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The function is not used for DDD systems.
8.7.21 Secondary functions (4.3)
Fig. 69 Secondary functions
Description
In the display, you can set functions that are secondary in relation
to the normal operation of the system. Secondary functions are
functions that offer additional functionality.
The display makes it possible to open these specific displays:
•
Stop function (4.3.1)
•
Pilot pump (4.3.2)
•
Soft pressure build-up (4.3.3)
•
Digital inputs (4.3.7)
•
Analog inputs (4.3.8)
•
Digital outputs (4.3.9)
•
Analog outputs (4.3.10)
•
Emergency run (4.3.5)
•
Pilot pump curve data (4.3.18)
•
Pump curve data (4.3.19)
•
Control source (4.3.20)
•
Fixed inlet pressure (4.3.22)
•
Flow estimation (4.3.23)
•
Reduced operation (4.3.24)
•
Remote sensors
(4.3.25).
38
8.7.22 Stop function (4.3.1)
Fig. 70 Stop function
Description
The function is used to stop the last pump if there is no or a very
small consumption.
Purpose of the function:
•
to save energy
•
to prevent heating of shaft seal faces due to increased
mechanical friction as a result of reduced cooling by the
pumped liquid
•
to prevent heating of the pumped liquid.
When a pilot pump is connected to the system, the
stop function parameters will be valid for the pilot
pump and not the main pump as the pilot pump will
be the last pump in operation
The description of the stop function applies to all DDD systems.
H
Start/stop band
Hset
Qmin
Normal operation
Fig. 71 Start/stop band
When the stop function is enabled, the operation is continuously
monitored to detect a low flow rate. When CU 354 detects no or a
low flow rate (Q < Qmin), it changes from constant-pressure
operation to on/off control of the last pump in operation.
Before stopping, the pump increases the pressure to a value
corresponding to Hset plus (distribution above setpoint / 100) x
start/stop band. The pump is restarted when the pressure is Hset
minus (100-distribution above setpoint) / 100 x start/stop band.
See fig. 72. The start/stop band can be distributed around the
setpoint.
Q
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