SMA SB 2800i Installation - Manual (Page 34)

Exchanging varistors Installation Guide
32 SMA Regelsysteme GmbH SB2800i-11:SE0504
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 instructions given in chapter 2 "Safety
Instructions" (p. 5).
6. Unscrew the lid of the Sunny Boy 2800i and remove it. Dis-
connect 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 use-
less. The position of varistors in the Sunny Boy 2800i can be
seen in the figure in chapter 3.1 "Device Description" (p. 7).
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 replacement
varistors). However, the terminal contacts can also provisio-
nally 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 (temperature, age,
induced surge voltages). We therefore strongly recommend
not only to exchange the defective one, but all two. These
varistors are specially manufactured for use in the Sunny Boy
2800i and are not commercially available. They have to be
purchased from SMA Regelsysteme GmbH direct (SMA
order name:“SB-TV4“).
The input port thus modified is no longer
protected against surge voltages! Equip the
inverter with varistors again as soon as
possible. The inverter should not be
operated without varistors in plants where
there is a high risk of surge voltages!
9. Reconnect the PE plug to the lid and close the Sunny Boy
2800i again.
10. Connect the faultless strings of the PV panel. Ensure correct
allocation to strings.