I have now measured 1 month again. The measurement of the solar part is almost 100%. But the measurement of the consumer does not correspond with the electricity meter of the electricity plant at all. IotaWatt measures about 50% more energy than the meter from the power company.
Today I made a try. I switched off the solar system and started a 15 kW compressor. IotaWatt then displayed a power factor of 0.80. Then I switched the solar system on again (about 5 kW power) without compressor and received a Pf 0.99 . Then solar and compressor together. IotaWatt then displayed no Pf .
I measure with a VT with Derived Reference. Sensor installation according to type 2.
I suspect that the power factor is not measured correctly on two phases. I do not know what I can do.