts seizing up, especially during periods
with a low cooling demand, when the outside temperature is low.
Switching is often specified by the drycooler manufacturers to
ensure a long operating life of fan motors that are only used a little
or not at all in these particular operating conditions.
56

14.4 - Fan stage assignment

The minimum configuration of the number of fan stages is 2 for
correct operation.
Depending on the drycooler capacity the number of fans can be
between 2 and 8. They can be controlled by one fan or by linked
pairs, if necessary.
A drycooler with 4 or 6 fans installed in series for example along
the length of the unit will result in a configuration of 4 or 6 fan
stages.
Reciprocally a drycooler with 8 or 12 fans arranged in pairs along
the length of the unit will also result in a configuration of 4 or 6 fan
stages.
Configuration with 4 and 6 stages (min. 2 - max. 8)
A 1
Fans linked in pairs - 4 and 6-stage configuration
(min. 2 - max. 8)
1
A
1
Legend
A Entering and leaving water manifold side
1 to 6 Fans
14.5 - Units without evaporator and condenser
pump, three-way valve configuration for low
outside temperature application
Units can be supplied from the factory without evapo-rator and
condenser pump. If year-round low-temperature operation is
planned, the unit will be installed with a three-way valve that is
not supplied with the unit.
In this case TouchPilot Junior should be configured for three-way
valve system control from an analogue 0-10 volt output on the
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, described in chapter
"Configuration of the number of fan stages and automatic
changeover of the fan stages" is identical in this case.

14.6 - Drycooler installation on units

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 unit pumps
- Maximum drycooler elevation in relation to the unit (relief
valve at 4 bar on the unit water circuit).
- Fan stage control (see "Fan stage control").
- Good positioning of the outside air temperature and drycooler
leaving water temperature sensors.
2 3 4 5
2 3 4 5
2 3 4 5
6
6
6