The messages ‘PE connection missing’ and ‘PE not connected’ relate to the grounding of the inverter: ‘PE’ stands for ‘Protective Earth’. The error can also be displayed as ‘event 901’ with a message about the ‘earth connection’.

Inverters are always connected to the earth of the home, just like all other electronic devices such as washing machines and refrigerators. If there is ever an incorrect electrical connection within the device, the grounding ensures that any dangerous voltage is conducted to earth, so that there is no danger if anyone touches the device.

SMA inverters continuously monitor the quality of this grounding. They do this by measuring the voltage difference between the neutral conductor (N) and the earth (PE). Normally there is hardly any voltage difference between these two conductors. If the voltage difference becomes greater than a few volts, the inverter gives this warning. As a precaution, the inverter then goes into fault mode and waits until the grounding is back to normnal before automatically starting up again.

What causes this message?

In the vast majority of cases, this message has nothing to do with the inverter or the solar panels. The cause lies more in the electrical installation in the home. For example, the grounding of the home may be inadequate: most homes have a so-called 'earth pin' that is driven into the ground, to which all grounding wires are connected. If this earth pin is not sufficiently deep in the ground, or if the connected wires have come loose somewhere, then the grounding is no longer in order.

Sometimes there are certain devices in the home or in the vicinity of the home that cause too high a voltage on the neutral conductor when operating. Here too, inadequate grounding in the home plays a role. This is often the case if the message appears at fixed times of the day; if the device in question is switched on at those times, then it is easy to trace the cause of the fault to that device.

What should you do if you receive this message?

This message is caused by the electrical installation in the home. You would be wise to have your home electrician come and measure your installation and fix the grounding. Inadequate earthing can lead to dangerous situations in the home, because the protection in the meter board may not work correctly, and because there may be voltage present on certain metal parts in the home.

Only in very rare cases is there something wrong with the inverter itself. This could be the case if you have the message constantly, and the inverter does not start working at all for days in a row. In that case, an earth wire between the inverter and the grounding rail in the meter board may be broken.

Incidentally, it is possible to switch off the ‘PE connection monitoring’ in the inverter; this does not solve the underlying problem, but your solar power system can continue to produce normally. We do not recommend this solution, because it does not encourage you to tackle a potentially dangerous situation in the home. If you still want to switch off the PE connection monitoring (temporarily), please contact our service.