Carrier 30KAV-ZE Series - Page 69

12.1.5 - Installation nominal water ow rate adjustment
Refer to the schematic diagram in the "Water connections"
paragraph for all item references in this chapter.
The water circulation pumps have been sized to allow the hydraulic
modules to operate in all likely system operating conditions, i.e.
at a range of temperature di󰀨erences between the water inlet and
outlet at full load from 5 to 15 K.
This temperature di󰀨erence required between the water inlet and
outlet determines the nominal ow rate of the system. Use the
specication provided when selecting the unit to determine the
system's operating conditions.
In particular, collect the data necessary for setting the installation
ow rate:
■ Unit with variable speed pump – control on xed speed: nominal
ow rate.
■ Unit with variable speed pump – control on temperature
di󰀨erence: nominal Delta T at the evaporator.
■ Unit with variable speed pump – control on constant outlet
pressure: pressure at the hydraulic module outlet.
■ Unit with variable speed pump – control on pressure di󰀨erential:
Delta P at the hydraulic module connections.
If this information is not available when activating the system,
contact the engineering and design department responsible for
the installation to obtain it.
Flow rates for a Delta T of 5K at the evaporator can be found in
the product technical literature. Flow rates for any other DeltaT
(between 3K and 10K) can be obtained from the “Electronic
Catalogue” selection program.
12.1.5.1 - Variable-speed pump - Setting a xed ow rate
for the system
The ow will be set to a nominal value. This value shall remain
constant and will not be dependent on variations in the installation's
load.
Contact the manufacturer's service department to implement the
procedures described below.
Hydraulic circuit cleaning procedure
Refer to the water circuit cleaning procedure.
Procedure for controlling the ow rate
Once the circuit has been cleaned, set the required water ow
rate by adjusting the pump frequency on the user interface.
Stop the forced operation of the pump and proceed to the
conguration of the unit for the required control mode.
Modify the control parameters:
■ Water ow rate control method (xed speed),
■ Constant frequency value.
12.1.5.2 - Variable speed – Temperature di󰀨erential control
The system ow rate has not been set to a nominal value.
The ow rate will be adjusted, by varying the pump speed, to
maintain an evaporator Delta T value dened by the user.
This is checked by the temperature sensors at the evaporator inlet
and outlet.
The system reads the measured temperature values, calculates
the corresponding Delta T, compares it with the setpoint value set
by the user and then modulates the pump speed.
■ This results in an increase in the ow rate if the Delta T° exceeds
the setpoint.
■ This results in a decrease in the ow rate if the Delta T° is less
than the setpoint.
This modulation is limited only by the maximum and minimum ow
rates for the unit and by the maximum and minimum allowable
pump speeds.
The resulting Delta T° may, in certain cases, di󰀨er from the setpoint
value:
■ If the setpoint value is too high (corresponding to a ow rate
lower than the minimum value or a frequency less than the
minimum value), the system will be limited to the minimum ow
rate or minimum frequency, which will result in a Delta T below
the setpoint,
■ If the setpoint value is too low (corresponding to a ow rate
higher than the maximum value or a frequency greater than
the maximum value), the system will be limited to the maximum
ow rate or maximum frequency, which will result in a Delta T
above the setpoint.
Contact the manufacturer's service department to implement the
procedures described below.
12 - OPTIONS
69