Installation Instructions
Troubleshooting SMA Solar Technology AG
38 SB11_12_17-IEN100132 Installation Guide
9.1.2 Checking the Function of the Varistors
Varistors are wearing parts. Their functioning becomes restricted through aging or due to repeated
responses as a result of overvoltages. It is therefore possible that one of the thermally monitored
varistors has lost its protective function, and thus the red LED is lit.
Check the function of the varistors as described below:
1. Open the Sunny Boy as described in section 7.1 "Opening the Sunny Boy" (page32).
2. With the aid of a multimeter, determine for both
varistors in the installed state whether a conductive
connection exists between connectors B and C.
Position of varistors
You can determine the position of the varistors with the help of the illustration below.
Observe the following allocation of the
terminals:
• Terminal A: outer terminal (varistor
connection with loop [crimp])
• Terminal B: middle terminal
• Terminal C: outer terminal (varistor
connection without loop [crimp])
Result Action
☑There is a conducting connection. There is probably another fault in the Sunny Boy.
• Close the Sunny Boy as described in section
7.2 "Closing the Sunny Boy" (page33).
• Contact the SMA Serviceline (see section
13 "Contact" (page47)).