Grundfos MAGNA3 25-80 Installation And Operating Instructions Manual page 25

7.3.7 Differential temperature
Select this control mode if the pump performance is to be
controlled according to a differential temperature in the system
where the pump is installed.
Characteristics and key benefits
• Ensures a constant differential temperature drop across
heating and cooling systems.
• Ensures a constant differential temperature between the pump
and the external sensor, see figures
• Requires two temperature sensors, the internal temperature
sensor together with an external sensor.
Technical specifications
H
Fig. 33 Differential temperature
The differential-temperature control mode is available in model B.
The model version is stated on the nameplate. See section
6.5 Model type.
Temperature sensor
To measure the temperature difference of the flow and return
pipe, you must use both the internal sensor and an external
sensor.
If the pump is installed in the flow pipe, the external sensor must
be installed in the return pipe and vice versa. Always install the
sensor as close as possible to the consumer (radiator, heat
exchanger, etc.). See fig. 34.
Fig. 34 Differential temperature
33 and 34.
Δt
Q
t
7.3.8 Constant flow
Note: Available for pumps with production code from 1838.
The pump maintains a constant flow in the system independently
of the head. See fig. 35.
Constant flow is suitable in applications such as air handling
units, hot-water systems and ground-source heating systems.
Characteristics and key benefits
• It is not possible to use an external sensor, instead, the pump
uses its internal sensor.
• In multipump systems constant flow is only available in
alternating and backup operation, not cascade operation.
H
Fig. 35 Constant flow rate
7.3.9 Constant curve
A constant curve is suitable for systems where there is a demand
for both constant flow and constant head, i.e.:
• heating surfaces
• cooling surfaces
• heating systems with 3-way valves
• air-conditioning systems with 3-way valves
• chiller pumps.
Characteristics and key benefits
• If an external controller is installed, the pump is able to change
from one constant curve to another, depending on the value of
the external signal.
• Depending on your preferences, the pump can be controlled
according to either a maximum or minimum curve.
Q
Q
set
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