Digital Inputs; Stop Function; Flow Switch; Dry Running - Grundfos CRE Instrucciones De Instalación Y Funcionamiento

4.4.7 Digital inputs

The digital inputs of the pump can be set to different functions.
Select one of the following functions:
• Min. (min. curve)
• Max. (max. curve)
• External fault
•

Flow switch

• Dry running (from external sensor) (only three-phase pumps).
The selected function is activated by closing the contact between
terminals 1 and 9, 1 and 10 or 1 and 11.
See also section 4.7 Digital input.
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.
External fault:
When the input is activated, a timer will be started. If the input is
activated for more than 5 seconds, the pump will be stopped and
a fault will be indicated. If the input is deactivated for more than 5
seconds, 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.
If the input is activated for more than 5 seconds, the stop function
incorporated in the pump will take over. See section
function.

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 these:
®
• a Grundfos Liqtec dry-running sensor
• 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.

4.4.8 Stop function

The stop function can be set to these values:
• Active
• Not active.
When the stop function is active, the pump will be stopped at very
low flows. The controller will stop the pump to protect the pump
as follows:
• avoid unnecessary heating of the pumped liquid
• reduce wear of the shaft seals
• reduce noise from operation.
Stop pressure
Start pressure
Fig. 15 Difference between start and stop pressures (H)
ΔH is factory-set to 10 % of actual setpoint.
ΔH can be set within the range from 5 % to 30 % of actual
setpoint.
Low flow can be detected in two different ways:
4.4.8 Stop 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. When the pressure has fallen to the start pressure
(actual setpoint - 0.5 x ΔH), the pump will restart.
When restarting, the pumps will react differently according to
pump type:

Three-phase pumps

1. If the flow is higher than the low-flow limit, the pump will return
to continuous operation at constant pressure.
2. If the flow is still lower than the low-flow limit, the pump will
continue in start/stop operation. It will continue in start/stop
operation until the flow is higher than the low-flow limit; when
the flow is higher than the low-flow limit, the pump will return
to continuous operation.
H
ΔH
Q
17