Grundfos MAGNA3 25-80 Installation And Operating Instructions Manual page 33

7.9.5 Heat energy monitor
The heat energy monitor calculates the heat energy consumption
within the system. The built-in flow estimation needed for the
calculation has a worst case accuracy of ± 10 % of the maximum
flow. The actual accuracy in a duty point will be shown in the
MAGNA3 display (available for pumps with production code from
1838). The temperature measurement accuracy also depends on
the sensor type. Therefore, you cannot use the heat energy value
for billing purposes. However, the value is perfect for optimisation
purposes in order to prevent excessive energy costs. See also
section 7.6 Flow estimation accuracy.
To counterbalance any inaccuracy on either the internal and
external sensor it is possible to manually enter a temperature
offset. The offset is entered in integers, for example 2 degrees.
The offset range is within ± 20 degrees celsius. To set the
temperature offset, see section
Note: Temperature sensor offset is available for pumps with
production code from 1838.
The flow and volume accuracy is calculated and shown in the
display, see sections "Estimated flow rate,
and "Accuracy of values", page 39.
The heat energy monitor requires an additional
temperature sensor installed in the flow pipe or
return pipe depending on where the pump is
installed.
kWh
t
F
t
R
Fig. 52 MAGNA3 with built-in heat energy monitor
You can measure both heating and cooling in the same system. If
a system is used for both heating and cooling, two counters are
automatically shown in the display. See section
page 39.
Monitoring heat energy in multipump systems
In a multipump system, the master pump calculates the heat
energy regardless of which pump, master or slave, is running.
If the master loses power or has a fault on the external sensor,
the accumulation of heat energy will not be counted until the
master is powered back on or the external sensor error is
remedied. If the master is replaced, the heat energy values for
the system is reset.
7.9.6 External setpoint function
You can use the analog input to influence the setpoint externally.
The external setpoint function can be used in two different ways:
• "Linear with Min."
• "Linear with Stop" (available for pumps with production code
from 1838)
In both modes the input signal range is influenced linearly.
8.7.4 "Controller settings".
accuracy", page 39,
"Heat energy",
"Linear with Min."
Here, a 0-10 V or 4-20 mA signal controls the pump speed range
in a linear function. The range of control depends on the minimum
speed, power and pressure limits of the pump. See figs
54.
H
(user setpoint)
Resulting
setpoint
0 2
Fig. 53 "Linear with Min.", 0-10 V
Control
0-2 V (0-20 %) Resulting setpoint is equal to minimum.
Resulting setpoint is between minimum and
2-10 V (20-100 %)
user setpoint.
Fig. 54 Control range and setpoint
The external setpoint function operates differently depending on
the model. For models A, B and C, the maximum speed is often
obtained at voltages lower than 10 V, as the span of control is
limited.
In models newer than A, B and C, the internal scaling has been
optimised making the dynamic area bigger, thus giving a better
control of the pump speed when using the external setpoint
function.
The same applies if the pump is receiving a setpoint from Building
Management Systems.
"Linear with Stop"
Note: Available for pumps with production code from 1838.
Here, if the input signal is below 10 %, the pump changes to
operating mode "Stop". If the input signal is increased above 15
%, the operating mode is changed back to "Normal".
H
0 2
4
Normal
Stop
Fig. 55 "Linear with Stop", 0-10 V
53 and
V
Analog
10
input
10 V
20 mA
33