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•
Let the pump run for two consecutive hours to clean
the hydronic circuit of the system (presence of solid
contaminants).
•
Repeat the flow rate reading and compare this value
with the initial value.
•
If the flow rate has decreased, this indicates that the
screen filter must be removed and cleaned, as the
hydronic circuit contains solid particles. In this case
close the shut-off valves at the water inlet and outlet
(item 17) and remove the screen filter (item 1) after
emptying the hydronic section of the unit (item 6).
•
Purge the air from the circuit (items 5 and 15).
•
Renew, if necessary, to ensure that the filter is not
contaminated.
pressure differential set point control procedure
Once the circuit has been cleaned, select the hydronic
circuit configuration for which the unit selection has been
made (in general, all receivers are open and all emitters
are in the on-state).
Read the flow rate on the user interface and compare the
value obtained to the theoretical selection value:
•
If the flow rate reading is higher than the specified
value, decrease the pump supply frequency to decrease
the flow rate value (consult the 30RB/RQ 017-160
Pro-Dialog+ control manual).
•
If the flow rate reading is lower than the specified
value, increase the pump supply frequency to increase
the flow rate value (consult the 30RB/RQ 017-160
Pro-Dialog+ control manual).
Continue this procedure until the nominal flow rate at the
required unit operating point is reached.
Read the pressure value at the unit outlet that corresponds
to the operating point reached (consult the control manual).
Stop the forced operation of the pump and proceed with
the configuration of the unit for the required control mode
(consult the 30RB/RQ 017-160 Pro-Dialog+ control
manual).
Adjust the control parameters (refer to the control manual):
•
Water flow rate control method (pressure)
•
Pressure value to be controlled
The unit default configuration is fixed speed, 50 Hz.
notes:
•
If the low or high frequency limits are reached before
the specified flow rate is reached, keep the frequency
control within the low or high limit and read the
pressure value at the unit outlet.
•
If the user knows the unit outlet pressure value to be
maintained in advance, this can be entered directly as
the correct parameter. The hydronic circuit cleaning
procedure must not be left out.
32
13.4 - Units with hydronic module and variable-speed
pump - temperature difference control
The system flow rate is not controlled by a nominal value.
It is adjusted by the system (pump speed variation) to
maintain the user-selected temperature difference value
(delta T) at the heat exchanger.
The temperature probes at the heat exchanger inlet and
outlet (items 8 and 9 in the typical hydronic circuit diagram)
are used as means of control.
The system reads the measured temperature values, calcu-
lates the corresponding temperature difference, compares
it with the user-selected set point value and modulates the
pump speed as necessary:
•
If a higher delta T value than the set point is measured,
the flow rate is increased.
•
If a lower delta T value than the set point is measured,
the flow rate is decreased.
This flow rate variation is realised, observing the minimum
and maximum admissible unit flow rates as well as the
minimum and maximum pump supply frequency values.
The delta T value maintained can in certain cases be
different from the set point value:
•
If the set point value is too high (achieved for a lower
flow rate than the minimum value or a lower frequency
than the minimum value), the system settles at the
minimum flow rate or minimum frequency and this
results in a lower delta T value than the set point.
•
If the set point value is too low (achieved for a higher
flow rate that the maximum value or a higher frequency
than the maximum value), the system settles at the
maximum flow rate or maximum frequency and this
results in a higher delta T value than the set point.
hydronic circuit cleaning procedure
Please refer to the hydronic circuit cleaning procedure
described in chapter 13.3.
Delta t set point control procedure
Once the circuit has been cleaned, stop the forced operation
of the pump and proceed with the configuration of the unit
for the required control mode (consult the 30RB/RQ 017-160
Pro-Dialog+ control manual).
There is no particular control, except the control used for
the unit control parameters of the delta T to be controlled.
Adjust the control parameters (refer to the30RB/RQ 017-160
Pro-Dialog+ control manual):
•
Water flow rate control method (delta T)
•
Delta T value to be controlled
The unit default configuration is fixed speed, 50 Hz.
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