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Frequently Asked Questions


After a firmware update some new features do not appear in the web interface

Make sure you reloaded the webinterface after the firmware update. This can be achieved, depending on your browser, by pressing either F5, Ctrl+F5 or just by clicking on the reload button.

After a firmware update OpenDTU does not get a proper IP via DHCP

In some cases it is required to perform a power cycle to get it working again.

A set up inverter does not appear in the live view

Double check whether the inverter type in Settings --> Inverter reflects your type or if it's unknown. If it's unknown it will not appear in the live view and you most likely inserted a invalid serial number.

Is it possible to reset the yield total value?

The yield total value comes directly out of the inverter. (Currently) there is no way to reset or change this value. Please consider it as the total kilometer counter in a car. On the other hand it's possible to add a yield offset to each inverter. This can be set up in the inverter properties (Settings --> Inverters --> Click on the pen icon)

Why get the daily yield values sometimes reset to zero at the evening?

The values are reset if the inverter restarts. At some (cloudy) evenings it can occur that the brightness fluctuates heavily during the dusk. This could lead to multiple restarts of the inverter and therefor zeros in the production values. You can enable the Yield Day Correction in the inverter settings.

OpenDTU shows wrong/unrealistic or just missing values

This is most likely the case because two DTUs are querying the same inverter. This is a not supported behavior and can lead to unexpected effects. Only one DTU is allowed to query a specific inverter.

Please also see #831, #727

With HMS-1800 or HMS-2000 the reactive power shows unrealistic value 6.553,5

This seems to be a issue with inverter Firmware 1.0.14. It contains a calculation mistake.

Reactive power seems to scale incorrectly / be calculated incorrectly and runs up with increasing power at sunrise from 0 to 0xFFFF and remains there, which can be observed at slow sunrise and sunset again (only in the very low watt range). Since the PF is calculated from P and Q and Q is insanely high, this results in a PF of almost 0.

Please also see #926

After the OpenDTU startup the limit is stated as zero but the inverter seems to work properbly

The limit is fetched every 2-4 minutes from the inverter. If its fetch more often the inverter will create error messages in the event log. Due to the fact that on OpenDTU startup its not know when the limit was last queried, a 4-minute delay is applied before the limit will be fetched.


How to observe the ESP32 boot process by looking at the serial console?

Please see here

The ESP does not boot anymore and the serial console shows 'Brownout detector was triggered'

This means that under certain circumstances (activation of WLAN/Ethernet or sending requests to the inverter) the supply voltage drops to such an extent that the ESP can no longer work reliably. This can be remedied, for example, with a 100uF capacitor between VCC and GND. In exceptional cases, the power supply unit also appears to be too weak. The cable cross-section of the USB cable can also have an influence.

After a reboot of the router or access point, OpenDTU does not reconnect immediatly to the WiFi

OpenDTU tries to reconnect to the WiFi for 30 seconds. If it can't find the WiFi within this time it stops reconnecting and waits for 10 minutes until a new connect attempt is done. This is done because all channels are tried during a connection attempt. This means that an end device that is connected to the "Admin Access Point" may lose the connection or is not be able to connect at all.

Build errors

OpenDTU does not build: error: 'bad_alloc' was not declared in this scope

The exact reason is not known. But it helps to delete the ~/.platformio/ folder.

Please also see #719

OpenDTU does not build: "C:/Users/<username>/.platformio/packages/framework-arduinoespressif32/cores/esp32/Arduino.h:33:10: fatal error: freertos/FreeRTOS.h: No such file or directory #include \"freertos/FreeRTOS.h\"

This is most likly a issue with your PlatformIO installation. As a workaround you can delete all packages within the C:/Users/<username\>/.platformio/packages/ folder. The content will be downloaded on the next compile attempt.