Grundfos MAGNA3 Manual page 21

MAGNA3
Temperature sensor
To measure the temperature difference of the flow pipe
and the 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. 24.
t
Fig. 24 Differential temperature
Constant curve
A constant curve is suitable for systems, where both a
constant flow rate and a constant head are required,
i.e.:
• Heat surfaces
• cooling surfaces
• heating systems with 3-way valves
• air condition system with 3-way-valve
• 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.
Technical specifications
H
Fig. 25 Constant-curve duty
The pump can be set to operate according to a
constant curve, like an uncontrolled pump. See fig. 25.
Depending on the pump model, you can set the
desired speed in % of the maximum speed. The span
of control depends on the minimum speed, power and
pressure limitation of the pump.
Note: If the pump speed is set in the range between
minimum and maximum, the power and pressure are
limited when the pump is running on the maximum
curve. This means that the maximum performance can
be achieved at a speed lower than 100 %. See fig. 26.
H
Speed setting from 0 to 100 %
Fig. 26 Power and pressure limitations influencing the
You can also set the pump to operate according to the
maximum or minimum curve, like an uncontrolled
pump:
• You can use the maximum curve mode in periods
where a maximum flow rate is required. This
operating mode is for instance suitable for hot-water
priority.
• You can use the minimum curve mode in periods
where a minimum flow rate is required. This
operating mode is for instance suitable for manual
night setback if automatic night setback is not
desired.
You can select these two operating modes via the
digital inputs.
In the control mode constant curve, you can obtain a
constant flow by choosing a setpoint at 100 % and
choosing the desired value for the flow rate with the
FLOW
LIMIT
estimation into consideration.
Q
Limited max. curve
maximum curve
function. Take the accuracy of the flow rate
4
Q
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