SMA are widely considered a premium brand of inverter. Their inverters are premium priced too, and for that you can expect quality. However, our experience is that many of the older single phase Sunny Boy models fail at around five years old, often just out of their warranty. Here are some of the most common faults (as shown on the LCD display):
PE conn. missing
This message means that the inverter thinks that something has gone wrong with the a.c. supply. It’s one of the more common error messages on Sunny Boy 3000TL-20, 3600TL-20, 4000TL-20 and 5000TL-20 inverters. Usually there is nothing wrong with the a.c. supply, it’s an internal fault in the inverter. We can get your inverter back up and running with a software fix. If you are too far away to benefit from our call-out service you can send your inverter to us. Click here for more information: SMA Sunny Boy TL-20 PE Connect software fix
Varistor defective
This message means that the inverter has detected a component failure. Varistors are sacrificial components that protect the inverter from overvoltages. They wear out with age and in an SMA inverter they are designed to be replaceable. SMA list replacement varistor kits for your their inverters but seemingly no UK supplier wants to stock such low value items. SMA varistors are simply a combination of two standard electronic components and it is possible to cheaply make compatible replacements.
However, this error message can also mean that the inverter just thinks that the varistors are faulty, whereas in fact the fault is with the inverter itself. If your inverter is displaying this error message then there is a chance that replacing the varistors will solve the issue. However, if the inverter is old enough to be out of warranty then it’s likely that other components are also probably on their way out. Our advice is not to throw any money at it; you are better off replacing the inverter and starting afresh with a ten year warranty.