Grundfos E-pumps

Grundfos E-pumps
2
Such a pumping system can be designed in two ways:
• The differential-pressure transmitter (DPT 1 in
fig. 16) is placed across the pump, and the system
is running with proportional differential-pressure
control.
• The differential-pressure transmitter (DPT 2 in
fig. 16) is placed close to the radiators, and the
system is running with proportional differential
pressure control.
The advantage of the first solution, which is equal to
a TPE Series 2000 pump solution, is that the pump,
PI controller, speed control and transmitter are placed
close to one another, making the installation easy.
This solution makes it possible to get the entire system
as one single unit. In order to get the system up and
running, pump curve data must be stored in the
controller. These data are used to calculate the flow
and likewise to calculate how much the setpoint, H set ,
has to be reduced at a given flow to ensure that the
pump performance meets the requirements.
The second solution involves higher installation costs
as the transmitter has to be fitted near the radiators
and extra cabling is required. The performance of this
system is more or less similar to the first system. The
transmitter measures the differential pressure at the
radiator and the PI controller compensates
automatically for the increase in required pressure in
order to overcome the increase in pressure losses in
the supply pipes, etc.
PI controller
The MLE has a built-in PI controller for speed control
of pumps. The factory setting of gain (Kp) and integral
time (Ti) can easily be changed. The controller can
operate in both normal and inverse mode.
Normal mode
Normal mode is used in systems in which an increase
in pump performance will result in a rise in the value
measured at the feedback sensor. This will typically be
the case in most MLE applications.
Normal mode is selected by setting the gain (Kp) to a
positive value in the control panel.
Inverse mode
Inverse mode is used in systems in which an increase
in pump performance will result in a drop in the value
measured at the feedback sensor. This mode will
typically be used for constant level operation (filling a
tank) and for constant temperature operation in cooling
systems.
Inverse mode is selected by setting the gain (Kp) to a
negative value in the control panel.
System/application
p
L [m]
p
p
t
t
Q
L [m]
L [m]
L [m]
t
Heating
systems
K p
0.5
0.5
Cooling
system
T i
0.5
L 1) < 16.4 ft: 0.5
L > 16.4 ft: 3
L > 32.8 ft: 5
0.5 0.5
0.5 0.5
0.5 –0.5 10 + 1.52L
0.5 10 + 1.52L
0.5 –0.5 30 + 1.52L
+2.5 100
Heating systems are systems in which an increase in pump
performance will result in a rise in temperature at the sensor.
Cooling systems are systems in which an increase in pump
performance will result in a drop in temperature at the sensor.
L) Distance in [ft] between pump and sensor
Product overview
19