Carrier 30KAV-ZE Series - Page 71

12.1.5.4 - Variable-speed pump - Pressure di󰀨erential control
The system ow rate has not been set to a nominal value.
This will be adjusted by the system, by varying the pump speed,
to maintain a constant Delta P value dened by the user.
This is checked by the pressure sensors at the hydraulic module
inlet and outlet.
The system calculates the value for the measured pressure
di󰀨erence, compares it with the setpoint value set by the user and
then modulates the pump speed module accordingly.
■ This results in an increase in the ow rate if the measurement
is below the setpoint,
■ This results in a decrease in the ow rate if the measurement
exceeds 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 maintained Delta P may, in certain cases, di󰀨er from the
setpoint value:
■ If the setpoint value is too high (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 P
below the setpoint.
■ If the setpoint value is too low (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 P above
the setpoint,
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 pressure di󰀨erential setpoint
Once the circuit is cleaned, place the hydraulic circuit in the
conguration for which the unit selection was performed (generally
all valves open and all cooling coils active).
Read the value of the ow on the user interface and compare it
with the theoretical value of the range:
■ If the ow rate read is greater than the specied value, reduce
the Delta P setpoint on the user interface to decrease the ow
rate value.
■ If the ow rate read is less than the specied value, increase
the Delta P setpoint on the user interface to increase the ow
rate value.
Repeat until the unit's nominal ow rate at the required operation
point is achieved.
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 (Delta P),
■ Required Delta P set point.
■ If necessary, the control PID parameters can also be adjusted
(refer to the control manual).
NOTE: If, during adjustment, the low or high frequency limits
are reached before reaching the specied ow rate, keep the
pressure di󰀨erential value at its lower or higher limit as the
control set point.
If the user knows in advance the pressure di󰀨erential value
at the unit outlet, this value can be entered directly. You should
not, however, avoid the sequence of cleaning the hydraulic
circuit.
12 - OPTIONS
71