Grundfos CUE Series Installation And Operating Instructions Manual page 26

10.7.8 Digital inputs 2, 3 and 4 (3.9 to 3.11)
The digital inputs of the CUE (terminal 19, 32 and 33) can
individually be set to different functions.
Select one of the following functions:
• Min. (min. curve)
• Max. (max. curve)
• Ext. fault (external fault)
• Flow switch
• Alarm reset
• Dry running (from external sensor)
• Accumulated flow (pulse flow, only terminal 33)
• Not active.
The selected function is active when the digital input is activated
(closed contact). See also section 13.1 Digital inputs.
Min.
When the input is activated, the pump will operate according to
the min. curve.
Max.
When the input is activated, the pump will operate according to
the max. curve.
Ext. fault
When the input is activated, a timer will be started. If the input is
activated for more than 5 seconds, an external fault will be
indicated. If the input is deactivated, the fault condition will cease
and the pump can only be restarted manually by resetting the
fault indication.
Flow switch
When this function is selected, the pump will be stopped when a
connected flow switch detects low flow.
It is only possible to use this function if the pump is connected to
a pressure sensor or a level sensor, and the stop function is
activated. See sections 10.7.10 and 10.7.11.
Alarm reset
When the input has been activated, the alarm is reset if the cause
of the alarm no longer exists.
Dry running
When this function is selected, lack of inlet pressure or water
shortage can be detected. This requires the use of an accessory,
such as:
®
• a Grundfos Liqtec dry-running switch
• a pressure switch installed on the suction side of a pump
• a float switch installed on the suction side of a pump.
When lack of inlet pressure or water shortage (Dry running) is
detected, the pump will be stopped. The pump cannot restart as
long as the input is activated.
Restarts may be delayed by up to 30 minutes, depending of the
pump family.
Accumulated flow
When this function is set for digital input 4 and a pulse sensor is
connected to terminal 33, the accumulated flow can be
measured.
26
10.7.9 Digital flow input (3.12)
This display appears only if a flowmeter has been configured in
display 3.11.
The display is used for setting the volume for every pulse for the
function Accumulated flow with a pulse sensor connected to
terminal 33.
Setting range:
• 0-1000 litre/pulse.
The volume can be set in the unit selected in the start-up guide.
10.7.10 Constant pressure with stop function (3.13)
Settings
The stop function can be set to these values:
• Active
• Not active.
The on/off band can be set to these values:
ΔH is factory-set to 10 % of actual setpoint.
•
ΔH can be set within the range from 5 % to 30 % of the actual
•
setpoint.
Descriptions
The stop function is used for changing between on/off operation
at low flow and continuous operation at high flow.
On/off operation
Stop pressure
ΔH
Start pressure
Fig. 38 Constant pressure with stop function. Difference
between start and stop pressures (ΔH)
Low flow can be detected in two different ways:
1. A built-in "low-flow detection function" which functions if the
digital input is not set up for flow switch.
2. A flow switch connected to the digital input.
1. Low-flow detection function
The pump will check the flow regularly by reducing the speed for
a short time. If there is no or only a small change in pressure, this
means that there is low flow.
The speed will be increased until the stop pressure (actual
setpoint + 0.5 x ΔH) is reached and the pump will stop after a few
seconds. The pump will restart at the latest when the pressure
has fallen to the start pressure (actual setpoint – 0.5 x ΔH).
If the flow in the off period is higher than the low-flow limit, the
pump will restart before the pressure has fallen to the start
pressure.
Continuous operation