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Installation and Operating Manual for RPI M15A M20A Solar Inverter V1.0 2016-03-18
6 Planning the installation
6.8 DC connection
NOTE
Incorrectly dimensioned solar installation.
An incorrectly dimensioned solar installation can
cause damage to the inverter.
► When calculating the number of solar
modules, always take heed of the inverter’s
technical specifications (input voltage range,
maximum current and maximum input
power).
NOTE
Overheating of the DC terminals.
Exceeding the maximum current can cause over-
heating of the DC terminals and lead to a fire.
► Always take into account the maximum cur-
rent through the DC terminals when planning
the installation.
6.8.1 Symmetric and asymmetric configuration
of the DC inputs
The inverter has an MPP tracker for each DC input (DC 1 and
DC 2).
The two MPP trackers work independently of one another; the
optimum operating point is thus set separately for DC 1 and DC 2
For this reason, the module strings on DC 1 and DC 2 can have
different alignments or dimensioning. A classic application exam-
ple is a building with a gable roof on which the roofs face east
and west.
Variant 1: Symmetric configuration of the DC inputs
The total input power is always evenly distributed (50%/50%)
between DC 1 and DC 2.
Variant 2: Asymmetric configuration of the DC inputs
The maximum permitted total input power can be distributed
between DC 1 and DC 2 in the range 67%/33% to 33%/67%.
Thus, for example, a distribution of 60%/40% or 45%/55% is
possible.
The percentages always refer to the instantaneous value of the
input power. Consequently for an east-west roof installation it
is possible to install 67% of the maximum input power on both
roofs. It is then possible to exploit the effect that the solar mod-
ules on the two roofs reach their maximum at different times of
the day.
7:00
13:00
19:00
kW
Total
East Roof
West Roof
East
West
Fig. 6.11: Design concept of a system with 2 MPP trackers with
asymmetric loading of the DC inputs
