Dutypoint VT Booster Set, O & M Manual

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English (GB)
25
7.17 Stop function (Low-flow stop function)
You can set the low-flow stop function to these values:
• Not active
• Energy-optimal mode
• High-comfort mode
• "User-defined mode" (Customised operating mode).
When the stop function is active, the flow is monitored. If the flow
becomes lower than the set minimum flow (Q
min
), the pump will
change from continuous operation at constant pressure to
start/stop operation and finally be stopped if the flow reaches
zero.
The advantages of enabling the low-flow stop function are the
following:
• no unnecessary heating of the pumped liquid
• reduced wear of the shaft seals
• reduced noise from operation.
The disadvantages of enabling the low-flow stop function may be
the following:
• The delivered pressure is not completely constant as it will
fluctuate between the start and stop pressures.
• The frequent starts/stops of the pump may in some
applications cause acoustic noise.
The impact of the above disadvantages very much depends on
the setting selected for the stop function.
The "High-comfort mode" setting will minimise pressure
fluctuations and acoustic noise.
If you select "Energy-optimal mode", the main priority will be to
reduce the energy consumption as much as possible.
Possible settings of the stop function:
• Energy-optimal mode:
The pump will automatically adjust the parameters for the stop
function so that the energy consumption during the start/stop
operation period is minimised.
In this case, the stop function will use factory-set values of
minimum flow (Q
min1
) and other internal parameters. See fig.
38 .
• High-comfort mode:
The pump will automatically adjust the parameters for the stop
function so that the disturbances during the start/stop
operation period are minimised.
In this case, the stop function will use factory-set values of
minimum flow (Q
min2
) and other internal parameters. See fig.
38 .
• User-defined mode (Customised operating mode):
The pump will use the parameters set for ∆ H and Q
min3
respectively for the stop function. See fig. 38 .
Fig. 38 Difference between start and stop pressures ( ∆ H) and
minimum flow
In start/stop operation, the pressure will vary between the start
and stop pressures. See fig.
38 .
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 will change to start/stop operation if the flow becomes
lower than Q
min
.
Q
min
is set in % of the nominal flow of the pump (see pump
nameplate).
In "User-defined mode" (Customised operating mode), Q
min
has
been factory-set to 10 % of nominal flow.
Factory setting
See section
16. 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 up for flow switch.
2. A flow switch connected to one of the digital inputs.
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 se 0.5 x
Δ
H)
is reached and the pump will stop. When the pressure has
fallen to the start pressure (actual setpoint - 0.5 x
Δ
H), the
pump will restart.
– If the flow is higher than the set minimum flow (Q
min
), the
pump will return to continuous operation at constant
pressure.
– If the flow is still lower than the set minimum flow (Q
min
), the
pump will continue 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 (Q
min
), the pump will
return to continuous operation.
2. Flow switch:
When the digital input is activated for more than 5 seconds
because there is low flow, the speed will be increased until the
stop pressure (actual se 0.5 x
Δ
H) is reached, and the
pump will stop. When the pressure has fallen to start
pressure, the pump will restart. If there is still no flow, the
pump will quickly reach the stop pressure and stop. If there is
flow, the pump will continue operating according to the
setpoint.
Pump variant
Stop function
(Low-flow stop function)
CME ●
CRE, CRIE, CRNE, SPKE, MTRE ●
TM
06 42
67 181
5
Q
Q
min2
Q
min1
Q
min3
H
Ƹ H
Stop pressure
Start pressure