Grundfos MAGNA3 50-40 F N Installation And Operating Instructions Manual page 24

12.3.4 Constant pressure
The pump maintains a constant pressure, irrespective of water
demand. See fig. 22.
H
Fig. 22 Constant pressure
12.3.5 Constant temperature
This control mode ensures a constant temperature. Constant
temperature is a comfort control mode that can be used in
domestic hot-water systems to control the flow to maintain a fixed
temperature in the system. See fig. 23. When this control mode is
used, no balancing valves must be installed in the system.
If the pump is installed in the flow pipe, an external temperature
sensor must be installed in the return pipe of the system. The
sensor must be installed as close as possible to the consumer
(radiator, heat exchanger, etc.).
We recommend to install the pump in the flow
Note
pipe.
If the pump is installed in the return pipe of the system, the
internal temperature sensor can be used. In this case, the pump
must be installed as close as possible to the consumer (radiator,
heat exchanger, etc.).
The constant-temperature control mode also reduces the risk of
bacterial growth (for example Legionella) in the system.
It is possible to set the sensor range:
• min. -10 °C
• max. +130 °C.
To ensure that the pump is able to control, we
Note
recommend to set the sensor range between
-5 and +125 °C.
H
Fig. 23 Constant temperature
24
12.3.6 Constant curve
The pump can be set to operate according to a constant curve,
like an uncontrolled pump. See fig. 24.
The desired speed can be set in % of maximum speed in the
range from 25 to 100 %.
H
Q
Fig. 24 Constant curve
Note
H [%]
100 %
Limited
max. curve
Fig. 25 Power and pressure limitations influencing the max.
Q
Depending on the system characteristic and the
duty point, the 100 % setting may be slightly
smaller than the pump's actual max. curve even
though the display shows 100 %. This is due to
power and pressure limitations built into the
pump. The deviation varies according to pump
type and pressure loss in the pipes.
Actual duty point
curve
Q
Max. curve
Q [m 3 /h]