Grundfos MAGNA3 Installation And Operating Instructions Manual page 25

13.3.4 Constant pressure
The pump maintains a constant pressure, irrespective of water
demand. See fig. 24.
H
Fig. 24 Constant pressure
13.3.5 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. 25. When this control
mode is used, no balancing valves must be installed in the
system.
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.).
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.).
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. +14 °F (-10 °C)
• max. +266 °F (+130 °C).
To ensure that the pump is able to control, we
Note
Note
recommend to set the sensor range between
+3 °F and +257 °F (-5 and +125 °C).
H
Fig. 25 Constant temperature
13.3.6 Differential temperature
This control mode ensures a constant differential temperature
drop across a heating system.
The pump should be installed in the flow pipe so the built-in
sensor measures the liquid temperature going out to the load.
An external temperature sensor must be installed in the system to
measure the liquid temperature returning from the heating load.
In this mode, the pump will maintain a constant temperature.
See fig. 26. and 27, differential between the pump and the
external sensor.
Q
Fig. 26 Differential temperature
Fig. 27 Differential temperature
Note
Note
Note
Note
Q
H
Δt
t
Changing K and T values are only possible with
p i
Grundfos GO.
Changing the K and T values will affect all
p i
control modes. If the control mode is to be
changed back to another mode you must set the
K and T values back to default values. For all
p i
other modes the default values are K
T = 0.5.
i
Q
= 0.5,
p
25