SMA SB 1200 Installation - Manual (Page 59)

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Installation Guide SB12-17-IA-en-52 59
9.3.2 Checking the Functioning of the Varistors
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, and thus the red LED is lit.
Check the function of the varistors as described below:
1. Open the inverter as described in section 7.2 ”Opening the Inverter” (page 45).
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 using 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 a different fault in the inverter.
• Contact the SMA Serviceline (see section
13 ”Contact” (page 70)).