SMA SB 700 - Manual (Page 42)

Replacing the varistors SMA Technologie AG
Page 42 SB700-11:SA2006 Installation Guide
5. Repeat points 3 and 4 for each string.
If you found a earth 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 earth 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 information in section 2 "Safety
information" (page 9):
6. Remove the screws that secure the lid and remove the lid from the Sunny Boy
700. Disconnect the PE connection from the lid. Make sure that no voltage is
present.
7. Using a continuity tester, check all the varistors to see if there is a conducting
connection between connectors 2 and 3. If there isn't, then that varistor is not
working. The positions of the varistors in the Sunny Boy 700 can be seen in
section 3.1 "Unit description" (page 11).
8. Replace the varistor concerned with a new one
as shown in the drawing to the right. Ensure the
varistor is installed the right way round! If you
do not receive a special tool for operating the
terminal clamps with your replacement
varistors, please contact SMA. As an
alternative, the terminal contacts can be
operated using a suitable screwdriver. Since the
failure of one varistor is generally due to factors
that affect all varistors in a similar way
(temperature, age, inductive overvoltages), it is
highly recommended that you replace both
varistors, not just the one that is obviously
defective. The varistors were specially
manufactured for use in the Sunny Boy 700 and
are not commercially available. They must be
ordered directly from SMA Technologie AG
(SMA order code: SB-TV1).
Insert the special tool to open
the terminal clamp.
The pole with the small loop
(crimp) must be fitted to
terminal 1 when replacing the
varistor.
Remove the varistor.
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