35
Fig. 51
Position of the check valve and pressure sensor in
system with suction lift operation
Fig. 52
Position of the check valve and pressure sensor in
system with positive inlet pressure
Diaphragm tank
The stop function requires a diaphragm tank of a certain minimum
size. The tank must be installed as close as possible after the
pump and the precharge pressure must be 0.7 x actual setpoint.
Recommended diaphragm tank size:
If a diaphragm tank of the above size is installed in the system,
the factory setting of
Δ
H is the correct setting.
If the tank installed is too small, the pump will start and stop too
often. This can be remedied by increasing
Δ
H.
17.7.11 Constant level 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:
•
Δ
H is factory-set to
10 % of actual setpoint
.
•
Δ
H can be set within the range from 5 % to 30 % of actual
setpoint.
A built-in low-flow detection function will automatically measure
and store the power consumption at approx. 50 % and 85 % of
the rated speed.
If
Active
is selected, proceed as follows:
1. Close the isolating valve to create a no-flow condition.
2. Press OK to start the auto-tuning.
Operating conditions for the stop function
It is only possible to use the constant level stop function if the
system incorporates a level sensor, and all valves can be closed.
Description
The stop function is used for changing between on/off operation
at low flow and continuous operation at high flow.
Fig. 53
Constant level with stop function. Difference between
start and stop levels (
Δ
H)
Low flow can be detected in two different ways:
1. With the built-in low-flow detection function.
2. With a flow switch connected to a digital input.
1. Low-flow detection function
The built-in low-flow detection is based on the measurement of
speed and power.
When low flow is detected, the pump will stop. When the level has
reached the start level, the pump will start again. If there is still no
flow, the pump will reach the stop level and stop. If there is flow,
the pump will continue operating according to the setpoint.
2. Low-flow detection with flow switch
When the digital input is activated because of low flow, the speed
will be increased until the stop level (actual setpoint – 0.5 x
Δ
H) is
reached, and the pump will stop. When the level has reached the
start level, the pump will start again. If there is still no flow, the
pump will reach the stop level and stop. If there is flow, the pump
will continue operating according to the setpoint.
17.7.12 Sensor 1 (3.15)
Setting of sensor 1 connected to terminal 54. This is the feedback
sensor.
Select among the following values:
•
Sensor output signal:
0-20 mA
4-20 mA.
•
Unit of measurement of sensor:
bar, mbar, m, kPa, psi, ft, m
3
/h, m
3
/s, l/s, gpm, °C, °F, %.
•
Sensor measuring range.
T
M
0
3
8
5
8
2
1
9
0
7
T
M
0
3
8
5
8
3
1
90
7
Rated flow rate of pump
[gpm]
Typical diaphragm tank size
[gallons]
0-26
2
27-105
4.4
106-176
14
177-308
34
309-440
62
Pressure sensor
Diaphragm tank
Check valve
Pump
Diaphragm tank
Pressure sensor
Pump
Check valve
T
M
03 90
99 33
07
Start level
Δ
H
Stop level
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