Additional Control Mode Features - Grundfos MAGNA3 25-80 Installation And Operating Instructions Manual

Technical specifications
H
Fig. 36 Constant-curve duty
The pump can be set to operate according to a constant curve,
like an uncontrolled pump. See fig. 36.
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.
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. 37.
H
Limited max. curve
Speed setting from 0 to 100 %
Fig. 37 Power and pressure limitations influencing the
maximum curve
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 in which a
maximum flow is required. This operating mode is for instance
suitable for hot-water priority.
• You can use the minimum curve mode in periods in which a
minimum flow 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 constant flow
by choosing a setpoint at 100 % and choosing the desired value
for the flow with the flow limit function FLOW
accuracy of the flow estimation into consideration.
26

7.4 Additional control mode features

MAGNA3 offers additional features for the control modes to meet
specific demands.
7.4.1 FLOW
The feature is an integrated part of the FLOW
but can also be used in:
• proportional-pressure mode
• constant-pressure mode
• constant-temperature mode
• constant-curve mode.
Characteristics and key benefits
Q
• A control mode feature that, when activated, ensures that the
rated maximum flow is never exceeded.
By enabling FLOW
authority, the rated flow is never exceeded, thus eliminating the
need for throttling valves.
Technical specifications
Fig. 38 FLOW
The factory setting of the FLOW
AUTO
The setting range for the FLOW
the pump. Do not set the FLOW
Q
duty point.
In the flow range between 0 and Q
according to the selected control mode. When Q
the FLOW
that the flow never exceeds the FLOW
system requires a higher flow due to increased resistance in the
system. See fig. 39,
H
H
H
set
2
. Take the
LIMIT
Fig. 39 Proportional-pressure control with FLOW
LIMIT
in systems where MAGNA3 has full
LIMIT
H Q
25 %
max
Setting range
Q
limit
LIMIT
LIMIT
factory setting meets the maximum curve.
ADAPT
LIMIT
LIMIT
limit
function will reduce the pump speed to ensure
LIMIT
40 or 41.
set
control mode,
ADAPT
Q
90 %
max
Q
is the flow where the
is 25 to 90 % of the Q of
max
lower than the dimensioned
, the pump will run
is reached,
limit
set, no matter if the
LIMIT
Normal
proportional-pressure
duty point
FLOW duty
LIMIT
point
Q
LIMIT