Refer to the diagram in the "Hydraulic connections" section for
all references points mentioned in this chapter.
The water circulation pumps for the units in the range have been
sized to allow the hydraulic modules to operate in all possible
congurations based on the operating conditions specic to the
system, i.e. at a range of temperature dierences between the water
inlet and outlet (Delta T) at full load which may vary from 3 to 10 K.
This temperature dierence required between the water inlet and
outlet determines the nominal ow rate of the system. Use the
specication provided when selecting the unit to determine the
system's operating conditions.
In particular, take down the data to be used for the control of the
system ow rate:
• Units without hydraulic module: the rated unit pressure drop.
This is measured with pressure gauges that must be installed
at the inlet and outlet of the unit (item 21).
• Units with xed speed pumps: nominal ow rate. The pressure
of the uid is measured by sensors installed at the inlet of the
pump and outlet of the unit (items 7 and 10). The controllers
then calculate the ow rate associated with this pressure
dierence and display the result on the user interface. (refer
to the unit control manual).
• Units with variable speed pumps: regulation of the constant
pressure dierential based on readings at the hydraulic module
inlet and outlet. The water buer tank module option is not
taken into account.
• Units with variable speed pumps: regulation of the temperature
dierence measured at the heat exchanger inlet and outlet.
If this information is not available when the system is commissioned,
contact the engineering and design department responsible for the
system to obtain it.
This data can be obtained either from the performance tables included
in the technical documentation (for cases where the evaporator
temperature delta is 5 K) or from the "Electronic Catalogue" selection
program for all other applicable temperature delta in the range of 3 to
10 K.
8.3 - Units without hydraulic module
8.3.1 - General information
The nominal ow of the unit will be set using a manual valve that
should be installed on the outlet of the unit (item 19 on the schematic
hydraulic circuit). Changing the pressure drop of the valve allows
adjustment of the system ow rate to achieve the design ow rate.
As the exact total system pressure drop is not known upon
commissioning, it is necessary to adjust the water ow rate with the
control valve to obtain the installation's specic ow rate.
8.3.2 - Hydraulic circuit cleaning procedure
• Open the valve completely (item 22).
• Start up the system pump.
• Read the pressure drop of the plate heat exchanger using the
pressure dierential gauge to nd the dierence between the
unit inlet and outlet (item 21).
• Let the pump run for 2 hours continuously to ush the system's
hydraulic circuit (presence of contaminating solids).
• Perform another reading.
• Compare this value to the initial value. A decrease in the
pressure drop value indicates that the lters in the system
need to be removed and cleaned. In this case, close the Shut-
o valves on the water inlet and outlet (item 19) and remove
then clean the lters (items 20 and 1) after draining the
hydraulic part of the unit (item 6).
• Remove the air from the circuit (items 5 and 17).
• Repeat until all fouling is removed from the lter.
8.3.3 - Procedure for controlling the water ow
Once the circuit has been decontaminated, read the pressures on
the pressure gauges (water inlet pressure - outlet pressure) to
determine the pressure drop across the unit terminals (plate heat
exchanger + internal pipework).
Compare the value obtained with the theoretical selection value.
If the pressure drop reading is above the specied value, this
indicates that the ow rate at the terminals of the unit (and hence
in the system) is too high. In this case, close the control valve and
read the new dierence in pressure. Repeat as necessary until a
specic pressure drop corresponding to the unit's nominal ow
rate at the operation point is achieved.
NOTE: If the network has an excessive pressure drop in
relation to the available static pressure delivered by the
system pump, the nominal water ow rate cannot be obtained
(resulting ow rate is lower) and the dierence in temperature
between the water inlet and outlet of the evaporator will be
increased.
To reduce the system's hydraulic network pressure drop:
• Reduce the pressure drops of individual components
(bends, level changes, valves etc.) as much as possible
• Use the correct pipe diameter;
• Avoid extending the hydraulic systems when possible.
8 - WATER CONNECTIONS
27
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