PV generator

Why can’t I use different solar modules in a string and why must each string have the same number of modules?
Different strings will also have different MPPs (maximum power points), which would lead to mismatching since the inverter only has one MPP tracker. This means that the PV generator would not operate in the optimum range, leading to a reduced return.

What should be the dimensioning ratio between the PV generator and inverter?
The PV generator should generally be between 5 and 15% larger. For an optimum design, please use the Fronius Solar.configurator and discuss with your installation engineer or Fronius Service Partner.

My modules are only partly covered with snow, but the output from my inverter is still practically zero.
The ratio between the area covered with snow and the energy fed in is non-linear. Even if only a tiny area is affected, this can greatly impact upon the power fed in since the module current is determined by the "weakest” module in a string.

How can I detect a fault in my PV generator or in a module?
A fast, but relatively inaccurate diagnosis can be obtained by measuring the open-circuit voltage and the short-circuit current (which should only be done by a qualified electrician). These values can then be compared against those on the datasheet. If the differences are large, it is very likely that a module is faulty.
It is very important, however, not to ignore the interaction between the irradiance and short-circuit current.

How does shading of the PV generator affect the return from my PV system?
Even small shades can have a considerable effect on the return from the system since the current in a string is determined by the "weakest” module. Shading should be avoided as far as possible.

What will happen if there is more than 500V DC at my Fronius IG?
The unit will be damaged by voltages in excess of 500V and this will also invalidate any potential warranty claims.

Do I need to take any particular lightning protection measures with my PV generator?
The applicable standards and regulations should be followed. These standards differ from one region to another, and may also be supplemented by your local electricity company.

If an insulation monitoring message is displayed on my inverter, how do I check the insulation of the PV generator?
In this case, you should first visually inspect the cables and plug-in connectors. If you cannot see any obvious damage, you must contact a licensed electrical contractor.