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10 Replacing the varistors
The Sunny Boy SB 1100LV is a complex high-technology device. As a result, the
possibilities for fixing faults on site are limited to just a few items. Please don't try to carry
out repairs other than those described here. Use the SMA Technologie AG 24-hour
exchange service and repair service instead.
If the red LED on the status display glows continuously during operation, you should first
of all make sure that there is no ground fault in the PV generator.
1.
Disconnect the Sunny Boy SB 1100LV from the
low voltage grid (switch the line circuit breaker
to its "off" position). Make sure the grid cannot
be inadvertently reconnected and that no
voltage is present.
2.
Switch off the DC circuit breaker.
3.
Open the Sunny Boy SB 1100LV as described in
chapter 7.1. Taking one DC plug connector at a
time, measure the voltages between one DC
plug connector of a string and earth potential.
Pay attention to the safety instructions!
Warning!
Dangerous high voltages may be present. Danger of death!
4.
If the measured voltages are constant and if their total is roughly the same as the
open circuit voltage of the string, then there is an ground fault in this string. Its
approximate location can be deduced from the relationships between the
voltages.
5.
Repeat points 3 and 4 for each string.
If you found a ground fault, it is probably not necessary to replace the varistors.
Instead, make sure the ground fault is fixed. Generally the PV generator's
installation engineer should be hired for this job. In this case continue as described
under point 10, but without reconnecting the faulty string. Instead of reconnecting
the string, protect its DC plug against accidental touch contact (e.g. by fitting the
protective caps or using sufficient high-voltage insulating tape).
If you did not find any ground fault in the PV generator, it is likely that one of the
thermally monitored varistors has lost its protective function. These components are
wearing parts. Their functioning diminishes with age or following repeated
Installation Guide
Replacing the varistors
Off
SB1100LV-11:SE2006
Page 47
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