• High-comfort mode: The pump automatically
adjusts the parameters for the stop function so
that the disturbances during the start-stop
operation period are minimised. In this case, the
stop function uses the factory-set values of the
minimum flow (Q
min2
) and other internal
parameters. See the figure below.
• User-defined mode (Customised operating
mode): The pump uses the parameters set for ΔH
and minimum flow (Q
min3)
respectively for the stop
function. See the figure below.
Q
Q min2
Q min1
Q min3
H
△ H
1
2
TM064267
Difference between start and stop pressures (ΔH)
and minimum flow rate
Pos. Description
1 Stop pressure
2 Start pressure
In start-stop operation, the pressure varies between
the start and stop pressures. See the figure above.
In User-defined mode (Customised operating
mode), ΔH has been factory-set to 10 % of the actual
setpoint. ΔH can be set within the range from 5 to 30
% of the actual setpoint.
The pump changes to start-stop operation if the flow
becomes lower than the minimum flow rate.
The minimum flow rate is set in percentages of the
nominal flow rate of the pump. See the pump
nameplate.
In User-defined mode (Customised operating
mode), the minimum flow rate has been factory-set to
10 % of the nominal flow rate.
Factory setting
See the section on factory settings.
Low-flow stop function
A low flow can be detected in two ways:
1. A built-in low-flow detection function which is
active if none of the digital inputs are set for flow
switch.
• Low-flow detection function: The pump checks
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 is increased until the stop pressure
(actual setpoint + 0.5 × ΔH) is reached and the
pump stops. When the pressure has fallen to
the start pressure (actual setpoint - 0.5 × ΔH),
the pump restarts.
• If the flow rate is higher than the set minimum
flow rate, the pump returns to continuous
operation at constant pressure.
• If the flow rate is still lower than the set
minimum flow rate (Q
min
), the pump continues
in start-stop operation until the flow rate is
higher than the set minimum flow rate (Q
min
).
When the flow rate is higher than the set
minimum flow rate (Q
min
), the pump returns to
continuous operation.
2. A flow switch connected to one of the digital
inputs.
• Flow switch: When the digital input is activated
for more than 5 seconds because there is low
flow, the speed is increased until the stop
pressure (actual setpoint + 0.5 x ΔH) is
reached, and the pump stops. When the
pressure has fallen to start pressure, the pump
restarts. If there is still no flow, the pump
quickly reaches the stop pressure and stops. If
there is flow, the pump continues operating
according to the setpoint.
Operating conditions for the low-flow stop
function
You can only use the stop function if the system
incorporates a pressure sensor, a non-return valve
and a diaphragm tank.
Always install the non-return valve before
the pressure sensor.
See the figures below.
TM038582
Position of the non-return valve and pressure
sensor in system with suction lift operation
68
English (GB)
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