SMA SB 3000TL-20 Installation - Manual (Page 81)

SMA Solar Technology AG Troubleshooting
Installation Guide SB30TL_40TL_50TL-IA-IEN120231 81
11.2 Checking the Function of the Varistors
If the inverter displays the event number "74", then one of the varistors is probably defective.
Varistors are wear parts. Their functional efficiency diminishes with age or following repeated
responses as a result of overvoltages. It is therefore possible that one of the thermally monitored
varistors has lost its protective function.
Check the varistors as described below:
1. Open the inverter as described in section 7.2 ”Opening the Inverter” (page 61).
2. Release the upper lid screws.
3. Pull the lid at the upper edge towards the front.
4. Push the lid upwards and remove it.
DANGER!
Danger to life due to high voltages in the inverter.
• Wait 5 minutes before opening the upper lid, in order to allow time for the capacitors
to discharge.