SMA SB 4200TL Multi-String Installation - Manual (Page 34)

Exchanging Varistors SMA Technologie AG
Page 34 SB4200TL-13:SE2006 Installation Guide
5. Repeat points 3 and 4 for the other 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 plant. In this case proceed with point 10, but
with-out reconnecting the faulty string! Protect its PV plug connectors against
touching (e. g. by protective caps or insulation strip with sufficient electric
strength).
If you have not found any ground fault in the PV generators, probably one of
the thermally monitored varistors has lost its protective function. The varistors
are subject to wear and tear and their function is reduced in the course of their
aging or in case of repeated strain placed on them by surge voltages. You can
now check the varistors as described below while following the safety instruc-
tions given in chapter 2 „Safety Instructions” (page 9).
6. Unscrew the lid of the Sunny Boy 4200TL Multi-String and remove it. Disconnect
the PE plug inside the lid. Test safe isolation from supply.
7. Test all varistors for an electric connection between terminals 2 and 3. If there
is no electric connection the varistor is useless. The position of varistors in the
Sunny Boy 4200TL Multi-String can be seen in chapter 3.1 „Device Description”
(page 11).
8. Replace the defective varistor by a new one as
shown in the figure on the left. Ensure correct
orientation of the varistor! Please contact SMA
if you have not received special tools to move
the terminals (included in delivery of replace-
ment varistors). However, the terminal contacts
can also provisionally be released one by one
with a suitable screwdriver. The failure of a
varistor is normally due to circumstances that
apply to all varistors in a similar manner (tem-
perature, age, induced surge voltages). We
therefore strongly recommend not only to ex-
change the defective one, but all four. These
varistors are specially manufactured for use in
the Sunny Boy 4200TL Multi-String and are not
commercially available. They have to be pur-
chased from SMA Technologie AG direct (SMA
order name:“MSWR-TV6“).
1
2
3
Unlock the varistor
with the
extractor tool
The wire with the little
dent must be inserted
into the terminal
number 1 when you
install the new varistor
Remove varistor