SMA SB 2800i Installation - Manual (Page 33)

Installation Guide Exchanging varistors
SB2800i-11:SE0504 SMA Regelsysteme GmbH 31
8 Exchanging varistors
The Sunny Boy 2800i is a very complex technical device.
Therefore there are only a few possibilities to repair failures on
site. Please do not try to make repairs other than described in this
document. Make use of our 24-hour exchange service and the
repair service of SMA Regelsysteme GmbH.
If the red status LED is permanently on during operation please
first make sure that there is no ground fault in the PV generator.
1. Disconnect the grid (switch off the circuit breaker), secure it
against accidental reactivation and ensure that it is discon-
nected.
2. Disconnect the Multi-Contact plug connectors of all strings.
Make sure that their allocation to the different inverter input
ports can still be recognized!
3. Measure voltages between one Multi-Contact plug connector
of each string and the ground potential. Follow all applicable
safety instructions!
The voltage from the strings is very dangerous!
Be very careful and pay attention to all
applicable safety regulations!
4. If the voltages measured are constant and their total is
approximately equal to the open-circuit voltage of the string,
there is a ground fault in this string. Its appoximate position
can be deducted from the ratios of voltages.
5. Repeat points 3 and 4 for each string.
If you have found a ground fault it is probably unnecessary
to exchange the varistors. Make sure to remove the ground
fault instead. This should normally be done by the installer of
the PV panel. In this case proceed with point 10, but without
reconnecting the faulty string! Protect its Multi-Contact plug
connectors against touching (e. g. by protective caps or insu-
lation strip with sufficient electric strength).
Ensure that the AC voltage is off
before you open the Sunny Boy!
Disconnect the PV strings!
Measure voltages between
Multi-Contact plug connectors and
the ground potential.