30Rw Unit Operation With A Drycooler; Operating Principle; Auxiliary Electronic Analogue Input And Output And Discrete Output Board (Aux1) For Control Of The Drycooler; Configuration Of The Number Of Fan Stages And The Automatic Changeover Of The Fan Stages - Carrier Aquasnap 30RW Installation, Operation And Maintenance Instructions

11 - 30RW UNIT OPERATION WITH A DRyCOOlER

11.1 - Operating principle

The 30RW units have been specially designed to optimise
the operation of systems, using drycoolers as heat rejection
system.
With a variable-speed condenser water pump integrated
into the 30RW, the complexity of traditional systems, using
a three-way valve has been eliminated.
The installation of an operational system is limited on the
condensing water loop side to connecting the drycooler
entering and leaving water piping to the 30RW unit.
The Pro-Dialog Plus control of the 30RW includes
algorithms to permit constant automatic optimisation:
• 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 -20°C outside
temperature without any additional control.
11.2 - Auxiliary electronic analogue input and output
and discrete output board (AUX1) for control of the
drycooler
J2 J3
CH CH CH CH CH CH
-- -- -- -- -- --
1 2 3 4 5 6
• Connector J2: Discrete outputs CH 1 to 4 for fan
stages 1 to 4.
• Connector J3: Discrete outputs CH 5 to 8 for fan
stages 5 to 8.
• Connectors J4 and J5: Analogue outputs 0-10 V dc not
used on the drycoolers (only used for fan speed variation
of the air-cooled condensers).
• Connector J6: Analogue inputs CH 11 and 12 for
ambient temperature and drycooler leaving water
temperature.
• Connector J9: Communication bus with NRCP master
board of the 30RW unit.
The electronic board specifically integrated in the control
box of the drycooler and a communication bus connected
to the microprocessor board of the 30RW are used for the
overall system control.
Pro-Dialog Plus 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.
30
STATUS SIO
CH14
T
P
V
T
P
V
CH13
J4 J5 J6
CH CH
-- -- CH CH
-- -- CH CH
-- --
7 8
9 10
11 12
The electronic board (AUX1) integrated in the control box
of the drycooler has analogue inputs for outside air
tempe-rature and drycooler leaving water temperature
sensors, as well as eight discrete outputs permitting control
of up to eight fan stages.
11.3 - Configuration of the number of fan stages and
the automatic changeover of the fan stages
Please refer to the instructions in the Pro-Dialog Plus 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 Pro-Dialog Plus service menu. The
number of discrete outputs controlling the fans are activated
by the control.
Pro-Dialog Plus controls the automatic changeover of all
fan stages, based on the operating time and the number of
start-ups of the different stages. This function is used to
prevent that fan motors only operate a little or not at all
and that their shafts seize up, especially during periods
when the demand for cooling is low and when the outside
temperature is low. This changeover is often specified by
the drycooler manufacturers to ensure the long operating
life of the fan motors that are only little or not at all used
in these particular operating conditions.

11.4 - 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 2
A
1 2
legend
A Entering and leaving water manifold side
1 to 6 fans
2 3 4 5
3 4 5
3 4 5
6
6
6