English (GB)
46
In start-stop operation, the pressure varies between
the start and stop pressures. See fig. 52.
In "User-defined mode" (Customised operating
mode), ∆H has been factory-set to 10 % of the actual
setpoint. ∆H can be set within the range from 5 to 30
% of actual setpoint.
The pump changes to start-stop operation if the flow
becomes lower than the minimum flow.
The minimum flow is set in % of the nominal flow of
the pump (see the pump nameplate).
In "User-defined mode" (Customised operating
mode), the minimum flow has been factory-set to 10
% of nominal flow.
Factory setting
See section 24. Factory settings.
"Low-flow detection"
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.
2. A flow switch connected to one of the digital
inputs.
1. 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 x ΔH) is reached
and the pump stops. When the pressure has
fallen to the start pressure (actual setpoint - 0.5 x
ΔH), the pump restarts.
– If the flow is higher than the set minimum flow,
the pump returns to continuous operation at
constant pressure.
– If the flow is still lower than the set minimum
flow (Q
min
), the pump continues in start-stop
operation until the flow is higher than the set
minimum flow (Q
min
). When the flow is higher
than the set minimum flow rate (Q
min
), the
pump returns to continuous operation.
2. 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.
Fig. 53 Position of the non-return valve and
pressure sensor in system with suction
lift operation
Fig. 54 Position of the non-return valve and
pressure sensor in a system with a
positive inlet pressure
"Set minimum flow"
Set the minimum flow (Q
min
) in this display. This
setting determines at which flow rate the system is to
change from continuous operation at constant
pressure to start-stop operation. The setting range is
5 to 30 % of rated flow.
Factory setting
See section 24. Factory settings.
Always install the non-return valve before
the pressure sensor. See figures 53 and
54.
TM03 8582 1907TM03 8583 1907
Pressure sensor
Diaphragm tank
Non-return
valve
Pump
Diaphragm tank
Pressure sensor
Pump Non-return valve
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