Flow Estimation Accuracy - Grundfos MAGNA3 Manual

4

Flow estimation accuracy

The internal sensor estimates the difference in
pressure between the inlet and outlet port of the pump.
The measurement is not a direct differential-pressure
measurement, but by knowing the hydraulic design of
the pump, you can estimate the differential pressure
across the pump. The speed and power are also used
to give a direct estimation of the current duty point of
the pump.
The calculated flow rate has an accuracy specified as
± xx % of Q . The less flow through the pump, the
max
less accurate the reading will be. The typical accuracy
of the flow reading is ± 5 % of the specific pump's
maximum flow. In extreme cases, such as closed valve
operation, the accuracy can be up to ± 10 % of the
maximum flow.
See also
Heat energy
24
monitor, page 26.
Example:
H
Min.
Fig. 31 Q
max
1. MAGNA3 65-60 has a Q
max
3
% accuracy means 2 m /h inaccuracy of Q
3
m /h.
2. This accuracy is valid for the entire QH area. If the
3
pump indicates 10 m /h, the measurement is 10 ± 2
3
m /h.
3. The flow rate can be 8-12 m
4. Note: Use of a water/ethylene glycol mixture will
decrease the accuracy.
MAGNA3
Max.
Q
Q
max
3
of 40 m /h. A typical 5
. ± 2
max
3
/h.