SMA SB 2800i - Manual (Page 22)

Device Description Operating Instructions
20 SMA Regelsysteme GmbH SB2800i-11:FE0504
Grid Impedance too High
When this failure occurs, the yellow failure LED is on for five
seconds and then starts the blinking code by staying off for three
seconds and then blinking three times in short intervals. The code
is sent three times.
If the failure persists, the signal starts from the beginning.
The Sunny Boy has detected a failure as the grid impedance
values are out of permissible range. If the inverter switches off
frequently during grid monitoring because of the above failure,
the reason might be that grid impedance is too high. A qualified
electrician can normally solve this problem by increasing the
cross-section of the grid cable. Other actions are possible as well.
Any modifications of the operating parameters require the
explicit permission of the public utility company.