Replacing the Varistors
SMA
Technologie AG
Page 52
SB25_30-11:SE0307
Installation Guide
6.
If the measured voltages are constant and their total is roughly the same as the
open circuit voltage of the string, then there is a ground fault in this string. Its
approximate location can be deduced from the relationships between the
voltages.
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 installer
should be hired for this job. In this case continue as described under point 10, but
without reconnecting the faulty string! Protect its DC plug against accidental touch
or 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 generators, 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
responses as a result of overvoltages. You can now check these varistors in the
following way, paying attention to the safety instructions in section 3 "Safety
Instructions" (Page 9):
7.
Remove the screws securing the cover and remove the cover from the Sunny Boy.
Disconnect the PE connection from the cover. Make sure that no voltage is
present.
8.
Use a continuity tester to check all the varistors and see if there is a conducting
connection between connectors 2 and 3. If there is no connection, then that
varistor is not working. The positions of the varistors in the Sunny Boy can be seen
in the figure in section 4.1 "Unit Description" (Page 11).
Summary of Contents for Sunny Boy SB 2500
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Page 6: ...Explanation of the Symbols Used SMA Technologie AG Page 6 SB25_30 11 SE0307 Installation Guide...
Page 10: ...Safety Instructions SMA Technologie AG Page 10 SB25_30 11 SE0307 Installation Guide...
Page 20: ...Installation Requirements SMA Technologie AG Page 20 SB25_30 11 SE0307 Installation Guide...
Page 62: ...The Communication Interface SMA Technologie AG Page 62 SB25_30 11 SE0307 Installation Guide...
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